A robust capacitive angular position sensor

Abstract

A noncontacting robust capacitive angular position sensor currently under development for industrial and automotive application is presented. The main advantages of this low-cost system are its simplicity, high accuracy (/spl plusmn/0,2/spl deg/) and resolution (/spl plusmn/0,04/spl deg/) over the range of up to 360/spl deg/, excessive temperature operating capability, insensitivity to dirt, moisture and dew on the sensor electrodes and fast measurement speed. The paper describes the working principle, derives the required relationships for computing the rotor position and discusses the sensor's properties in relation to those of established encoder principles. The sensitivity of the sensor to mechanical errors like radial and axial axis offset, tilted axis, and tilted electrodes is explained. Finally the sensor electronics and its realization is discussed and data obtained from prototype sensors is presented.