論文 - 村上　俊之

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年02月

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年02月

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年

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年

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年

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年

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年

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年

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年

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年

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年10月

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年10月

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年10月

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年10月

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年10月

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年10月

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年07月

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年05月

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年05月

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年05月

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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