Tracking controller design by relay method

For high speed high accuracy 3D machining, the controller design is very important. The object of the control system is to minimize the contour error which is related to the tracking error of each individual servo axis. From the analysis of the tracking error, both the phase delay and the gain difference generate tracking error. In this paper we propose a new relay auto-tuning method for the tracking control. First the critical points on the Nyquist graph of the servo dynamic is identified using the relay feedback method, then the PID controller and the feedforward controller is designed based on the system performance criteria. The simulation and the experimental results show the performance of the control system.