Design And Experimental Research On An Ultrasonic Motor With Composite Bending And Torsional Vibration Modes

Ultrasonic motors (USM) are new actuator integrated mechanical vibration,materialogyphysics, physics and many other subjects. They have a better applicationvalue in many fields as the advantages of high accuracy and quick response ability, etc.However they have not been industrialization because of the general weaknesses such aslow efficiency, small torque,and short lifetime problem, etc.Recently, the bolt-clamped composite type ultrasonic motors, which are alsoknown as standing wave ultrasonic motors, are usually to implement the liner motionthat is becoming the hotspot in USM field. The composite type standing wave ultrasonicmotors, always make use of the d33or d15mode of piezoelectric ceramic(PZT), whichhave characteristics of high piezoelectric constant and eletromechanical couplingcoefficient, high mechanical quality fator and low dielectric loss tangent.The tangentially polarized PZT of torsional vibration is excited by d15mode. It hasmany advantages, such as large piezoelectric strain constant and high eletromechanicalcoupling coefficient (k15), which is ideal for driving directly. However, the research onthe USM of torsional vibration is still less, especially for the ultrasonic motor withcomposite bending and torsional vibration modes. Therefore, in this paper, a new typelinear ultrasonic motor using the bending and the torsional mode is proposed. In thisnew design, bending vibration is excited by d33mode, which controls the preloadpressure, and torsional vibration is excited by d15mode, which generates the drivingforce. the motor has a large advantage in the mechanical output characteristics andelectromechanical coupling efficiency.In this paper, the motor structure of the ultrasonic motor with composite bendingand torsional vibration modes was designed firstly. The polarization mode andinstallation arrangment of the PZT were shown. The formation of elliptical vibratingtrace and the actuating mechanism of the motor was analyzed. The selection ofmaterials of each parts and the equivalent circuit were researched. Then resonancefrequency quation of torsional vibrations was derived and parametric model of the statoris established using ANSYS APDL. After the degeneration of resonant frequencies ofthe two vibration modes was accomplished through the structure design of compoundindex type horn, the characteristics and trajectories of driver feet are studied by transientanalysis. Finally, a prototype was fabricated and tested. The motor gained the no-loaddriving speed of380mm/s and a maximum thrust force of13N.