A MEMS-Based Three-Ring Capacitive Angular Position Sensor with an Absolute Zero Position Feature

In this paper, we propose a novel three-ring capacitive angular position sensor with an absolute zero position feature based on microelectromechanical system (MEMS) technology. The sensor utilizes an inner absolute zero position detection ring to provide easily analyzable zero position information within a 15 degrees angular range. The sensor also incorporates an outer precise angular position detection ring to offer high-precision measurements. The excitation-coupling electrode ring provides a carrier signal and enables noncontact measurement between the stator and the rotor. To validate the design, we fabricated a sensor with a sensing structure outer diameter of 21.3 mm and a thickness of less than 1 mm, and we then tested the sensor with a traveling wave micromotor rotating platform. Experimental results show that the sensor achieved an angular resolution of 0.003 degrees and an online detection accuracy of 0.029 degrees for angular position. The abrupt change in the voltage amplitude caused by the absolute zero position feature exhibited good repeatability and periodicity, and this feature helped the micromotor successfully achieve zero self-calibration with a precision of 0.73 degrees. Our results validate the practicality of the absolute zero position and break through the bottleneck of current MEMS-based capacitive angular position sensors that can only detect angular increments.