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Ultrasonic Motors
Eric Ruben
Mechatronics Literature Survey
Dept. of Electrical and Computer Engineering
Utah State University
E: [email protected]
T: 801-916-2400
2/17/2009
Slide-2
Outline
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Introduction
History
Classifications
Basic Principle
Linear USM
Spherical USM
Future Work
Works Cited
ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-3
Introduction
• An ultrasonic motor (USM) converts ultrasonic
vibrations into linear or rotary motion.
• USMs plays an important role a few niche markets where
the size, torque, speed or other requirements could not
be satisfied by the traditional EM motor.
• The two largest markets for
USMs are cameras and
automotive but they are also
found in medical equipment
(MRIs) and as robotic servo
motors.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-4
Introduction
• USMs are often called solid state motors because they
have very few moving parts and they can be fabricated
like integrated circuits to be either macroscopic or
microscopic.
• For the last 29 years USMs have found their way into a
number of applications requiring compact, efficient and
intermittent motion.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-5
Introduction
Some applications where USMs have been used are:
1.
2.
3.
4.
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Camera lens autofocus.
Spacecraft planetary instruments.
Medical equipment (MRIs etc).
Small robotic joints.
ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-6
Introduction
The major advantages of USMs are:
1.
2.
3.
4.
5.
6.
7.
8.
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Compact, lightweight, flexible and robust.
High positioning accuracy.
High low-speed torque and holding torque.
Unaffected by external electric or magnetic fields.
Quiet drive system.
Hard brake with no backlash.
Variable stroke.
Quick response.
ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-7
History
• 1980. The first USM was developed by Sashida.
• 1986. Cannon pioneers the ring type USM for use in
SLR camera lens autofocus.
• 1990. The first micro USM is developed by Canon to for
a new camera autofocus.
• 2003. Cannon released a new micro USM that is ½ the
size of the first with the same output torque.
• 2005. An international conference was held in
Yokohama Japan to aid development of multiple DOF
USMs.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-8
Classifications
USMs can be classified in the following ways:
1. Mode of operation:
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Static
Resonant
2. Type of motion:
•
•
Rotary
Linear
3. Shape of implementation:
•
•
•
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Beam
Rod
Disk
ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-9
Basic Principle
• One thing all USMs have in common is their use of
piezoelectric material to transform electrical energy to
mechanical energy.
• USMs typically use ceramics
derived from lead-zirconate
titanate (abbreviated PZT).
• After the PZT ceramic is
shaped and fired, it is then
electric field polarized. This
allows the material to deform
with a changing electric field.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-10
Basic Principle
• Here we will discuss the operation of a ring type USM.
Like traditional motors, USMs have a stator and a rotor.
• Some USMs use a toothed
stator to increase the holding
torque. Other motors simply
rely on frictional forces.
• As shown in the illustration
on the right, the bottom layer
of the stator is composed of
the PZT material mentioned
earlier.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-11
Basic Principle
• Two electrical signals with orthogonal modes (like
sin(wt) and cos(wt)) are introduced in the stator
material.
• If a constant phase difference exists between the two
modes a traveling wave is created in the stator.
Otherwise the wave is standing.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-12
Basic Principle
• The repeated rolling motion of the stator creates
microscopic orbit of the stator’s surface particles
(much like water drops in a water wave. These small
movements move the rotor forward.
• Thus, the traveling wave in the flexural stator material
moves in the opposite direction of the rotor spin.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-13
Basic Principle
• The stator may drive the rotor using tiny teeth or
simply the force of friction.
• While the angular velocity of the rotor is proportional
to the frequency of the traveling wave, that does not
mean they are equal. The traveling wave may pass
through the stator several times for a single rotation of
the rotor.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-14
Linear USM
• Linear USMs, sometimes called “tube” or “rod”
USMs, also use piezoelectric metals or ceramics for
actuation.
• Show here is a picture of New Scale Technologies tiny
“Squiggle” motor.
• The Squiggle motor weighs
about 30g and boasts a stall
force of 10N. Micro
deformations also give
resolutions as high as 1nm,
and max speeds of 15mm/sec.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-15
Linear USM
• The Piezo LEGS motor, developed by MicroMo
Electronics Inc., illustrates one popular technique for
linear USM actuation.
• Like other USMs, the
LEGS motor generates
motion in discrete steps.
• 4 bimetallic
metal/ceramic “legs” are
positioned around a
single nut on a threaded
rod.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-16
Linear USM
• Applying voltage to a PZT leg causes it to change
shape. This strain in the leg causes the nut to bend and
shift on the threaded rod.
• By synchronizing the 4
legs an elliptical force
pattern moves the rod in
either the forward or
reverse direction.
• Because deformations are
small, several thousand
pulses/sec are needed.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-17
Spherical USM
• Spherical USMs may be employed when more than
one degree of freedom is needed. Potential
applications include surgical robots or robotic eyes.
• The concept of a
spherical USM is simple.
Three separate ring
USMs control actuation
in the x, y and z
directions. Thus, the
sphere can be given any
orientation in 3 space.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-18
Future Work
USMs have lots of potential for use in medical
applications. One very promising research area is in
medical diagnostic instruments.
The Robotics Institute of
Carnegie Mellon
University and the
Division of Cardiac
Surgery at the University
of Pittsburgh are teaming
up to create a tiny robot
called the HeartLander.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-19
Future Work
The HeartLander is a tiny robot that surgeons could insert
into a patient’s chest cavity through a minimally invasive
incision. This tiny robot could then move along the surface
of the heart and perform
interventions. The
surgeon would be able to
control every movement
via a controller and
monitor external to the
patients body.
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-20
Works Cited
• Canon. (2007). Using Ultrasonic Vibrations to Drive
Focus and Zoom Lenses. Retrieved March 2, 2009, from
Canon:
http://www.canon.com/technology/canon_tech/explanati
on/usm.html
• Carnegie Mellon University. (2007). HeartLander.
Retrieved February 22, 2009, from CMU:
http://www.cs.cmu.edu/~heartlander/index.html
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
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Works Cited
• Kenedy, B. (2007, July). Piezoelectric motors: big
power, small package. Retrieved March 2, 2009, from
Micro manufacturing:
http://micromanufacturing.com/showthread.php?t=517
• Shyh-Shiuh Lih, Y. B.-C. (1997, March). Rotary
Ultrasonic Motors Actuated By Traveling Flexural
Waves. Retrieved March 3, 2009, from Nasa Papers:
http://ndeaa.jpl.nasa.gov/nasa-nde/lommas/spieusm97.htm
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-22
Works Cited
• Toyama, D. S. (2008, April). Sherical ultrasonic motor,
piezoelectric actuator, spherical sensing system.
Retrieved March 2, 2009, from TUAT:
http://www.tuat.ac.jp/~crc/m/img/m_05_MT4_Spherical
%20Ultrasonic%20Motor%20Shigeki%20Toyama.pdf
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ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators