Hiroaki Ichii

A Cascaded Feedback Control Scheme for Trajectory Tracking of Robot Manipulator Systems with Actuator Dynamics

In the case of control for nonlinear mechanical systems, which have complex actuator dynamics, the total system becomes high-order and nonlinear. Generally speaking, it is not easy to tune feedback gains for state feedback. In this paper, we propose a feedback control scheme for motion control of nonlinear high-order systems. We prove that the proposed scheme can improve the trajectory tracking performance of a robot manipulator system with actuator dynamics. Moreover, some simulation results demonstrate the effectiveness of the proposed control scheme.

Planning and Control of Robot Motion based on Time-Scale Transformation and Iterative Learning Control

Usefulness of time-scale transformation and iterative learning control for nonlinear complex dyanamics is presented in this paper. In the proposed method in this paper, ideal feedforward input patterns obtained through iterative learning control can be transformed to another ideal feedforward input patterns by using time-scale changing. This method is useful when a robot has contact with mechanical environment which has nonlinear impedance or complicated dynamics. Moreover, it is claimed that the proposed method is applied to optimal control without parameter estimation Finally, we propose a motion planning method based on time-scale transformation and iterative learning control to realize desired force patterns between a robot and mechanical enviroment with nonlinear impedance.

Trajectory Tracking Feedback Control of Robot Manipulators with Coupled Dynamics of Force and Position

When a robot manipulator contacts an object, a Coulomb friction force occurs in the motion direction on the surface. Therefore, it seems that the previously proposed control methods can not obtain good control performance with trajectory tracking. This paper proposes a new trajectory tracking control method for cases that there is a Coulomb friction force between a robot and an object. It is mathematically proven that trajectory tracking errors between actual motions and desired motions can be effectively reduced as position and velocity feedback gains increase. The trajectory tracking performance of the proposed feedback control method is demonstrated by some simulation results.

A coupling constraint force problem with Coulomb friction between an end effector of a robot and a constraint surface and its solution

This paper points out that there is another singular point with Coulomb friction when an end effector of a robot contacts a surface of an object. The characteristics of Coulomb friction singular points are revealed by both of theoretical and numerical approaches. From the results, it is shown that contact forces dramatically increase as the robot closes Coulomb friction singular points. In this paper we also propose a new control method to overcome problems of Coulomb friction singular points. The effectiveness of the proposed method is demonstrated by some simulation results.