Design and Realization of a Compact High-Precision Capacitive Absolute Angular Position Sensor Based on Time Grating

Abstract

This article proposes a compact and high precision capacitive absolute angular position sensor based on time grating. The sensor consists of a stator and a rotor with three concentric capacitor structures forming primary and auxiliary angular displacement measurement components. The primary component combines a single middle-row capacitive structure with an outer-row capacitive structure to obtain high-precision displacement measurements composed of N measurement periods. The auxiliary component employs a single inner-row capacitive structure with a single spatial period over the 360° measurement range of the sensor in conjunction with a remodulation scheme to obtain displacement measurements composed of N - 1 measurement periods. Combining the measurements of the primary and auxiliary components in a manner similar to vernier calipers yields high-precision absolute angular position measurements. The sensor design and remodulation scheme facilitate good sensor compactness. The measurement performance of the proposed design is evaluated via tests of a prototype sensor with an outer diameter of 60 mm fabricated by printed circuit board technology. The prototype sensor is demonstrated to obtain a measurement resolution of 3" and a measurement accuracy of ±10" over the 360° measurement range of the sensor, indicating that the proposed sensor design has considerable potential for high precision applications.