Design of Improved Integral Sliding Mode Observer for Surface-Mounted Permanent Magnet Synchronous Motor

Abstract

An improved integral sliding mode observer (SMO) is proposed for the double closed-loop control system of Surface-Mounted Permanent Magnet Synchronous Motor(SPMSM) in this paper. By observing the stator current, the extended back Electromotive Force(back-EMF)of the motor is estimated, and the position and angle of the rotor are obtained by using the Phase-Locked Loop (PLL) structure. The improved integrated SMO control system not only ensures the system to converge to the equilibrium point in finite time, but also reduces the steady-state error. A new exponential reaching law is also designed in which the sgn (s) of the constant velocity term is replaced by the sigmoid (s). For improving the reaching speed, the gain adaptive function is added to the exponential term of the approaching law to make its coefficient change with the system state. Simulation results compared with the traditional SMO show that the control system based on the improved SMO can reduce observation error, enhance robustness, and suppress chattering phenomenon.