A comparative study on the effect of switching functions in SMO for PMSM drives

This paper presents a comparative study on the performance of Sliding Mode Observer (SMO), for various switching functions. SMO is widely used to realize the sensorless control of Permanent Magnet Synchronous Motor (PMSM). Chattering is a major drawback of Sliding Mode observers. Chattering creates oscillations, performance degradation and even instability to the system. Studies on the effect of chattering in PMSM drives with three control laws namely:- Signum function, Saturation function and Sigmoid function are carried out in this work. The complexity introduced by signum and saturation functions is avoided by the sigmoid function. MATLAB/SIMULINK is used as the tool for the study.