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A piezoelectric motororpiezo motoris a type ofelectric motorbased upon the change in shape of apiezoelectric

materialwhen anelectric fieldis applied. Piezoelectric motors make use of the converse piezoelectric effect whereby

the material produces acoustic orultrasonicvibrations in order to produce a linear or rotary motion. In one

mechanism, the elongation in a single plane is used to make a series of stretches and position holds, similar to the

way acaterpillarmoves.[1]

Contents

[hide]

1 Current designs

o 1.1 Locking mechanisms

o 1.2 Stepping actions

o 1.3 Direct drive actions

o 1.4 Speed and precision

2 Other designs

o 2.1 Single action

3 Patents

4 See also

5 References

[edit]Current designs

A slip-stick actuator.

Motors are made in bothlinearandrotarytypes.

Of these, one drive technique is to use piezoelectric ceramics to push a stator. These piezoelectric motors use three

groups of crystals: two of which are Locking and one Motive, permanently connected to either the motor's casing or

stator (not both) and sandwiched between the other two, which provides the motion. These piezoelectric motors are

http://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Ultrasonic_motorhttp://en.wikipedia.org/wiki/Ultrasonic_motorhttp://en.wikipedia.org/wiki/Ultrasonic_motorhttp://en.wikipedia.org/wiki/Caterpillarhttp://en.wikipedia.org/wiki/Caterpillarhttp://en.wikipedia.org/wiki/Caterpillarhttp://en.wikipedia.org/wiki/Piezoelectric_motor#cite_note-1http://en.wikipedia.org/wiki/Piezoelectric_motor#cite_note-1http://en.wikipedia.org/wiki/Piezoelectric_motor#cite_note-1http://en.wikipedia.org/wiki/Piezoelectric_motorhttp://en.wikipedia.org/wiki/Piezoelectric_motorhttp://en.wikipedia.org/wiki/Piezoelectric_motorhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Current_designshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Current_designshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Locking_mechanismshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Locking_mechanismshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Stepping_actionshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Stepping_actionshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Direct_drive_actionshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Direct_drive_actionshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Speed_and_precisionhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Speed_and_precisionhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Other_designshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Other_designshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Single_actionhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Single_actionhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Patentshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Patentshttp://en.wikipedia.org/wiki/Piezoelectric_motor#See_alsohttp://en.wikipedia.org/wiki/Piezoelectric_motor#See_alsohttp://en.wikipedia.org/wiki/Piezoelectric_motor#Referenceshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Referenceshttp://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=1http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=1http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=1http://en.wikipedia.org/wiki/Linearhttp://en.wikipedia.org/wiki/Linearhttp://en.wikipedia.org/wiki/Linearhttp://en.wikipedia.org/wiki/Rotationhttp://en.wikipedia.org/wiki/Rotationhttp://en.wikipedia.org/wiki/Rotationhttp://en.wikipedia.org/wiki/File:Slip-stick_actuator_operation.svghttp://en.wikipedia.org/wiki/File:Slip-stick_actuator_operation.svghttp://en.wikipedia.org/wiki/File:Slip-stick_actuator_operation.svghttp://en.wikipedia.org/wiki/File:Slip-stick_actuator_operation.svghttp://en.wikipedia.org/wiki/Rotationhttp://en.wikipedia.org/wiki/Linearhttp://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=1http://en.wikipedia.org/wiki/Piezoelectric_motor#Referenceshttp://en.wikipedia.org/wiki/Piezoelectric_motor#See_alsohttp://en.wikipedia.org/wiki/Piezoelectric_motor#Patentshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Single_actionhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Other_designshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Speed_and_precisionhttp://en.wikipedia.org/wiki/Piezoelectric_motor#Direct_drive_actionshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Stepping_actionshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Locking_mechanismshttp://en.wikipedia.org/wiki/Piezoelectric_motor#Current_designshttp://en.wikipedia.org/wiki/Piezoelectric_motorhttp://en.wikipedia.org/wiki/Piezoelectric_motor#cite_note-1http://en.wikipedia.org/wiki/Caterpillarhttp://en.wikipedia.org/wiki/Ultrasonic_motorhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Electric_motor

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fundamentallystepping motors, with each step comprising either two or three actions, based on the locking type.

Another mechanism employs the use ofsurface acoustic waves(SAW) to generate linear or rotational motion.

