Letter to the EditorPMSM sensorless control with separate control strategies and smooth switch from low speed to high speed

This paper proposes a smooth switching scheme with separate control strategies on low speed mode and high speed mode for permanent magnet synchronous motor (PMSM) sensorless control to improve the overall performance in full speed range. Constant voltage/frequency tuning method is used on low speed mode because the rotor position can hardly be estimated precisely at low speed. Along with the increasing speed, the control strategy can be switched to high speed mode smoothly when current and speed meet the given requirements. In this high speed mode, the current tracking with a sliding mode observer (SMO) and speed tracking with a sliding mode controller (SMC) are handled, respectively. Experimental demonstration is presented to show the desired performance in full speed range of the PMSM sensorless control using the proposed control scheme in this paper.