Technology:
Piezo Actuators with Guiding and Preload

Simple lever amplification.
The point contact decouples
shear forces and thus tensilestress on the piezo ceramic

Preloaded and Cased Actuators
Piezoceramic actuators are insensitive to pushforces, but must be protected from pulling andshearing stress. A case mechanically decouples lateral forces and insulates contacting.
Between the case and the piezo ceramic, apreload can be applied, e.g. by means of aspring, which allows dynamic operation ofhigher loads.
Flexure Guides Direct Motion and Maintain
Stiffness
Precise straight motions require the piezo
actuator to be embedded in a guide. This is
usually a flexure guide, which is frictionless
and allows hysteresis-free motion at the possible travel ranges of up to a few millimeters.
Ideally this mechanical guiding concept also
integrates force decoupling and preloading
without an adverse effect on the system stiffness.

The piezo ceramic stack ismechanically preloaded
against the housing by meansof a spring. This preventspull forces, such as the ones
caused by the inert mass of
the load in dynamic operation

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Lever Amplification Allows Travel Ranges ofup to 1 mm
The displacements of piezo stack actuators
are typically up to a few ten millimeters anda few 100 micrometers maximum. The flexure
guide can be designed such that it will act likea mechanical lever. This mechanically amplifies the displacement of the piezo actuator andguides it into a different direction, if necessary.
Lever-amplified systems have an extremely
demanding design: On the one hand, they aresupposed to prevent lateral migration and, on
the other, to always guide it in a straight line,
even though the lever always leads througha pivot point. Moreover, increasing the travel
range is at the cost of stiffness.
The flexure guide can be designed such thatfurther integration does not require any additional guide.

From Stack Actuator to 6-Axis Stage
Integration levels of piezo actuators

Stack Actuators

Lever-AmplifiedActuators

Positioning Systems

Travel ranges

up to approx. 300 μm

to 1 mmto 1 mmMoving axes

one

one

up to 3 linear axes and 3 tip/tilt axes

Sensor technology

optional SGS

optional SGS

SGS or direct measuring
capacitive sensors

Linearity

up to 99.8 %up to 99.8 %more than 99.9 %Guidingnone

flexure joints fortilts <10°flexure joints fortilts <2°

Space requirement

low

low

depending on conﬁguration

Price

low

low

depending on configuration

averagelow

lowIntegration effort

PiezoMove® OEM Flexure Actuators with
Built-In Guiding
PiezoMove® actuators combine guided motion
with long travel ranges of up to 1 mm andprovide precision in the 10 nanometer range
if ordered with the position sensor option.
Their high-precision, frictionless flexureguides achieve very high stiffness and excellent straightness of motion. This makes themeasier to handle than a simple piezo actuator,
but still keeps them extremely compact. The
number and size of the piezo actuators used
determine stiffness and force generation.
These features, their small dimensions andcost-efficient design make PiezoMove® flexure
actuators suitable in particular for OEM applications. For open-loop applications, versions
without sensors are available.
In addition to the standard steel models, special invar and nonmagnetic versions are available on request.
This lever mechanism with flexure guides transforms the actuator travel range (vertical)
to an even, straight motion (horizontal)

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TEC72 Piezo Actuators with Guiding and Preload 10/2017 Subject to change without notice. © Physik Instrumente (PI) GmbH & Co. KG 2017

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