ULTRASONIC MOTOR

PREPARED BY:-CHANDAN BEHERA

ELECTRICAL ENGINEERING DEPARTMENTREGISTRATION NO:-0901106167

COLLEGE OF ENGINEERING & TECHNOLOGYBHUBANESWAR

CONTENTS

1. INTRODUCTION

2. ELECTROSTICTION NOTION

3. POLING

4. ULTRASONICMOTOR NOTION

5. EQUATIONS

6. BASIC PRINCIPLE

7. CONSTRUCTION

8. PARTS OF ULTASONIC MOTOR

9. TYPES OF ULTRASONIC MOTOR

10. DRIVER CIRCUIT OF ULTRASONIC MOTOR

11. CONTROL TECHNIQUE OF ULTRASONIC MOTOR

12. MAJOR APPLICATION

13. ADVANTAGES & DISADVANTAGES

14. CONLUSION

15. REFERENCE

INTRODUCTION

The first ultrasonic motor was developed by V.V lavrinko in 1965.

Conversion of electric energy into motion by inverse piezoelectric effect.

In this tpye of motor efficiency is insensitive to size,& these are superior in the mm-sized motor area.

ELECTROSTICTION NOTION

Inverse piezoelectricity – generation of mechanical stress in response to electric voltage.

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),PZT(Lead-Zirconium-Titanium).

HOW IT OCCURS?? When voltage is applied across the crystal, the atoms

experience electrcal pressure. So they move to rebalance themselves, & thus

deformation is produced. If the voltage is applied in the direction of poling

voltage the material will elongate & its diameter reduces else length decreases & diameter increases.

If AC is applied then the material will lengthen & shorten cyclically, at the frequency of applied voltage.

POLING It is process of polarization of the

piezoelectric material.

EQUATIONS The relationships between an applied voltage & the

corresponding increase or decrease in a piezoelectric ceramic element's thickness, length, or width are:Δh = d33vS = d33EΔl / l = d31EΔw / w = d31Ewhere l: initial length of ceramic elementw: initial width of ceramic elementΔh: change in height (thickness) of ceramic elementΔl: change in length of ceramic elementΔw: change in width of ceramic elementd31,d33: piezoelectric charge constants in different directionV: applied voltageS: strain (change in height / original height of element)E: electric field

ULTRASONICMOTOR NOTION

It is named so ,as it uses voltage of frequency higher than 20kHz.

It is based on inverse piezoelectricty. It can be abbreviated as USM. It is driven by ultrasonic vibration of transducer. The ultrasonic vibration is transformed into output torque

(in rotary USM) or thrust (in linear USM) by the friction between the stator and the rotor (in rotary USM) or the moving part (in linear USM).

BASIC PRINCIPLE

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

CONSTRUCTION

PARTS OF ULTRASONIC MOTOR

The Stator part transmits vibration. Stator consists of:

The Rotor which is a rotation part. The Shaft which transmits rotation. The Bearing.

The Piezo-Electric Ceramics which generate vibration.The Stator metal which makes vibration amplify.The Friction material which contacts with a rotor.

WORKING•If voltage is made to apply to piezo-electric ceramics, the shape of piezo-electric ceramics will be changed or distorted. The modification amplifies and spreads with stator metal, and generates a traveling wave on the surface of stator metal.

•Here, the stator metal touches the rotor only at each peak of a traveling wave, and each of that peak carries out elliptical movement. A rotor rotates in response to the influence of the elliptical movement.

•The direction of movement of this ellipse is in accordance to the direction which a traveling wave follows. And a rotor rotates in the direction contrary to a traveling wave under the influence.

