A Novel Absolute Magnetic Rotary Sensor

TLDR

The paper develops an absolute magnetic rotary sensor for measuring motor and joint angles, offering a small, lightweight, robust, and easily integrated solution. The sensor employs two MEMS‑fabricated inductors—one code disc and one signal processor—each containing a large planar spiral coil and smaller coils, with copper sheets on the disc; mathematical analysis and finite‑element simulations guide the design to generate optimal sine and cosine signals for absolute position measurement, which is validated by experiments on high‑ and low‑speed platforms. Finite‑element simulations demonstrate that each inductor can generate optimal sine and cosine signals, and experimental results confirm the sensor’s effectiveness and accuracy.

Abstract

To measure the angular position of motors, robot joints, etc., an absolute magnetic rotary position sensor is developed, which possesses small-size, light, robust, and easy-to-integrate properties. The sensor consists of two inductors, i.e., a code disc and a signal processing part. Both of the two inductors are embedded with a big planar spiral copper coil and four smaller copper coils by employing microelectromechanical system (MEMS) technology, and there are two circles of regular copper sheets listing on the surface of the code disc. In addition, mathematical analyses of the inductor structure as well as the relationships of position and dimension among the coils and the copper sheet are addressed. Finite-element simulation results demonstrate that one group of the optimal sine and cosine signals can be generated by each inductor. Then, the absolute position measurement method is validated by a mathematical method. Finally, experiments are performed on the high-speed and the low-speed testing platforms to assess effectiveness and accuracy of the sensor.