PIEZOELECTRIC POSITION SENSOR FOR ULTRASONIC EFM MOTORS

In the last few years, attempts have been made to miniaturize ultrason ic motors by using silicon micromachining techniques. In particular, t he motion of small plates or the rotation of lenses using travelling w aves on thin piezoelectric activated diaphragms has been observed. We have recently reported on a new micromachined ultrasonic motor called the elastic force motor (EFM). In this new family of motors, the flexu re waves of a circular diaphragm are converted to a net torque by elas tic tilted legs attached to the rotor. The main interest for this type of micromechanical device is its potential use in microsystems. For t his type of application, detection of the angular position of the roto r will be of crucial importance. In this paper, we report on prelimina ry results of the influence of a point contact force applied on a flex ural vibrating plate. Electrical detection of this force by an integra ted piezoelectric sensor is also described.