Embedded position detection for permanent magnet synchronous motor with built-in magnets

Accurate rotor position is essential for a permanent magnet synchronous motor (PMSM) to execute vector control. Due to the big volume, the resolver and the encoder as standard position sensors cannot be used in the space-limited application. The sensor-less methods whose characteristic are sensitive to the parameter of the motor cannot be used in mass-produce. Therefore, this paper presents tunnel magnetoresistance (TMR) sensors as a sensing element embedded into the PMSM to detect the magnetic field applied by the built-in magnets and high-frequency time pulses served as a measurement standard to measure the position. TMR sensors excited by the altering voltage are integrated with the PMSM without taking up extra space. Besides, the rotation position is measured by counting the time pulses corresponding to the phase shift of the TMR sensor's output signal, which is a simple and effective method to detect the position. Related design aspects include the corresponding signal circuit, and the sensing element is introduced in detail in this paper. Experimental results prove the validity of the proposed method, and multi-group TMR sensors are used to get higher detection accuracy. Although developed for the PMSM, the presented embedded position detecting approach can be used for where the space is limited or the other types of actuators to make it integration.