Finite element based modeling of a parametrically excited peizo driven ultrasonic micro motor

Ultrasonic micro motors, driven parametrically by the base vibration were previously demonstrated by Kaajakari et al.. These motors consist of a polysilicon stator and rotor, fabricated using surface micromachining technology. The rotor is actuated using a PZT plate at 3.78 MHz., producing speeds up to 500 cycles/s in air. Mechanism of actuation for these motors was conjectured to be due to generation of circumferential travelling waves in the stator, which couples to the rotor, causing its motion. Due to limitation of computational resources, this wasn't verified explicitly using numerical simulations. In this work we present a Finite Element analysis of this system which captures the detailed nonlinear response such as contact and sub harmonic resonant modes and can be used for parametric study.