• It has been known for more than 30 years.
• The first ultrasonic motor was introduce by v.v
lavrinko in 1965.
• 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
• Conversion of electric energy into motion by
inverse piezoelectric effect.
• To obtain the levels of torque speed
characteristics of USM using conventional motors
we require to add a gear system to reduce the
• These characteristics of USM makes them
attractive for robotic applications where small
motions are required.
• This motor achieves high speed and drive
forces, while still permitting the moving part to
be positioned with high accuracy.
The piezoelectric effect is understood as the linear
electromechanical interaction between the mechanical and the
electrical state in crystalline materials with no inversion
• Piezoelectricity – generation of voltage in response of
• The word is derived from the Greek piezein, which means to
squeeze or press.
• This effect is also reversible.
• Deformation is only 0.1 % of the original dimension.
• Piezoelectric material- quartz(SiO2), barium titanate (BaTiO3)
lead zirconate titanate and occasionally lithium niobate .
Electromagnetic motors are notorious for consuming high
amount of power and creating high ambient motor
temperatures respect to USM
The electromagnetic motors produce strong magnetic fields
which cause interference. Ultrasonic motors use piezoelectric
effect and hence no magnetic interference.
Electromagnetic motor has high input to output energy loss
USM High positional accuracy respect to Electromagnetic Motor.
• Generation of gross mechanical motion through the
amplification and repetition of micro-deformations of
• The active material induces an orbital motion of the
stator at the rotor contact points .
• Frictional interface between the rotor and stator
rectifies the micro-motion to produce macro-motion of
• Working frequency-20 KHz to 10 MHz
• Amplitude of the actuator motion – 20 to 200nm
This type of motors use three groups of
crystals: two of which are Locking and
First, one group of locking crystals is
activated — this gives one locked side
and one unlocked side of the 'sandwich'.
Next, the motive crystal group is
triggered and held — the expansion of
this group moves the unlocked locking
group along the motor path. This is the
only stage where motor movement takes
This type of motor commonly known under the names
of Inchworm, Piezo LEGS or PiezoWalk motors
• Superposition of multiple standing wave create
a traveling wave.
• Representation of travelling wave
U(x ,p)= A cos(k x) cos(wt) + A cos(k x - 90)
• Phase difference is 90 degree
•The active material excites a traveling flexural wave within the
stator that leads to elliptical motion of the surface particles.
•Teeth are used to enhance the speed that is associated with the
propelling effect of these particles.
•The rectification of the micro-motion an interface is provided by
pressing the rotor on top of the stator and the frictional force between
the two causes the rotor to spin.
• Camera auto focus lenses
• Driving fluid
• Watch motors and compact
• Optoelectronics area
• In micro surgery and sensor
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.