ULTRASONIC MOTORS

PREPARED BY-NAWNEET KUMAR

(1100121058) EE,3rd year

ULTRASONIC MOTORS

content

s

IntroductionPiezoelectric EffectAdvantages of USMBasic Principal Fundamental

constructionTypes of USMWorking MechanismApplicationConclusion

Introduction• 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.

Introduction

What is Piezoelectric Effect?

• 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 .

The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry.

Advantage of Piezoelectric MotorElectromagnetic 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.

VS.

Piezoe

lectric

Actuat

or

Rotor

HOW !T LOOKS…

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

Fundamental Construction of USM

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

OPERATING PRINCIPLEa) Based on the use of reverse piezo-electric

effect for continuous conversion of electric power into mechanical energy.

b) The process of energy conversion can be seperated into two parts:

Ultrasonic vibration generation Conversion of this vibration into the

slider(rotor) movement.

OPERATING PRINCIPLEWhen a voltage is applied to a

peizoelectric-ceremic element,alternating expansion and contraction occur either in the ceremic body itself or in the elastic body

The magnitude of this oscilation is very small

The conversion of ultrasonic vibration in the rotor movement is based on the elliptic motion displacement of the surface points of the contact zone between stator and rotor

The displacement can be produced independently through two individual vibrating bodies or by a single vibrator

ULTRASONIC MOTOR

STANDING WAVE TYPE

LINEAR MOTOR

ROTARY MOTOR

TRAVELLING WAVE TYPE

LINEAR MOTOR

ROTARY MOTOR

Standing Wave USM

This type of motors use three groups of crystals: two of which are Locking and one Motive.

First, one group of locking crystals is activated — this gives one locked side and one unlocked side of the 'sandwich'.

Next, the motive crystal group is triggered and held — the expansion of this group moves the unlocked locking group along the motor path. This is the only stage where motor movement takes place.

• Mechanism

Standing wave USMRepresentation u( x, t) = A coskx coswtIt 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 USMRectangular plate

ultrasonic motor.Resonant

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

senders.

ROTATING TYPE STANDING WAVE USMTorsional 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%.

This type of motor commonly known under the names of Inchworm, Piezo LEGS or PiezoWalk motors

• Mechanism

STANDING WAVE USM

Low costone vibration sourceHigh 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

pressure

TRAVELING WAVE USM• Superposition of multiple standing

wave create a traveling wave.• Representation of travelling wave U(x ,p)= A cos(k x) cos(wt) + A cos(k

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

TRAVELING WAVE USM•The active material excites a traveling flexural wave within the stator that leads to elliptical motion of the surface particles. •Teeth are used to enhance the speed that is associated with the propelling effect of these particles. •The rectification of the micro-motion an interface is provided by pressing the rotor on top of the stator and the frictional force between the two causes the rotor to spin.

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.

ADVANTAGES DISADVANTAGES Low costHigh efficiencyNo magnetic

interferenceCompact sizeHigh torque/weight

ratioEnergy saving

Use of high frequency power supply

Less constancyDrooping torque

speed characteristicSupppression of

heat is required

MAJOR APPLICATION

• Camera auto focus lenses• Driving fluid• Watch motors and compact

paper handling.• Optoelectronics area• In micro surgery and sensor

scanning.

CONCLUSIONThese 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

Thank You….