Stator-rotor interaction is one of the least understood part of piezoelectric ultrasonic motors. In one particular motor design, the rotor is pressed into contact with a pretwisted beam stator that vibrates both axially and torsionally at an ultrasonic frequency. The stator’s axial vibration modulates the oscillating frictional torque at the stator-rotor interface so that a non-zero net torque is applied to the rotor. Past analysis of the rotor either neglected the axial motion or assumed it to be fixed in space, with the interaction modelled as a periodic spring contact. In this paper, the rotor is viewed as repeatedly separating and colliding with the stator, a situation analogous to the classic problem of bouncing ball on a vibration platform, except that in this case, the platform also has torsional oscillation. A model assuming Coloumb friction, coefficient of restitution, impulsive friction, and uniform contact pressure is used to investigate the dynamics of the rotor.
展开▼
