A Non-Smooth Composite Control Approach for Direct Torque Control of Permanent Magnet Synchronous Machines

Considering the effects of disturbances in permanent magnet synchronous motor (PMSM), in this paper, a non-smooth composite control approach, which includes finite time disturbance observer (FTDO) for feedforward compensation and finite time control (FTC) for feedback control, is proposed to improve the anti-disturbance performance of PMSM. First, the FTDO is used to estimate the lumped disturbances, such as friction, parameter perturbation, and load variation. Then, the observed value is added to the speed controller as a feedforward compensation to eliminate the effect of disturbance. Second, FTC is introduced into the feedback control design part. In the end, by utilizing Lyapunov theory, the stability analysis of the overall closed-loop system is demonstrated. In contrast to the conventional asymptotically stable control strategy, the proposed composite scheme can provide not only a faster dynamic response but also a stronger capacity of disturbance rejection. The simulation and experimental tests are presented to demonstrate the superior properties of the proposed control scheme.