REPORT ON ULTRASONIC MOTOR.

1. A
REPORT ON
ULTRASONIC MOTOR
DEPARTMENT OF ELECTRICAL ENGINEERING
SEMINAR CO-ORDINATOR: BY:
ER. ALOK KUMAR YADAV ASHUTOSH SRIVASTAVA
( 1375120016 )
KIPM-COLLEGE OF ENGGINEERING AND TECHNOLOGY
Gida, Gorakhpur
Affiliated to Dr. A P J ABDUL KALAM Technical University,
Lucknow

2. CERTIFICATE
This is certify that i have presented a presentation on “UltraSonic Motor” in 3rd year
seminar of Bachelor of Technology in Electrical Engineering at KIPM-College Of
Engineering And Technology , affiliated to Dr. A P J Abdul Kalam Technical University,
Lucknow, U.P. Under your supervision and guidance during the academic session 2015-2016.
SEMINAR CO-ORDINATOR: HEAD OF DEPARTMENT:
Er. Alok Kumar Yadav Er. Krishna Kumar Pandey
(Lecturer, Dept. of Electrical Engg.) (HOD, Dept. of Electrical Engg.)

3. ACKNOWLEDGEMENT
It gives me great pleasure on bringing on report untitled“UltraSonic Motor” my deep sense of
gratitude and sincere regards to our guide Er. Alok Kumar Yadav. His timely guidance and
friendly discussions had helped me immensely in selecting his current topic and completing this
work. I am thankful to our faculty members for providing me all the helpful facilities during the
work. Finally, I would like to thank all those who directly or indirectly helped me during my
work.
Finally, I would like to thank all those who directly and indirectly helped me during my work.
SEMINAR CO-ORDINATOR: BY:
Er. Alok Kumar Yadav Ashutosh Srivastava

4. TABLE OF CONTENT
 Abstract
 Introduction
 ULTRASONIC MOTOR
 Piezoelectric effect
 USM Prototypes
1. Linear ultrasonic motors
I) DOF planar pin-type actuator
II) Bi-directional linear standing wave USM
2. Rotary ultrasonic motor
3. Spherical ultrasonic motor
 Design & Modeling of USMs
1. Equivalent Circuit
2. Vibration Analysis
3. Contact Mechanism
 Advantages of ultrasonic motor over electromagnetic motor
1. Little influence by magnetic field:
2. Low speed, high torque characteristics, compact size and quiet operation:
3. Compact-sized actuators:
 Piezoelectric Ultrasonic Motor Technology
 Structure of Ultrasonic Motor
 MECHANISM
 Types of Ultrasonic Motors
 Working of the Ultrasonic Motors
 Features & Merits of Ultrasonic Motors
 Demerits of Ultrasonic Motors
 Applications of Ultrasonic Motors
 Construction
 Principle Of Operation
 PRINCIPLE OF WORKING
 Principle of Ultrasonic Motor

5.  Feature of Ultrasonic Motor
 Typical Feature
 Conclusion
 Reference

6. Abstract
We propose an ultrasonic motor of high torque with a new configuration for application in
automobiles. The newly designed stator is a two sided vibrator consisting of a toothed metal disk
with a piezoelectric ceramic ring bonded on both faces of the disk which generates a flexural
traveling wave along the circumference of disk. In this configuration, the displacement on the
surface of stator may not be confined. It also produces a large vibrating force and amplitude
because the vibrator is sandwiched by two piezoelectric plates. It is possible to increase the
torque by improving the vibration characteristics. We used the finite element method to compute
the vibration mode of the motor of diameter 48 mm. A sixth mode was chosen as the operation
mode with a resonance frequency of about 73 kHz. We fabricated a prototype according to this
design and measured its performance. The performance measurement of the prototype motor
showed that its stall torque was about 1.8 Nm and efficiency was 37% at 60% of the maximum
torque. Compared to a conventional motor which employed a single sided piezoelectric vibrator
of the same outer diameter, we obtained, with this prototype, a maximum torque of about twice
as great. The motor may be useful to apply as an actuator in a mobile car.
Ultrasonic rotary motors have the potential to meet this NASA need and they are
developed as actuators for miniature telerobotic applications. These motors are being adapted for
operation at the harsh space environments that include cryogenic temperatures and vacuum and
analytical tools for the design of efficient motors are being developed. A hybrid analytical model
was developed to address a complete ultrasonic motor as a system. Included in this model is the
influence of the rotor dynamics, which was determined experimentally to be important to the
motor performance. The analysis employs a 3D finite element model to express the dynamic
characteristics of the stator with piezoelectric elements and the rotor. The details of the stator
including the teeth, piezoelectric ceramic, geometry, bonding layer, etc. are included to support
practical USM designs. A brush model is used for the interface layer and Coulomb's law for the
friction between the stator and the rotor. The theoretical predictions were corroborated
experimentally for the motor. In parallel, efforts have been made to determine the thermal and
vacuum performance of these motors. To explore telerobotic applications for USMs a robotic
arm was constructed with such motors.

