Auxiliary Linear Extended State Observer for Position Tracking Control of PMSM Based on Sliding Mode Control

An auxiliary linear extended state observer and a position-velocity integral sliding mode controller based on improved reaching law are proposed to address position-tracking control issues in servo systems. Servo systems are always affected by internal or external disturbances, making it hard to meet the requirements of precise and fast positioning. Firstly, sliding mode control due to its merit of insensitivity to parameter variations and fast response is introduced. Secondly, an auxiliary linear extended state observer is designed for the estimation of the time-varying uncertainty, which makes up for the disadvantage of only robust to matched disturbances in sliding mode control. Next, to address the chattering issue in the sliding mode control method based on the exponential reaching law, the switching function is substituted with the saturation function, while introducing a power term of the sliding surface magnitude to track the input reference faster, resulting in an improved reaching law. Finally, the proposed approach is compared with other methods. Numer-ous simulation results demonstrate that the method we proposed improves positioning accuracy, tracks the input reference faster, reduces chattering, and has a certain robustness.