Papers - Murakami, Toshiyuki

Wide-Bandwidth Estimation of Cross-Coupling Factors for Advanced Position-Sensorless Control of IPMSM

Shimamoto, K; Murakami, T

IEEJ JOURNAL OF INDUSTRY APPLICATIONS 14 ( 1 ) 111 - 119 2025

ISSN  2187-1094

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Vibration Suppression and Disturbance Rejection Based on Equivalent Mass and Stiffness Matrices

Ito J., Murakami T.

2025 IEEE International Conference on Mechatronics, ICM 2025  2025

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This paper proposes vibration suppression and disturbance rejection methods for multi-degrees-of-freedom (MDOF) manipulators with flexible joints in the workspace. The proposed methods utilize an equivalent mass matrix (EMM) and equivalent stiffness matrix (ESM) that represent the mass and stiffness in the workspace, respectively. In conventional methods, variations of EMM and ESM can degrade vibration suppression and disturbance rejection performances. Therefore, the proposed methods employ a workspace observer (WOB), resonance ratio control, and load-side workspace observer (LWOB). The WOB and resonance ratio control fix the EMM to constant values and realize stable vibration suppression. The LWOB improves ro-bustness by compensating for disturbances. The stability analyses reveal the parameter conditions. The simulation results show that the proposed methods suppress vibrations and disturbances in the workspace.

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A Remote Control Method for Transport Two-Wheeled Mobile Robot

Kuwata M., Murakami T.

2025 IEEE International Conference on Mechatronics, ICM 2025  2025

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This paper investigates the deployment of transport Two-Wheeled Mobile Robots (TWMRs) within warehouse environments. TWMRs have superior maneuverability and a smaller footprint compared to conventional steering-type Autonomous Mobile Robots (AMRs). This feature makes TWMRs well-suited for narrow spaces and high-reach tasks. Despite these advantages, TWMRs are inherently unstable, necessitating sophisticated control systems to maintain balance. In this study, we propose a control system that enables remote operation of the TWMR, allowing the operator to adjust the pitch angle command. The TWMR is equipped with various control mechanisms, including Disturbance Observer (DOB), PD controller and Lyapunov controller. These components work in conjunction to stabilize the TWMR and enhance the translational position tracking performance. Simulation results demonstrated the effectiveness of our approach, showing that the proposed system successfully stabilized the TWMR and reduced pitch angle variations, especially under load conditions. It also suggested the potential of integrating human control ability with advanced control systems for improved TWMR performance.

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A PID-backstepping Hybrid Position and Attitude Control of a Bi-copter AUV with a Moving Mass

Muto K., Murakami T., Simetti E.

2025 IEEE International Conference on Mechatronics, ICM 2025  2025

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This research aims to design a bi-copter AUV and evaluate its feasibility. Autonomous Underwater Vehicles (AUVs) that sail independently without cables and human operators are in the spotlight as an alternative to human divers. To miniaturize AUVs to operate in narrow spaces, we propose an AUV with two thrusters and two pitch angle servo motors: a 'bi-copter' AUV. The bi-copter is expected to be power efficient, and have high turning performance. However, precise and robust control performance is required to overcome its underactuated characteristics and disturbances. To enhance pitch motion stability, a Pitch Motion Compensator (PMC) with a Pitch Angle Disturbance Observer (PADO) is implemented and controls the position of a moving mass inside the AUV body. We propose a PID-Backstepping Hybrid (PBH) control composed of the PID position controller and the backstepping attitude (roll and yaw motion) controller for the position and attitude control. In addition, We propose the yaw angle reference value calculation methodology to control the y position indirectly. Our proposed method is evaluated by the simulations using MATLAB/Simulink and Simscape including wave disturbance and its feasibility is confirmed.

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Topology Optimization for Motor Slot with Heat Generation Rate Depending on Winding Occupancy

Katsuno, A; Murakami, T

IEEJ JOURNAL OF INDUSTRY APPLICATIONS 13 ( 4 ) 453 - 462 2024

ISSN  2187-1094

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Experimental Study of Tracked Vehicle Velocity Using Estimated Disturbance and Machine Learning for Application to Environments Different from Those in Training

Kuwahara H., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  13 ( 2 ) 146 - 154 2024

ISSN  21871094

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This study examines the training policies and environmental robustness of a neural network used in velocity estimation for a tracked vehicle with slippage. In the proposed method, the velocity is estimated by a neural network whose input is an estimated disturbance to the driving axle that includes slippage information. First, we experimentally clarify the proposed method’s scope of applicability and effectiveness under different environmental conditions in training and estimation. Subsequently, we experimentally confirm that the estimated disturbance is robust to environmental changes and complementary to environmental information. Finally, the neural network trained on a flat surface is validated in combination with gravity compensation for acceleration to apply it to driving on a slope.

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A Robust Constrained Control of Upper-Limb Exoskeleton for Isometric Rehabilitation Exercises

Pavia M., Murakami T.

IEEE International Symposium on Industrial Electronics  2024

ISSN  21635137

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The research field of muscle rehabilitation and strength recovery is constantly evolving with new techniques and assistive devices being proposed every year. In particular, the need of specialised structures and clinicians, the cost of the rehabilitation and the rising numbers of patients among injured athletes and elderly people, are making rehabilitation robotics a cost-effective alternative. In the last years, researchers have mainly focused on proposing assistive devices to be used during the rehabilitation or new techniques, in order to make the whole process more effective. Nonetheless, the accessibility and the cost of most of the treatments, still leaves a lot of room to improve for a more inclusive access. Besides giving the freedom to the patient to carry out the rehabilitation at home, it is crucial to properly choose the exercise according to the muscles which need to be trained and the condition of the subject. Especially for injured athletes and for the elderly, isometric exercises and static strength training are a good solution to prevent stressing the joints and moving the damaged muscles. Hence, this paper aims to introduce a new musculoskeletal-specific design framework for upper-limb isometric exercises, after having evaluated with a Hexagon Distribution (HD) the muscle condition of the subject. In addition, a 2-DOF wearable and lightweight exoskeleton is introduced to maintain the correct posture of the arm while performing the task. Finally a randomized controlled trial (RCT) is conducted with a cohort of different groups to show the effectiveness of the proposed method.

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Robust Position Control System of MDOF Manipulator with Flexible Joints

Ito J., Murakami T.

IEEE International Symposium on Industrial Electronics  2024

ISSN  21635137

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This paper proposes a disturbance rejection method for a multi-degrees of freedom (MDOF) manipulator with flexible joints. Mechanical transmitters in joints have low stiffness and the arms of the manipulator vibrate during a fast motion. A motor/arm-side encoder that detects motor and arm angles directly is useful for precise position control. In this paper, the MDOF manipulator has motor/arm-side encoders. The system with flexible joints has motor dynamics between the input and torsional reaction torque. It deteriorates disturbance rejection by acceleration control. The proposed method comprises a torque controller compensating for motor dynamics and a filter improving disturbance rejection. The proposed method enables position control that maintains vibration suppression and improves robustness by utilizing both the motor and arm angle. The validity of the proposed method was confirmed by simulations.

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Disturbance Rejection Improvement in Robust Motion Control of Series Elastic Actuator

Ito J., Murakami T.

Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics    1599 - 1604 2024

ISSN  21551774

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Contact safety and high control performance are important for human assistive collaborative robots and wearable technology. A series elastic actuator (SEA) has a spring inserted between the motor and the load, which has high compliance. A motor/load-side encoder that acquires motor and load angles enables precise control. SEA with a motor/load-side encoder is appropriate for a human assistive system. However, resonant poles due to the low stiffness of SEA cause resonant vibration and low robustness. Human assistive systems need to achieve control that is precise and robust to disturbances from humans and the environment. This paper proposes a novel control system design that achieves vibration suppression and high robustness. The proposed method consists of torsion torque control and an inverse system filter. By dividing the suppression of resonant pole effects and improving robustness into different controllers, the proposed method makes it easier to design appropriate gains for human assistive systems than conventional methods. The validity of the proposed method and the effect of stiffness error were verified by simulations of position and force control.

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Position-and-Torque-Sensorless Admittance Control with State Estimation Considering dq-axis Cross-Coupling Factors

Shimamoto K., Murakami T.

IFAC-PapersOnLine (IFAC-PapersOnLine)  56 ( 2 ) 6075 - 6080 2023.07

ISSN  2405-8963

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This paper presents a position estimation compensation method considering dq-axis cross-coupling factors of Interior Permanent Magnet Synchronous Motors (IPMSMs) inductance for position-and-torque-sensorless admittance control. The cross-coupling factors are from dq-axis mutual inductance and deteriorate control and position estimation performance in control methods without the model. Since dq-axis cross-coupling factors of inductance vary with the rotor position and the current, measurement and estimation of the values are difficult. The proposed method estimates the cross-coupling factors and position estimation errors using dq-axis current variation from the injected voltage. In addition, the proposed method compensates the estimated position based on a voltage equation, including the dq-axis cross-coupling factors, by adding the estimated error. As a result, the vibration of current, velocity, and estimated reaction torque were reduced, and the performance of a position-and-torque-sensorless admittance control system was improved. The experimental results show the proposed method's validity and response by the sensorless admittance control.

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Assistance Torque Control Based on Musculoskeletal Hexagon Output Distribution for Upper Limb Exoskeleton

Morishita H., Murakami T.

Proceedings - 2023 IEEE International Conference on Mechatronics, ICM 2023 (Proceedings - 2023 IEEE International Conference on Mechatronics, ICM 2023)   2023

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Upper limb exoskeletons are a current focus of technology for rehabilitation and assistance. Although the exoskeletons are actively researched and various applications are being explored, it poses many challenges because of their robot-human fusion of dynamics. In particular, control strategy is one of main problems to solve. Important points of the exoskeleton control are safety, usability, and prevention of insufficient/excessive assistance. Control of physical HumanRobot Interaction (pHRI) without electromyographic (EMG) measurements is one of solutions for the first and the second points. However, the exoskeletons assist based on only payload information in conventional researches and they have disadvantages in third point. Since ease of output of muscles is affected by the limb posture, assistance should be determined based on both payload and musculoskeletal information of each user. Hence, this paper aims to realize musculoskeletal model-based assistance considering ease of output of muscles. For this aim, hexagon distribution (HD)-based assistance torque calculator is proposed. HD expresses human output characteristics of a hand tip by modeling muscles of an upper limb including bi-articular muscles as 6 muscle groups. In proposed control strategy, first, the maximum human output is derived by HD. Second, it is judged whether assistance is sufficient or insufficient. Finally, assistance torque is adjusted in the case of insufficient assistance. To verify effectiveness of the proposed method, an experiment is conducted. As a result, it is confirmed that the proposed method can assist users based on their musculoskeletal characteristics.

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Determination of the Optimal Number of Phases of a Multiphase Bidirectional Chopper Considering AC Loss in Inductor

Nakamura Takayuki, Murakami Toshiyuki

IEEE ACCESS 11   55814 - 55823 2023

ISSN  2169-3536

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Force Sensorless Hybrid Position/Force Control with Equivalent Mass Matrices Switching for Decoupled Rubbing Motion

Shimamoto K., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  12 ( 2 ) 107 - 116 2023

ISSN  21871094

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This paper presents a force sensorless workspace hybrid position/force control method with equivalent mass matrices switching for rubbing motion. The equivalent mass matrices express an interference between control axes. Since the determinant of the matrix computed from the design values of robots becomes near zero around the singular configuration of robots, the utilized matrices are often arbitrarily designed. However, inappropriate matrices conditions deteriorate control performance and could cause vibration during rubbing motion. This study reveals suitable equivalent mass matrices for rubbing motion depending on the velocity of the force control axes. Moreover, a hybrid controller with equivalent mass matrices switching depending on the expected velocity of the force control axes in tasks is proposed. The validity of the proposed hybrid controller is demonstrated by the experimental response of rubbing motion with a parallel link type direct-drive four-link manipulator.

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Posture Stabilization Control Compensating Variation of Body Center of Gravity in Underactuated System

Yajima H., Ishizaki K., Miyata Y., Nawa M., Kato N., Murakami T.

Proceedings - 2023 IEEE International Conference on Mechatronics, ICM 2023 (Proceedings - 2023 IEEE International Conference on Mechatronics, ICM 2023)   2023

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With the recent decreasing birthrate and aging population, cooperative robots are attracting attention for a new workforce. As cooperative robot, robots with a small footprint and high center of gravity, like humans, can be considered more suited. Robots with these features are generally unstable, and posture stabilization control becomes important when the center of gravity is shifted due to holding objects or other factors. Therefore, in this study, we select a two-wheeled robot as the target robot and carrying luggage as the target motion, and establish the posture stabilization. Many studies about two-wheeled transport robots do not adequately consider the shift in the center of gravity, which may lead to rapid acceleration and negatively affect position tracking performance. The purpose of this paper is to compensate the shift in the center of gravity of the vehicle, and can perform transport operations in a steady state. To achieve this purpose, we propose to apply Repulsive compliance control(RCC) to a two-wheeled transport robot. Several experiments show its effectiveness.

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Development of Optical Distance, Normal Force, Shear Force Sensor

Baba T., Murakami T., Krebs H.I., Nozaki T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  12 ( 5 ) 894 - 900 2023

ISSN  21871094

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Proximity and tactile sensors have been widely used to control robots. However, each of these sensors has its own shortcomings. Visual sensors have blind spots, whereas tactile sensors cannot acquire information when non-contact. To overcome these problems, this study develops an optical sensor that can measure the distance and two-axis forces using a beam structure and photo reflectors. The sensor is inexpensive owing to its simple structure. Moreover, the sensor is demonstrated to have sufficient accuracy for both the distance and force measurements at 0.2, 0.5, and 1.0 Hz. Additionally, the usefulness of the sensor is confirmed based on reduced impact control at the time of contact and force control.

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Development of Optical Proximity/Biaxial Force Sensor and Application to Contact Movement

Baba T., Murakami T., Krebs H.I., Nozaki T.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2023-June 2023

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Proximity sensors measure the distance to an object and detect contact. Hence, proximity sensors are typically mounted and used in end-effectors. There might be situations where it is necessary to acquire information on not only distance and contact; but also the normal force and shear force. The conventional proximity/biaxial force sensor utilizes beam deflection but brittle material and interference limit its performance. Here we present a novel proximity/decoupled biaxial force sensor made of sturdy materials, springs, and photo reflectors. We demonstrate this sensor's performance and advantage of the proposed sensor in teleoperation and during a task requiring rubbing an object.

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Individual Pitch Control of Wind Turbine System by Estimating Wind Speed Using Pitching Moment

Yamada M., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  12 ( 5 ) 1008 - 1014 2023

ISSN  21871094

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Wind energy conversion systems (WECS) have become increasingly common in recent years as a result of global warming. WECS needs to release the wind through pitch control during high winds. In this study, a novel method for individual pitch control (IPC) via pitching moment estimation is designed. The conventional IPC method considers the blade load, without keeping the rotor speed at the rated value. This study proposes the application of a reaction force observer (RFOB) to the pitch actuators to estimate the pitching moment of each blade. Using the pitching moment information, we estimate the wind speed for each blade, enabling IPC to simultaneously achieve load reduction and maintain the rotor speed at the rated value. The effectiveness of the proposed method is verified via simulations and experiments.

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Lumped Parameter Thermal Model of Heat-Generating General Geometry in Cylindrical Coordinate System

Katsuno, A; Murakami, T

IEEE ACCESS 11   139249 - 139259 2023

ISSN  2169-3536

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Model-Based Pitch Angle Compensation for Center of Gravity Variation in Underactuated System with an Arm

Kanazawa H., Ishizaki K., Miyata Y., Nawa M., Kato N., Murakami T.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2023-June 2023

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Two-wheeled robots are expected to be used at sites where humans work together. The subject of this paper is a two-wheeled robot with an arm, which can take out loads from shelves in the same manner as a human. When the center of gravity (CoG) of the two-wheeled robot shifts back and forth due to placing a load on the arm, the wheel position control performance deteriorates. A possible method to compensate for the shift in the CoG is to use repulsive compliance control (RCC). However, RCC has the disadvantages that the parameters must be adjusted experimentally and the CoG compensation is slow because the pitch angle is determined dynamically. To address these disadvantages, this paper proposes a method that uses model-based CoG compensation and position control for pitch angle. The model-based controller design simplifies parameter setting and achieves fast CoG compensation by statically determining the desired pitch angle. The validity of the proposed method is confirmed through experiments. The obtained results show that the performance of wheel position control is improved when the load is placed on the arm.

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Position-and-Force-Sensorless Control Considering Equivalent Mass Matrix and Cross-Coupling Factors

Shimamoto K., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))   2023

ISSN  21624704

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This paper presents a hybrid position/force control with equivalent mass matrices for position-and-force-sensorless manipulators and the evaluation of the control system. Position and force estimation methods in the controller are cascaded to estimate the position and force according to the respective characteristics of the electrical and mechanical systems. The proposed controller is designed to reduce vibration of the force control axes' motion from the cross-coupling factors of the dq-axis inductance, which cause position estimation error, and the cross-coupling effects among control axes from equivalent mass matrices, which expresses the relationship between the workspace force and acceleration. The position estimation based on the voltage equation, including the cross-coupling factors, derives compensation terms of the estimation error. The cross-coupling effects between position and force control axes in the equivalent mass matrices are designed to suppress the undesired force response vibrations. The experimental results show that the proposed system kept contact with an object during the rubbing motion by a 4-degree-of-freedom manipulator without position and force sensors. The utilized equivalent mass matrix reduced the force vibration caused by the vibration of the position estimation.

