ULTRASONIC MOTORS

INTRODUCTION

“An ultrasonic motor is a type of electric motor powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider depending on the scheme of operation (rotation or linear translation).”

The ultrasonic motor is invented in 1980..

GENERATIONS

PIEZOELECTRIC NOTIONS

“Piezoelectricity is the ability of certain crystals to generate a voltage in response to applied mechanical stress. The word is derived from the Greek piezein, which means to squeeze or press. The piezoelectric effect is reversible in that piezoelectric crystals, when subjected to an externally applied voltage, can change shape by a small amount.” 

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CONSTRUCTION

A linear ultrasonic motor was designed using a combination of the first longitudinal and the fourth bending mode. The motor consisted of a straight metal bar bonded with a piezo-ceramic element as a driving element. The resulting displacement was amplified by two teeth and transmitted by the frictional force between the motor and the rail in a linear motion. The basic design is discussed and simulations are compared with the experimental results.

ULTRASONIC MICRO MOTOR STRUCTURE

The combination of materials and simplicity of the innovative piezoelectric motor design give:  •High power delivery (breathing mode)

•A simple friction drive Driving 1-2 micrometers at 50- 80kHz

•Simple assembly

•Scalable size without loss of performance

WORKING PRINCIPLEDry friction often used in contact, and the ultrasonic vibration induced in the stator is used both to impart motion to the rotor and to modulate the frictional forces present at the interface. The friction modulation allows bulk motion of the rotor (i.e., for farther than one vibration cycle); without this modulation, ultrasonic motors would fail to operate.

TYPES OF USM

•Bi-directional linear standing wave USM

•Rotary Ultrasonic Motor

•Spherical ultrasonic motor

ADVANTAGES

•Piezoelectric ultrasonic motors are small and light weight. •Because they use ultrasonic power, piezoelectric ultrasonic motors cause no noise and little electromagnetic interference. •Due to these advantages, piezoelectric ultrasonicmotors are typically used in lens drive units of expensive.

 

DISADVANTAGES

Consequently, it is difficult to control the ultrasonic motor while maintaining performance.

Very small, so complicated.

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• This new breed of motors has many excellent performances and features such as high torque, low speed, simple and compact structure with great variability in design, not interfering or being affected by magnetic field when in operation, power off self-brake, etc.

FEATURES

MAJOR APPLICATIONS

•Camera auto focus lenses,

•Watch motors and compact paper handling.

•Medical application within micro-surgery and sensor scanning

•Driving fluids

•Optoelectronics area

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