Design of a sliding mode observer for sensorless control of SPMSM operating at medium and high speeds

This paper presents design of a sliding mode observer (SMO) for sensorless control of surface-mounted permanent magnet synchronous motor (SPMSM) operating at medium and high speeds. The proposed SMO design uses saturation function instead of signum function which is commonly used in the conventional SMO design. The advantage and novelties of the proposed SMO design lie in the following aspects. First, the proposed design is simple in computing. The saturation function naturally smoothes the estimated back-emf signal, while in the conventional SMO design, an extra low pass filter has to be applied to smooth the discontinuous switching signals. Second, the proposed SMO is easy to implement because the design allows intuitive selection and tuning of observer parameters. Third, the estimation performance is analytically studied and the proposed SMO reveals accurate estimation of the rotor position. The effectiveness of the proposed method is verified through simulations and experimental testings.