Contour error pre-compensation for three-axis machine tools by using cross-coupled dynamic friction control

This paper focuses on improving the contouring performance for CNC machine tool by pre-compensated strategy. The predicted model of tracking error is established by utilizing the characteristic property of servo structure. Besides considering the frictional damping of transmission mechanism, a LuGre friction force compensated strategy is presented in the presence of both frictions and external disturbances. The contour error model based on the spatial relationship between the tracking error and contour error reduces the complex conventional iterative calculation and presents more flexibility. In order to acquire higher contouring accuracy, an adaptive cross-coupled pre-compensation controller is proposed to regulate the compensated values. Its central structure consists of a Fuzzy PID controller, and a modified particle swarm optimization is used to optimize the bottom parameters of membership functions. Compared with traditional cross-coupled control method, this new strategy has higher control accuracy and better robustness and universality. To validate the effectiveness, the proposed method is verified by several experiments, and the results show that the proposed method remarkably improves tracking performance and reduces contour error.