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Underactuated Control for Two-Wheeled Mobile Robot with an Arm Using Torque Constraint Conditions and Disturbance Observer

Ito J., Murakami T.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2023-June 2023

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This paper presents an underactuated control system for a two-wheeled mobile robot (TWMR). TWMR is expected to use as an autonomous mobile robot (AMR) that works in human-collaborative spaces. TWMR has a smaller footprint and higher center of gravity (CoG), than typical AMRs. Furthermore, in this study, TWMR has an arm. Therefore, TWMR is superior in handling loads in human-presence spaces. However, TWMR is the underactuated system in the body's translational position and tilting angle. In addition, TWMR is affected by disturbances caused by loads. As a robust underactuated control system, the cascade PI/PD and synthesized pitch angle disturbance observer (SPADO) are considered. The cascade PI/PD results in significant translational position error and oscillatory responses. To cope with this problem, a proposed method minimizes both errors of the translational position and tilting angle within torque constraints. The proposed method utilizes the predictive functional control (PFC) for the underactuated control considering constraints. SPADO improves the accuracy of an internal model of PFC. The validity of the proposed method was confirmed compared with the cascade PI/PD through the simulation.

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A Method of Predicting Posture-related Pain Using Biomechanical Parameters for Patients with Lumbar Spinal Disc Herniation

Hatsushiro A., Tawaki Y., Murakami T.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS (Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS)   2023

ISSN  1557170X

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Lumbar spinal disc herniation is a disease in which the protruding nucleus pulposus presses on the nerve due to actions that place loads on the disc, causing pain in the lower back and lower limbs. About 80% of treatments of disc herniation are conservative treatments, and although it is necessary to live with pain for a long time, there have been no studies that clearly define the relationship between pain and biomechanical parameters. In this study, we proposed a method of identifying biomechanical parameters that predict posture-related pain in patients with lumbar spinal disc herniation. The pain values were quantitatively evaluated by the Numerical Rating Scale (NRS) and the biomechanical parameters were analyzed by OpenSim. Lasso regression was performed to narrow down the biomechanical parameters that were related to pain and derive the mathematical model of the relationship. Therefore, many of the parameters of the obtained mathematical model were related to the lumbar spine and were consistent with areas that be related to lumbar spinal disc herniation.

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Identification of unknown object properties based on tactile motion sequence using 2-finger gripper robot

Thompson J., Kasun Prasanga D., Murakami T.

Precision Engineering (Precision Engineering)  74   347 - 357 2022.03

ISSN  01416359

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The purpose of service robots is to work and handle a wide range of objects in a human environment. Therefore, they must have the ability to grasp unknown objects with the appropriate force, by dynamically identifying their stiffness, mass, and surface-interaction properties. To ensure the successful grasping of unknown objects, it is significant to estimate the object response properties. In this paper, the cognitive functions to efficiently perform such operations with only tactile motion data and supervised learning using limited data, have been demonstrated. The study uses pinch-grasping performed by a 2-fingered robot experimental setup with a pre-designed motion sequence, over 7 different objects having a wide range of properties to capture the motion data. The proposed approach avails pre-processed motion data to train neural networks for accurately predicting object response properties for 3 unseen test objects. We have done a comparative study among three neural network architectures CNN, LSTM, and CNN-LSTM and we found that novel CNN-LSTM outperforms the other two models in terms of accuracy. The CNN-LSTM regression model achieves 0.98 and 0.97 of R2 value for the prediction of stiffness and mass, respectively and the CNN classification model achieves 94% of accuracy for the surface interaction classification.

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Cognitive Grasping and Manipulation of Unknown Object with Control Grip Force using Cyber Physical System Approach

Thompson J., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  11 ( 6 ) 744 - 751 2022

ISSN  21871094

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Service robots working in human environments must have the ability to grasp a wide variety of unseen objects with appropriate grip force without knowing their properties and its response to action in a human environment. This research uses a novel Cyber Physical System framework to estimate and apply minimum grasping force for unknown objects under a task motion using only tactile motion data captured from sensor-less acceleration-based controlled common gripper. The goal is to use this novel framework for developing functions for position-controlled robots to perform real-time cognitive grasping and enable quick implementation across multiple robots. This paper uses soft sensing inputs from the earlier research to characterize unknown object properties like stiffness, mass and surface interaction and show how a data-based analytics algorithm learns a wide range of object properties and slip status along with task action dynamics features, to propose the grasping action with minimum applied force. We validated that the minimum grasping force is able to hold the object firmly during any task motion. In order to improve the learning, the paper proposes a part of the framework to use virtual simulation to gather more learning data and show results that compare well between simulated results with experimental data. We use the simulated data to train Reinforcement Learning approach and show that small variation in object width can be learnt to identify optimum gripping position.

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Comparison of Filtering Methods in Measuring Human ZMP Using Kinect Sensor

Nagasawa T., Tawaki Y., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2022-October 2022

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This paper aims to verify the detection accuracy of Zero Moment Point (ZMP) measurements of the human body using the Kinect sensor. In this paper, ZMP is measured based on a multi-link model of the human body. ZMP calculation algorithms using a Low Pass Filter (LPF) and Savitzky-Golay (SG) filter were constructed to investigate filtering methods that can measure ZMP with high accuracy and small lag. The accuracy and responsiveness of these filters were evaluated through experiments measuring ZMP during human walking. Experimental results show that the detection error in ZMP is dominated by the differential noise in the acceleration calculation, and applying the filter only to measured acceleration values increases responsiveness with the same accuracy as when applied to ZMP. We also found that the SG filter is superior to LPF in noise suppression and responsiveness of ZMP measurements, though it occurs overshoot in measurements.

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Evaluation of Mathematical Models for Postural Sway Based on Reproducibility of SDA Parameters

Sakae K., Tawaki Y., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2022-October 2022

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Evaluation of the falling risk is significant for older people not to fall and become in need of care. The static posturography test is adopted to evaluate the lack of balance ability that causes the falling. This test measures the center of pressure (COP) of humans and evaluates it by analyzing the data. There are three main analysis methods: descriptive statistics, stabilogram diffusion analysis (SDA), and mathematical modeling. Descriptive statistics and SDA represent only statistical values without the mechanism of the posture control system. However, mathematical modeling evaluates the system from the model coefficients containing physical meanings, and we focus on it. The stochastic differential equation of stiffness, viscosity, and stochastic terms are introduced to the mathematical model for the static posturography test. The COP trajectory reproducibility of the model is evaluated using SDA. SDA is a time-based analysis suitable for evaluating the dynamic posture control system. In the experiment, we compare the SDA parameters between older and younger subjects and evaluate the reproducibility of the model using the SDA parameters. As a result, we confirm that the SDA parameters can classify based on age to a certain extent, and the model has higher reproducibility than the conventional model against SDA.

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Position and Cross-Coupling Factors Estimation for Sliding Mode Current Control based Position-Sensorless Control of IPMSM

Shimamoto K., Murakami T.

IEEE Access (IEEE Access)   2022

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This paper presents a control method with an estimation method of cross-coupling factors of Interior Permanent Magnet Synchronous Motors (IPMSM) inductance for position-sensorless servo drive systems. The cross-coupling factors are from dq-axis mutual inductance. Conventionally, the cross-coupling factors have been ignored in the IPMSM model and deteriorate control performance. That has caused decreasing robustness and velocity vibration in the low-speed range. Since the cross-coupling factors vary with the rotor position and the current, it is hard to measure them. Therefore, the proposed method utilizes a high-frequency voltage injection method to estimate the cross-coupling factors online. In addition, the proposed current control method utilizes a sliding mode control and voltage disturbance observer based on the voltage equation, including the dq-axis mutual inductance model. The estimated cross-coupling factors are reflected in the proposed current controller instantaneously. Experimental results show that the proposed method considering cross-coupling factors increases the robustness to the disturbance force and reduces the velocity vibration.

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Performance Evaluation of Force Control and Reaction Force Estimation in Force Sensorless Hybrid Control for Workspace Based Controller

Shimamoto Keita, Murakami Toshiyuki

2022 IEEE 17TH INTERNATIONAL CONFERENCE ON ADVANCED MOTION CONTROL (AMC)    231 - 236 2022

ISSN  1943-6572

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Velocity and Attitude Control of Quadcopter with Suspended-payload using Disturbance Observer with Payload Inclination Suppression

Sugaya Taketo, Murakami Toshiyuki

2022 IEEE 17TH INTERNATIONAL CONFERENCE ON ADVANCED MOTION CONTROL (AMC)    414 - 419 2022

ISSN  1943-6572

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Position Control Considering Slip Motion of Tracked Vehicle Using Driving Force Distribution and Lateral Disturbance Suppression

Kuwahara H., Murakami T.

IEEE Access (IEEE Access)  10   20571 - 20580 2022

ISSN  2169-3536

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Complex slippage and nonholonomic constraints can disturb the precise movement of tracked vehicles. In this study, a position control system using driving force control and virtual-turning velocity control (VTVC) was established for a tracked vehicle. Slippage in the translational direction can be suppressed by controlling the driving force of the crawlers, estimated using the vehicle velocity. However, the driving forces interfere with each other in a turning motion. Therefore, a driving force distribution method was developed using the instantaneous turning center of a vehicle to decouple the forces. This distribution induced slippage in the direction of turning. In addition, a virtual reference was derived from the vehicle velocity and lateral disturbance, which described the effects of the nonholonomic constraints and skidding of the tracked vehicle. Next, a VTVC method was developed to suppress the lateral disturbance by controlling the turning velocity to follow the virtual reference. The experimental results confirm that the proposed approach ensures high-performance position tracking and adequate slippage of the tracked vehicle.

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Estimation of Jacobian Matrix without accelerometer on Omni-directional Mobile Walker

Ominato Kentaro, Murakami Toshiyuki

2022 IEEE 17TH INTERNATIONAL CONFERENCE ON ADVANCED MOTION CONTROL (AMC)    329 - 334 2022

ISSN  1943-6572

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Frequency Characteristics of Power Transformer for Isolated DC-DC Converter

Nakamura T., Murakami T.

IEEE Access (IEEE Access)  10   11633 - 11641 2022

ISSN  2169-3536

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The operational frequency of a transformer is an important factor in the configuration of an isolated DC-DC converter. However, discussions of this frequency are inadequate. This study focuses on the frequency characteristics of the transformers. The frequency characteristics of the impedance and loss of the transformer were obtained to explain their fundamental attributes. When a transformer is employed in a power electronic transformer (PET), the waveform of the voltage is rectangular. The loss under this waveform was obtained in order to observe its characteristics. Furthermore, the problems with the isolated DC-DC converter are explained. The natural frequency, composed of leakage inductance and equivalent-parallel capacitance, determines the performance of the isolated DC-DC converter. When the operational frequency of the isolated DC-DC converter is below its natural frequency, the loss increases under the no-load or light-load conditions. This increase in the loss is caused by the current, which contains the natural frequency of the transformer owing to the ringing.

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Model-Free Detection of Penetration and Automatic Stop Control in Dental Implant Surgery Based on Differential Value of Torque

Kido Yusuke, Kawana Hiromasa, Asoda Seiji, Nozaki Takahiro, Murakami Toshiyuki

2022 IEEE 17TH INTERNATIONAL CONFERENCE ON ADVANCED MOTION CONTROL (AMC)    144 - 149 2022

ISSN  1943-6572

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Object Detection in Motion Reproduction System with Segmentation Algorithm

Sun Xiaobai, Nozaki Takahiro, Ohnishi Kouhei, Murakami Toshiyuki

2022 IEEE 17TH INTERNATIONAL CONFERENCE ON ADVANCED MOTION CONTROL (AMC)    42 - 47 2022

ISSN  1943-6572

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Classification of Older and Fall-Experienced Subjects by Postural Sway Data using Mass Spring Damper Model.

Yuta Tawaki, Takuichi Nishimura, Toshiyuki Murakami

IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society (IEEE Transactions on Neural Systems and Rehabilitation Engineering)  30   40 - 49 2022

ISSN  15344320

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The quiet standing test is used to detect diseases of the postural control system. The descriptive statistics of the center of pressure (COP) of older people during the test tend to be larger than those of healthy young people, but they cannot indicate structural problems in postural control. COP trajectories can be mathematically modeled with structural parameters such as viscosity, stiffness, and stochastic terms; however, the classification accuracy of older and fall-experienced people using such parameters has not been sufficiently verified. In this study, six structural parameters of a mass-spring-damper (MSD) model were estimated using two datasets, in which a total of 212 subjects performed quiet standing tests under four conditions. The estimated parameters were used for classification with a random forest algorithm to examine the differences in classification accuracy compared to seven conventional descriptive statistics methods. For the classification of older subjects, the classification accuracy of the MSD parameter method was the highest in foam condition, with positive likelihood ratios approximately 8.0. For the classification of fall-experienced subjects, the positive likelihood ratio of the MSD parameter method was 5.0, which is better than conventional descriptive statistics. Various MSD parameters revealed that aging and changing the floor surface and visual conditions cause oscillations in the COP behavior. While the MSD parameters were confirmed to help classify older subjects more accurately than the conventional descriptive statistics, there was room for further improvement in the classification accuracy of fall-experienced subjects.

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An Approach of Load-Side Disturbance Rejection Control for Series Elastic Actuators

Hiraoka Atsushi, Murakami Toshiyuki

2022 IEEE 17TH INTERNATIONAL CONFERENCE ON ADVANCED MOTION CONTROL (AMC)    18 - 23 2022

ISSN  1943-6572

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Realization of Synchronized Movement between Caregiver and Electric Wheelchair

Hirata K., Murakami T., Sasayama M.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2021-June 2021.06

ISSN  2163-5137

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A caregiver has an important role to not only help patients with high levels of disability to move around, but also be aware and manage the patient's state of health. Visual cues on the patient's expression is an especially important source of information on the patient's well-being, especially for those with high levels limitations on cue sending, such as Amyotrophic Lateral Sclerosis (ALS) patients. Thus, this paper proposes a system that enables the caregiver to control the movement of the wheelchair while waking alongside the wheelchair where they can also interact with the patient directly. The proposed approach has been validated through experiments.

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Trajectory Tracking Control with Estimated Driving Force for Tracked Vehicle Using Disturbance Observer and Machine Learning

Kuwahara H., Murakami T.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2021-June 2021.06

ISSN  2163-5137

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This paper proposes a tracking control method that suppresses slippage by using the driving force of a tracked vehicle. First, the velocity of the tracked vehicle including slippage is estimated using a disturbance observer and machine learning technique. This estimated velocity is utilized to design an observer that can estimate the driving force of the crawler. By distributing and controlling the driving force, tracking control with reduced slippage can be realized. The experimental results demonstrate the tracking performance of the proposed control system.

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Assessment of human walking stability using the gait sensitivity norm with wearable sensors

Masuda H., Fukutoku K., Murakami T.

2021 IEEE International Conference on Mechatronics, ICM 2021 (2021 IEEE International Conference on Mechatronics, ICM 2021)   2021.03

ISSN  9781728144429

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Quantifying walking stability is needed in order to evaluate the various walking assist methods. It can also allow the planning of individualized interventions for elderly people or patients with disorders. The Gait Sensitivity Norm (GSN) is a new measure of the walking stability developed for passive dynamic walkers and has been reported to show a strong correlation with the fall risk. The GSN is a method based on the idea of the H2 norm, which allows us to know the dynamic response of the system of walkers by measuring the impulse response. The reliability of the GSN quantification has been confirmed in passive dynamic walkers and neuromusculoskeletal walking models. However, it has not yet been applied to humans. In this paper, we proposed a method to apply the GSN to the analysis of human walking. To apply the GSN to a human gait, wearable sensors were used to analyze human walking. The validity of quantifying gait stability with the GSN is assessed in the experiments comparing abnormal walker (with some weight or blindfold) and normal walkers. The result is consistent with the intuitive idea that blind walking is more unstable than normal walking.

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Admittance control-based bilateral control system considering position error

Kimura S., Nozaki T., Murakami T.

2021 IEEE International Conference on Mechatronics, ICM 2021 (2021 IEEE International Conference on Mechatronics, ICM 2021)   2021.03

ISSN  9781728144429

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This paper proposes a bilateral control system implementing an admittance control system. Bilateral control system realizes teleoperation of a remote robot with a sense of touch. We focus on an admittance-based bilateral control system, which needs only two communication channels and has almost the same control performance as an acceleration-based bilateral control system, which is one of the highest transparent teleoperation systems. However, the conventional admittance-based system assumes an ideal communication situation where there is no communication time delay and no packet loss and has possible to increase position error as time goes on in practical use. The proposed admittance-based system achieves the same control performance as the conventional structure without increasing position error even if there is a communication delay. The validity of the proposed system is confirmed through simulations and experiments.

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Disturbance observer for DC motor based on Savitzky-Golay filters and application to bilateral control

Hazaz M., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  10 ( 2 ) 227 - 235 2021.03

ISSN  21871094

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This paper describes the implementation of a disturbance observer-based controller after Savitzky-Golay filters. The cutoff frequency is a bottleneck for the conventional disturbance observers in DC motors with position measurement. The measurement noise limits the cutoff frequency of the pseudo-derivative in the design of the conventional disturbance observers. This study proposes an implementation of a disturbance observer based on Savitzky-Golay filters to improve the performance in noisy conditions with respect to the cutoff frequency of the time derivative. The proposed method was verified through various numerical simulations and experiments, thereby demonstrating its applications in bilateral control.

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Development of neural network-based explicit force control with disturbance observer

Okano T., Nozaki T., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  10 ( 2 ) 153 - 164 2021.03

ISSN  21871094

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Human support robots are in high demand and the performance enhancement through force control has been extensively studied. However, the design of the force controller and selection of appropriate gains are sometimes difficult because they are affected by the conditions of motion such as environmental impedance or model uncertainties. This study discusses force control with a disturbance observer and applies a neural network (NN) into its controller; the NN works as both the feedback and feedforward components. The contribution of this study is to show the development method of force control using disturbance observer and a NN, which enhances the performance of force control from the perspective of both feedback and feedforward components. The structure of the controller and composition of the NN were selected through simulation results; moreover, the compensator based on NN was designed in a frequency range higher than the cutoff frequency of the observer with a small number of hidden layers. Moreover, this study discusses a training method of weights in real time. Simulations and experiments were performed for showing the effectiveness of the proposal.

