An Improved Delay-Suppressed Sliding Mode Observer for Sensorless Vector-Controlled PMSM

This paper presents a delay-suppressed sliding mode observer (SMO) to observe the real-time rotor position of a permanent magnet synchronous machine (PMSM) controlled by vector control (VC) algorithms. Firstly, in order to solve the low pass filter (LPF) delay problem existing in the traditional signum function-based sliding mode observer (SMO), a brand-new hyperbolic function is initially selected as the switching function. Because a hyperbolic function with proper boundary layer is capable of reducing the chattering phenomenon of a SMO, it is not necessary to re-employ LPFs to eliminate the adverse impacts of chattering on the position estimation accuracy. In order to ensure the reachability and stability of the hyperbolic function-based SMO, the observer gain is calculated by the means of a Lyapunov function in this paper. Secondly, to solve the problem of calculation delay caused by digital computation, a current pre-compensation scheme based on dual-sampling strategy in one switching period is proposed. After compensating the calculation delay, the accuracy of position estimation as well as the motor control performance can be improved. Finally, the proposed SMOs with and without delay compensation are verified by both simulation and experiments which are conducted on a three-phase 1.5kW PMSM drive prototype.