7. Introduction
What is an ultrasonic motor
An ultrasonic motor is driven by the vibration of piezoelectric elements, and produces
force for rotation or horizontal movement by harnessing the elements ultrasonic resonant of over
20 KHz. An ultrasonic motor is a type of electric motor formed from the ultrasonic vibration of a
component, the stator, placed against another, the rotor or slider depending on the scheme
of operation (rotation or linear translation). Ultrasonic motors differ from piezoelectric actuators
in several ways, though both typically use some form of piezoelectric material, and most often
lead zirconate titanate and occasionally lithium niobate or other single-crystal materials. The
most obvious difference is the use of resonance to amplify the vibration of the stator in contact
with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation or
sliding distances, while piezoelectric actuators are limited by the static strain that may well be
induced in the piezoelectric element.
Piezoelectric ultrasonic motors are a new type of actuator. They are characterized by high
torque at low rotational speed, simple mechanical design and good controllability. They
also provide a high holding torque even if no power is applied. Compared to electromagnetic
actuators the torque per volume ratio of piezoelectric ultrasonic motors can be higher by an order
of magnitude.
The ultrasonic motor is characterized by a “low speed and high torque”, contrary to the
“high speed and low torque” of the electromagnetic motors. Two categories of ultrasonic motors
are developed at our laboratory: the standing wave type and the traveling wave type.
The standing wave type is sometimes referred to as a vibratory-coupler type, where a
vibratory piece is connected to a piezoelectric driver and the tip portion generates flat-elliptical
movement. Attached to a rotor or a slider, the vibratory piece provides intermittent rotational
torque or thrust. The travelling-wave type combines two standing waves with a 90¡-phase
difference both in time and space. By means of the traveling elastic wave induced by the thin
piezoelectric ring, a ring-type slider in contact with the surface of the elastic body can be driven.

8. Piezoelectric ultrasonic motors (PUMs) have a number of advantages over
electromagnetic motors. PUMs can achieve positioning accuracies in the range of several tens of
nanometers. They hold their positions even when powered down and thus consume less energy.
PUMs can be constructed with significantly fewer parts. The efficiency of electromagnetic
motors falls as their dimensions are reduced, but that of PUMs stay virtually constant.
Linear electromagnetic motors are very difficult to design; in contrast PUMs are quite
simple. Interest in PUMs is growing, especially for used as miniature drives in mass-produced
costumers electronic products.
In 1980, The world’s first ultrasonic motor was invented which utilizes the
piezoelectric effect in the ultrasonic frequency range to provide its motive force resulting in a
motor with unusually good low speed, high torque and power to weight characteristics.
Electromagnetism has always been the driving force behind electrical motor
technology. But these motors suffer from many drawbacks. The field of ultrasonic seems to be
changing that driving force.
As the ultrasonic motor uses ultrasonic vibrations as its driving force, it comprises a
stator which is a piezoceramic material with an elastic body attached to it, and a rotor to generate
ultrasonic vibrations. It therefore does not use metal or coil. Therefore there is no problem of
magnetic field and interference as in case of electric motor.
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). Ultrasonic motors differ from piezoelectric
actuators in several ways, though both typically use some form of piezoelectric material, most
often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials.
The most obvious difference is the use of resonance to amplify the vibration of the stator in
contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation
or sliding distances, while piezoelectric actuators are limited by the static strain that may be
induced in the piezoelectric element. One common application of ultrasonic motors is in camera
lenses where it, as part of the autofocus system, is used to move lens elements. It's replacing the
noisier and often slower conventional micro-motor. Piezoelectric ultrasonic motors are a new

9. type of actuator. They are characterized by high torque at low rotational speed, simple
mechanical design and good controllability. They also provide a high holding torque even if no
power is applied. Compared to electromagnetic actuators the torque per volume ratio of
piezoelectric ultrasonic motors can be higher by an order of magnitude. The ultrasonic motor is
characterized by a “low speed and high torque”, contrary to the “high speed and low torque” of
the electromagnetic motors. Two categories of ultrasonic motors are developed at our laboratory:
the standing wave type and the traveling wave type.
Electromagnetic motors were invented more than a hundred years ago. While these
motors still dominate the industry, a drastic improvement cannot be expected except through new
discoveries in magnetic or superconducting materials. Regarding conventional electromagnetic
motors, tiny motors smaller than 1 cm3 are rather difficult to produce with sufficient energy
efficiency. Therefore, a new class of motors using high power ultrasonic energy—ultrasonic
motors—is gaining widespread attention. Ultrasonic motors made with piezo ceramics whose
efficiency is insensitive to size are superior in the mini-motor area. Fig no.6 shows the basic
construction of ultrasonic motors, which consist of a high-frequency power supply, a vibrator
and a slider. Further, the vibrator is composed of a piezoelectric driving component and an
elastic vibratory part, and the slider is composed of an elastic moving part and a friction coat.
The standing-wave type, in general, is low in cost (one vibration source) and has high
efficiency (up to 98% theoretically), but lack of control in both clockwise and counter clockwise
directions is a problem. By comparison, the propagating-wave type combines two standing
waves with a 90 degree phase difference both in time and in space. This type requires, in general,
two vibration sources to generate one propagating wave, leading to low efficiency (not more than
50%), but is controllable in both rotational directions. Table 1 summarizes the motor
characteristics of the vibration coupler standing wave type (Hitachi Maxel), surface propagating
wave type (Shinsei Industry) and a compromised ‘teeth’ vibrator type (Matsushita).
The ultrasonic motor, invented in 1980, utilizes the piezoelectric effect in the ultrasonic
frequency range to provide the motive force. (In conventional electric motors the motive force is
electromagnetic.) The result is a motor with unusually good low-speed high-torque and power-
to-weight characteristics. It has already found applications in camera autofocus mechanisms,
medical equipment subject to high magnetic fields, and motorized car accessories. Its