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Identification of Contact Position and Force Estimation on Manipulator Using Force Sensor Implemented on Base Frame

Handa Hinako, Nozaki Takahiro, Murakami Toshiyuki

IEEJ JOURNAL OF INDUSTRY APPLICATIONS (IEEJ Journal of Industry Applications)  10 ( 3 ) 324 - 330 2021

ISSN  2187-1094

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Sensing is essential in human cooperative robots to realize safe and powerful operations against contact with the surrounding environment. Contact sensing has been studied for manipulators to avoid accidents caused by collisions between humans and robots. Conventional research has demonstrated that contact sensing requires many sensors or has a limited measurable range. In the conventional research without sensors, modeling systems, such as frictional force and plant parameters, have been used to estimate the contact force. However, a high reduction ratio mechanism for achieving powerful operations hinders accurate force estimation. This study proposes a method to estimate the contact force and contact position on a manipulator with a high reduction ratio mechanism by installing only one force/torque sensor on the base frame of the manipulator. By using the proposed method, the contact force and contact position can be detected regardless of the location where the contact force is applied. Furthermore, when the contact force is applied in a location where the contact position cannot be accurately estimated, an estimated disturbance or a link motion is used to determine the contact position. The effectiveness of the proposed method is validated through experiments.

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A Robust Hybrid Position/Force Control Considering Motor Torque Saturation

Ohhira T., Yokota K., Tatsumi S., Murakami T.

IEEE Access (IEEE Access)  9   34515 - 34528 2021

ISSN  2169-3536

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This paper proposes a robust hybrid position/force control (HPFC) system for multi-degree of freedom manipulators (MDoFMs) with torque constraints on each joint. General HPFC systems can control the interactive contact forces and positions of manipulators in various environments. In HPFC systems, to improve the control performance for MDoFMs, motor torque saturation should be considered. Thus, a robust HPFC system that considers torque constraints by predictive functional control (PFC) is proposed in this paper. The proposed method simultaneously handles the response characteristics and torque constraints of actuators by using PFC as joint space position controllers. Additionally, the robustness of actuators against external forces is enhanced, and the model parameter errors are compensated by the disturbance observer technique. Moreover, implicit force control law and inverse kinematics are introduced for the workspace position/force control to implement the joint space position controllers. Consequently, the stability and robustness of the actuators are considered, and suitable position/force control can be performed even if the torque is saturated. The validity of the proposed method is tested with three planar manipulator joints with a uniaxial force sensor.

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Variable forgetting factor-based adaptive Kalman filter with disturbance estimation considering observation noise reduction

Ohhira T., Shimada A., Murakami T.

IEEE Access (IEEE Access)  9   100747 - 100756 2021

ISSN  2169-3536

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This paper addresses the influence reduction of quantization and observation noises in a disturbance observer (DOB) technique. DOB is a disturbance estimation method that makes control systems robust. However, in implementing low-resolution sensors, disturbance estimates from DOB are considerably influenced by observation and quantization noises. In this paper, a novel DOB design method for simultaneous estimation of state and unknown disturbances, including the reduction of noise influences, is proposed. The proposed method is divided into two components. The first component is a Kalman filter (KF)-based DOB for simultaneous estimation of state and unknown disturbances. To improve the estimation performance through the KF-based DOB, a forgetting factor-based adaptive KF (FAKF) was employed. The second component is an adaptive law for the forgetting factor in the FAKF. The adaptive law is used for balancing the estimation accuracy and observation noise reduction. Simulation results involving various types of noise environments demonstrate the effectiveness of the proposed method.

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Linear Langevin-Based Models Providing Predictive Descriptive Statistics for Postural Sway

Tawaki Y., Nishimura T., Murakami T.

IEEE Access (IEEE Access)  9   114485 - 114494 2021

ISSN  2169-3536

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Elderly and disabled people frequently experience falls that may require early assessment and training. The quiet standing test provides descriptive statistics such as the center of pressure (COP) sway data, which can be used to analyze the decline in balance ability. Generally, higher descriptive statistics indicate lower balance ability. Stochastic models can model COP trajectories, and such equation parameters were previously used to assess the balance of patients. However, the model equation is a hypothesis and should be verified. In this study, we evaluated whether stochastic models can predict the descriptive statistics of observed COP trajectories. We estimated the model parameters by fitting postural sway data from 49 individuals in four linear stochastic models, and the prediction accuracy was verified by comparing the observed descriptive statistics with the predicted COP trajectories. We observed that the prediction accuracy of the models with stiffness was much higher than those with viscosity only, and the models with the center of mass (COM) had higher prediction accuracy than COP-only models. Therefore, we identified that coefficients from Langevin-based models contained descriptive statistics about a subject's COP trajectory, which suggested that these coefficients can be used to effectively assess balance issues.

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Tracked Vehicle Velocity Estimation by Disturbance Observer and Machine Learning, and its Application to Driving Force Control for Slippage Suppression

Kuwahara H., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  11 ( 1 ) 69 - 75 2021

ISSN  21871094

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Tracked vehicles generally involve slippage owing to the interaction between the road and track surfaces, which renders accurate motion control difficult. This paper proposes a velocity estimation method for a tracked vehicle with slippage, and its application to driving force control. In this method, the disturbance estimated by a disturbance observer was used as information related to slippage, and a neural network was constructed for velocity estimation. In addition, a driving force observer was designed using the estimated velocity. The driving control of the tracked vehicle to suppress slippage was achieved by using the feedback of the estimated driving force. The proposed method was evaluated experimentally through the velocity estimation performance and slip suppression performance tests.

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Hybrid Position-Force-Posture-Moment Control Based on Euler Angle/Quaternion Feedback

Nakamura Y., Murakami T.

2020 21st International Conference on Research and Education in Mechatronics, REM 2020 (2020 21st International Conference on Research and Education in Mechatronics, REM 2020)   2020.12

ISSN  9781728162249

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This paper proposes the robust system to control the position, force, posture, and moment of the multi-link manipulators. Disturbance Observer (DOB) has been researched as an effective method for the robust motion control, however the rotational components such as posture and moment had not been considered in conventional studies. This paper expands the existing DOB-based translational position control to the position-posture control in 6 Degrees-of-Freedom workspace using Euler angle/Quaternion which are the representative methods to describe the posture. Furthermore, the position-force-posture-moment hybrid control is proposed based on the position-posture control. Through the numerical simulation, the effectiveness of the proposed method was confirmed.

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Monitoring of Gait Features during Outdoor Walking by Simple Foot Mounted IMU System

Tawaki Y., Nishimura T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2020-October   3413 - 3418 2020.10

ISSN  9781728154145

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The world population is ageing. In the aged society, grasping the body condition of the elderly is helpful to choose appropriate rehabilitation. This research focuses on the outdoor walking analysis by use of the simple foot mounted IMU system. The walking feature values are estimated by the algorithm, and they are combined with the GPS data obtained by smartphone to compare the feature values of frail elderly and healthy subject. The differences of walking feature values that are calculated by this system show the usefulness of developed system. The developed system is simple, but useful to grasp the gait features changing of the user.

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Online Motion Modification by Operator in Motion Reproduction System

Sun X., Nozaki T., Ohnishi K., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2020-October   668 - 673 2020.10

ISSN  9781728154145

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© 2020 IEEE. This paper proposes a novel online motion modification method in motion reproduction system. Motion reproduction is used to reproduce human motion saved through bilateral control. Bilateral control is a teleoperation which can transmit both position and force. Human judgement is needed for compensating the saved motion when the environment is different. However, conventional motion reproduction system only relies on saved motion or environment in slave side. Therefore operators in master side cannot modify the motion after motion has been saved. Instead of just reproducing the motion data, the proposed method adds master system at motion reproduction phase so that an operator can modify the motion. If the master system is simply added to motion reproduction system, the operator's motion and saved motion will interfere each other. Therefore, we propose to use weightings to suppress the interference. Simulated results validates the effectiveness of the proposal.

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Bilateral Control under Time Delay by Using Adjustment of Equilibrium Acceleration

Takenouchi T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2020-October   118 - 123 2020.10

ISSN  9781728154145

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© 2020 IEEE. This paper aims to lower the operational force for bilateral control under time delay while guaranteeing stability. Bilateral teleoperation system enables humans to work in remote places. However, time delay on network impairs the stability and the performance. The conventional method has trade-off problem between stability and operationality. This paper introduces the concept of equilibrium acceleration, which includes both position and force information, and proposes a method to detect vibration based on the difference of equilibrium acceleration. As a result, the algorithm can be considered simply, and it is possible to stabilize only during vibration and improve the operationality in free motion. Since this paper does not focus on frequency, but vibration, damping control works only during vibration and the operational force can be reduced compared to the conventional method. The effectiveness of the proposed method is verified by simulations and experiments.

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A Standing-up Assist Control Method Considering Movement Speed

Hiraoka A., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2020-October   71 - 76 2020.10

ISSN  9781728154145

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© 2020 IEEE. With the rapid aging population, the need for standing-up assist device has grown because standing-up movement is essential for independent living. The standing-up assist controller needs to accomplish high trajectory-following without high rigidity. Therefore, compliant force coordinate transformation control (CFCT) is applied to the controller. This control method induces user to model trajectory effortlessly. Moreover, this paper proposes the algorithm which considers the differences of standing-up movement speed. The proposed algorithm enables the assist device to support the user regardless of the difference of movement speed. The controller is evaluated through experiments.

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A Stabilization Control in Two-Wheeled Walker with Passive Mechanism for Walking Support

Ominato K., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2020-October   65 - 70 2020.10

ISSN  9781728154145

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© 2020 IEEE. The aim of this study was to stabilize the posture of a two-wheeled walker in a torque saturated situation during turning. A two-wheeled walker increases the torque of one of the wheels during a turn, which may result in the torque saturation. There was a problem that the posture stability could not be maintained due to this torque saturation. Therefore, this paper proposes to generate a torque reference value in a torque saturation situation when a two-wheeled walker is turning. The simulation in the proposed method was compared with the case without considering the torque saturation. The simulation results showed that both the posture stability and the turning performance were improved. This indicates that the generation of the torque reference value considering the torque saturation is effective. And, we also propose a method to make the two-wheel walker stand still.

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An approach to human walking analysis based on balance, symmetry and stability using COG, ZMP and CP

Kim S., Murakami T.

Applied Sciences (Switzerland) (Applied Sciences (Switzerland))  10 ( 20 ) 1 - 17 2020.10

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© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The parameters of walking have been studied from the viewpoints of joint rotation and translation of body. The balance and symmetry of walking are indispensable features to understand for healthy walking, while also being a personal characteristic. However, quantification has not been easy to carry out in the case of the conventional gait parameters COG (center of gravity) and ZMP (zero moment point). In this approach, the CP (crossing point) is proposed to quantify the concept of symmetry and balance by comparing it to the COG and ZMP. The CP is estimated based on the intersection between the hip line and the ankle line. While the hip line is fixed on the upper body where the COG is, the ankle line is altered depending on the each footfall, where the ZMP is. Therefore, the values of COG, ZMP, and CP have similar or different tendencies in terms of whether balanced walking results in symmetry or not. The validity of this is verified by carrying out a simulation with robot walking, and an experiment using human walking. Through additional experiments, it was noticed that the CP was able to improve the role of COG and ZMP in terms of not only stability, but also its relationship with the movement range of the lower limbs.

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A multi-sensory dataset for the activities of daily living

Ruzzon Marco, Carfi Alessandro, Ishikawa Takahiro, Mastrogiovanni Fulvio, Murakami Toshiyuki

DATA IN BRIEF 32 2020.10

ISSN  2352-3409

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An approach to evaluation index-based gain scheduling for acceleration-based four-channel bilateral control

Okano T., Nozakt T., Murakami T.

Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering (Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering)  86 ( 9 ) 720 - 730 2020.09

ISSN  09120289

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© 2020 Japan Society for Precision Engineering. All rights reserved. Teleoperation is one of the technologies for supporting operators, and its development is strongly demanded. Acceleration-based four-channel Bilateral Control (ABC) is known as a method of teleoperation and achieves highly precise impedance transmission. The gain scheduling for bilateral contrai has basically been focused on the stability by the model-based approach. However, describing the contact motion and precise identification of some nonlinear terms are sometimes highly difficult. Moreover, the gain parameters between the master and slave tend to be set the same although the transfer function of them are different. Therefore, this paper considers the gain setting from the perspective of precise impedance transmission and proposes the evaluation index-based gain scheduling for A B C by using the experimental data. This paper also discusses the designing of gradient-descent algorithm for an actual gain setting by taking the obtained knowledge from evaluation index-based gain scheduling into consideration. The effectiveness of proposed gain scheduling and gain tuning methods were verified through experiments.

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An Approach to Architecture Design of Bilateral Control System based on a Layer Structure

Tanida K., Okano T., Murakami T., Ohnishi K.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  9 ( 4 ) 318 - 330 2020.07

ISSN  21871094

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©2020 The Institute of Electrical Engineers of Japan. A bilateral control system aims at realizing a fine haptic transmission between a human operator and a remote environment object. Such a system is expected to realize multiple requirements in practical applications, and the architecture design based on a layer structure has to be considered. This paper treats a surgery robot system as an example, and its system has two requirements: "large workspace"and "fine haptic sensation". Using the conventional bilateral control system to realize these requirements simultaneously is difficult because mechanical and control designs are separately discussed. At the same time, a system that has multiple requirements such as a fine/coarse system is often designed only using position information. This study proposed to consider not only mechanical/control design but also the position/force information simultaneously from the perspective of an architecture design. The proposed architecture decomposes the functions into each motor/robot by defining roles and combining each role in the layer structure. The advantage of the proposal is that a complex system can be designed as a entire by combining multiple sub-functions that can be simply designed. As a result, the surgery robot system is designed by considering its requirements, and the experiments are carried out to verify if the requirements are satisfied. Â

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An approach to success-based data compression considering position/force task

Okano T., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2020-February   363 - 368 2020.02

ISSN  9781728157542

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© 2020 IEEE. The number of robots has been increasing and they would widely conduct activities in a variety of situations. The amounts of motion data distribution would also become larger and larger: therefore, the amounts of each motion data are expected to be compressed. The compression of motion data has been widely discussed, but this study focuses on the success-based approach and considering a position/force task. Since the purpose of machine automation is to conduct some tasks, the data can be compressed in the extent that the task is safely and successfully completed. The sampling time of command loading is changed for reducing the amount of motion data. The algorithm for investigating the required sampling times in each motion period and each degrees-of-freedom is developed and applied, and the appropriate values were experimentally obtained. The data compression of motion commands was confirmed as well as the task success based on its compressed motion command.

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Independent Drive of Multiple AC Motors Using Amplitude Modulation

Yamada Y., Nozaki T., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2020-February   181 - 186 2020.02

ISSN  9781728157542

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© 2020 IEEE. With the recent development of electric drive technology, systems with multiple electric motors are increasingly used in various applications. Among them, methods of driving multiple electric motors by using only one power source is studied. This multi-motor drive system contributes to the reduction of the number of power supplies and electric parts. Because of these characteristics, the system is effective in reducing the weight and the size of whole system. Therefore, this paper proposes a circuit that can control motors by frequency separation using the principle of amplitude modulation. As a result, it is possible to drive a plurality of motors independently and simultaneously with only one power supply. The simulations of multiple motor drives by the proposed circuit was conducted.

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Extended T-type boost inverter for capacitance reduction

Sugimoto T., Nozaki T., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2020-February   474 - 479 2020.02

ISSN  9781728157542

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© 2020 IEEE. In these days, multilevel inverters are focused thanks to their advantages, such as small voltage stress, low electromagnetic interferences, and harmonics reduction. Generally, renewable energy sources output a low DC voltage. From the viewpoint of efficiency, a single-stage conversion system which can directly change the lower DC-link voltage to higher AC voltage is required. Some single-stage conversion systems have been proposed before. However, these systems have large energy storage such as an inductor and a capacitor. This paper proposes a multilevel boost inverter stepping up the AC output peak voltage at any boost ratio by changing the number of switched capacitors. To reduce the capacitance, the proposed inverter has multiple conduction patterns when the output voltage is boosted. This characteristic distributes the discharging time to multiple capacitors. This inverter can set any maximum boost ratio and apply to the multiphase applications. The operation principle and the boost ability with multiple boost ratios were confirmed by simulations and experiments. The capacitance reduction was also confirmed by simulations.

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Pushing control of mobile robot by adjusting deceleration time according to estimated friction effect

Sekiya K., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2020-February   389 - 394 2020.02

ISSN  9781728157542

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© 2020 IEEE. Recently, attention has been paid to pushing task by robots. A flexible mobile robot with a spring was devised to achieve safe contact during the pushing task. In this paper, two types of pushing task were assumed, one is pushing a fixed object and second is pushing a mobile object. A control law for flexible mobile robots to perform these tasks was proposed. The first is resonance ratio control for force control on a fixed object. Second, deceleration time adjustment method was proposed to carry mobile object without overrunning the target position. Also an observer to estimate friction was proposed, which is an index for adapting deceleration time. The performance of the proposed methods ware verified by simulation.

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Stable traveling control considering slip of wheels in two-wheel mobile robot

Nomura M., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2020-February   89 - 94 2020.02

ISSN  9781728157542

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© 2020 IEEE. Recently, two-wheel mobile robot such as Segway is expected to be applied to a personal mobility. And it has the advantage of easy turning and stepping over and the disadvantage that many sensors are required for stabilization. In conventional researches, the stability and operability of the two-wheeled mobile robot were improved. These are established by assuming that 'the wheels do not slip'. However, a slip of the wheels cannot be ignored in actual driving, so that it is difficult to stably travel on a slippery road. In this paper, we consider the body-velocity by assuming 'the wheels slip in the modeling'. Sliding mode control system by using the body-velocity was proposed. Then, the acceleration observer is introduced to compensate the acceleration on body velocity. We consider both the body-velocity tracking and the pitch angle stabilization and achieve stable traveling control on slippery road. The validity of the proposed method is confirmed by simulation results and experimental results.

