Rotor Position Detection Based on Magnetically Coupled Resonant Principle and Its Implementation

Rotor position sensing is necessary in electric traction applications to enhance the reliability of control, and inductive-based sensors such as resolvers and eddy current sensors are most used due to their working well in harsh environment. Since the existing methods show some limitations, it is significant to explore the new type of sensor to improve the performance. This paper introduces a novel angular sensor with novel structure based on magnetically coupled resonant principle. It is made using printed circuit board (PCB), consisting of the excitation circuit and receiving circuit located at the stator side, and the feedback circuit located at the rotor side. Besides, the coil of each circuit is in series with corresponding capacitors to make the whole system work at the same resonant frequency. With this structure, the sensor has sufficient output gain without ferromagnetic material used. The working principle and structural design of the sensor are described in detail, and in the finite element analysis (FEA) the coil structure is calculated to preliminarily verify the sensing accuracy, finally a sensor prototype was fabricated for precision test and its sensitivity test with respect to the stator's misalignment. The experiment results show that the peak-to-peak value of the error is within 1° (electric angle) under quasi-static state, 2.234° (electric angle) at the speed of 20000rpm, and the output gain is about 2.6. Moreover, the test of sensitivity to misalignment shows that the air-coupling-based sensor has good sensing stability with non-negligible mounting shift of the stator, to reflect the reliability in harsh conditions.