Embedded Position Estimation Using Tunnel Magnetoresistance Sensors for Permanent Magnet Linear Synchronous Motor Systems

Abstract This paper presents an embedded position detection method for permanent magnet linear synchronous motor (PMLSM) using magnetic sensor. Tunnel magnetoresistance (TMR) sensors with the single axis sensitive direction are chosen as the sensing element to show the practicality. Differing from the common magnetic displacement sensor packaged with a magnetic grid, the proposed scheme takes the magnet of the PMLSM as a part of the sensor. With the motion of the PMLSM, TMR sensors separated by half of the pole pitch and excited with alternating voltages are utilized to pick up the changing magnetic field. The phase shift of output signals is proportional to the displacement of the PMLSM. High frequency time pulses are served as a measurement standard to realize the phase detection and the position is measured by counting the time pulses. From the industrial perspective, the proposed method is advantageous since it is high resolution, non-contact, and miniaturization.