Development of a 2-DOF Planar Ultrasonic Motor Using Longitudinal-Bending Hybrid Transducer

A novel 2-DOF planar liner ultrasonic motor (USM) based on longitudinal and bending hybrid transducer was proposed and investigated. The USM is a piezoelectric single-oscillator, which consists of a cross orthogonal horn with a driving foot at the intersection. Longitudinal and bending vibration are excited and superimposed in stator and forms elliptical trajectory on the driving foot to cause the stator to move straightly in any direction on the XOY plane. An analytical model of the rigid multi-DOF driving foot trajectories has been developed, thereafter a composite vector driving method was propose and analyzed to realize arbitrary motion direction of the motor. In structure design, the sensitivity analysis of the stator parameters to modal shapes and resonant frequencies was performed using the FEM software ANSYS, and then the longitudinal and bending frequencies were degenerated to 23.9 kHz by choosing the most sensitive parameter. The prototype motion direction agreed well with the proposed composite vector driving method results with an error less than 3 degree.