Speed sensorless control of a linear synchronous motor using state observer on d-q reference frame

Long stator linear synchronous motors (LSLSM) are being used widely in many areas, for its high dynamic response, robustness and accuracy. But because linear structure increases the cost and complication of position sensor, speed sensorless control methods become more important for linear motor than rotary motor. The paper presents a modified estimation method to get velocity and position of mover based on d-q rotary coordinate system. This method utilizes a reduced order observer to estimate electromotive force (EMF) in d-q frame, and then extracts phase error between estimated position and real position by EMF. A PI regulator is followed to regulate phase error to zero and output mover velocity. Then position is calculated by integration of velocity.