Robust output feedback control of PMSM using cascaded sliding mode and high gain observers

This work considers the problem of speed sensorless vector control of a three-phase PMSM using nonlinear control methods. An improved design of continuous sliding mode observer (SMO) is provided with a comprehensive analysis of sigmoid boundary layer to establish its relation with the estimation accuracy. The idea of cascaded SMO and high gain observer (HGO) is proposed for robust speed estimation that reduces chattering, improves accuracy and requires neither a filter nor any boundary layer adaptation. For the speed control problem, a robust integral sliding mode control (ISMC) scheme is developed that works under varying load and parametric uncertainties. Simulation results have been used to evaluate the performance of proposed observers and controller.