10. applications will increase as designers become more familiar with its unique characteristics. This
book is the result of a collaboration between the inventor and an expert in conventional electric
motors: the result is an introduction to the general theory presented in a way that links it to
conventional motor theory. It will be invaluable both to motor designers and to those who design
with and use electric motors as an introduction to this important new invention.
Ultrasonic motors were invented in 1965 by V.V Lavrinko. In general we are aware of the fact
that the motive force is given by the electromagnetic field in the conventional motors. But, here
to provide a motive force, these motors utilize the piezoelectric effect in the ultrasonic frequency
range, which is from 20 kHz to 10 MHz and is not audible to normal human beings. Hence, it is
termed as piezoelectric USM technology. Ultrasonic technology is used by the USMs which
utilize the ultrasonic vibration power from a component for their operation.

11. ULTRASONIC MOTOR
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
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). Ultrasonic motors differ from piezoelectric
actuators in several ways, though both typically use some form of piezoelectric material, most
often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials.
The most obvious difference is the use of resonance to amplify the vibration of the stator in
contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation
or sliding distances, while piezoelectric actuators are limited by the static strain that may be
induced in the piezoelectric element.
One common application of ultrasonic motors is in camera lenses where they are used
to move lens elements as part of the auto-focus system. Ultrasonic motors replace the noisier and
often slower micro-motor in this application.
In 1980, The world’s first ultrasonic motor was invented which utilizes the
piezoelectric effect in the ultrasonic frequency range to provide its motive force resulting in a
motor with unusually good low speed, high torque and power to weight characteristics.
Electromagnetism has always been the driving force behind electrical motor
technology. But these motors suffer from many drawbacks. The field of ultrasonic seems to be
changing that driving force.
As the ultrasonic motor uses ultrasonic vibrations as its driving force, it comprises a
stator which is a piezo ceramic material with an elastic body attached to it, and a rotor to
generate ultrasonic vibrations. It therefore does not use metal or coil. Therefore there is no
problem of magnetic field and interference as in case of electric motor.

12. In ultrasonic motor, piezoelectric effect is used and therefore generates little or no
magnetic interference.
All of us known that motor is a machine which produces or imparts motion, or in
detail it is an arrangement of coil and magnets that converts electrical energy to mechanical
energy and ultrasonic motors are the next generation motors.
In December 25,1986. The completely new motor which uses neither a Coil nor any
Magnet for driving force was put on the market from SHINSEI CORPORATION.
The motor is just an Ultrasonic Motor.
The name of the production is USR-60-4-100. The motor is first type of the present
Ultrasonic Motor: USR series.
Ultrasonic Motor rotates using modification when voltage is applied to piezo-electric
ceramics.
The name of an ultrasonic motor was named from the frequency of the voltage that is
exceeding people's audible sound region.(Over 20kHz).
Then, the SHINSEI CORPORATION's Ultrasonic Motor repeated improvement aiming at
improvement in functionality and reliability.
The concentration of the technology is USR30 series：diameter 30mm and USR60 series :
diameter 60mm.
By the result of continuous improvement, USR30 series and USR60 series are adopted in
many companies and academic organizations in the world. And because USR30 series and
USR60 series have obtained high evaluation, it is considered as a de-facto standard of Ultrasonic
Motor.
The lineup of USR30 series and USR60 series are the Standard Model Motor assuming the
use in general environment and the Non-Magnetic Model Motor assuming the use in high
magnetic field environment.
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.

13. 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).
This wave rotates the rotor which is in contact with the stator. High holding power of
Ultrasonic Motor : High pressure is applied between the rotor and the stator. For this reason, the
biggest frictional force at the time of a stop is the holding power of an ultrasonic motor.
Ultrasonic motors, which have superior characteristics like high torque at low ... The stator
of an ultrasonic motor that is excited by piezoelectric elements in.
Ultrasonic motors motor is a newly developed motor, and it has excellent performance and
many useful features, e.g.: high-torque density, low speed, compactness in size, no
electromagnetic interferences, and so on. USM is a kind of piezo motor. The proposed speed
control scheme is assumed for these applications because they require quick and precise speed
control of actuators for various load conditions. A speed control method of USM using adaptive
control is proposed.
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) . In ultrasonic motor Dry friction is 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 and without this modulation, ultrasonic motors would fail to
operate...and two different ways are generally available to control the friction along the stator-
rotor contact interface, "travelling-wave vibration" and "standing-wave vibration".

