2. INTRODUCTION
• 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.
• These motors offer high torque density at low
speed, high holding torque, simple construction
and have a quick response.
3. • To obtain the levels of torque speed
characteristics of USM using conventional
motors we require to add a gear system to
reduce the speed.
• USM’s are fundamentally designed to
have high holding force,providing zero
backlash.
• These characteristics of USM makes them
attractive for robotic applications where
small motions are required.
4. WORKING OF USM
• A travelling wave is established over the
stator surface,which behaves as an elastic
ring and produces elliptical motion at the
inter face with the rotor.
• This elliptical motion of the contact surface
propels the rotor and the drive shaft
connected to it.
• The teeth which are attached to the stator
are intended to increase the moment arm
to amplify the speed.
6. Principle of operation
• The general principle of operation of the
ultrasonic motors is to generate gross
mechanical motion through the
amplification and repetition of micro
deformations of the active material.
• The active material, induces an orbital
motion of the stator of the stator at the
rotor contact points to produce macro
motion of the stator.
7. • The active material which is a peizo
electric material excites a traveling flexural
wave within the stator that leads to the
elliptical motion of the stator.
• Teeth are used to enhance the speed that
is associated with the propelling effectof
these particles.
• The frictional force between the stator and
rotor causes the rotor to spin.
9. Mechanism
• Dry friction is often used in contact and the
the ultra sonic vibration induced in the
stator is used both to impart motion to the
rotor and to modulate the frictional force
present at the interface.
• An exceptionally high torque ‘hybrid
transducer’ ultrasonic motor uses
circumferentially poled and axially poled
piezoelectric elements to combine axial
and torsional vibration.
10. Applications
• Canon was one of the pioneers of the
ultrasonic motors and made it famous for
the manufacture of the autofocus lenses.
• USM’s are also used in watch motors and
compact paper handling,in spacecraft
instruments and subsystems.
12. Conclusion
• Hence the ultrasonic motors, which is a
new step in the miniaturized electrical
technology has got many applications in
small appliances because of its high
torque at low density.
