Natural Frequencies Of Stator Research Articles

A novel model of ultrasonic motors with effect of radial friction in contact mechanism

This paper is concerned with a development of the contact model of traveling wave type rotary piezoelectric ultrasonic motor, which takes into account a new three-dimensional operation mechanism between the stator and rotor. First the vibration characteristics and harmonic response of the stator are analyzed based on the mathematical model. With the derivation of the kinematical equations representing the motion of the stator surface points, the three-dimensional driving mechanism is investigated at the contact interface between the stator and rotor. We found that the distributed contact forces have not only the axial and circumferential components but also the radial component at the interface. The traditional contact model should be improved by the consideration of radial friction at the interface. So we defined driving angle α, which describes how the radial friction distributes at the interface. Furthermore it is shown that the radial friction can lead to considerable energy losses. A set simulation of motor performances based on the proposed contact mechanism is found in good agreement with experimental results. We also tried to explain how the applied normal preload force on rotor affect the natural frequency of stator by the contact interface, as is shown in our experiments.