論文 - 村上　俊之

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年

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年

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年06月

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年06月

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年03月

ISSN  9781728144429

　概要を見る

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年03月

ISSN  9781728144429

　概要を見る

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年03月

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年03月

ISSN  21871094

　概要を見る

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年

ISSN  2187-1094

　概要を見る

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年

ISSN  2169-3536

　概要を見る

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年

ISSN  2169-3536

　概要を見る

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年

ISSN  2169-3536

　概要を見る

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年

ISSN  21871094

　概要を見る

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年12月

ISSN  9781728162249

　概要を見る

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年10月

ISSN  9781728154145

　概要を見る

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年10月

ISSN  9781728154145

　概要を見る

© 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年10月

ISSN  9781728154145

　概要を見る

© 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年10月

ISSN  9781728154145

　概要を見る

© 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年10月

ISSN  9781728154145

　概要を見る

© 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年10月

　概要を見る

© 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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