This paper presents a contactless capacitive angular speed sensor for automotive applications. The sensor is based on a passive rotating electrode placed between two mechanically static and electrically active electrodes. The different characteristics of the charge transfer at various sensor positions is utilized as an input for the calculation of the rotational speed. The main advantages of this low cost system are its capability to operate at high temperatures and humidity as well as its insensitivity to vibrations, dirt, dew and moisture deposited on the three sensor electrodes. 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.
['Tibor Fabian', 'Georg Brasseur']
A robust capacitive angular speed sensor