22-08-2012, 11:44 AM
Ultrasonic Motors
Ultrasonic Motors.ppt (Size: 736 KB / Downloads: 117)
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.
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.
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.
Basic Principle
One thing all USMs have in common is their use of piezoelectric material to transform electrical energy to mechanical energy.
Basic Principle
Here we will discuss the operation of a ring type USM. Like traditional motors, USMs have a stator and a rotor.
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.
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.
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.
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.
Linear USM
The Piezo LEGS motor, developed by MicroMo Electronics Inc., illustrates one popular technique for linear USM actuation.
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.
Spherical USM
Spherical USMs may be employed when more than one degree of freedom is needed. Potential applications include surgical robots or robotic eyes.
Future Work
USMs have lots of potential for use in medical applications. One very promising research area is in medical diagnostic instruments.
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
Works Cited
Canon. (2007). Using Ultrasonic Vibrations to Drive Focus and Zoom Lenses. Retrieved March 2, 2009, from Canon: http://www.canontechnology/canon_tech/ex...n/usm.html
Carnegie Mellon University. (2007). HeartLander. Retrieved February 22, 2009, from CMU: http://www.cs.cmu.edu/~heartlander/index.html
Works Cited
Kenedy, B. (2007, July). Piezoelectric motors: big power, small package. Retrieved March 2, 2009, from Micro manufacturing: http://micromanufacturingshowthread.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/lomma...-usm97.htm
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_MT...Toyama.pdf