Piezo Electric Ultrasonic Motors

By • It has been known for more than 30 years. • The first ultrasonic motor was introduce by v.v lavrinko in 1965. • An Ultrasonic motor is a type of electric motor formed from the ultrasonic vibration of a component, the stator being placed against another, the rotor depending on the scheme of operation.

• Conversion of electric energy into motion by inverse piezoelectric effect. • To obtain the levels of torque speed characteristics of USM using conventional motors we require to add a gear system to reduce the speed. • These characteristics of USM makes them attractive for robotic applications where small motions are required. • This motor achieves high speed and drive forces, while still permitting the moving part to be positioned with high accuracy. The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry.

• Piezoelectricity – generation of voltage in response of mechanical stress. • The word is derived from the Greek piezein, which means to squeeze or press. • This effect is also reversible. • Deformation is only 0.1 % of the original dimension. • Piezoelectric material- quartz(SiO2), barium titanate (BaTiO3) lead zirconate titanate and occasionally lithium niobate . Electromagnetic motors are notorious for consuming high amount of power and creating high ambient motor temperatures respect to USM

The electromagnetic motors produce strong magnetic fields which cause interference. Ultrasonic motors use piezoelectric effect and hence no magnetic interference. Electromagnetic motor has high input to output energy loss ratios USM High positional accuracy respect to Electromagnetic Motor. • Generation of gross mechanical motion through the amplification and repetition of micro-deformations of active material. • The active material induces an orbital motion of the stator at the rotor contact points .

• Frictional interface between the rotor and stator rectifies the micro-motion to produce macro-motion of the ROTOR. • Working frequency-20 KHz to 10 MHz • Amplitude of the actuator motion – 20 to 200nm USM Ultrasonic motor Standing wave bidirectional Traveling wave unidirectional The excitation representation by Blocks Representation blocks of rotor movement Blocks representing the modules and their connections in the complete model of motor Motor Speed as a function of time for different loads Motor Torque for a function of time for different loads

• Camera auto focus lenses • Driving fluid • Watch motors and compact paper handling. • Optoelectronics area • In micro surgery and sensor scanning. Hence the ultrasonic motors, which is a new step in the miniaturized electrical technology has got many applications in small appliances because of its high torque at low density. • • • • • • • •

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Dynamische Kontaktprobleme bei Schwingungsantrieben. DFGAbschlußbericht, DFG-Projekt: Wa 564/6, September 1996. Maas, J., Ide, P., Fröhleke, N. and Grotstollen, H.: Simulation Model for Ultrasonic Motors powered by Resonant Converters. Reprint of a paper for the 30th IEEEIAS Annual Meeting, Orlando, Florida, October 1995. Hagood, N., McFarland, A. :

Modeling of piezoelectric rotary ultrasonic motor, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 42,March1995, pp. 210-224. Daimler-Benz AG, 1991 Daimler-Benz AG, Druckschrift TE/ P67052104000791 Gregor Kandare and Jorg Wallaschek, Smart Mater. Struct. 11(2002)565-574