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Energy Analysis Method and Walking Simulation with Exoskeleton Assistive Devices

Fukutoku Kaiki, Tsuji Maximilien, Ominato Kentaro, Hiraoka Atsushi, Murakami Toshiyuki

2020 IEEE 16TH INTERNATIONAL WORKSHOP ON ADVANCED MOTION CONTROL (AMC)    345 - 350 2020

ISSN  1943-6572

An underwater quadrotor control with wave-disturbance compensation by a UKF

Ohhira T., Kawamura A., Shimada A., Murakami T.

IFAC-PapersOnLine (IFAC-PapersOnLine)  53 ( 2 ) 9017 - 9022 2020

ISSN  2405-8963

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This paper proposes an unscented Kalman filter (UKF) with disturbance estimation for an underwater quadrotor control system by utilizing backstepping control. Autonomous underwater vehicles (AUVs) have been attracted attention to scientific and commercial applications. The tasks in those applications are such as surveys and inspections for various objects underwater in narrow space. In this study, a quadrotor type robot, in which high-performance results are obtained for aerial application, is regarded as AUVs. The quadrotor robot is a smaller system than general AUVs and has suitable merits for work in a narrow place. On the other hand, since the quadrotor system is small and light in weight, it is more susceptible to underwater waves than conventional AUVs. Therefore, consideration of a technique to suppress or to reject the influences of the waves in the control systems is a must. This paper proposes a UKF system including a second-order model of input disturbance for estimating the influence of waves and an accurate quadrotor state simultaneously. Additionally, the disturbance estimation performance assists in make robustness as its estimated disturbance is rejected to actual disturbance. Finally, the usefulness of the proposed system is shown via simulations of position control for the underwater quadrotor affected by a wave effect model.

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A Method to Make a Robot Understand What was a Target Object in Motion Copying System

Sun Xiaobai, Nozaki Takahiro, Murakami Toshiyuki, Ohnishi Kouhei

2020 IEEE 16TH INTERNATIONAL WORKSHOP ON ADVANCED MOTION CONTROL (AMC)    241 - 246 2020

ISSN  1943-6572

An Approach to Force Control by Model Predictive Velocity Control with Constraints

Ohhira Takashi, Murakami Toshiyuki

2020 IEEE 16TH INTERNATIONAL WORKSHOP ON ADVANCED MOTION CONTROL (AMC)    247 - 252 2020

ISSN  1943-6572

Measurement of joint moments using wearable sensors

Fukutoku K., Nozaki T., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  9 ( 2 ) 125 - 131 2020

ISSN  21871094

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© 2020 The Institute of Electrical Engineers of Japan. Advanced rehabilitation requires a measurement system that quantitatively analyzes the actions of each individual. Joint moment is an indice used to quantitatively evaluate an individual's actions. Conventionally, force plates and highspeed cameras have been used to analyze joint moments. However, these devices need to be fixed in a laboratory, which limits the measurable motions and measurement range. Further, these sensors are expensive. Hence, it is difficult to use them in medical or nursing care facilities. Therefore, this study aimed to estimate joint moments using inexpensive and wearable sensors. This paper proposes a practical joint moments estimation system using inertial measurement units, which is a wearable sensor. The proposed method uses wearable sensors to measure continuous motion without limitation. It is also cheaper than conventional systems. The effectiveness of the proposed system was verified by comparison with the method using force sensors.

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Control of two-wheeled wheelchair considering a model of step climbing and human posture

Yokota K., Murakami T.

Lecture Notes in Electrical Engineering (Lecture Notes in Electrical Engineering)  588   779 - 786 2020

ISSN  9789813294363

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© Science Press 2020. In recent years, the practical use of personal mobility of wheeled inverted pendulum mobile robot such as Segway has been advanced. In this paper, this paper focuses on a two-wheeled wheelchair, which is a sitting-type wheeled inverted pendulum personal mobility. In order to improve the traveling performance, the purpose of this paper is to efficiently climb over the steps of the two-wheeled wheelchair. In a situation where the wheelchair climbs over a step, there is a drawback that is a trade-off between stabilizing the posture and applying a torque large enough to climb over the step. In order to solve this drawback, modeling is carried out including the model of the passenger in the situation where the wheelchair climbs over a step. This paper shows a control system to feedback the gravity term applied to the wheel when the wheelchair climbs over a step. By these proposals, the improvement of the traveling performance at the time of climbing over a step is realized. The usefulness of the proposed method is confirmed via the simulation result.

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Compliance control during cooperative transport using multiple mobile robots

Tatsumi S., Murakami T.

Lecture Notes in Electrical Engineering (Lecture Notes in Electrical Engineering)  588   787 - 793 2020

ISSN  9789813294363

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© Science Press 2020. In recent years, there has been concern over labor shortages. Robots are being introduced for transportation and other tasks. When robots are used in the environment with humans, it is desirable that the size is small and the output is relatively small from a viewpoint of safety. However, in the case of using one robot, there is a limit to the transport capacity. To address this issue, this paper describes the cooperative control of two mobile robots to realize the transportation ability that cannot be achieved by one robot. In the cooperative control, external force detection from the environment is important to enhance the adaptability of the robot. In the previous studies, force sensor was used for each robot, and it was possible to transport even when an external force is applied to the robot. However, the cost increases as the number of robots used increases. Therefore, this paper proposes compliance control that enables transport with reduced force fluctuation without external force sensor. Position control and sensorless force control are assigned to each robot, and when an external force is applied to sensorless force control robot, the control method is switched between the robots to realize the fluctuation suppression of the grasping force.

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Selection of required controller for position-and force-based task in motion copying system

Okano T., Oboe R., Ohnishi K., Murakami T.

Journal of Robotics and Mechatronics (Journal of Robotics and Mechatronics)  32 ( 1 ) 113 - 127 2020

ISSN  09153942

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© 2020, Fuji Technology Press. All rights reserved. With the remarkable development of related technologies, the number of robots has been gradually increasing and their presence is becoming much more familiar in our daily lives. The motion copying system (MCS) is utilized as the method for conducting some tasks by robots. This system enables tasks to be reproduced when the environmental conditions are not changed. The task reproduction performance is degraded when environmental variations occur, and human-like adaptable motion is expected to be developed in the MCS. This study reveals the dominant element of motion, and the control strategy is varied at each time in each axis by considering the task realization. The flexibility of motion is learned from both the operator and the task implementation. The task reproduction experiments by MCS are conducted to verify the effectiveness of the proposal.

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Pitching Vibration Suppression Control of Vehicle System by Frequency-weighted Linear Quadratic Integrator for Driving Motor

Nakamura Y., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2019-October   485 - 490 2019.10

ISSN  9781728148786

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© 2019 IEEE. This paper aims to realize the pitching vibration suppressing control for the Electrical Vehicle(EV). Over many years, the active suspension has been studied as an effective technology to suppress the vehicle vibration, however it requires additional parts and consumes the enormous electric power. This paper shows the vibration suppressing method utilizing the inertial force generated by the driving motor, and it achieves the low power consumption. Through realizing the control method considering the passengers' comfortability, Frequency-weighted Linear Quadratic Gaussian was expanded to Linear Quadratic Integrator system in this paper. To validate the effectiveness of the proposed method, the simulation has been carried out, and it was confirmed to suppress the vehicle body vibration.

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Observer Structure Considering Reluctance Torque of IPMSM for Noise Resistance

Yamada Y., Nozaki T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2019-October   461 - 466 2019.10

ISSN  9781728148786

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© 2019 IEEE. In this paper, Disturbance OBserver (DOB) and Reaction Torque OBserver (RTOB) considering reluctance torque is proposed. By changing the structure of DOB when performing Maximum Torque Per Amplitude Control (MTPAC), a high torque and a robust control system is designed. Specifically, a control system resistant to noise is designed by considering the reluctance torque in the torque constant part. The proposed method is effective in situations where noise is large, as in position sensorless control. Due to the noise resistance, the vibration of the current or torque is reduced. Also, by considering the reluctance torque, the estimated value of the reaction torque can be estimated accurately. Therefore the performance of the force control is improved. The effectiveness of the proposed method is confirmed by simulation.

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Motion Support for Tremor Suppression by Frequency Resolved Impedance Control

Kunii T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2019-October   5407 - 5412 2019.10

ISSN  9781728148786

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© 2019 IEEE. There are many patients with Parkinson's disease in Japan. The one of the initial symptom is tremor, which is involuntary oscillations of the body. Medications and deep brain stimulation are utilized as treatments for the tremor. However, side effects and the invasiveness to the brain are regarded as problems. Hence, the demand for the support equipment is increasing in order to suppress the tremor from outside the body. There are tremor suppression robots attached to hands and upper limbs. In other words, most researches focus on the tremor of arms. Therefore, this paper proposes the tremor suppression robot for a finger. Since the frequency of the tremor and the human intended movement are different from each other, the tremor suppression control is based on the frequency resolution. This proposed control achieves the following the human motions. The validity of the proposed method is confirmed by the simulation and experiment.

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Extended T-Type Boost Inverter Using Switched Capacitors

Sugimoto T., Nozaki T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2019-October   1756 - 1761 2019.10

ISSN  9781728148786

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© 2019 IEEE. Recently, for renewable energy applications, multilevel inverters are an attractive option due to their advantages, such as harmonics reduction, low electromagnetic interferences, and small voltage stress. Additionally, lower DC-link voltage should be converted to higher AC voltage, which needs an inverter and a DC-DC boost converter or a transformer. However, the two-stage conversion reduces efficiency and reliability in renewable energy applications. Hence, a single-stage conversion system which can directly change the lower DC-link voltage to higher AC voltage is required. Some single-stage conversion systems have been proposed before. However, the maximum boost ratio and the level of these systems are constant, which limits applications. This paper proposes a multilevel boost inverter stepping up the AC output peak voltage at any boost ratio by changing the number of switched capacitors. The operation principle and the boost ability with multiple boost ratios are confirmed by simulations.

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Estimation of Posture and Position Based on Geometric Calculation Using IMUs

Murata Y., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2019-October   5388 - 5393 2019.10

ISSN  9781728148786

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© 2019 IEEE. In IMUs, three sensors, acceleration, gyroscope, and magnetic, are implemented. Data get from these sensors are used to acquire posture and position of each sensor. Theoretically, from a simple integration of an acceleration and an angular velocity, position and posture could be calculated. The IMU is applied to many fields due to its user friendly structure. Human motion detection is one of interesting applications. However, small error in the measured data are also integrated, hence position error and posture error, which is also called drift, occur. The purpose of this paper is to estimate position and posture using IMUs without human model. Two IMUs are used to estimate posture and position. For posture estimation, complementation of posture angle are done from an 'angular velocity' and a 'gravity acceleration'. For position estimation, complementation by relative relationship between 2 sensors has been proposed. This is the novel part of this paper. Two ways of position complementation algorithm are proposed. One method is complementation by Kalman Filter, and the other is complementation by error estimation. Error estimation is based on a theory of mode transfer between relative space and world space. The validation of proposed method is done by experiment.

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Continuously Variable Transmission by High-speed Path Switching of Linear Electro-hydrostatic Actuator

Sugihara K., Nozaki T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference))  2019-October   3603 - 3608 2019.10

ISSN  9781728148786

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© 2019 IEEE. In robotic systems, reduction drives are utilized to increase actuators' force. Actuators with a constant reduction ratio can not achieve characteristics of both high velocity driving and high force driving. In order to perform various tasks, high force drive and high velocity drive are required for robotic actuators since required driving characteristics are different among tasks. Therefore, a mechanism which can change a reduction ratio continuously is needed. This paper proposes a mechanism that can change a reduction ratio with a linear electro-hydrostatic actuator (EHA). The proposed mechanism switches between two discrete reduction ratios by switching two oil paths with solenoid valves. Furthermore, this paper realizes a continuously variable reduction ratio by switching the solenoid valves quickly. This paper confirms that the reduction ratio changes continuously and widely by simulations.

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Evaluation of Langevin Model for Human Stabilogram Based on Reproducibility of Statistical Indicators

Tawaki Y., Murakami T.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS (Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS)     1934 - 1939 2019.07

ISSN  9781538613115

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© 2019 IEEE. Fall risk is a serious problem especially for the elderly. Fall accident causes fracture, and it leads to bedridden. Early detection of balance inability and rehabilitation training is important to decrease the risk. Quiet standing test is one of the physical tests to assess the balance inability of human. When the human is standing, he/she controls the plantar force to keep the balance. Center of pressure (COP) is the representative parameter to explain the plantar force movement. During the quiet standing test, COP fluctuates unconsciously. There are many researches that analyze the relationship between the COP fluctuation and balance inability. Many statistical indicators have been developed to assess the fluctuation specification.In contrast, several researchers have been tried to reveal the COP fluctuation mechanism by introducing stochastic mathematical model. Ornstein-Uhlenbeck process and diffusion equation are often introduced to the model. The mathematical models have been developed, and analyzed how visual input is related to the model parameters. If the mathematical model can explain the COP fluctuation completely, it becomes easier to assess the balance ability by comparing the model parameters.However, statistical indicators are still used in the clinical cases, thus there is room to discuss which statistical indicators to be used for assessment. The purpose of this research is to explore the relationship between statistical indicators and numerical model by evaluating whether the numerical model reproduces the same values with real data. The reproduced indicators and original indicators are compared, and the magnitude of the errors are evaluated.

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A Decentralized Force Controller Synthesis for Compliant Robots Driven by Series Elastic Actuators

Sariyildiz E., Mutlu R., Nozaki T., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 (Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019)     661 - 666 2019.05

ISSN  9781538669594

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© 2019 IEEE. This paper deals with the decentralized force control problem of compliant robots driven by Series Elastic Actuators (SEAs). The decentralized force control problem of a compliant robot manipulator is transformed into the robust position control problem of a servo system by using Hooke's law and lumping the nonlinear dynamics and unknown disturbances of the robot manipulator into a fictitious disturbance variable. In order to precisely follow the reference force trajectories at joint space, i.e., the position trajectories of the servo systems, the robust controller is synthesized by using Disturbance Observer (DOb) and Sliding Mode Control (SMC). Although the robust force controller can be synthesized by using only SMC, the force control signal may suffer from high control signal chattering as the force reference input is increased. In addition to improving the robustness of force control, DOb significantly suppresses the discontinuous control signal chattering by allowing to decrease the SMC gain. When the proposed decentralized robust force controller is implemented, the compliant robot can precisely track desired force trajectories and safely contact to different environments. The validity of the proposed force controller is verified by giving the simulation results of a redundant robot manipulator.

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Bilateral Control between Manipulators with Different Structure Considering Fluctuation of Equivalent Mass Matrix

Lyu W., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 (Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019)     370 - 375 2019.05

ISSN  9781538669594

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© 2019 IEEE. This paper proposes the bilateral control method for a pair of manipulators which have different structures considering the fluctuation of an equivalent mass matrix. Bilateral control is one of the methods that controls position and force bidirectionally between two actuators. By using this method, operators can get haptic sensation from the remote environment during teleoperation. When considering the practical situation, the desired structure of robots would be different between the operator and remote sides depending on a task or environment. Therefore, bilateral control between two manipulators with different structure needs to be considered. In the method using Workspace Observer (WOB), conventionally, the nominal value is used for the equivalent mass matrix. However, an error occurs between the nominal and true values of equivalent mass matrix, and this error deteriorates the stability or noise-sensitivity of the system. In addition, it deteriorates the accuracy of the force estimation since Workspace Reaction Force Observer (WRFOB) estimates external force including this error. To overcome this problem, the control system needs to be designed based on the equivalent mass, which fluctuates depending on the posture of manipulators. By using the estimated equivalent mass matrix for WOB, the mass fluctuation can be considered, however, the interference between position control and force control occurs as the equivalent mass is different between the master and slave. Therefore, in the proposed method, Modal space Disturbance Observer (MDOB) with estimated task mass matrix is used to reduce the interference. Experiments were conducted to validate the proposed method.

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Variable Slave Force Gain for Oblique Coordinate Control under the Presence of Time-Delay

Okano T., Ohnishi K., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 (Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019)     249 - 254 2019.05

ISSN  9781538669594

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© 2019 IEEE. Teleoperation gets a significant attention from the society, and 4ch bilateral control is known as a method to realize the haptics transmission. Its controller is able to achieve the rich haptics transmission, but the performance is degraded under the presence of time-delay due to the interference between the position and force controllers. In particular, its interference becomes larger when position and force scaling are set more than 1 and the mass difference between the master and slave is large. 3ch architecture has proposed to tackle with the performance deterioration when the position and force scaling are set more than 1, but no researches have conducted for considering both the scaling and mass difference. This paper considers the situation that the scaling are set and the mass difference is existed in addition to the time-delay. Oblique coordinate control is utilized, and the superiority of 4ch and 3ch architectures are discussed. The proposal takes the superiority of these two architectures, and its effectiveness was verified through simulations and experiments.

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Sensorless Bilateral Control Using Hall ICs

Akutsu S., Nozaki T., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 (Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019)     243 - 248 2019.05

ISSN  9781538669594

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© 2019 IEEE. Sensorless bilateral control has been studied to improve fault-tolerance of teleoperation without using torque sensors, position sensors, and other mechanical sensors. However, sensorless control often has less control accuracy due to model errors, parameter variations, and other unexpected factors. Feedback control with some position sensors is practically required for teleoperation. Therefore, this study aims at sensorless bilateral control using Hall ICs. A proposed bilateral control does not necessarily require disturbance observers unlike a conventional method originally using high-resolution sensors. Owing to this advantage, low-resolution sensors are applicable to the proposed bilateral control. Experiments showed that the proposed method succeeded bilateral control using Hall ICs without mechanical sensors, although the conventional control did not work using the low-resolution sensors. Therefore, the proposed method will be able to enhance fault-tolerance of teleoperation systems.

