Improved Low-Frequency Disturbance Rejection Property for Position Control of PMSM Using Generalized Extended State Observer

In the conventional active disturbance rejection (ADR) controller for position control, a classical third-order extended state observer (ESO) is used, and thus, the system is only able to reject a constant disturbance. Though generalized ESO (GESO) has been reported in speed control systems to enhance the low-frequency disturbance rejection property, its implementation in position control system differs because additional position feedback affects the system dynamic performance. In this article, the ADR controller integrating proportional and derivative (PD) feedback control and a fourth-order GESO is developed to improve the low-frequency disturbance rejection property. The effect of using different position feedback is analyzed. To simplify the design process, the position controller is modified to have a comparable structure to the speed controller, allowing design methodologies used in the speed control system to be applied to the position control system. Experimental results are presented to demonstrate the effectiveness of the proposed method.