Sensorless Position Control of SPMLSM based on High-Gain Observer

摘要

—This paper presents a novel sensorless position control for a surface permanent magnet linear synchronous motor (SPMLSM). The position and speed of the SPMLSM drive is obtained through a closed loop observer by only measuring phase voltages and currents. Estimation of speed is done using difference between estimates of the current derivatives in the dq frame, which calculated two different ways: one using a high-gain observer, another using the motor model. Estimation of the mover position is done through integrating the estimation of speed. In addition, an initial position of the SPMLSM is the key to starting smoothly, therefore, an estimation method of initial position for the SPMLSM is also developed in this work. The principle of the estimation is based on low frequency voltage injection. The amplitude and phase of the voltage is controllable. When a rotating voltage vector is injected to the motor at standstill, there is a microinching when the voltage phase is line to the direct axis of the motor. Then the current will decrease due to the back electromotive force. The initial mover position is identified by this change. Sensorless control of a SPMLSM based on the proposed strategy has been investigated by comprehensive computer simulation. The experimental testing results verify the effectiveness of the proposed approach.