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In previous research, the back-forward drivability of load-side torque control system based on a motor-side acceler­ation control has proven to be high, but contact motion has not yet been realized in human-robot interaction such as powered exoskeleton and direct teaching. To address this issue, this study proposes a load-side torque control system that achieves both bouncing suppression and human-interaction. This paper focuses on load-side acceleration because the bouncing motion at environmental contact and the human-robot interaction motion are able to be evaluated to its performances intuitively. Human-robot interaction is applied in low-frequency, and bouncing suppression is applied in high-frequency. The experimental results verify the effectiveness of the proposed method.

To operate two-inertia systems with high speed and precision, a control method to suppress mechanical resonance is required. A conventional current control system consists of a proportional integral controller and decoupling controller, and the conventional current control system has high motor torque control performance. However, the conventional current control system tends to excite mechanical resonance. This paper proposes a new current control system to suppress the resonance of a two-inertia system by using the cross-coupling term of a surface permanent magnet synchronous motor. The proposed control system consists of a proportional controller and voltage disturbance observer to estimate the voltage disturbance without including the cross-coupling term that is used as a damping control. The effectiveness of the proposed control system is validated by numerical simulations and experiments.

In this paper, the aim of precise motion control, considering thrust vector selection method that allows Surge, Sway and Yaw motion of the 4-axis driven electric ship. As a thrust vector selection method, we propose a method of actively changing the position of the center of thrust vector. The proposed method controls Yaw angular velocity and Sway velocity. Compared to the conventional method of Yaw angular velocity control, confirm the improvement of the motion performance of the proposed method. By experiments, the usefulness of the proposed method is confirmed.

This paper proposes force sensorless force control using the notch-type friction free disturbance observer. The force control is structured by acceleration and speed controllers. The reaction force estimation system reduces the effect of the static friction using a dither signal. A conventional friction free disturbance observer becomes unstable when a low-frequency dither signal is applied. To solve this problem, the notch-type friction free disturbance observer is employed, which allows the use of low-frequency dither signals. This paper explains the difference between the conventional design method and the proposed design method. The validity of the proposed notch- type friction free disturbance observer is verified through the experimental results using an actual industrial robot.

This paper considers the contact phase in a sensorless torque control system for a two-mass system. A plant system is a two mass system with an environmental switch. The environmental switch is used for considering unstable contact behavior. The state observer (SOB) and zero-order disturbance observer (ZODOB) are used to estimate the state variable of a plant system. In sensor-less torque control system, the ZODOB has better performance than the SOB. When plant system is not in contact with the environment the estimated value using the SOB is not good for control system. It makes control system becomes instability in some cases. When the ZODOB is fed back to torque control system, the stability of control system is preserved. Experiments are performed to confirm the effectiveness of using the ZODOB in sensor-less torque control system.