Design and Implementation of Sensorless Control Drive System for Permanent Magnet Synchronous Motor

In order to realize the wide speed range of the sensorless control for permanent magnet synchronous motor (PMSM), a composite control strategy of $I/f$ startup control combined with the sliding mode observer (SMO) control is proposed. In low-speed region, $I/f$ control with speed open loop and current closed loop is adopted. The rotor is accelerated from standstill to a certain speed by following gradually increasing frequency. In high-speed region, the SMO is used to achieve sensorless control, where the saturation function is adopted to decrease the chatter. When the rotor speed reaches the target value, the smooth transition of the two control strategies is achieved by designing a proper transition status. As a result, the experimental results verify that the sensorless control system can work reliably and stably with smooth switching transition and good control performance.