Electromechanical conversion in an ultrasonic motor using a non-axisymmetric (1,1) mode

An ultrasonic motor using a non-axisymmetric (1,1) mode has been built in our laboratory. Such motors are based on a double energy conversion: the piezoelectric material in the stator converts electrical energy into mechanical vibrations; a rotor pressed on the vibrating stator moves due to the frictional force at the interface. These two conversions have been modelled by using electromechanical circuits derived from the Mason model. The mechanical performance of the whole motor has been experimentally determined. The losses which occur during the electromechanical conversion have been studied. Our work points out that they depend on the ratio between the inner radius and the outer radius of the annular ceramic plate used for the stator and the electromechanical characteristics of the chosen ceramic material. A criterion based on an electrical model is given in order to make a better choice between different PZT materials.