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Grasping Point Estimation Based on Stored Motion and Depth Data in Motion Reproduction System

Sun X., Nozaki T., Murakami T., Ohnishi K.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 (Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019)     471 - 476 2019.05

ISSN  9781538669594

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© 2019 IEEE. Most countries are running shortage of working force due to the aging population and reduction in the birthrate. Robot manipulators are expected to replace human work. However, it it still difficult for manipulators to do simple tasks such as fruit harvesting, foods cooking or toy assembling. A problem for robotic automation arise in the difficulty in teaching how much force manipulators should use for a task execution. Motion reproduction system, which uses bilateral control to store motion data, is one of a method to teach manipulators motion including position and force. The problem concerning motion reproduction system is that the motion reproducing fails if environment is changed between motion saving phase and motion reproducing phase. Motion reproduction system which can understand and adapt to environment is required. Vision sensor can sense environment. Computer vision is mainly focus on how to classify objects. Vision information is seldom combined with motion control especially force motion. Therefore, I propose a motion reproduction system in which reproduced motion is decided based on several motions and collected depth data. Convolutional Neural Network(CNN) was used to estimate a motion command from a depth image. Saved force data was used to generate labels for training. The label decision is different from conventional Machine learning alzorithm.

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A Control of under Actuated AUV by Nonlinear Controller

Kawamura A., Okano T., Murakami T.

Proceedings of the 2019 IEEE/SICE International Symposium on System Integration, SII 2019 (Proceedings of the 2019 IEEE/SICE International Symposium on System Integration, SII 2019)     295 - 300 2019.04

ISSN  9781538636152

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© 2019 IEEE. Technologies for machine automation are strongly demanded in some developed countries for achieving various tasks which should be treated by the robot. Autonomous Underwater Vehicles (AUVs) are currently being utilized for scientific and commercial applications. To achieving these tasks, it is required autonomous the guidance and the control systems. Therefore, modeling, system identification and control strategy of these vehicles are still major areas of research and development. Normally, the full actuated AUV is considered for facilitating its control and the disturbance compensation. However, it increases the cost to create and maintain. And thus in author's previous research, an under actuated AUV which still can be controlled when the disturbance exists, was considered to decrease the cost with the same performance as the full actuated one. However, some disturbance effects could not be compensated because of severe nonlinearity of it and the non-holonomic constraint. Therefore, the new control strategy which is considered its nonlinearity, is proposed in this paper and the simulation supports this argument.

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A fusion control of impedance and vibration suppression for a manipulator with flexible base

Mori R., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2019-February   42 - 47 2019.02

ISSN  9781538663769

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© 2019 IEEE. Accidents caused by a collision between an environment and a robot become a problem, so safety strategies of robots are indispensable. Since the impact force sharply increases at the time of a collision, position-based impedance control which has low responsiveness to the collision can not sufficiently reduce the damage. This paper proposes the manipulator with passive and flexible base for collision force suppression. The proposed flexible base has a rotating structure and it is possible to suppress the collision from any direction when an environment contacts the working manipulator. When a large external force is applied, the variable impedance control according to the strain amount of the base spring in order to avoid the strain limit of flexible base is proposed. Also, when the external force is estimated with force sensorless, the estimation error increases due to the friction model error of the motor, and the position followability deteriorates. Therefore, the contact state is judged by the strain amount of the flexible base, and correction is added to the estimated reaction force, thereby improving the position followability of the impedance control in non-contact.

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Impedance Field Expression of Bilateral Control for Reducing Data Traffic in Haptic Transmission

Nozaki T., Shimizu S., Murakami T., Oboe R.

IEEE Transactions on Industrial Electronics (IEEE Transactions on Industrial Electronics)  66 ( 2 ) 1142 - 1150 2019.02

ISSN  02780046

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© 1982-2012 IEEE. It is expected that bilateral control will find broad applications such as mobile robot exploration and operations in extreme environments. However, the transmission of vivid haptic sensation requires a rapid data-transfer rate of haptic data due to the short sampling period and high-frequency communication. The objective of this paper is aimed at the traffic reduction of haptic data by exploiting an impedance field equivalence of a standard bilateral control. The proposed approach theoretically clarifies the equivalence of the standard bilateral control and impedance control in terms of haptic transmission. Based on this equivalence, the same performance of a standard bilateral control can be achieved by only communicating the force information that determines the equilibrium position of the impedance control. The validity of the proposed approach is confirmed through both simulations and experiments. The obtained results show that the proposed approach successfully reduced the amount of communicated haptic data without any disadvantages compared with the standard acceleration-based bilateral system. This paper shows novel interpretation that haptic transmission is realized by controlling the equilibrium force, which contributes reducing data traffic in haptic transmission and understanding motion generation.

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Design of bilateral control based on equivalent circuit model

Akutsu S., Nozaki T., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2019-February   1351 - 1356 2019.02

ISSN  9781538663769

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© 2019 IEEE. Haptic teleoperation has been studied as an attractive technology for a long time. Although the haptic teleoperation has been already realized by conventional methods, their physical meanings are remained vague and unclear. This paper explains bilateral control for the haptic teleoperation using an equivalent circuit model. Owing to the circuit model, which takes into account characteristics of electrical actuators, a control strategy and its physical meanings are clearly illustrated. Torque (force) control and position (velocity) control for the haptic teleoperation can be designed independently because of mode decomposition. Feedback controller design for each control is based on analyses of sensitivity derived from the equivalent circuit. The control strategy derived from the equivalent circuit have been confirmed by experiments and resulted in the haptic teleoperation.

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An approach to air pressure interface for position control of manipulator

Amma Y., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology (Proceedings of the IEEE International Conference on Industrial Technology)  2019-February   54 - 59 2019.02

ISSN  9781538663769

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© 2019 IEEE. Nowadays, a low birthrate and longevity are proceeding in developed countries. Due to the low birthrate and longevity, there is a shortage of caregivers. Therefore, an assistance of nursing care is necessary. Also, according to a multidisciplinary advance of robots, robots increase opportunities for operating in environment in which human intervene. Operating a robot in human presence is a dangerous for human. Therefore, a signal transmission between human and robots is necessary. This paper uses a cuff of sphygmomanometer as an interface of signal transmission. This interface is attached to an arm of user and an air pressure of interface is controlled to constant. An error between pressure command and response caused by a muscle bulge of user is regarded as an intention of user. An integration of error is given to a manipulator as a position command. According to this system, the interface user can operate a position of manipulator based on the user's intention.

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Simultaneous bipedal locomotion based on haptics for teleoperation

Prasanga D., Tanida K., Ohnishi K., Murakami T.

Advanced Robotics (Advanced Robotics)  33 ( 15-16 ) 824 - 839 2019

ISSN  01691864

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© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group and The Robotics Society of Japan. This paper proposes a novel, simultaneous bipedal locomotion method using haptics for remote operation of biped robots. In general, traditional biped walking methods require very high computational power and advanced controllers to perform the required task. However, in this proposed method, a master exoskeleton attached to the human’s lower body is used to obtain the trajectory and haptic information to generate the trajectory of the slave biped robot in real time. Lateral motion of the center of mass of the biped is constrained in this experiment. Also, it is considered that no communication delay is presented in between the two systems in this experiment, and they are not discussed in this paper. Since a direct motion transmission is used in the proposed method, this method is quite straight forward and a simultaneous walking can be realized at the same time with high performance. Also, it does not require an exact dynamic model of the biped or specific method to plan the trajectory. The gait pattern of the biped is directly determined by that of the human. Also, the operator can feel the remote environment through the exoskeleton robot. Results obtained from the experiments validate the proposed method.

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Multilevel inverter topology using current path change for zero current switching

Sugimoto T., Nozaki T., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  8 ( 2 ) 250 - 255 2019

ISSN  21871094

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© 2019 The Institute of Electrical Engineers of Japan. In motor drive applications, a high switching frequency is required to mitigate current harmonics, which cause a copper loss. However, the high switching frequency makes the switching loss large. Hence, some switching loss reduction techniques have been studied in the past. These techniques have some problems. This paper proposes a multilevel inverter topology for switching loss reduction. Because of provision of multiple current paths, the proposed inverter realizes the zero current switching. Consequently, a loss of the whole system including an inverter and motor can be reduced with a higher switching frequency. The switching loss of the proposed inverter is smaller than that of the conventional one. It was verified that the proposed inverter has some advantages at high switching frequency, through calculations.

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Control Structure Determination of Bilateral System based on Reproducibility and Operationality

Tanida K., Okano T., Murakami T., Ohnishi K.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  8 ( 5 ) 767 - 777 2019

ISSN  21871094

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© 2019 The Institute of Electrical Engineers of Japan. The 4ch bilateral control is a teleoperation method that transmits the position and force information between the master and slave, and the reproducibility and operationality are often used to evaluate it. Conventionally, the reproducibility and operationality have been utilized only for performance evaluation, although many controllers based on the 4ch bilateral control scheme have been proposed. Therefore, the aim of this paper is to determine the controller structure based on the target reproducibility and operationality in advance. The contribution of this paper is to develop an appropriate controller from the reproducibility and operationality through numerical computations and analyses. The structure of the proposed controller is verified through simulations and experiments.

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Advanced deceleration control considering driving resistance by predicting the position of pedestrians

Nakamura Y., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  8 ( 2 ) 334 - 341 2019

ISSN  21871094

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© 2019 The Institute of Electrical Engineers of Japan. This study aims to realize an automated deceleration system to avoid the collision of a vehicle with a pedestrian. The proposed system can predict a pedestrian’s future position from the current position, and detect the collision probability. Furthermore, the controller employing model predictive control, which can compensate the driving resistance and the modeling error is also proposed. The effectiveness of the proposed method is verified through a simulation and experiment.

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Design of iterative learning control for force control considering environmental impedance

Fukui M., Akutsu S., Okano T., Nozaki T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society (Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society)     4569 - 4574 2018.12

ISSN  9781509066841

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© 2018 IEEE. In this paper, a new approach for high-precise force control in repeated tasks is proposed. In the general force control, the feedback control tends to be used for a matching the output force to the desired force safely. However, when the feedback control is used, the input of the plant does not change until the error is observed. The characteristic makes reactivity bad. In the position control, the model-based feedforward control is often used to solve this problem. However, the model-based feedforward control cannot be used in force control due to the difficulty of making the accurate model. The main reason of this problem is the uncertainty of the environmental impedance. Owing to the uncertainty, the model-based feedforward control cannot work properly. To solve this problem, Iterative Learning Control (ILC) is used in this paper. ILC does not require the accurate model, and it is able to match the output force to the desired one through repeated trials. However, the convergence condition in force control has not been analyzed until now. In this paper, by taking account of the environmental impedance of the object, a new convergence restriction is proposed. Under the proposed condition, the force control in repeated tasks becomes more precise. The procedure was demonstrated on simulations.

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Verification of the knee exoskeleton controller using novel gait phase detection method

Tawaki Y., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society (Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society)     3304 - 3309 2018.12

ISSN  9781509066841

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© 2018 IEEE. Gait motion is the essential function for human being. Some diseases make it difficult for people to walk. Walking assist robot has been developed to assist gait motion for disabled people. Knee Exoskeleton is one of the walking assist robots. Knee Exoskeleton generates the assist torque for knee flexion or knee extension. The direction of the assist torque is controlled by the gait phase detection method. However, the conventional robot interferes with human intention because it generates flexion torque consistently in stance phase. In early stance phase, the user wants assist torque to support knee extension, but he wants knee flexion assist torque in late stance phase. The conventional controller does not detect late stance phase. In the previous study of the author, the novel gait phase detection algorithm is proposed to distinguish late stance phase. In this research, the novel algorithm is introduced for the proposed controller. A subject walks on the treadmill while wearing the knee exoskeleton. In the experiment, the exoskeleton is controlled by the conventional controller and the proposed controller. EMG of the popliteal muscle during gait motion is analyzed to evaluate whether the proposed controller succeeds to prevent interference with user's intention. Through the experiment, it is verified that the proposed controller succeeds to decrease the EMG of knee muscle by distinguishing early stance phase and late stance phase.

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Selective wireless power transfer via magnetic resonant coupling by using variable impedance circuit

Nakagawa T., Sugimoto T., Nozaki T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society (Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society)     4834 - 4839 2018.12

ISSN  9781509066841

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© 2018 IEEE. Recently, Wireless Power Transfer (WPT) via Magnetic Resonant Coupling is especially focused around the world. Since a space will have a lot of devices in the future, WPT considering multiple devices will be required. It is important to consider not only power transfer efficiency but also power distribution when power is wirelessly transferred to multiple devices. The amount of received power in a receiver depends on the impedance of the receiver and the ratio of power distribution has the relation to the impedance. Conventional WPT system requires a few controllable repeaters and the large size of the receiver. In this paper, a variable impedance circuit for power distribution is proposed. Using the proposed circuit controllable by DC voltage, the problem for the conventional system is solved. In the future when WPT is popular, the circuit realizes electrically controllable power distribution.

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Real-time foot clearance and environment estimation based on foot-mounted wearable sensors

Ishikawa T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society (Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society)     5475 - 5480 2018.12

ISSN  9781509066841

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© 2018 IEEE. The ambulatory gait monitoring systems (AGMS) using wearable devices have a great attention for health monitoring of individuals. Foot clearance is one of gait parameters and an indicator of gait quality and safety. Conventionally, foot clearance is calculated by post-processing using several methods such as extended Kalman filter (EKF), a weighted Fourier linear combiner (WFLC), a simple biomechanical foot model, zero velocity update (ZVU), and optimally filtered direct and reverse integration (OFDRI). However, real-time foot clearance (FC) estimation is required to apply to control of neural prostheses and assistive devices to prevent falling down. In addition, since humans adapt to several environments during gait motion, walking patterns are different among leveled walk, ramp walk, and stair walk. Therefore, environmental recognition also has an important role for the devices. Aim of this study is an implication of a system which performs real-time foot clearance and environment estimation in several situations. Different configurations of infrared (IR) distance sensors are utilized with a foot-mounted inertia measurement unit (IMU: an acceleration sensor, a gyro sensor, a magnetometer, and an air pressure sensor) sensor. Two IR sensors are attached to both sides of a shoe with different orientation. Developed system is tested in case of leveled walk, ramp walk, and stair walk. As the result, the developed system can estimate foot clearance and find characteristics of walking in different gait motion.

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Position and torque sensorless motion transmission using parameter identification based on least mean squares method

Akutsu S., Nozaki T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society (Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society)     5098 - 5103 2018.12

ISSN  9781509066841

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© 2018 IEEE. Motion transmission is a technology which is expected to be used for teleoperation systems. Sensorless control can improve fault tolerance of teleoperation robots exposed to harsh environments. However, sensorless control methods are generally sensitive to parameter errors of an actuator. A previously proposed sensorless motion transmission method especially requires the accurate value of resistance. Therefore, this work aims to identify resistance of two direct current motors used as a master slave system. Taking account of the master slave system of which common mode and differential mode correspond respectively to torque transmission and velocity synchronization, a least mean squares method jointly using a voltage injection is newly applied to the differential mode. Simulation results validated the proposed identification method and indicated that the sensorless motion transmission succeeded using the identified resistance value. The proposed novel method will improve the usefulness of sensorless motion transmission by adaptability to parameter errors.

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Multilevel inverter topology for switching loss reduction

Sugimoto T., Nozaki T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society (Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society)     1345 - 1350 2018.12

ISSN  9781509066841

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© 2018 IEEE. In motor drive application, a high switching frequency is required in order to mitigate current harmonics which cause a copper loss. However, the high switching frequency makes the switching loss large. Hence, some switching loss reduction techniques have been studied before. However, they requires complicated circuits. This paper proposes a multilevel inverter topology for a switching loss reduction. By changing current paths, the proposed inverter realizes the zero current switching. It was experimentally verified that the proposed inverter realizes the zero current switching by a foundation circuit.

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An estimation method of end-point impedance based on bilateral control system

Okano T., Ohnishi K., Murakami T.

Advanced Robotics (Advanced Robotics)  32 ( 21 ) 1151 - 1167 2018.11

ISSN  01691864

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© 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group and The Robotics Society of Japan. This paper aims at developing an estimation method of end-point impedance. Human operators are constantly changing their end-point impedance for adapting to the surrounded environment and executing some complicated tasks, and it is highly meaningful to investigate these variations for the further understanding of human motion. Most of the conventional researches, however, have considered non-contact-point impedance or tasks that is only holding the vibrated sticks due to the experimental constraints. This paper proposes the estimation method of end-point impedance by using bilateral control system. The extra signal is added to the force controller for the impedance estimation. In addition, the effect of the bilateral controller is estimated and removed from the impedance estimation process for securing the applicability of moving tasks. The proposed method was validated through simulations and an experiment. The experimental result showed that the end-point stiffness can be estimated properly even if the operator robot was moving and changed its end-point impedance.

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Fall Prevention and Vibration Suppression of Wheelchair Using Rider Motion State

Takahashi I., Murakami T.

2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018 (2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018)     575 - 582 2018.10

ISSN  9784886864055

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© 2018 IEEJ Industry Application Society. In recent years, with the declining birthrate and the aging of the population, the demand for nursing care support equipment is increasing. Among them, wheelchairs are already common as nursing care support equipment. Therefore, demand for wheelchair research is high, and electric wheelchair is required to have higher functionality. In this paper, prevention of falling of the wheelchair as a part of enhancing the functionality of the electric wheelchair is described. Several studies on prevention of rollover of electric wheelchairs have already been reported, but since rider motion state is not taken into account in the calculation of rollover conditions, there is a problem that the rollover conditions does not conform to the actual situation. Therefore, the purpose of this study is to estimate the state of the rider by IMU sensor and to calculate accurate rollover condition. Several simulation results are shown to confirm the proposed approach.

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An Approach to Energy Harvesting Considering Passive Action during Walking

Kamiyama K., Murakami T.

