A state-constrained second-order sliding mode control for permanent magnet synchronous motor drives

The article proposes a state-saturated-like second-order sliding mode (SOSM) algorithm to tackle the state constraint in permanent magnet synchronous motor system, which not only regulates the speed perfectly but also offers the maximum domain of attraction in the predefined state constraints. Unlike the traditional speed controller, the proposed controller is based on the SOSM control theory, and the saturation function is introduced in the design, which means that the controller has the better robustness and is capable of constraining the states, thereby mitigating the risk of excessive transient currents that may pose a threat to circuit safety. The stability of the proposed speed controller is fully proven using the Lyapunov theory. Finally, the validity of the proposed control scheme is verified through simulations and experiments. For a comparative study, three different control strategies, that is, the proposed control, proportional integral control, and conventional sliding mode control, are carried out to demonstrate the superiority of the proposal. These results indicate that the proposed algorithm exhibits the superior performance in terms of robustness, as well as in limiting startup transient current and ameliorating overshoot simultaneously.