Integrated Control Strategy for Nonlinear PID Cross-Coupling Contour Error Compensation Based on Active Disturbance Rejection Control

Improving the contour control accuracy of multi-axis servo system is one of the most significant applications of modern CNC machining. At present, the cross-coupling control (CCC) and proportional integral differential (PID) control are the most popular method to reduce contour error for multi-axis contour following tasks. Since the traditional CCC method has poor contour tracking accuracy for free-curve trajectory, and the traditional PID control system has poor interference immunity and robustness, a novel integrated control strategy of cross-coupling contour error compensation based on active disturbance rejection control, which consists of a free-curve contour error real-time estimation model, a NURBS interpolator, a novel non-linear PID (NLPID) position servo controller for position loop feedback control and contour error compensation (TNP-ADRC) and a variable gain cross-coupling controller based on non-linear PID control, is proposed. Several simulations are carried out in Matlab/Simulink environment. Firstly, the tracking performance of the proposed TNP-ADRC is simulated by the square wave signal, and then the non-uniform rational B-spline (NURBS) curve is used to simulate the contour accuracy. The simulation results indicate that compared with the commonly used integrated control strategy of cross-coupling contour error compensation which consists of CCC method and PID method, the proposed integrated control strategy can not only effectively improve the robustness and anti-interference ability of the system, but also significantly improve the contour control accuracy of the biaxial motion control system.