Position control for PMSM servo system using non-smooth feedback and disturbance estimation compensation

In order to improve the control precision and disturbance rejection property of the PMSM position servo system, a novel composite controller is presented in this paper. First, a non-smooth feedback (NSF) control technique is employed to replace the conventional PI controller in the feedback path of both the position and speed loops. Second, considering the unavoidable and unmeasured disturbances in real applications, a feedforward compensation is adopted in the speed-loop, which is based on an extended state observer (ESO) to estimate unknown disturbances. In addition, a differential feedforward control is introduced in the position-loop to attain a better tracking performance. Simulation and experimental results show that compared with the conventional feedback control, the proposed method achieves a better position response and is more robust to load disturbance.