MPC-based robust contouring control for a robotic machining system

Recently, robot manipulators have been adopted to perform machining tasks, instead of only automation tasks. The key machining task is to follow a desired contour. Therefore, the machining accuracy can be improved by reducing contour error. However, only a few researches concentrate on solving the contouring problem in the robotic machining system. In this paper, a model predictive control (MPC)-based contouring control scheme is proposed for a machining system based on a 5-DOF dual-arm robot. The contouring control problem is transformed into the regulation problem by using the method of equivalent errors. An MPC algorithm is developed to minimize the contour error by optimizing a sequence of control actions under torque constraints. In addition, robustness is upgraded by integral sliding mode control (ISMC). Experiments are carried out for the proposed methods and two other conventional methods. The results show that the proposed control scheme can achieve much better contouring performance than the conventional methods, indicating the effectiveness of the proposed controller.