piezoelectric ultrasonic motor

Presented ByA.Anbarasu,P.Arulprakash,Third year EEE,Excel College Of Engg.&Tech.

STRUCTURE OF THE

PRESENTATION:

•Introduction

•Construction

•Principal Operation

•Classification

•Application

•Advantages

•Conclusion

•In contrast to piezoelectric positioning devices for

one-stroke operation, several types of piezoelectric

linear motors have been developed, which, in

principle, are able to deliver an unlimited stroke.

•Their moving part, the ‘rotor’, comes into contact

with the stator by normal forces and is driven by

frictional forces generated at the interface. In this

way, microscopic small motions of the stator, induced

by piezoelectric elements, are transferred to a

macroscopic linear motion of the rotor.

•This paper deals with ultrasonic motors using

resonant vibrations. Following the historical

background, various ultrasonic motors are

introduced.

INTRODUTION

•Ultrasonic motor construction tends to be simpler than

EM type motors. Fewer assembly parts mean fewer

moving parts and consequently less wear. The number

of components required to construct an USM is small

thereby minimizing the number of potential failure

points.

CONSTRUCTION

•As the ultrasonic motor uses ultrasonic vibrations as its

driving force, it comprises a stator which is a

piezoelectric ceramic material with an elastic body

attached to it, and a rotor to generate ultrasonic

vibrations. It therefore does not use magnets or coils.

•Therefore there is no problem of magnetic field and

interference as in the case of electric motors. In

ultrasonic motors, piezoelectric effect is used and

therefore generates little or no magnetic interference.

Principal Operation•Many polymers, ceramics and molecules are

permanently polarized; that is some parts of the

molecules are positively charged, while other parts are

negatively charged. When an electric field is applied to

these materials, these polarized molecules will align

themselves with the electric field, resulting in induced

dipoles within the molecular or crystal structure of the

material.•Furthermore a permanently polarized material such as

Quartz (SiO2) or Barium Titan ate (BaTiO3) will produce an

electric field when the material changes dimensions as a

result of an imposed mechanical force. These materials

are piezoelectric and this phenomenon is known as

piezoelectric effect.•Conversely, an applied electric field can cause a

piezoelectric material to change dimensions. This is known

as Electrostriction or Reverse piezoelectric effect.

•Therefore does not make use of coils or magnets. It is

a motor with a new concept that does not use

magnetic force as its driving force. It also overcomes

the principles of conventional motors. The wave drives

the comb of the piezoelectric ring.

•When applied, the piezoelectric combs will expand

or contract corresponding to the traveling wave form

and the rotor ring which is pressed against these

combs start rotating.

•When a voltage having a resonance frequency of more

than 20 KHz is applied to the piezoelectric element of an

elastic body (a stator), the piezoelectric element expands

and contracts. If voltage is applied, the material curls. The

direction of the curl depends on the polarity of the applied

voltage and the amount of curl is determined by how many

volts are applied.

Classification

Ultra sonic motor

Standing

wave type

Propagatin

g wave

type

Travelling

wave type

The standing-wave type is sometimes referred to

as a vibratory-coupler type or a ‘woodpecker’

type, where a vibratory piece is connected to a

piezoelectric driver and the tip portion generates

flat elliptical movement.

Standing-wave type

Propagating-wave type

•By comparison, the propagating-wave type

(a surface-wave or ‘surfing’ type) combines two standing

waves with a 90 degree phase difference both in time and in

space. A surface particle of the elastic body draws an

elliptical locus due to the coupling of longitudinal.

•This type requires, in general, two vibration sources to

generate one propagating wave, leading to low efficiency

(not more than 50%), but it is controllable in both the

rotational directions.

Travelling wave type

•The motors consist of a stator that uses piezoelectric

elements to excite vibrations with a frequency in the

ultrasonic range and a rotor (rotary motors) or a slider

(Linear motors) that is driven by a stator via frictional force.

•Rotary ultrasonic motors have been investigated for

several years. Their key features are high thrust forces

related to their volume, a high holding torque without

supply, high torque at low speed and good position

accuracy.

Applications•CD, DVD mastering, testing

•Image stabilization, resolution enhancement

•Photonics alignment & packaging

•Fiber optic switches

•Interferometer

•Vibration cancellation

•Laser beam steering

•Adaptive optics

•Scanning microscopy

•Auto-focus systems

•Nan metrology

•Wafer and mask positioning / alignment

• Microlithography

Advantages•High torque, exceptional

resolution and fast reaction

time.

•piezoelectric motors offer great

potential for miniaturization and can

be used without a gear drive in many

applications.

•As such, they offer significant benefits in motion

and flow control applications throughout diverse

industries, including; medical device, aerospace,

semiconductor, telecommunications,

industrial and automotive

Conclusion

All three motors were characterized individually.

Admittance spectra of the free stators, torque,

power and efficiency values of each motor were

presented. Driving of the motor was enabled by a

switching power supply. It is conventional and cheap.

The design, fabrication and characterization of a

piezoelectric ultrasonic micro motor have been

investigated.