14. PIEZOELECTRIC EFFECT
Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to
applied mechanical stress. The word Piezoelectric is derived from the Greek piezein, which
means to squeeze or press, and piezo, which is Greek for “push”.
One of the unique characteristics of the piezoelectric effect is that it is reversible, meaning that
materials exhibiting the direct piezoelectric effect (the generation of electricity when stress is
applied) also exhibit the converse piezoelectric effect (the generation of stress when an electric
field is applied).
When piezoelectric material is placed under mechanical stress, a shifting of the positive and
negative charge centers in the material takes place, which then results in an external electrical
field. When reversed, an outer electrical field either stretches or compresses the piezoelectric
material.
The piezoelectric effect is very useful within many applications that involve the production and
detection of sound, generation of high voltages, electronic frequency generation, microbalances,
and ultra fine focusing of optical assemblies. It is also the basis of a number of scientific
instrumental techniques with atomic resolution, such as scanning probe microscopes (STM,
AFM, etc). The piezoelectric effect also has its use in more mundane applications as well, such
as acting as the ignition source for cigarette lighters.
The History of the Piezoelectric Effect:
The direct piezoelectric effect was first seen in 1880, and was initiated by the brothers Pierre and
Jacques Curie. By combining their knowledge of pyroelectricity with their understanding of
crystal structures and behavior, the Curie brothers demonstrated the first piezoelectric effect by
using crystals of tourmaline, quartz, topaz, cane sugar, and Rochelle salt. Their initial
demonstration showed that quartz and Rochelle salt exhibited the most piezoelectricity ability at
the time.

15. Over the next few decades, piezoelectricity remained in the laboratory, something to be
experimented on as more work was undertaken to explore the great potential of the piezoelectric
effect. The breakout of World War I marked the introduction of the first practical application for
piezoelectric devices, which was the sonar device. This initial use of piezoelectricity in sonar
created intense international developmental interest in piezoelectric devices. Over the next few
decades, new piezoelectric materials and new applications for those materials were explored and
developed.
During World War II, research groups in the US, Russia and Japan discovered a new class of
man-made materials, called ferroelectrics, which exhibited piezoelectric constants many times
higher than natural piezoelectric materials. Although quartz crystals were the first commercially
exploited piezoelectric material and still used in sonar detection applications, scientists kept
searching for higher performance materials. This intense research resulted in the development of
barium titanate and lead zirconate titanate, two materials that had very specific properties
suitable for particular applications.
Piezoelectric Materials:
There are many materials, both natural and man-made, that exhibit a range of piezoelectric
effects. Some naturally piezoelectric occurring materials include Berlinite (structurally identical
to quartz), cane sugar, quartz, Rochelle salt, topaz, tourmaline, and bone (dry bone exhibits some
piezoelectric properties due to the apatite crystals, and the piezoelectric effect is generally
thought to act as a biological force sensor). An example of man-made piezoelectric materials
includes barium titanate and lead zirconate titanate.
In recent years, due to the growing environmental concern regarding toxicity in lead-containing
devices and the RoHS directive followed within the European Union, there has been a push to
develop lead free piezoelectric materials. To date, this initiative to develop new lead-free
piezoelectric materials has resulted in a variety of new piezoelectric materials which are more
environmentally safe.

16. Applications BestSuited for the Piezoelectric Effect:
Due to the intrinsic characteristics of piezoelectric materials, there are numerous
applications that benefit from their use:
High Voltage and Power Sources:
An example of applications in this area is the electric cigarette lighter, where pressing a button
causes a spring-loaded hammer to hit a piezoelectric crystal, thereby producing a sufficiently
high voltage that electric current flows across a small spark gap, heating and igniting the gas.
Most types of gas burners and ranges have a built-in piezo based injection systems.
Piezoelectric Motors:
Because very high voltages correspond to only tiny changes in the width of the crystal, this
crystal width can be manipulated with better-than-micrometer precision, making piezo crystals
an important tool for positioning objects with extreme accuracy, making them perfect for use in
motors, such as the various motor series offered by Nanomotion.
Regarding piezoelectric motors, the piezoelectric element receives an electrical pulse, and then
applies directional force to an opposing ceramic plate, causing it to move in the desired direction.
Motion is generated when the piezoelectric element moves against a static platform (such as
ceramic strips).
The characteristics of piezoelectric materials provided the perfect technology upon which
Nanomotion developed our various lines of unique piezoelectric motors. Using patented
piezoelectric technology, Nanomotion has designed various series of motors ranging in size from
a single element (providing 0.4Kg of force) to an eight element motor (providing 3.2Kg of
force). Nanomotion motors are capable of driving both linear and rotary stages, and have a wide
dynamic range of speed, from several microns per second to 250mm/sec and can easily mount to
traditional low friction stages or other devices. The operating characteristics of Nanomotion’s
motors provide inherent braking and the ability to eliminate servo dither when in a static
position.