Proceedings - 2018 12th France-Japan and 10th Europe-Asia Congress on Mechatronics, Mecatronics 2018 (Proceedings - 2018 12th France-Japan and 10th Europe-Asia Congress on Mechatronics, Mecatronics 2018)     277 - 282 2018.10

ISSN  9781538629826

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© 2018 IEEE. Along with a development of the industry, wearable devices are spreading. These devices often have a problem of a battery exhaustion. Biomechanical energy harvesting is one of the methods to solve this problem. As methods of biomechanical energy harvesting, the shoes which attached piezoelectric elements and the system which attached a generator to the knee were researched.This paper focuses on the surplus energy when walking down a slope. In order to determine the amout of the surplus energy, a passive walking model is utilized. Additionally, a method to recover surplus energy while maintaining walking stability is introduced. Finally, PI control of the boost chopper is utilized to adjust a braking torque and the amount of the generation. The validity of the proposed method is confirmed by simulation.

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Motion Control Considering Fusion of Mechanical and Virtual Impedance in Mobile Robot Systems

Sekiya K., Murakami T.

Proceedings - 2018 12th France-Japan and 10th Europe-Asia Congress on Mechatronics, Mecatronics 2018 (Proceedings - 2018 12th France-Japan and 10th Europe-Asia Congress on Mechatronics, Mecatronics 2018)     367 - 372 2018.10

ISSN  9781538629826

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© 2018 IEEE. In recent years, the applications of robots have diversified, and interest in application to human living environment has increased. To co-exist with robots,it is necessary to ensure safety against collision. Conventional collision detection with a force sensor and collision mitigation by impedance control only have low adaptability. In thispaper, collision mitigation by combination of flexible structure and impedance control is proposed. Collision detection is performed by Load Disturbance OBserver (LDOB). In addition, switching control of the collision mitigation and damper control based on the estimated disturbance torque according to the environmental situation is proposed. Simulations are conducted forverifying the proposed approach.

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Bandwidth improvement of Disturbance Observer with Low Pass Derivative FIR Filter

Hazaz M., Murakami T.

Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018 (Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018)     921 - 926 2018.09

ISSN  9781538648292

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© 2018 IEEE. Disturbance observer based compensation is a popular technique in motion control to compensate for the difference between an actual plant and its nominal model. Conventional implementation with pseudo derivative performs poorly when the measurement noise is large and the bandwidth has to be decreased. Low pass derivative FIR filters provide a frequency response closer to the ideal response than comparable pseudo derivative filters. This paper proposes a disturbance observer with low pass derivative FIR filter for DC motor with position measurement. The proposal is validated with numerical simulations.

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Scaling Adjustment Method for Motion Copying System with Environmental Variations

Okano T., Ishikawa T., Murakami T.

Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018 (Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018)     418 - 423 2018.09

ISSN  9781538648292

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© 2018 IEEE. Machine automation is getting significant attention from the society due to the declining labor population in Japan. This paper considers Motion Copying System (MCS) that is known as the machine automation method. MCS is able to play back the saved motion if environmental conditions between the saving and loading phases are the same. The variation of environmental condition, however, degrades the motion reproduction performance because the tactile information needs the bilateral communication between the master and the slave, which can also be said of the sender and the receiver, unlike the visual or audio information. This paper proposes the scaling adjustment method for compensating the environmental impedance variation between the saving and loading phases. The effectiveness of the proposal was verified through simulation.

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Robust Control Strategy for AUV with Workspace Observer

Kawamura A., Okano T., Murakami T.

Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018 (Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018)     412 - 417 2018.09

ISSN  9781538648292

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© 2018 IEEE. Technologies for machine automation are strongly demanded in some developed countries due to achieve various tasks which could not be treated by human. Autonomous Underwater Vehicles (AUVs) are currently being utilized for scientific, commercial and military applications. These vehicles require autonomous guidance and control systems in order to perform underwater tasks. Modeling, system identification and control strategy of these vehicles are still major areas of research and development. Various disturbance effects perturb a vehicle in underwater, but it is not really discussed by conventional control strategy. And thus this paper proposes a new control strategy which is still effective under the circumstances when the disturbance exists. Simulations were conducted for supporting the argument.

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Comparative study of soft motion for motion copying system with environmental variations

Okano T., Oboe R., Ohnishi K., Murakami T.

IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM (IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM)  2018-July   646 - 651 2018.08

ISSN  9781538618547

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© 2018 IEEE. Technologies for the skill succession and machine automation are strongly demanded in some developed countries under the circumstance of declining working population due to the lower birth rate and the aged society. Motion copying system (MCS) is one of the methods for the skill succession and machine automation. MCS is able to play back the saved motion in the case that the environmental conditions between the saving and the loading phases are the same. Conventionally, the pure position controller, the pure force controller, or Hybrid Position and Force Control (HPFC) is applied to MCS. The reproduction performance is, however, degraded when the environmental variations happen. In such case, impedance control is applicable to MCS instead of HPFC. The purpose of this paper is to conduct the comparative study of some control strategies: position control, force control, HPFC, the Position-Based Impedance Control (PBIC), and the Force-Based Impedance Control (FBIC), and clarify which control strategy is appropriate for the tasks. Simulations were conducted for supporting the argument.

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Compensation Method for Environmental Variations of Motion Reproduction System Based on the Different Control Impedance

Okano T., Ohnishi K., Murakami T.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2018-June   1045 - 1050 2018.08

ISSN  9781538637050

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© 2018 IEEE. Some developed countries will encounter the shortage of working population, and machine automation is considered as one of the promising methods to overcome its issue. This paper considers Motion Reproduction System (MRS) as a method of the machine automation. MRS can be easily repeated the executed motion; however, this system is sensitive to environmental variations. One of simple countermeasures is introducing compensation values that are designed based on the environmental variations, but these values contain errors and degrade the motion reproduction. This paper proposes the modification of control impedance on the basis of the type of environmental variations, and the trustworthy information is much more weighted. The effectiveness of the proposal is verified through simulation and experiments.

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Evaluation of Gait Phase Detection Methods for Walking Assist Robot

Tawaki Y., Okano T., Murakami T., Ohnishi K.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics)  2018-June   1051 - 1056 2018.08

ISSN  9781538637050

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© 2018 IEEE. Lower paralysis interrupts the mobility and depresses quality of life. Some incomplete paraplegia have an ability to walk in rehabilitation. However, incomplete paraplegia consumes larger energy for the gait motion than able-bodied people. Therefore, it is difficult for them to walk a long time. To solve this problem, many walking assist exoskeletons have been developed. In the case of walking assist, assist timing is one of the essential factors. The mismatch of assist timing interferes user's motion, thus it is required to adjust the assist timing. To control the assist timing, gait phase detection methods are used. Gait motion is divided into several phases. Many researchers introduce the gait phase detection method to control the assist timing. However, there is a mismatch between assist torque and ideal torque which is required by the user. There are no researches to evaluate the gait phase detection methods based on the analysis of the transition of assist torque required by the user. The purposes of this research are to propose the novel FSBM and evaluate the gait phase detection methods. In the experiment, a subject walks on the treadmill with wearing knee exoskeleton. The motor of the exoskeleton is controlled by the bilateral controller. Therefore, the assist torque can be adjusted to be suited to the user by manipulating master side motor. After the experiment, the assist torque and detected gait phases of proposed FSBM are compared to the conventional methods.

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An approach to power assist hand exoskeleton for patients with paralysis

Uchida H., Murakami T.

Proceedings - 2018 IEEE 15th International Workshop on Advanced Motion Control, AMC 2018 (Proceedings - 2018 IEEE 15th International Workshop on Advanced Motion Control, AMC 2018)     657 - 662 2018.06

ISSN  9781538619469

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The aim of this paper is to propose a novel robotic hand exoskeleton which can assist disabled people with grasping objects. Existing exoskeletons cannot measure force during contact motion, and this makes it difficult to achieve accurate grasp assistance. In the proposed system the exoskeletal finger is attached to the index and middle fingers, and the robotic finger is place on the palm side, which functions as a substitute of a thumb. The upper exoskeletal finger exerts assistive force on operator's fingers, and the lower robotic finger works as a force sensor by the use of Reaction Torque Observer. Thus, human grasping force is measured during grasping, and the environmental and human forces are estimated from measured torque. The proposed system realizes power assist control without using additive sensors like force sensors or EMG sensors. The effectiveness of the proposed method is demonstrated through simulation and experiment.

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Human Motion Analysis and its Application to Walking Stabilization with COG and ZMP

S. Kim, K. Hirota, T. Nozaki, T. Murakami

IEEE Transactions on Industrial Informatics (IEEE Transactions on Industrial Informatics)  14 ( 11 ) 1 - 9 2018.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  15513203

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A stability index has been generally used in a gait system of formulaic structure. In this standardized structure, a human model has a center of gravity (COG), while a robot device has a zero moment point (ZMP) with COG as the stability standard in the walking motion. In the gait system of wearable type, the stability of human model is closely related with the robot device, in other words, the COG and ZMP are located in the limited domain of human motion and robot task. In this paper, the human and device are designed individually and the knee joint of human is unconstrained from the device work to allow the human reliance. The stability index that includes the COG and ZMP is defined. The validation of this index is guaranteed through a few tests to describe a correlation between the stability index and the human model condition. Based on the validity of the stability index, the experiment for the walking stabilization is implemented with the ZMP estimation by reaction torque observer.

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Translation and Inclination Control for Intelligent Tension Pole Based Mode Decoupling Method

R. Hanaoka, T. Nozaki, and T. Murakami

IEEJ Journal of Industry Applications 7 ( 2 ) 158-165 2018.03

Research paper (scientific journal), Joint Work, Accepted

Position and Torque Sensorless Motion Transmission Using Voltage Compensation

S. Akutsu, H. Sekiguchi, T. Nozaki,and T. Murakami

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  7 ( 2 ) 150-157 - 157 2018.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  21871094

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© 2018 The Institute of Electrical Engineers of Japan. This paper aims to realize position and torque sensorless motion transmission between a generator and a motor. The proposed voltage compensation method requires only one current sensor on the generator side. Since the motor side is completely sensorless, this system is suitable for operation under harsh environments. Comparative analyses indicate that the proposed method satisfies the conditions for the transmission of an actual tactile sensation. Simulations and experiments confirmed that motion transmission is realized using the proposed method.

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A novel detection procedure for mutations in the 23S rRNA gene of Mycoplasma pneumoniae with peptide nucleic acid-mediated loop-mediated isothermal amplification assay (vol 141, pg 90, 2017)

Sakai Jun, Maeda Takuya, Tarumoto Norihito, Misawa Kazuhisa, Tamura Shinsuke, Imai Kazuo, Yamaguchi Toshiyuki, Iwata Satoshi, Murakami Takashi, Maesaki Shigefumi

JOURNAL OF MICROBIOLOGICAL METHODS 144   192 - 192 2018.01

ISSN  0167-7012

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Translation and inclination control for Intelligent Tension Pole based on mode decoupling method

Hanaoka R., Nozaki T., Murakami T.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  7 ( 2 ) 158 - 165 2018

ISSN  21871094

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© 2018 The Institute of Electrical Engineers of Japan. An aging society is a serious problem in many developed countries. Due to this issue, there has been a significant increase in the demand for assist devices that can support human motion. This paper proposes a novel assist device, Intelligent Tension Pole (ITP), to assist in indoor activities of daily living (ADL), and it is expected to provide support for achieving self-reliance, space saving, and stability. The structure and control system of this assist device are presented. This novel assist device is based on a movable handrail, and therefore wheels are added to the lower and upper ends of the tension pole. In addition, a ball screw, which enables the ITP to move while stretching to the floor and ceiling at any time using force control, is added. In order to improve user comfort and reduce the risk of falling down of the ITP, translation and inclination controls of the ITP are applied to the wheel control. These controls are controlled independently by the mode decoupling method. Experiments are conducted to verify the effectiveness of the proposed device and its control system.

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Application of active driving assist to remotely controlled car in collision avoidance

Rouzier B., Hazaz M., Murakami T., Xu W.

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications)  7 ( 4 ) 289 - 297 2018

ISSN  21871094

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© 2018 The Institute of Electrical Engineers of Japan. Road traffic accidents are a leading cause of avoidable deaths, especially among young persons. Because driver behavior is a major cause for these the incidents, any device able to help the driver should lower casualties. As an intermediary step between autonomous vehicles and human driven ones, active driving assistance technology can help the driver maintain a safe trajectory. Applying remote control to vehicles could also decrease the probabilities of accidents, by facilitating the reduction of the duration of the driving sessions, especially in fret transport applications, decreasing drowsiness of the driver, a factor that increases the occurrence of accidents. However, the addition of remote control conducts to a communication time delay that can be dangerous in cruising situations. This paper presents the application of an active driving assistant to compensate for the effects of the communication time delay in collision avoidance scenarios using a small-scale vehicle.

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Line Crossing Assistance Based on Situation Modulated Potentials Using Stereo Camera Detection

B. Rouzier and T. Murakami1

IEEJ Journal of Industry Applications 6 ( 4 ) 286-294 2017.11

Research paper (scientific journal), Joint Work, Accepted

A General Framework for Designing SISO-Based Motion Controller With Multiple Sensor Feedback

A. Suzumura, Y. Fujimoto, T. Murakami and R. Oboe

IEEE Transactions on Industrial Electronics 63 ( 12 ) 7607-7620 2016.12

Research paper (scientific journal), Joint Work, Accepted

IMU Sensor based Human Motion Detection and Its Application to Braking Control of Electric Wheeled Walker for Fall-prevention

K. Hirota and T. Murakami1

IEEJ Journal of Industry Applications 5 ( 4 ) 347-354 2016.07

Research paper (scientific journal), Joint Work, Accepted

Full-Speed Range Self-Balancing Electric Motorcycles Without the Handlebar

C. Yang and T. Murakami

IEEE Transactions on Industrial Electronics 63 ( 3 ) 1911-1922 2016.03

Research paper (scientific journal), Joint Work, Accepted

Comparison of Force Control Performance Based on Only Acceleration Sensor with KF/EKF

N. Kobayashi and T. Murakami1

IEEJ Journal of Industry Applications 4 ( 5 ) 559–567 2015.09

Research paper (scientific journal), Joint Work, Accepted

Principle for the Validation of a Driving Support using a Computer Vision-based Driver Modelization on a Simulator

B. Rouzier and T. Murakami

International Journal of Advanced Robotic Systems    1729-8806 2015.07

Research paper (scientific journal), Joint Work, Accepted

Walking-Assist Principle Analysis for a Multi-Legged System

C. Yang and T. Murakami

IEEJ Journal of Industry Applications 4 ( 3 ) 294–300 2015.05

Research paper (scientific journal), Joint Work, Accepted

Parameter Design of Disturbance Observer for a Robust Control of Two-Wheeled Wheelchair System

Aiko Dinale,Kazuya Hirata,Matteo Zoppi,Toshiyuki Murakami

Journal of Intelligent & Robotic Systems, Springer 77 ( 1 ) 135-148 2015.01

Research paper (scientific journal), Joint Work, Accepted

画像空間オブザーバに基づいたビジュアルサーボ系の性能評価

沖山 航, 村上 俊之

電気学会論文誌D 134 ( 11 ) 930-938 2014.11

Research paper (scientific journal), Joint Work, Accepted

Novel Walking Assist Device Based on Mobile Manipulator and Inertial Measurement Unit

C. Yang and T. Murakami

IEEJ Journal of Industry Applications 3 ( 5 ) 381–387 2014.09

Research paper (scientific journal), Joint Work, Accepted

Stability analysis of disturbance observer based controllers for two-wheel wheelchair systems

K. Hirata and T. Murakami

Advanced Robotics 28 ( 7 ) 467-477 2014.02

Research paper (scientific journal), Joint Work, Accepted

二輪車椅子における段差乗り越え支援制御とその快適性評価

平田 和也, 村上 俊之

電気学会論文誌D Vol.133 ( No. 12 ) 1120-1127 2013.12

Research paper (scientific journal), Joint Work, Accepted

スレーブロボットに受動的移動機構を有するバイラテラルシステムにおける自由動作での操作性向上制御

小牟田 清俊, 村上 俊之

電気学会論文誌D Vol.133 ( No. 8 ) 771-779 2013.08

Research paper (scientific journal), Joint Work, Accepted

搭乗者の快適性を考慮した二輪駆動型車椅子の多機能化制御

河村 琢郎, 村上 俊之

電気学会論文誌D Vol.133 ( No. 4 ) 404-413 2013.04

Research paper (scientific journal), Joint Work, Accepted

スライディングモード微分器を用いたオブザーバ設計による劣駆動システムの安定化制御

鈴木 健, 村上 俊之

電気学会論文誌D Vol.132 ( No. 11 ) 1024-1032 2012.11

Research paper (scientific journal), Joint Work, Accepted

多自由度力センサレスバイラテラルシステムの作業空間における制御設計法と性能評価

堀江 亮介, 村上 俊之

電気学会論文誌D Vol.132 ( No. 7 ) 755-763 2012.07

Research paper (scientific journal), Joint Work, Accepted

電動自転車におけるロバストな姿勢安定化制御

河村 琢郎, 村上 俊之

電気学会論文誌D Vol.132 ( No. 6 ) 651-658 2012.06

Research paper (scientific journal), Joint Work, Accepted

Power Assist Control of Pushing Task by Repulsive Compliance Control in Electric Wheelchair

T. Shibata and T. Murakami

IEEE Transactions on Industrial Electronics 59 ( 1 ) 511-520 2012.01

Research paper (scientific journal), Joint Work, Accepted

Virtual Force Field Based Force-feedbacks of Road Condition for　Driving Assistant Design in Electric Vehicle

J. Carlier and T. Murakami

International Journal of Automation Technology 5 ( 6 ) 908-915 2011.11

Research paper (scientific journal), Joint Work, Accepted

ハプティックアクセルペダルを用いた電気自動車の環境適応型走行支援制御

井苅 佳秀, 村上 俊之

電気学会論文誌D Vol.131 ( No. 9 ) 1135-1140 2011.09

Research paper (scientific journal), Joint Work, Accepted

A Novel Approach to Master and Slave Control by Force Feedback Based Virtual Impedance Controller

Nobuhiro Iwase, Ryosuke Horie and Toshiyuki Murakami

Journal of Control Engineering and Applied Informatics 13 ( 2 ) 9-13 2011.06

Research paper (scientific journal), Joint Work, Accepted

Center of Gravity Compensation for Dynamically-Balanced Two-Wheeled Wheelchair System

C. Acar, T. Murakami

電気学会論文誌D Vol.131 ( No. 5 ) 714-720 2011.05

Research paper (scientific journal), Joint Work, Accepted

Center of Gravity Compensation for Dynamically-Balanced Two-Wheeled Wheelchair System

Cihan Acar, Toshiyuki Murakami

電気学会論文誌D 131 ( 5 ) 714-720 2011.05

Research paper (scientific journal), Joint Work, Accepted

Vibration Suppression of Two-Wheel Mobile Manipulator Using Resonance-Ratio-Control-Based Null-Space Control

Abeygunawardhana, P. K. W. Murakami, T.

