PMSM Speed Control using Enhanced Discrete Sliding Mode Control under Disturbance

Disturbance rejection ability of controller is important to make precise control of Permanent Magnet Synchronous Machine (PMSM). In this paper, to improve disturbance rejection ability, Sliding Mode Control (SMC) is proposed. Discrete time is used to design instead of continuous time. To simplify the controller design, the controller is split into two loops that are current loop as inner-loop and speed loop as outer-loop. Discrete Sliding Mode Current Controller (DSMCC) is proposed for the current loop. Meanwhile, Discrete Sliding Mode Speed Control (DSMSC) and Discrete Integral Sliding Mode Speed Control (DISMSC) are proposed for speed loop. Moreover, Discrete Sliding Mode Observer (DESMO) with modified reaching law using the sigmoid bipolar function is used to estimate external disturbance. The estimation of disturbance is added into the speed loop controller to reject the influence of disturbance. To validate the proposed algorithm, simulation is carried out. Comparison between DSMSC with DISMSC result that the system with DISMSC is more robust with RMSE 4.9037 than DSMSC with RMSE 4.9038. While the comparison between proposed DESMO and conventional DESMO result that proposed DESMO can reduce chattering better than conventional DESMO.