Investigation of Displacement and Force Characteristics of Piezoelectric Multilayer Actuator for Active Preload Control System in Ultrasonic Motors

The paper represents both numerical simulations and experimental investigations of a piezoelectric active preload system that is foreseen to be applied to the active preload control system of rotors of ultrasonic piezoelectric motors. The investigated preload system is based on the piezoelectric multilayer actuator and disc-shaped spring, which is attached at end of the actuator. The total volume and mass of the preload system are 275 mm³ and 4.3 g, respectively. The results of investigations demonstrate strong agreement between the experimental and simulation data, showing nearly linear displacement and output force responses within an input voltage range of 20 V to 75 V in the frequency range from DC to 200 Hz. In the investigated ranges, the active preload system is able to ensure up to 1 N force with displacement amplitude up to 30 µm, which were obtained at a driving signal of 75 V. These results show that the investigated active preload system can replace passive preload devices in ultrasonic piezoelectric motors which are subjected to strict requirements in terms of their mass and mounting volume.