17. USM Prototypes
1. Linear ultrasonic motors
I) DOF planar pin-type actuator
The objective of this project is to design and develop a piezoelectric actuator based on the
fundamental operating mechanism of ultrasonic motors. Two pin-type prototypes with
piezoelectric bimorph plate and a contact pin for generating driving force in the X-Y direction
were designed and fabricated. A test rig was also constructed for the evaluation of the two
prototypes and basic characteristics of the actuators were investigated. The working principle of
the actuator was verified and proven during the experiment. Basically, the optimal driving speed
of an actuator is dependent on the driving frequency, the input voltage, the contact surface and
the friction coefficient between the stator and motor. An analytical study of the prototypes has
been carried out by means of finite element analysis utilizing ANSYS5.4. With comparison to
the experimental results, it was proven that the optimal driving condition occurred at the specific
resonant mode depending on the pin vibration. Maximum unloaded driving speed was obtained
to be approximately 0.68 cm/s at a frequency of 14.8 kHz and the optimum input voltage was
found to be approximately 70 Vp-p.
II) Bi-directional linear standing wave USM
A standing wave bi-directional linear ultrasonic motor has been fabricated. This linear
USM has very simple structure and can be easily mounted onto any commercially available
linear guide. A high precision positioning x-y table was built by mounting these individual
movable linear guides together. The basic parameters of our linear USM are: moving range

18. 220mm(variable depending on the linear guide), no-load speed 80mms/s, ratings 23mm/s at
300gf, stall force 700gf, starting thrust 500gf, resolution<50nm, response time of 12ms from
stationary status to constant velocity(80mm/s) with a initial mass of 260g.
2. Rotary ultrasonic motor
The characteristics of the rotary disc type motor will be investigated and theoretical
model will be formed to relate the important components on the power of the motor. The scope
includes designing different motor with various dimensions, form ulation of the analytical model,
experimental testing and ultimately, setting a standard for practical application of this particular
type of USM. This project will lay the foundation of the characteristics and performance of the
rotary disc type USMs for future application.
3. Spherical ultrasonic motor
Presently a new type of spherical USM is under investigation. This particular USM
consists of a thin square plate, 30x30mm in area. It can rotate in more than 4 individual
directions. Now we are trying to compile rotation in any dirction by using a computer to control
the 4 individual directions properly.

19. Design & Modeling of USMs
1. Equivalent Circuit
It is often useful to represent a problem in mechanics by an equivalent circuit. The basic
idea of the circuit is to determine the static and dynamic behavior in force and velocity
transmission of a system where friction plays an essential role. The equivalent circuit expression
for a piezoelectric vibrator is very convenient for understanding its operating characteristics and
for applying it in practice. Shown in Fig. 1 is an equivalent circuit representing free vibration of
a stator with no loads and includes two resistors which symbolizes losses. Cm and Lm is the
piezoceramic equivalent capacitance and inductance and capacitance, Cd is due to the element’s
dielectric properties called the “blocking capacitance”. r0 is the internal resistance of the motor.
There are two power transformation involved in the running of a USM: 1) electric energy is
transformed into mechanical vibrational energy of the stator by converse piezoelectric effect;
2)vibrational energy of the stator is transformed into continous moving energy of the rotor(or
moving part) due to frictional interaction between the stator and the rotor(or moving parts).
Correspondingly, modeling a USM normally includes two aspects: 1) piezoelectric vibration
analysis for the stator which is a piezoceramic-metal composite structure; 2) the frictional
actuation mechanism between the the vibrator and the rotor.
2. Vibration Analysis
An uniformizing method for the vibration analysis of metal-piezoceramic composite thin
plates has been proposed. Using this method, piezoelectric composite thin plates with different
shapes can be uniformized into equivalent uniform single-layer thin plates which have the same
vibrational characteristics as the original piezoelectric composite thin plates. Hence the
vibrational characteristics of metal-piezoceramic composite thin plates can be obtained through
calculating the natural frequencies and the vibration modes of the equivalent uniform single-

20. layer thin plates using single-layer thin plate theory. Furthermore mid-plane of piezoelectric
composite thin plate can also be obtained, which is significant when designing thin plate type
USMs.
3. Contact Mechanism
In the existing study on the friction actuation mechanism of USMs, the dynamic normal
contact between the stator and the rotor in the ultrasonic range has not been taken into
consideration. In fact this is a vital factor which causes the reduction of the coefficient of friction
between the stator and rotor when the motor is in motion. In our research we take a traveling
wave USM as an example and model the normal ultrasonic dynamic contact of the stator and
rotor using elastic Hertzian contact theory. Result shows that the rotor is levitated in normal
direction by the ultrasonic dynamic contact of the stator. Concurrently, the real area of contact of
the stator and rotor decreases. Under the assumption that friction force is proportional to real area
of contact, frictional coefficient of stator/rotor decreases under ultrasonic dynamic contact. Our
contact model can give good explanation for the phenomena of reduction in the coefficient of
friction when a USM is in operation. The normal contact model we have established has great
significance in understanding real contact condition of stator/rotor in a USM and also building
accurate friction driving model. In order to validate the normal dynamic contact model, we also
tested the normal levitation of rotor. Tested results gave good agreement with the theoretical
model.
Rotary USM Micro linear USM Rotary USM
Animation Video/v-usm-linear.mpg, Video/v-usm-rotary.mpg,