IEEE Transactions on Industrial Electronics 57 ( 12 ) 4137 – 4146 2010.12

Research paper (scientific journal), Joint Work, Accepted

同軸二輪駆動型移動マニピュレータにおける零空間制御を用いた起き上がり・着地制御

藤本祐介，村上俊之

電気学会論文誌D 130 ( 10 ) 1161-1168 2010.10

Research paper (scientific journal), Joint Work, Accepted

A Robust Control of Two-Wheeled Mobile Manipulator with Underactuated Joint by Nonlinear Backstepping Method

Cihan Acar, Toshiyuki Murakami

電気学会論文誌D 130 ( 6 ) 742-751 2010.06

Research paper (scientific journal), Joint Work, Accepted

A Control of Two Wheels Driven Redundant Mobile Manipulator Using A Monocular Camera System

Hideaki Tai and Toshiyuki Murakami

International Journal of Intelligent Systems Technologies and Applications Vol.8 ( No.1-4 ) 361-381 2010

Research paper (scientific journal), Joint Work, Accepted

Comparison of simulation and experiment on levitation force between GdBCO bulk superconductor and superconducting magnet

S. Arakia, K. Nagashimab, H. Seinob, T. Murakamia and K. Sawaa

Physica C: Superconductivity 469 ( 15-20 ) 1829-1834 2009.10

Research paper (scientific journal), Joint Work, Accepted

Sliding-Mode Control Scheme for an Intelligent Bicycle

M. Defoort and T.Murakami

IEEE Transactions on Industrial Electronics 56 ( 9 ) 3357-3368 2009.09

Research paper (scientific journal), Joint Work, Accepted

Discussions About Measurement Results of Levitation Force and Its Time Relaxation Between GdBCO Bulk Superconductors and Superconducting Magnet With a High Magnetic Field Gradient

Araki, Satoshi;Nagashima, Ken; Seino, Hiroshi;Miyazaki, Yoshiki; Takeuchi, Koji;Murakami, Masato; Suzuki, Tomoyuki;Murakami, Toshiyuki; Sawa, Koichiro

IEEE Transactions on Applied Superconductivity 19 ( 3 ) 2111-2115 2009.06

Research paper (scientific journal), Joint Work, Accepted

Adaptive Control for Virtual Steering Characteristics on Electric Vehicle using Steer-by-Wire System

Y.Yamaguchi and T.Murakami

IEEE Transactions on Industrial Electronics 56 ( 5 ) 1585-1594 2009.05

Research paper (scientific journal), Joint Work, Accepted

A Stabilization Control of Bilateral System with Time Delay by Vibration Index -Application to Inverted Pendulum Control-

T.Ohta and T.Murakami

IEEE Transactions on Industrial Electronics 56 ( 5 ) 1595-1603 2009.05

Research paper (scientific journal), Joint Work, Accepted

A Study on Straight Line Tracking and Posture Control in Electric Bicycle

Y.Tanaka and T.Murakami

IEEE Transactions on Industrial Electronics 56 ( 1 ) 159-168 2009.01

Research paper (scientific journal), Joint Work, Accepted

路面反力のフィードバックによる2輪駆動型移動マニピュレータの安定化制御

野﨑康平，村上俊之

電気学会論文誌D Vol.129 ( No.9 ) 874-880 2009

Research paper (scientific journal), Joint Work, Accepted

ハプティックベダルによるブレーキアシストに基づいた小型電気自動車のスリップ抑制制御

小倉啓，村上俊之

電気学会論文誌D Vol.129 ( No.12 ) 1147-1154 2009

Research paper (scientific journal), Joint Work, Accepted

Null Space Motion Control by PID Control Considering Passivity in Redundant Manipulator

T.Shibata and T.Murakami

IEEE Transactions on Industrial Informatics 4 ( 4 ) 261-270 2008.11

Research paper (scientific journal), Joint Work, Accepted

Stability Improvement of Two Wheel Driven Manipulator Using Nonlinear PD Controller

Pradeep K.W. Abeygunawardhana, T.Murakami

電気学会論文誌D 128 ( 10 ) 1149-1156 2008.10

Research paper (scientific journal), Joint Work, Accepted

v–phi-Coordinate-Based Power-Assist Control of Electric Wheelchair for a Caregiver

J.Miyata, Y.Kaida and T.Murakami

IEEE Transactions on Industrial Electronics 55 ( 6 ) 2517-2524 2008.06

Research paper (scientific journal), Joint Work, Accepted

バックステッピングを用いた電動自転車の姿勢安定化制御

山口高志，柴田剛慶，村上俊之

精密工学会誌 74 ( 05 ) 509-513 2008.05

Research paper (scientific journal), Joint Work, Accepted

Step Passage Control of a Power-Assisted Wheelchair for a Caregiver

S.Tashiro and T.Murakami

IEEE Transactions on Industrial Electronics 55 ( 4 ) 1715-1721 2008.04

Research paper (scientific journal), Joint Work, Accepted

An Approach to Guidance Motion by Gait Training Equipment in Semi-Passive Walking

K. Nakano and T. Murakami

IEEE Transactions on Industrial Electronics 55 ( 4 ) 1707-1714 2008.04

Research paper (scientific journal), Joint Work, Accepted

A Stability Control by Active Angle Control of Front-Wheel in Vehicle System

H. Ohara and T. Murakami

IEEE Transactions on Industrial Electronics 55 ( 3 ) 1277-1285 2008.03

Research paper (scientific journal), Joint Work, Accepted

高磁場勾配超電導マグネットと二つの高温超電導体Gd-Ba-Cu-Oとの間に働く浮上力と浮上力緩和測定

荒木聡史，長嶋賢，清野寛，宮崎佳樹，竹内宏次，村上雅人，鈴木智之，村上俊之，澤孝一郎

日本AEM学会誌 16 ( 02 ) 114-119 2008.02

Research paper (scientific journal), Joint Work, Accepted

Nonholonomic Equivalent Disturbance Based Backward Motion Control of Tractor-Trailer with Virtual Steering

K. Matsushita and T. Murakami

IEEE Transactions on Industrial Electronics 55 ( 1 ) 280-287 2008.01

Research paper (scientific journal), Joint Work, Accepted

冗長マニピュレータにおける受動性に基づく零空間力制御

柴田剛慶，村上俊之

精密工学会誌 73 ( 11 ) 1238-1245 2007.11

Research paper (scientific journal), Joint Work, Accepted

受動性理論を用いた2軸駆動型移動マニピュレータにおける零空間制御

柴田剛慶，村上俊之

電気学会論文誌D 127 ( 11 ) 1109-1116 2007.11

Research paper (scientific journal), Joint Work, Accepted

零空間動作を考慮した柔軟機構を含む冗長マニピュレータの振動制御

佐々木孝治，村上俊之

電気学会論文誌D 127 ( 10 ) 1043-1049 2007.10

Research paper (scientific journal), Joint Work, Accepted

流体モデルを用いた自律移動ロボットの軌道追従制御

宮田淳一，村上俊之

電気学会論文誌D 127 ( 3 ) 315-321 2007.03

Research paper (scientific journal), Joint Work, Accepted

重心変動に基づいた電動車椅子の振動抑制制御

永瀬美和，村上俊之

電気学会論文誌Ｄ Vol.126 ( No.7 ) 1041-1048 2006.07

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，重心変動に基づいた共振比制御による振動抑制制御手法を示している．提案した手法の有効性は実機実験により示されている．

An Approach to Absolute Position Control Based on Object Coordinate

K. Nakano and T. Murakami

Electrical Engineering in Japan Vol.155 ( No.3 ) 53〜61 2006.03

Research paper (scientific journal), Joint Work

　View Summary

本論文では，オブジェクト座標系に基づいた絶対位置制御手法を示している．提案した手法の有効性は実機実験により示されている．

Vibration Control of Flexible Arm by Multiple Observer Structure

M. Hosaka and T. Murakami

Electrical Engineering in Japan Vol.154 ( No.2 ) 68〜75 2006.02

Research paper (scientific journal), Joint Work

　View Summary

本論文では，多重オブザーバ構成によるフレキシブルアームの防振制御手法を示している．提案した手法の有効性は実機実験により示されている．

電動車椅子における入力トルクのセンサレス検出とパワーアシスト

開田有紀子，村上俊之

電気学会論文誌Ｄ Vol.126 ( No.2 ) 137-142 2006.02

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，路面負荷情報に基づいた複数台移動ロボットの負荷分配制御手法を示している．提案した手法の有効性は実機実験により示されている．

ハンドル制御による電動自転車の走行安定化に関する一考察

仁木宏，村上俊之

電気学会論文誌Ｄ Vol.125 ( No.8 ) 779-785 2005.08

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，路面負荷情報に基づいた複数台移動ロボットの負荷分配制御手法を示している．提案した手法の有効性は実機実験により示されている．

多自由度能動ステレオビジョンシステムによる移動物体の３次元位置計測

塩崎智行，　村上俊之

電気学会論文誌Ｄ Vol.125 ( No.6 ) 561-567 2005.06

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，多自由度ステレオビジョンシステムにおいて3次元位置計測の精度を高めるため．カメラ位置を決めるマニピュレータの姿勢制御をその操作性と対象物の可認識性から決定する手法を示している．提案した手法の有効性は実機実験により示されている．

オブジェクト座標系に基づいた絶対位置制御法

中野圭介，　村上俊之

電気学会論文誌Ｄ Vol.125 ( No.6 ) 554-560 2005.06

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，作業対象物に定義されたオブジェクト座標系の情報に基づいた絶対座標系でのマニピュレータの制御手法を示している．提案した手法の有効性は実機実験により示されている．

Trajectory Tracking Control of Mobile Robot by Time-Based Spline Approach

J. Miyata, T. Murakami and K. Ohnishi

Electrical Engineering in Japan Vol.151 ( No.4 ) 65-71 2005.04

Research paper (scientific journal), Joint Work

　View Summary

本論文では，時間スプライン近似法を用いた自律移動ロボットの軌道追従制御手法を示している．提案した手法の有効性は実機実験により示されている．

２次元平行３噴流群における流速分布のフィードバック制御

山本和之，　村上俊之，　菱田　公一

日本機械学会論文集 Vol.70 ( B-No.696 ) 103-109 2004.08

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，2次元平行3噴流郡のフィードバック制御により速度または濃度分布の時間的なばらつきを減少させる手法を示している．提案した手法の有効性は実機実験により示されている．

複数台移動ロボットのフォーメーション制御のための環境情報に基づいた負荷分配制御

辻　和治，村上　俊之

IEEJ.電気学会論文誌 Vol.124-D ( No.8 ) 767-773 2004.08

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，路面負荷情報に基づいた複数台移動ロボットの負荷分配制御手法を示している．提案した手法の有効性は実機実験により示されている．

多重オブザーバ構成によるフレキシブルアームの防振制御

保坂　元明，村上　俊之

IEEJ.電気学会論文誌 Vol.124-D ( No.7 ) 693-698 2004.07

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，多重オブザーバ構成による柔軟構造システムの防振制御手法を提案し，その設計例を示している．提案した手法の有効性は実機実験により示されている．

在宅医療・介護ロボットによる支援

前田　利之，村上　俊之

電気学会誌 (電気学会)  Vol.124 ( No.4 ) 235-238 2004.04

Research paper (scientific journal), Joint Work

　View Summary

本解説では，在宅医療におけるロボット利用の例を紹介し，さらなる応用に関する今後の展望を述べている

パラレルメカニズムの作業空間におけるモーションコントロール

森澤　光晴，村上　俊之，大西　公平

精密工学会誌 Vol.70 ( No.2 )  2004.02

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，パラレルリンク構造を有する２足歩行ロボットの新構造を提案し，同構造に関する運動学解析と制御手法を提案している．提案した手法の有効性は実機実験により示されている．

等価質量と仮想インピーダンス設定による人間と移動マニピュレータの協調動作

山中 絵理，村上　俊之，大西　公平

IEEJ.電気学会論文誌 Vol.123-D ( No.10 ) 1227-1233 2003.10

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，人を誘導するあるいは人が安定に誘導できる移動マニピュレータシステムを実現するため，等価質量行列を用いた人間と移動マニピュレータの協調制御手法を提案している．提案した手法の有効性は実機実験により示されている．

ロバストモーションコントロールにおける力制御と環境認識

村上 俊之

精密工学会雑誌 (精密工学会)  Vol.69 ( No.10 ) 1387-1390 2003.10

Research paper (scientific journal), Single Work

　View Summary

本解説では，ロバストセンシングにおけるオブザーバ利用の現状を紹介し，現在の産業用ロボットシステムへの応用に関する展望を述べている

時間スプライン近似法を用いた自律移動ロボットの軌道追従制御

宮田　淳一，村上　俊之，大西　公平

IEEJ.電気学会論文誌 Vol.123-D ( No.７ ) 778-783 2003.07

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，移動ロボットの軌跡追従制御において時間スプライン近似を用いた手法を提案している．提案手法は，加速度まで連続な軌跡を生成できるため，移動ロボットの滑らかな移動制御が実現できる．提案した手法の有効性は実機実験により示されている．

把持対象物の絶対位置情報に基づいた複数台移動マニピュレータの協調制御

菅原　俊晴，村上　俊之

IEEJ.電気学会論文誌 Vol.123-D ( No.6 ) 689-695 2003.06

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，ＰＳＤの絶対位置情報に基づいた協調マニピュレータの制御手法を示している．提案手法では，協調対象物に設定された座標系において，対象物の絶対位置を検出し，同位置情報に基づいた安定な協調システムの制御構成を提案している．

可変速歩行のためのトルクリミットを考慮した２足歩行ロボットの歩容制御

伊藤　大樹,村上　俊之,大西　公平

IEEJ.電気学会論文誌 Vol.122-D ( No.5 ) 489-494 2002.05

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，２足歩行ロボットの歩行制御に関して，関節のトルクリミットを考慮した制御系構成法を提案している．これにより，路面状況の変化に適応した歩行制御が実現できる．提案した手法の有効性は実機実験により示されている．

Visual Feedback Using Virtual Object Points in Stereo Vision Based Manipulator

D.Purwanto,　T.Murakami, and K.Ohnishi

IEEJ.電気学会論文誌 Vol.122-D ( No.4 ) 403-410 2002.04

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

本論文では，ビジュアルトラッキングシステムのための制御系の構成を提案している。本論文では，位置と姿勢の指令値と速度の指令値を独立に入力することができる点に特徴がある。提案した手法の有効性は実機実験により示されている．

摩擦によるアーム外乱を考慮したフレキシブルマニピュレータの防振制御

鈴木純， 村上俊之, 大西公平

IEEJ.電気学会論文誌 Vol.122-D ( No.3 ) 235-240 2002.03

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，摩擦によるアーム外乱を考慮したフレキシブルマニピュレータの防振制御手法を開発している。提案する手法では，摩擦を推定し，モデル化する．ことで，振動を抑制することができる。提案した手法の有効性は実機実験により示されている．

Robust Motion Control based Projection Plane in Redundant Manipulator

T.Murakami, K.Kahlen, and Rik.W.De Doncker

IEEE. Trans. on Industrial Electronics Vol.49 ( No.1 ) 248-255 2002.02

Research paper (scientific journal), Joint Work, Accepted

　View Summary

冗長ロボットの制御系構成を簡略化するため，投影平面を用いた新しい制御系構成法を提案している．とくに，零空間動作応答の改善と特異点回避が行える投影平面の切替アルゴリズムを提案し，シミュレーションによりその有効性を示している．

ツインドライブシステムを用いたセンサレスバイラテラルロボットマニピュレータ

林田亘宏， 矢向高弘， 村上俊之， 大西公平

精密工学会誌 Vol.67 ( No.11 ) 1834-1838 2001.11

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，モータの摩擦の影響を低減できるツインドライブシステムを提案し，センサレスバイラテラシステムに応用している。本システムでは微力な外力を推定することができる。提案した手法の有効性は実機実験により示されている．

A Motion Control of Mobile Manipulator with External Force

F.Inoue, T.Murakami, and K.Ohnishi

IEEE/ASME. Trans. on Mechatronics Vol.6 ( No.2 ) 137-142 2001.08

Research paper (scientific journal), Joint Work, Accepted

　View Summary

本論文では，移動マニピュレータのための外力を考慮した制御手法を提案した．提案した手法では，外力が加えられても滑らかに動作できる点に特徴がある。提案した手法の有効性は実機実験により示されている．

Position-Velocity-Based Trajectory Control for Manipulator and Its Application to Visual Tracking System

D.Purwanto,　T.Murakami, and K.Ohnishi

IEEJ.電気学会論文誌 Vol.121-D ( No.8 ) 894-901 2001.06

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

本論文では，ビジュアルトラッキングシステムのための制御系の構成を提案している。本論文では，位置と姿勢の指令値と速度の指令値を独立に入力することができる点に特徴がある。提案した手法の有効性は実機実験により示されている．

環境変動を考慮した３次元２足歩行ロボットの可変コンプライアンス

西川直樹，藤本康孝，村上俊之，大西公平

電気学会論文誌D 119 ( 12 ) 1507-1513 2000.12

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

固定座標を有さない２足歩行ロボットにおいて，環境外乱に対して安定な歩行動作を実現するため腰点を基点としたコンプライアンス制御と作業空間オブザーバによる霊空間制御の併用を提案している。提案手法の有効性は実機実験いより実証されている．

