A smooth and fast transition method for PMSM SMO based sensorless control

A simple sliding-mode back electromotive-force (EMF) based speed sensorless control for permanent magnetic synchronous machine (PMSM) is realized in this paper. In order to perform the smooth and fast transition from the open-loop control to the closed-loop field oriented control (FOC), this paper analyzes the system behavior in the vicinity of the switching instant, then proposes a novel transition method for switching process. The method adopts an integral controller to regulate the Iq current reference, during the transition process, according to the deviation between estimated angle and reference angle. The method can provide fast and smooth transition, and it is also easy to be implemented by DSP. The simulation and experiment results show the validity and feasibility of the proposed method.