21. Advantages of ultrasonic motor over electromagnetic motor:
1. Little influence by magnetic field:
The greatest advantage of ultrasonic motor is that it is neither affected by nor creates a
magnetic field. Regular motors which utilize electromagnetic induction will not perform
normally when subjected to strong external magnetic fields. Since a fluctuation in the magnetic
field will always create an electric field (following the principle of electromagnetic induction),
one might think that ultrasonic motors will b affected as well. In practice, however, the effects
are negligible. For example, consider a fluctuation in the flux density by, say, 1T (which is a
considerable amount), at a frequency of 50 Hz , will create an electric field of 100 volts per
meter. This magnitude is below the field strength in the piezoelectric ceramic and hence can be
ignored.
2. Low speed, high torque characteristics, compact size and quiet operation:
Ultrasonic motors can be made very compact in size. The motor generates high torques at
low speeds and no reduction gears are needed unlike the electromagnetic motors. The motor is
also very quiet, since its drive is created by ultrasonic vibrations that are inaudible to humans.
3. Compact-sized actuators:
The ultrasonic motor’s small size and large torque are utilized in several applications.
The ultrasonic motors hollow structure is necessary for an application in several fields such a
robotics etc where it would be very difficult to design a device with an electromagnetic motor
and satisfy the required specifications.
Their main advantages over the conventional electromagnetic devices are:
1. Different velocities without gear-mechanisms,
2. High positioning accuracy due to the friction drive,
3. High holding torque (braking force without energy supply).
4. Simplicity and flexibility in structural design.

22. 5. No magnetic noise.
6. High output torque at low speed.
7. High force density.

23. Piezoelectric Ultrasonic Motor Technology
Simply we can call the ultrasonic technology as inverse of the piezoelectric effect because, in
this case, the electric energy is converted into motion. Hence, we can call it as a Piezoelectric
USM Technology.
The piezoelectric material named Lead zirconate titanate and quartz are used very often for
USMs and also for piezoelectric actuators even though the piezoelectric actuators are different
from the USMs. The materials like lithium niobate and some other single crystal materials are
also used for USMs and piezoelectric technology.
The major difference between the piezoelectric actuators and USMs is stated as the vibration of
the stator in contact with the rotor, which can be amplified by using the resonance. The
amplitude of the actuator motion is in between 20 to 200nm.

24. Structure of Ultrasonic Motor
Ultrasonic motor: The main structures of USR series is the followings.
 The Stator part transmits vibration
 The Rotor which is a rotation part
 The Shaft which transmits rotation
 The Bearing
Furthermore, the structure of a stator part is the following.
 The Piezo-Electric Ceramics which generate vibration
 The Stator metal which makes vibration amplify
 The Friction material which contacts with a rotor
The structure of Ultrasonic Motor
(SHINSEI CORPORATION's) is a very simple.
However, each element is calculated strictly and the following capability is realized.
 Stable Rotation Performance
 High Holding Power
 High Silence
The component of a Standard Model Motor and a Non-magnetic Model Motor do not generate
electromagnetic waves.
Furthermore, the Non-magnetic Model Motor uses for stator metal and a bearing the material
which is not affected at all by the influence of magnetic.

25. MECHANISM
A key observation in the study of ultrasonic motors is that the peak vibration that may be
induced in structures occurs at a relatively constant vibration velocity regardless of frequency.
The vibration velocity is simply the time derivative of the vibration displacement in a structure,
and is not (directly) related to the speed of the wave propagation within a structure. Many
engineering materials suitable for vibration permit a peak vibration velocity of around 1 m/s. At
low frequencies — 50 Hz, say — a vibration velocity of 1 m/s in a woofer would give
displacements of about 10 mm, which is visible. As the frequency is increased, the displacement
decreases, and the acceleration increases. As the vibration becomes inaudible at 20 kHz or so, the
vibration displacements are in the tens of micrometers, and motors have been built that operate
using 50 MHz surface acoustic wave (SAW) that have vibrations of only a few nanometers in
magnitude . Such devices require care in construction to meet the necessary precision to make
use of these motions within the stator.
Dry friction is 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.
Two different ways are generally available to control the friction along the stator-rotor contact
interface, travelling-wave vibration and standing-wave vibration. Some of the earliest versions of
practical motors in the 1970s, by Sashida , for example, used standing-wave vibration in
combination with fins placed at an angle to the contact surface to form a motor, albeit one that
rotated in a single direction. Later designs by Sashida and researchers at Matsushita, ALPS, and
Canon made use of travelling-wave vibration to obtain bi-directional motion, and found that this
arrangement offered better efficiency and less contact interface wear. An exceptionally high-
torque 'hybrid transducer' ultrasonic motor uses circumferentially-poled and axially-poled
piezoelectric elements together to combine axial and torsional vibration along the contact
interface, representing a driving technique that lies somewhere between the standing and
travelling-wave driving methods.

