Disturbance-Observer-Based Sensorless Control of PMSM Using Integral State Feedback Controller

The objective of this article is to design robust speed control of a permanent magnet synchronous motor (PMSM). The mathematical model of the PMSM is highly nonlinear with uncertainties and disturbances. The most obvious method is to estimate these disturbances and design a robust controller to attenuate the effect of disturbances from the output. In this article, the load torque, which typically occurs as disturbance in the servo system, is estimated using a disturbance observer (DO). A nonlinear model of the PMSM is linearized using the Jacobian linearization around an operating point, and a state feedback controller with an integral term is designed at this operating point. Novelty of the proposed method lies in the way the DO is used to update this operating point, which is similar to the gain scheduling approach. To extend this method for a sensorless operation, a sliding-mode observer is used with the DO in cascade. The proposed scheme is validated using simulations on MATLAB/Simulink and an experimental setup using TMS320F28027. The results show improved performance as compared to traditional methods over a wide range of speed.