On-line self-tuning of PI controllers for high performance PMSM drives

In this paper, a new and practical gain self-tuning method for PI controllers has been formulated and implemented, using the speed control of a permanent magnet synchronous motor (PMSM) drive system as testbed. While the novel strategy enhances the performance of traditional PI controller greatly and proves to be a completely model-free approach, it also preserves the simple structure and features of PI controllers. The essential idea is: (1) according to the system dynamics to step variation, define a performance index to evaluate the system response; (2) based on the monotonous relationship between the performance index and an intermediate PI gain parameter, the intermediate PI gain parameter is estimated with a modified binary search algorithm in the direction of improving the performance index; and (3) finally PI gains are calculated and renewed according to the estimated intermediate gain parameter. Experiments have been thoroughly carried out to test the proposed method under different conditions. Besides being simple and easy to implement for real-time applications, the proposed method also possesses the features such as versatility, stability and effectiveness.