•So, When a traveling wave progresses in the clockwise direction (CW) on the circumference of a stator, each peak of the traveling wave in contact with a rotor carries out elliptical movement in the clockwise direction (CW).And the rotor in contact with the peak of the wave rotates in the counterclockwise direction (CCW).By controlling the speed and direction of this traveling wave, control of an Ultrasonic Motor is possible

TYPES OF ULTRASONIC MOTOR

ULTRASONIC MOTOR

STANDING WAVE TYPE

LINEAR MOTOR

ROTARY MOTOR

TRAVELLING WAVE TYPE

LINEAR MOTOR

ROTARY MOTOR

STANDING WAVE USM

Representation u( x, t) = A coskx coswt

It is also referred as vibratory coupler type or wood pecker type.

A vibrator is connected to the piezoelectric driver,it produces bending, so its tip produces flat elliptical motion to drive the rotor.

LINEAR TYPE STANDING WAVE USM Rectangular plate

ultrasonic motor. Resonant

frequency-98kHz. Efficiency-65% Applications- card or paper

senders.

ROTATING TYPE STANDING WAVE USM Torsional coupler

ultrasonic motor. Provides high

speed than linear motors because of high frequency (160kHz)& amplified vibration.

Provides speed of 1500 rpm, torque of 0.08 Nm & efficiency of 80%.

STANDING WAVE USM

Low cost one vibration source High efficiency Unidirectional

TRAVELING WAVE USM

Superposition of multiple standing wave create a traveling wave.

Representation of travelling wave U(x ,t)= A cos(k x) cos(wt) + A

cos(k x - 90) cos (wt-90). Phase difference is 90 degree

LINEAR TYPE TRAVELLING WAVE USM Linear motor using

bending vibration. Consists of two

piezoelectric vibrators installed at both the ends.

Load resistance is adjusted for perfect travelling wave.

ROTARY TYPE TRAVELLING WAVE USM Two voltage sources

are used to produce travelling wave.

Vibrations of the piezoelectric material is amplified by the stator teeths.

Due to frictional forces rotor rotates.

Resonant frequency-46kHz.

TRAVELLING WAVE USM

Requires two vibrating source. Controllable in both direction. Silent operation, so suitable to video

cameras with microphone. Thinner design, leading to space

saving. Low efficiency.

EQUIVALENT CIRCUIT OF USM STATOR

Cd is the capacitance due to the dielectric property of piezo crystal i.e tank capacitance.

Rm,Cm,Lm are the resistance ,capacitnce & inductance of stator.

Their combined impedance is given by

( + 1 /      +      ). 𝑅𝑚 𝑗 𝜔 𝐶𝑚 𝑗 𝜔 𝐿𝑚

DRIVER CIRCUIT OF USM

DRIVER CIRCUIT OF USM Nref and Uref are the given value of

rotating speed and amplitude of driving voltage, respectively.

An optoelectric encoder, E, is used to measure the rotating speed of ultrasonic motor.

 𝑄 1 ∼   8 are power MOSFETs, T1 and T2 𝑄are transformers, and L1 and L2 are series compensating inductances.

PWM1~PWM8 are the PWM control signals for   1 ∼   8. 𝑄 𝑄

DSP is used to implement the control strategies & CPLD is used to produce the phase-shift PWM control signals PWM1 ~ PWM8 for H-bridge.

CONTROL TECHNIQUE OF USM

PWM control is used. Motor is operated at

resonance frequency(low impedance) to reduce losses & to reduce pressure on piezoelectric material.

Various control methods are :

MAJOR APPLICATION

Camera auto focus lenses Watch motors and compact

paper handling. Conveying machine parts In micro surgery and sensor

scaning.

ADVANTAGES DISADVANTAGES Low cost High efficiency No magnetic

interference Compact size High torque/weight

ratio Energy saving

Use of high frequency power supply

Less constancy Drooping torque

speed characteristic

Supppression of heat is required

CONCLUSION These motors are advantageous. Electromagnetic interference is not

there. It is in great demand in the area of

automation & miniaturiztion. Energy efficient. Light weight & compact size

ANY QUERIES??

REFERENCE

www.google.com www.yahoo.com www.slideworld.com www.pdf-searchengine.com www.ask.com http://www.americanpiezo.com/piezo

_theory/piezo_theory.pdf

THANK YOU ALL