A Robust Capacitive Angular Speed Sensor

This paper presents a contactless capacitive angular speed sensor for automotive applications. The sensor is based on a passive rotating electrode plated between two mechanically static and electrically active electrodes. Differing characteristics of the charge transfer at various sensor positions is utilized as an input for the determination of the rotational speed. The mathematical model of the sensor further enables the optimization of the sensor characteristics for specific applications. Experimental results from a prototype designed for the speed measurement of a steering wheel show a relative speed error of /spl plusmn/4% at a resolution better than 1/spl deg//s.