Rotor Position and Speed Estimation Method for Magnetically Suspended PMSM Based on Modified Sliding Mode Observer

This paper proposes a method of rotor position and speed estimation for magnetically suspended permanent magnetic synchronous motor (PMSM) based on modified sliding mode observer(SMO). In order to weaken the chatting phenomenon, the estimated back-EMF is brought in the current model and a hyperbolic tangent function is used. In order eliminate the high-order harmonic components in the estimated back-EMF, an adaptive low-pass filter whose cutoff frequency varies with the motor electrical frequency is adopted. The stability of the algorithm is proved by the Lyapunov stability theory. Finally, the validity of the method is verified by simulation and experiment.