Decoupling Control of Nonlinear Systems Using Disturbance Observer. Decoupling Control of DD Robot in Task Space.

Abstract

Almost all real systems are nonlinear and their mathematical models cannot be obtained exactly. In particular, it is very difficult to design control systems for nonlinear multi-input and multi-output systems such as robot manipulators because of their nonlinear interactions. In recent years, control methods of exact decoupling and exact linearization have been widely investigated by using differential geometric approach. But they have problems; they need exact models of systems and controllers become very complicated. In this paper, we firstly propose a method of decoupling control for general class of nonlinear systems by disturbance observer. The proposed method can decouple nonlinear systems not exactly but approximately, but controllers become very simple, and it is applicable even if exact models of systems are not available. Secondly, we propose a method of decoupling of robot manipulators by applying the proposed method. There have been a lot of studies on decoupling control of robot manipulators based on disturbance observers. But most of them realize decoupling of robots only in joint coordinate space. On the other hand, the proposed method can easily realize decoupling of robots in the task coordinate. Finally, in order to illustrate performance of the proposed method, experimental results by using a 3-degree-of-freedom series DD robot are shown.