A Co-operative Transferring Task by Mobile Manipulators

K.Yasui, T.Murakami, and K.Ohnishi

Journal of Robotics and Mechatronics Vol.12 ( No.6 ) 712-717 2000.06

Research paper (scientific journal), Joint Work, Accepted

　View Summary

移動ロボットを複数台利用した場合の協調制御手法について提案している．基本的に，零空間指令を利用した衝突回避，トルク飽和回避等を含め，多数台への拡張が容易な制御構成となっている点に特徴がある．

推定反力フィードバックと複数の加速度フィードバックに基づくフレキシブルマニピュレータの振動抑制制御

木野卓，森田登，村上俊之，大西公平

電気学会論文誌D Vol.119-D ( No.12 ) 1477-1483 2000.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

１リンクフレキシブルマニピュレータを３慣性系としてモデル化し，従来提案している共振比制御と加速度フィードバックの組み合わせにより，防振のみならずアーム外乱に対してもロバストな防振制御手法を提案している．提案手法の有効性は実機実験により評価を行っている．

外力を考慮した複数台マニピュレータのロバストな協調運動制御

エディレクソノ，村上俊之，大西公平

精密工学会誌 Vol.64 ( No.5 ) 690-694 1998.05

Research paper (scientific journal), Joint Work, Accepted

　View Summary

複数台マニピュレータを用いた安定な把持作業を行なうためには，外力に対してロバストな制御系構成を行なう必要がある．本論文では，作業空間オブザーバと関節空間オブザーバを利用した運動制御系の応答を比較し，両制御系の外力に対するロバスト性の評価を行なっている．

作業空間での外乱オブザーバに基づ　　　いた可変コンプライアンスゲインを有す　　　る複数台マニピュレータの協調制御

エディレクソノ，村上俊之，大西公平

電気学会論文誌D Vol.118-D ( No.1 ) 16-23 1998.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

複数台のマニピュレータを用いて同一の対象物に対する把持作業を実現しようとした場合，安定な把持だけではなく，外力に対しても安定化を行なわなければならない．提案手法では，可変インピーダンスを導入し，安定把持と外力に対するインピーダンス応答を同時に実現する手法を示している．

階層インピーダンス冗長マニピュレータの分散制御

空尾謙嗣，村上俊之，大西公平

電気学会論文誌D Vol.118-D ( No.1 ) 31-37 1998.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

冗長マニピュレータの制御では，その自由度の増加に伴い制御系の構成が急激に複雑化することが知られている．そこで，提案手法ではシステムの分割化に基づいた階層インピーダンスと呼ばれる新しい概念を導入することによって制御系の簡略化を行なっている．さらに本制御系の特徴は，予め階層構造の分割数を設定せずとも制御系の設計が可能な点にある．

インピーダンス制御による2足歩行ロボットの歩行制御

空尾謙嗣，村上俊之，大西公平

電気学会論文誌D Vol.117-D ( No.10 ) 1227-1233 1997.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

　View Summary

環境適応型の移動システムとして注目されている2足歩行ロボットの制御では，固定座標点を持たないため，安定な運動制御系の構成が非常に困難になっている．そこで，提案手法では腰の座標点を中心とした接触脚に対するインピーダンス制御系を構成することによって，安定な歩行を実現している．

ゼロ空間による冗長マニピュレータの拡張コンプライアンス制御

小田尚樹，太田秀樹，村上　俊之，大西公平

精密工学会誌 Vol.63 ( No.10 ) 1432-1438 1997.10

Research paper (scientific journal), Joint Work, Accepted

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従来から提案されている冗長マニピュレータの制御手法では，位置情報に基づいた姿勢制御は問題なく実現することが出来たが，力情報に基づいた姿勢制御を実現することは出来なかった．提案手法では，冗長マニピュレータの姿勢制御において力情報に基づいたコンプライアンス制御を示している．

フレキシブルアームのための推定反力に基づいた力センサレス制御

柴田　昌明，磯村　賢一，村上　俊之，大西　公平

精密工学会誌 Vol.63 ( No.2 ) 198-202 1997.02

Research paper (scientific journal), Joint Work, Accepted

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ロボットの軽量化，高速動作を実現しようとした場合，機械剛性の低下による振動発生を無視することは出来ない．さらに未知対象物との接触を伴なう力制御では対象物の動特性をも加味した力フィードバックを行なわなければならない．提案手法では，上記を考慮に入れた力センサレス制御系の一構成法を示している．

A Robust Control Strategy of Redundant Manipulator by Workspace Observer

N. Oda, T. Murakami and K. Ohnishi

Journal of Robotics and Mechatronics Vol.8 ( No.3 ) 235〜242 1996.03

Research paper (scientific journal), Joint Work

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本論文では，作業空間オブザーバを用いた冗長マニピュレータのロバスト制御手法を提案している．提案手法の有効性は実機冗長マニピュレータの実験により実証している．

オブザーバに基づく冗長マニピュレータの局所トルク最適化

小田　尚樹，村上　俊之，大西　公平

日本機会学会論文集Ｃ Vol.62 ( No.602 ) 48-54 1996.02

Research paper (conference, symposium, etc.), Joint Work, Accepted

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本論文では，冗長マニピュレータの新たな制御手法として，局所トルク最適化指標に基づいた零空間の利用法を提案している．提案手法では，従来から用いられている零空間指令の直接計算を行なわずとも局所トルク最適化を実現できるところに特徴がある．アルゴリズムの有効性はシミュレーションおよび実機実験により検証を行なっている．

Motion Control for Advanced Mechatronics

K.Ohnishi, M.Shibata, and T.Murakami

IEEE. ASME. Trans. on Mechatronics Vol.1 ( No.1 ) 56-67 1996.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

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本論文では，外乱オブザーバに基づいたロバスト制御系の構成手法を制御系設計の立場から明確に示している．さらに，オブザーバを外乱補償だけではなく，物理モデルとの対応付を行なうことによって様々な知的制御に応用した例を示している．

歪めコンフィギュレーション空間に基づくマニピュレータのための障害物回避軌道の高速計画法

柴田　昌明，村上俊之, 大西公平

電気学会論文誌D Vol.115-D ( No.12 ) 1476-1483 1995.12

Research paper (conference, symposium, etc.), Joint Work, Accepted

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本論文では，作業空間での障害物回避軌道を関節空間での各関節への回避軌道に変換するため歪み変換を利用する手法を提案している．これにより，関節空間での障害物回避軌道を高速に算出することが出来る．また，滑らかな軌道を生成するために必要な歪み関数の選定も行なっている．

3次元平行移動体のための障害物回避経路の高速計画法

柴田　昌明，村上俊之, 大西公平

電気学会論文誌D Vol.115-D ( No.12 ) 1476-1483 1995.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

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ロボットの動作計画は，一般にロボットユーザにとって認識の行いやすい作業空間が利用される．しかし，計画された動作経路に障害物が存在する場合の障害物認識や障害物を回避するための回避経路の計算が非常に複雑となる．そこで，本論文では作業空間での障害物回避経路の高速計算アルゴリズムを提案している．本手法の有効性は数値シミュレーションにより検証されている．

作業空間オブザーバに基づく冗長マニピュレータのロバスト制御

小田尚樹，村上俊之, 大西公平

電気学会論文誌D Vol.115 ( No.8 ) 991-998 1995.08

Research paper (conference, symposium, etc.), Joint Work, Accepted

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多自由度ロボットの動作特性をより柔軟なものとするためには，その自由度を増すことが必要となる．そこで，本論文ではより多くの自由度を有する多自由度冗長マニピュレータの簡略化制御系の構成法を示している．特に，制御系の構成空間としてロボットユーザにとって認識の行いやすい作業空間を利用し，ロボットの姿勢制御を行う零空間の計算過程の簡略化手法も提案している．

A Motion Control Strategy Based on Equivalent Mass Matrix in Multidegree-of-Freedom manipulator

T.Murakami, N.Oda, Y.Miyasaka and K.Ohnishi

IEEE. Trans. on Industrial Electronics Vol.42 ( No.2 ) 259-265 1995.04

Research paper (scientific journal), Joint Work, Accepted

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多自由度ロボットの動作制御を行うにあたり，作業空間と呼ばれるロボットユーザにとって認識の行いやすい空間を利用すると，作業空間上での各動作方向の応答を非干渉化することが重要となる．本論文では，この非干渉化制御を実現するにあたり，等価質量行列と呼ばれる行列を定義し，等価質量行列に基づいた作業空間での力制御系の基本構成法を提案している．

A Unified Approach to Position and Force Control by Fuzzy Logic

M.Shibata, T.Murakami, and K.Ohnishi

IEEE. Trans. on Industrial Electronics Vol.43 ( No.1 ) 81-87 1995.02

Research paper (scientific journal), Joint Work, Accepted

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ロボットの動作制御では，位置制御と力制御の動作方向は完全に独立しており，各方向の応答は干渉しないという仮定の下に制御系が構成されている．しかしながら，一般的な動作制御では位置と力の動作方向が同一となるケースも多々見られる．本論文では，位置と力の動作方向が同一となった場合にも制御可能な位置と力の融合制御系の構成手法を提案し，実機実験によりその有効性を示している．

多自由度垂直多関節ロボットにおける絶対位置の一推定法

柴田　昌明，大森　芳行，村上俊之, 大西公平

電気学会論文誌D Vol.115 ( No.1 ) 88-89 1995.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

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ロボット制御において，ロボット動作を定義する幾何学的な位置関係を明確化するため，その絶対位置を知ることは非常に重要である．従来では，ロボットの絶対位置決定は人が行っていたが，本論文ではロボットに作用する重力の効果を利用し，ロボットの絶対位置を絶対定義するための指標としている．提案する手法の有効性は，多自由度垂直多関節ロボットを用いた実機実験により検証されている．

ミリマシン技術による多自由度システムの制御

村上俊之、大西公平

精密工学会雑誌 (精密工学会)  Vol.60 ( No.3 ) 352〜357 1994.10

Research paper (scientific journal), Joint Work

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本解説では，ミリマシン技術による多自由度システムの構成法を提案し，その制御アルゴリズムの紹介を行っている．また、現在の産業用ロボットシステムへの応用に関する展望を述べている．

Parameter Identification of A Direct-　　drive Robot by A Disturbance Observer

Advanced Robotics 　 Vol.7 ( No.6 ) 559〜574 1993.12

Research paper (scientific journal), Joint Work

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ロボット制御において，その動特性を知ることは知的かつ高性能な動作を実現するために必要不可欠である．しかしながら，時変のパラメータを多く含むロボットの動特性を精確に同定することは非常に難しい．本論文では，外乱オブザーバを導入することによって，ロボットの動力学方程式に含まれる時変のパラメータを同定する手法を提案している．提案する手法の有効性は，実機による比較実験により検証されている．

Vibration Control of a 2 Mass Resonant System by the Resonance Ratio Control

K. Yuki, T. Murakami and K. Ohnishi

電気学会論文誌D Vol.113 ( No.10 ) 1162-1169 1993.10

Research paper (scientific journal), Joint Work, Accepted

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機械系の制御においては，その機械的柔軟機構に起因する振動を機械系の応答特性を劣化せずに抑制することが重要となる．本論文では，機械振動系の振動抑制制御を応答特性を極力劣化せずに実現するため，共振比と呼ばれる新たな概念を提案し，その設計手法を提案している．提案する手法の有効性は，フレキシブルジョイントを含む機械駆動システムを用いた実験により示されている．

Structure of a Simulated Muscle System

T.Murakami, H.Ishibashi and K.Ohnishi

Electrical Engineering inJapan Vol.113 ( No.5 ) 102-113 1993.08

Research paper (scientific journal), Joint Work

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近年，急速に発展を遂げた産業用ロボットは，大量生産を目的とした生産ラインに適用されていた．しかしながら，仕様に応じた変種変量生産へと変遷しつつある現在では，より柔軟な動作を行えるロボットの実現に多大な関心が寄せられている．本論文では，筋肉システムをモデルとした多自由度システムの構成法を提案し，その制御アルゴリズムを確立している．

反作用力推定オブザーバに基づいた多自由度ロボットの力センサレスコンプ+A163ライアンス制御

村上俊之, 中村　亮，郁　方銘，大西公平

日本ロボット学会論文誌 Vol.11 ( No.5 ) 165-168 1993.07

Research paper (conference, symposium, etc.), Joint Work, Accepted

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ロボットの制御において重要となるコンプライアンス制御では，ロボットが外界から受ける外力を力センサ等を利用して検出することが必要となる．しかしながら，この場合力センサが設置された個所でのみコンプライアンス制御が有効となる．本論文では，ロボットの任意の箇所でコンプライアンス動作を実現するため，力センサレスコンプライアンスの制御系構成法を提案し，実機実験によりその有効性を示している．

ロバスト制御に基づいた多自由度ロボットの安定性および作業空間での非干渉制御に関する一考察

村上俊之, 大西公平

電気学会論文誌D Vol.113 ( No.5 ) 639-646 1993.05

Research paper (conference, symposium, etc.), Joint Work, Accepted

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多自由度マニピュレータの制御では，マニピュレータ先端の動作制御を精確なものとするため，マニピュレータに作用する外乱を抑制することが重要となる．本論文では，この外乱抑制のために外乱オブザーバを導入している．特に，オブザーバが適用できる制御空間を定義し，各制御空間にオブザーバを適用した場合の制御系の安定性を論じ，数値シミュレーションによりその解析結果の検証を行っている．

作業環境のパラメータ推定に基づいた多自由度マニピュレータの力制御

村上俊之, 大西公平

電気学会論文誌D Vol.113 ( No.4 ) 503-509 1993.04

Research paper (conference, symposium, etc.), Joint Work, Accepted

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接触を伴う多自由度ロボットの力制御では，その力応答特性が接触対象物の動特性に依存する．特に，対象物のスチフネスが高い場合には応答が不安定となりやすい．そこで，本論文では対象物の動力学パラメータをオンライン推定し，推定パラメータに基づいた制御系のゲイン調整則を提案している．提案する制御系の有効性は実機実験により示されている．

Torque Sensorless Control in Multi-Degrees-of-Freedom Manipulator

T.Murakami, F.Yu and K.Ohnishi

IEEE. Trans. on Industrial Electronics Vol.40 ( No.2 ) 259-265 1993.04

Research paper (scientific journal), Joint Work, Accepted

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従来よりロボットの動作制御として，最も重要視されていたのは位置制御であった．しかしながら，ロボットの適用範囲が多様化するにつれ，高精度力制御の実現にも多大な関心が寄せられている．しかしながら，実際の応用においては力応答を検出するための力センサの取り付けが問題となる．そこで，本論文では，力センサレスの制御系構成アルゴリズムを提案し，実機実験にてその有効性を示している．

外乱オブザーバによる多自由度ロボッ　　トの動特性同定法

村上俊之, 大西公平

日本ロボット学会論文誌 Vol.11 ( No.1 ) 131-139 1993.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

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ロボット制御において，その動特性を知ることは知的かつ高性能な動作を実現するために必要不可欠である．しかしながら，時変のパラメータを多く含むロボットの動特性を精確に同定することは非常に難しい．本論文では，外乱オブザーバを導入することによって，ロボットの動力学方程式に含まれる時変のパラメータを同定する手法を提案している．提案する手法の有効性は，実機による比較実験により検証されている．

A Structure of Workspace Force Controller in Multi-Degrees-of-Freedom Manipulator

T. Murakami and K. Ohnishi

電気学会論文誌D Vol.112 ( No.5 ) 453-458 1992.05

Research paper (conference, symposium, etc.), Joint Work, Accepted

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ロボットの制御空間は，主に関節空間と作業空間に大別される．一般に，ロボットを駆動するアクチュエータは関節空間に設置されるが，ユーザにとって認識しやすい制御空間は作業空間となる．そこで，関節空間と作業空間の幾何学的な関係を明確化し，作業空間において高性能なサーボ系を実現している．提案する手法の有効性は，ダイレクトドライブロボットを用いた高精度位置制御の実験により確認されている．

A Structure of Pseudo Muscle System

T. Murakami, H. Ishibashi and K. Ohnishi

電気学会論文誌D Vol.111 ( No.12 ) 1038-1046 1991.12

Research paper (conference, symposium, etc.), Joint Work, Accepted

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近年，急速に発展を遂げた産業用ロボットは，大量生産を目的とした生産ラインに適用されていた．しかしながら，仕様に応じた変種変量生産へと変遷しつつある現在では，より柔軟な動作を行えるロボットの実現に多大な関心が寄せられている．本論文では，筋肉システムをモデルとした多自由度システムの構成法を提案し，その制御アルゴリズムを確立している．

Collision detection and recovery motion for industrial robot based on signal of disturbance observer

T. Murakami, S. Takakura and K. Ohnishi

電気学会論文誌D 　　 Vol.110 ( No.11 ) 1155-1162 1990.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

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ロボットの産業応用において，衝突事故を含め人対ロボットの安全性を確保することは非常に大切である．また，ロボット自身の保守性を向上させる意味でも，作業対象物との衝突を回避することは必要不可欠である．本論文では，衝突を検出するための外界センサを一切用いずに，内界センサにより衝突を検知するアルゴリズムを提案している．さらに，検出された衝突情報に基づいた障害物回避モーションを提案している．

Force feedback control of multi-degrees-of-freedom robot based on acceleration

駒田諭, 村上俊之, 大西公平

電気学会論文誌D Vol.113 ( No.5 ) 325-332 1989.05

Research paper (conference, symposium, etc.), Joint Work, Accepted

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多自由度ロボットの制御を行う上で，そのサーボ特性を最大限に向上させるには，発生加速度までが連続に制御できることが望ましい．本論文では，外乱オブザーバを適用することによって，ロボットの各関節に作用する外乱トルクを相殺し，加速度制御系を実現する手法を提案している．得られた加速度制御系は，力フィードバック制御に適用され，実機実験によりその有効性が示されている．