Generalized Proportional Integral Observer Based Sliding Mode Control for Biaxial Motion Control System with Mismatched Disturbances

In the biaxial motion system, nonlinearities and mismatched disturbances always have adverse effects on the contouring accuracy, which are often neglected. Most of existing advanced control methods are developed only to suppress matched disturbances. In this paper, the necessity of taking the contour error as the control target is explained. Then, four generalized proportional integral observers (GPIOs) are developed to estimate both matched and mismatched lumped disturbances. Then, based on contour error, a sliding mode controller is developed for the biaxial motion system. By introducing the disturbance estimations into the modified sliding surface design, a composite controller is proposed. The proposed method effectively improves the contouring accuracy and suppress the mismatched disturbances, while the chattering caused by large switching gains is alleviated. The stability analysis of the system is established by means of the Lyapunov function. Finally, to demonstrate the superiority and effectiveness of the controller, simulation results of the biaxial motion control system are presented in various working cases.