A second drive technique is illustrated by the Squiggle motor, in which piezoelectric elements are bonded

orthogonally to a nut and their ultrasonic vibrations rotate and translate a central lead screw. This is a direct drive

mechanism.

[edit]Locking mechanisms

The non-powered behaviour of the first type of piezoelectric motor is one of two options: Normally

Locked orNormally Free. When no power is being applied to a Normally Locked motor, thespindleorcarriage(for

rotary or linear types, respectively) will not move under externalforce. For a Normally Free motor, the spindle or

carriage will move freely under external force. However, if both locking groups are powered at rest, a Normally Free

motor will resist external force without providing any motive force.

A combination of mechanical latches and crystals could be used, but this would restrict the maximum steppingrateof

the motor.

The non-power behaviour of the second type of motor is locked, as the drive screw is locked by the threads on the

nut. Thus it holds its position with the power off.

[edit]Stepping actions

Piezoelectric motor

Fig. 1: Stepping stages ofNormally Freemotor

Regardless of locking type, stepping type piezoelectric motors both linear and rotary use the same mechanism

to provide movement.

First, one group oflockingcrystals 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 lockinggroup

along the motor path. This is the only stage where motor movement takes place.

http://en.wikipedia.org/wiki/Stepper_motorhttp://en.wikipedia.org/wiki/Stepper_motorhttp://en.wikipedia.org/wiki/Stepper_motorhttp://en.wikipedia.org/wiki/Surface_acoustic_wavehttp://en.wikipedia.org/wiki/Surface_acoustic_wavehttp://en.wikipedia.org/wiki/Surface_acoustic_wavehttp://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=2http://en.wikipedia.org/wiki/Spindle_(tool)http://en.wikipedia.org/wiki/Spindle_(tool)http://en.wikipedia.org/wiki/Spindle_(tool)http://en.wikipedia.org/wiki/Carriagehttp://en.wikipedia.org/wiki/Carriagehttp://en.wikipedia.org/wiki/Carriagehttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Rate_(mathematics)http://en.wikipedia.org/wiki/Rate_(mathematics)http://en.wikipedia.org/wiki/Rate_(mathematics)http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=3http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=3http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=3http://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezosteps.pnghttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/wiki/File:Piezomotor_type_inchworm.gifhttp://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=3http://en.wikipedia.org/wiki/Rate_(mathematics)http://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Carriagehttp://en.wikipedia.org/wiki/Spindle_(tool)http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=2http://en.wikipedia.org/wiki/Surface_acoustic_wavehttp://en.wikipedia.org/wiki/Stepper_motor

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Then the lockinggroup triggered in stage one is released (in Normally Lockingmotors, the other is triggered). Then

the motive group is released, retracting the 'trailing' lockinggroup. Finally, both lockinggroups are returned to their

default states.

[edit]Direct drive actions

The direct drive piezoelectric motor uses continuous ultrasonic vibrations to provide movement. A two-channel

sinusoidal or square wave is applied to the piezoelectric elements at an ultrasonic frequency of 40 kHz to 200 kHz,

matching the first bending resonant frequency of the threaded tube. This creates an orbital motion which drives the

screw.

[edit]Speed and precision

The growth and forming of piezoelectric crystals is a well-developedindustry, yielding very uniform and consistent

distortion for a given appliedpotential difference. This, combined with the minute scale of the distortions, gives the

piezoelectric motor the ability to make very fine steps manufacturers claim precision to thenanometerscale.

The high response rate and fast distortion of the crystals also allows the steps to be made at very high frequencies

upwards of 5MHz. This gives a maximum linear speed of approximately 800 mm per second, or nearly 2.9 km/h.

[edit]Other designs

http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=4http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=4http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=4http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=5http://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Potential_differencehttp://en.wikipedia.org/wiki/Potential_differencehttp://en.wikipedia.org/wiki/Potential_differencehttp://en.wikipedia.org/wiki/Nanometerhttp://en.wikipedia.org/wiki/Nanometerhttp://en.wikipedia.org/wiki/Nanometerhttp://en.wikipedia.org/wiki/MHzhttp://en.wikipedia.org/wiki/MHzhttp://en.wikipedia.org/wiki/MHzhttp://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=6http://en.wikipedia.org/wiki/MHzhttp://en.wikipedia.org/wiki/Nanometerhttp://en.wikipedia.org/wiki/Potential_differencehttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Piezoelectric_motor&action=edit&section=4