Positioning of a Flexible Rotating Arm in Water using Sliding Mode Control and Optimal Control.

Abstract

A controller for the manipulator of an underwater robot must position it speedily and accurately, even when it grips an unknown body. In addition, an underwater manipulator system is nonlinear. Therefore, a sliding mode control is suitable, because it has robustness and is able to deal with nonlinear systems. However, chatter due to switching delay of input is a serious problem. In this study, a discrete-time sliding mode control, which is able to suppress the chatter, is applied to the positioning controller of a flexible rotating arm in water driven by a thruster. However, it is found that stable equivalent control cannot be obtained. Therefore a positioning controller is developed using a combination of discrete-time sliding mode control and optimal control. The hyperplane is defined by the feedback gain of optimal control, and the equivalent control is replaced by the optimal control. Then, positioning experiments are carrried out. The performance of the developed controller is confirmed.