With the development of portable intelligent instrumentations, the demand for high-precision, absolute-positioning, low-cost and compact-size angular position sensors has substantially increased. In this paper, a novel miniaturized capacitive angular position sensor based on time-grating, which adopts a reflective structure to realize absolute position measurement and simultaneously achieve high-precision, is proposed. The sensor is comprised of a stator and a rotor both covered with three rings of metal electrodes. The middle ring of the sensor adopts a single-row structure to obtain a high-precision initial travelling signal and reflect it to the stator through the outer ring. The inner loop obtains the final travelling signal through the second modulation signal. The phase difference between the final travelling wave signals and initial travelling wave signals varies periodically with a period of 360° when the rotor rotates; thus, this phase difference can be used to realize the coarse absolute position measurement. Phase detection is realized using the time pulses interpolation technology of time-grating, and the angular displacement is measured with time. High-precision absolute angular positioning is achieved through a compact structure. A prototype sensor with an outer diameter of 60 mm and an inner diameter of 24 mm is fabricated by printed circuit board technique to evaluate the performance. Experimental results show that the proposed sensor achieves a ±3″ measurement accuracy over an entire circumference. Moreover, the rotor is wireless owing to the reflective structure, which has a wider range of applications in engineering.
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