26. A key observation in the study of ultrasonic motors is that the peak vibration that may be
induced in structures occurs at a relatively constant vibration velocity regardless of frequency.
The vibration velocity is simply the time derivative of the vibration displacement in a structure,
and is not (directly) related to the speed of the wave propagation within a structure. Many
engineering materials suitable for vibration permit a peak vibration velocity of around 1 m/s. At
low frequencies — 50 Hz, say — a vibration velocity of 1 m/s in a woofer would give
displacements of about 10 mm, which is visible. As the frequency is increased, the displacement
decreases, and the acceleration increases. As the vibration becomes inaudible at 20 kHz or so, the
vibration displacements are in the tens of micrometers, and motors have been built[2] that
operate using 50 MHz surface acoustic wave (SAW) that have vibrations of only a few
nanometers in magnitude. Such devices require care in construction to meet the necessary
precision to make use of these motions within the stator.
More generally, there are two types of motors, contact and non-contact, the latter of which is rare
and requires a working fluid to transmit the ultrasonic vibrations of the stator toward the rotor.
Most versions use air, such as some of the earliest versions by Hu Junhui. Research in this area
continues, particularly in near-field acoustic levitation for this sort of application. (This is
different from far-field acoustic levitation, which suspends the object at half to several
wavelengths away from the vibrating object).
Types of Ultrasonic Motors:
The USMs are classified into different types based on different criteria, which are as
follows:
Classification of USMs based on the type of motor rotation operation
o Rotary type motors
o Linear type motors
Classification of USMs based on the shape of the vibrator
o Rod type

27. o П shaped
o Cylindrical shaped
o Ring (square) type
Classification based on the type of vibration wave
o Standing wave type – it is further classified into two types:
1. Unidirectional
2. Bidirectional

28. Working of the Ultrasonic Motors
The vibration is induced into the stator of the motor, and it is used for conveying the motion to
the rotor and also to modulate the frictional forces. The amplification and (micro) deformations
of active material are utilized for generation of the mechanical motion. The macro-motion of the
rotor can be achieved by the rectification of the micro-motion using the frictional interface
between the stator and the rotor.
The ultrasonic motor consists of stator and rotor. The operation of the USM changes the rotor or
linear translator. The stator of the USM consists of piezoelectric ceramics for generating
vibration, a metal of the stator for amplifying the generated vibration and a friction material for
making contact with the rotor.
Whenever voltage is applied, a travelling wave is generated on the surface of the stator metal
which causes the rotor to rotate. As the rotor is in contact with the stator metal, as mentioned

29. above – but only at each peak of the travelling wave – which causes the elliptical movement –
and, with this elliptical movement, the rotor rotates in the direction conversely to the direction of
the travelling wave.

30. Features & Merits of Ultrasonic Motors
o These are small in size and are excellent in response.
o These have low speed of ten to several hundred rpm and high torque, and hence reduction gears
are not required.
o These consist of high-holding power, and even if the power is turned off, they don’t need brake
and clutch.
o They are small, thin and have less weight compared to other electromagnetic motors.
o These motors don’t contain any electromagnetic material and they do not generate
electromagnetic waves. So, these can be used even in high magnetic field areas as these are
unaffected by the magnetic field.
o These motors don’t have any gears, and an inaudible frequency vibration is used for driving
these motors. So, they do not generate any noise and their operation is very quiet.
o Accurate speed and position control are possible with these motors.
o The mechanical time constant for these motors is less than 1ms and the speed control for these
motors is step less.
o These motors have very high efficiency, and their efficiency is insensitive to their size.
Demerits of Ultrasonic Motors
o A high-frequency power supply is required.
o As these motors operate on friction, durability is very less.
o These motors have drooping speed-torque characteristics.

31. Applications of Ultrasonic Motors
o Used for the autofocus of camera lens.
o Used in compact paper handling devices and watches.
o Used in conveying machine parts.
o Used for drying and ultrasonic cleaning.
o Used to inject oil into the burners.
o Used as the best motors known to offer high potential for miniaturization of equipments.
o Used in MRI magnetic resonance imaging scanning in medicine.
o Used to control the disk heads of computer like floppies, hard disk and CD drives.
o Used in many applications in the fields of medicine, aerospace and robotics.
o Used to automatically control Rolling screen.
o In future, these motors may find applications in the fields like automobile industry, nano-
positioning, microelectronics, Micro Electro Mechanical System technology and consumer
goods.

32. Construction
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.
As the ultrasonic motor uses ultrasonic vibrations as its driving force,it comprises a stator which
is a piezoceramic 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.
Principle Of Operation:
Piezoelectric Effect:
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 Further more a permanently polarized material such as Quartz(SiO2) or Barium Titanate
(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.

33. Conversely, an applied electric field can cause a piezoelectric material to change
dimensions. This is known as Electrostriction or Reverse piezoelectric effect. Current ultrasonic
motor design works from this principle, only in reverse.
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.
Eg: Quartz, Rochelle salt, Tourmaline, Lead Zirconium Titanate
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 working principle is based on a traveling wave as the driving force. 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.
This wave rotates the rotor which is in contact with the stator. High holding power of
Ultrasonic Motor. High pressure is applied between the rotor and the stator. For this reason, the
biggest frictional force at the time of a stop is the holding power of an ultrasonic motor.

