Time-Varying Disturbance Observer Based Improved Sliding Mode Single-Loop Control of PMSM Drives With a Hybrid Reaching Law

To simplify the control structure, improve transient performance and disturbance rejection ability of the permanent magnet synchronous motor (PMSM), a hybrid reaching law (HRL) based sliding mode control (SMC) and a time-varying nonlinear disturbance observer is proposed for the speed-current single-loop control. Firstly, a HRL including variable terminal term and variable exponential term based sliding mode control is proposed. The chattering is analyzed, and the results indicate that the convergence time is effectively accelerated and the chattering is reduced. Then, a non-singular terminal sliding mode speed controller with single-loop structure is designed. The present scheme has better transient response and higher tracking performance. Furthermore, to strength the anti-disturbance ability and eliminate the estimated peak at the initial time, a time-varying nonlinear disturbance observer (TVNDO) is proposed to estimate both matched and mismatched disturbances, respectively, and they are carried out to provide disturbances compensation for the proposed controller. Subsequently, the convergence time is calculated, and the stability of the control system is analyzed and proved by the Lyapunov theory. Comparative experiments indicate that HRL+TVNDO has better speed control performance, such as smaller overshoot, faster transient response, higher control accuracy and stronger robustness under different operating conditions.