Influences to the mechanical performances of the travelling wave ultrasonic motor by varying the prestressing force between stator and rotor

Based on a mathematical model, simulation results show how the mechanical performances of the motor are sensitive to the prestressing force. A test bench has been developed in the laboratory for experimental measurements. The motor is driven by a two-phase resonant converter controlled by a DSP in order to realize a flexible control scheme. An hysteresis brake dynamometer controlled by PC make it possible to generate any load profile. Results obtained by measurement confirm the motor sensitivity to the variation of the prestressing force, as shown in the simulation result. Thus, it makes it possible to validate the model and proves that the choice of the prestressing force is very important to optimize the motor design.