34. PRINCIPLE OF WORKING
The working principle of Ultrasonic motor is shown in figure. High order curling vibration is
generated on the surface of the elastic vibrator (stator) and travelling eaves are made by
excitation of the piezoceramic vibrator. And the certain pressure causes the slider to propagate
on stator by the friction between them. Driving force of Ultrasonic motor is obtained by
travelling-wave type elastic curling wave. This type of motor is named as travelling wave type
Ultrasonic motor. For generating elastic curling wave on the elastic annular plate, adhere the
piezoceramic vibrator beneath the annular plate and exploit the expanding and contracting wave.
That is piezoceramic vibrator beneath the elastic annular plate is polarized and when AC voltage
is applied to the vibrator, sectional expanding and contracting move occurs and elastic curling
waves are generated on the elastic annular plate.
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. Further more a permanently polarized material such as Quartz(SiO2) or Barium
Titanate(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.
Current ultrasonic motor design works from this principle, only in reverse.

35. When a voltage having a resonance frequency of more than 20KHz 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.
Eg:Quartz,Rochelle salt,Tourmaline,Lead Zirconium Titanate
t 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 working principle is based on a traveling wave as the driving force. 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.

36. Principle of Ultrasonic Motor
Summary ：
The Ultrasonic Motor uses piezo-electric ceramics for the source of a drive. If voltage is
impressed to piezo-electric ceramics, the form of piezo-electric ceramics will change.
The modification is made to amplify and spread with stator metal, and a traveling wave is
generated on the surface of stator metal. This wave rotates the rotor which is in contact with the
stator.
High holding power of Ultrasonic Motor ：
High pressure is applied between the rotor and the stator.For this reason, the biggest
frictional force at the time of a stop is the holding power of an ultrasonic motor.
Rotation principle of Ultrasonic Motor :
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 a direction contrary 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 counterclockwise direction (CCW).
And the rotor in contact with the peak of the wave rotates in the counterclockwise
direction (CCW).

37. By controlling the speed and direction of this traveling wave, control of an Ultrasonic
Motor is possible.

38. Feature of Ultrasonic Motor:
SHINSEI CORPORATION's Ultrasonic Motor: USR series is small size, a low speed, and high
torque,
and is excellent in a response and silence.
Moreover, because it has high holding power at the time of un-applying an electric current,
the moving part which does not use reduction gears can be built.
Because the Ultrasonic Motor uses neither the coil nor the magnet, it is not affected about
operation
of a motor by the influence of magnetic.
And an ultrasonic motor does not generate magnetism during rotation.For this reason, the
stable operation
in strong magnetic field environments, such as near MRI and superconductivity experiment
equipment, is possible.
Now, Ultrasonic Motor is used for the following uses.
・ Autofocus of a camera
・ Control part of a measuring instrument
・ Actuator of the lens mirror of optical equipment
・ Control device of the antenna of an artificial satellite
・ Gripper for the robots for industry
・ Automatic controller of a rolling screen
・ Conveying machine of parts
・ Attitude control of the measuring instrument near MRI
・ Actuator within High Magnetic Field Environment

39. Typical Feature
High Torque and Low Speed:
The feature of Ultrasonic Motor is high torque at the low speed of 10 – several 100 [rpm].
Neither reduction gears nor a brake is needed, and the direct drive is possible.
It is possible to make the actuator of the backlash.
High Holding Power with no electric current:
Ultrasonic Motor keeps up high holding power, also in the condition that the power is
turned off.
For this reason, a brake and a clutch are unnecessary to an ultrasonic motor.
It is possible to make a lightweight actuator without an electromagnetic brake or a clutch.
High Response and High Controllability:
Because the inertia of a rotor is small and the braking effort by friction between rotor
stators is large,
the response at the time of a stop is excellent.
Because speed control is stepless, and a mechanical time constant is also below 1 [ms],
it is very excellent also in controllability.
For this reason, highly accurate speed control and position control are possible.
Usable in a High Magnetic Field and Not generate Electromagnetic Waves:
Since neither winding nor a magnet nor a coil is used, an ultrasonic motor does not
generate electromagnetic waves.
Specially, since a nonmagnetic type ultrasonic motor does not use a magnetic material at
all, it operates without being affected in a high magnetic field environment by the
influence of magnetic.

40. Small, Thin and Lightweight:
Compared with the Electromagnetism Motor of torque of the same degreea, Ultrasonic
Motor is Small, Thin, and Weight is several percent.
By using as an articulated robot's arm or an actuator of a leg, weight of each joint can be
made light.
Improvement in the response of a robot or the whole system and improvement in weight
capacity are expectable by adopting Ultrasonic Motor.
High Silence:
Because vibration used for a drive is the frequency of a non-auditory area, its operation
sound is very quiet.
Moreover, it is possible to avoid generating of the noise of a drive by not using a gear.

41. Conclusion
The main contribution of the work presented in this paper consists in description
development rotary traveling wave ultrasonic motor as structure, principle function and
application form in according to its working characteristics.
As technical example of ultrasonic motor, Daimler-Benz AWM90-X motor is presented,
using the measurements values obtained from the manufacturer data and it simulation
implemented that we have developed.
After 25 years of active search and nowadays piezoelectric rotary motors have
considerable advantages and represent a truth concurrent for conventional electromagnetic
motors.
For the new needs of applications domains, several types of piezoelectric ultrasonic
motors have been suggested and designed and developed, to be used as standard as
efficient, particularly the rotary traveling wave ones which are now commercially available
and applied as auto-focus cameras, in robotics, in medical domain and in aerospace.

42. References
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