Composite speed control based on an improved gain-adaptive super-twisting sliding mode observer for a permanent magnet synchronous motor

Abstract

To solve the problem that the speed control system of a surface-mounted permanent magnet synchronous motor is prone to external disturbances and time variations in motor parameters, a non-singular fast terminal sliding mode (NSFTSM) composite control method based on a gain-adaptive super-twisting sliding mode lumped disturbance observer (GA-STLD-SMO) is proposed. First, a mathematical model of PMSM with disturbance is established. Second, the traditional current loop PI control is replaced by proportional integral-Quasi-proportional resonance (PI-QPR) control, so that the current control has better precision. The speed loop controller is designed as a non-singular fast terminal sliding mode controller (NSFTSMC) to avoid singularity and jitter phenomena. Moreover, a sliding mode observer of rotational inertia (SMOORI) is designed based on the perturbations observed by the GA-STLD-SMO. The observed disturbance and moment of inertia are compensated into the speed controller. The stability and convergence of the system in finite time are proven by Lyapunov’s second method, and the performance of the proposed controller is tested and simulated. The final experimental results indicate that in the step response, the control method proposed in this paper is 8.9% smaller in overshooting, 85.8% faster in regulation time, and 20.8% smaller in steady-state error than the control method with the worst control effect among the comparative methods; meanwhile, in the anti-disturbance experiments, the control method in this paper is the smallest in the disturbed bias, and has a superior robustness.