Investigation of the Linear Alternative of the SMO Switching Function used for Self-Sensing High-Speed PMSM

This paper presents a reduced-order observer structure for self-sensing control of a Permanent Magnet Synchronous Machine (PMSM). The design is based on the classical Sliding Mode Observer (SMO) but it uses a linear observer gain instead of the switching function. This solves several problems faced by the SMO and can be designed in systematic way. Moreover, it delivers a more accurate estimation of the rotor angle even at high-speeds and low calculation frequencies. Design hints and a suitable rule are given. The properties of the proposed observer are compared to traditional implementation of the SMO with a signum switching function. Experimental results of a high-speed PMSM are presented to validate the approach.