Piezomechanik

Amplifiers, D/A Converters, Electronic HV-Switches for piezoactuators
1. Introduction
Piezoelectrical actuators are innovative driving systems,
which show increasing application potential for highly sophisticated
driving/positioning tasks in a great variety of technological
fields. The main areas of interest include
• the extreme positioning sensitivity, enabling such
systems to handle dimensions in the atomic scale
• extreme force generation resulting for example in high
acceleration rates during dynamic operation.
For some applications no practicable alternative to piezoactuators
exist
• Piezoelectric actuators are used for the ultraprecise positioning
of components and mechanical setups ranging
from low weight optical elements, up to heavy loads such
as tooling machines. The newest scanning microscope
General considerations for electronic supplies for piezoactuators:
In the simplest case a piezoactuator should move according
to an external signal i.e. from a sinewave generator, or other
source. In most cases, this original signal cannot be applied
directly to the piezoactuator because voltage and power
usually do not match the actuator’s requirements. An amplifier
has to be used to convert the signal to result in sufficient
travel and dynamics of the actuator.
This is an important aspect of actuator’s application:
The adaptation of a piezoelement to a distinct task is determined
only in part by its mechanical properties and geometrical
size. Equally important for the system’s performance
are the properties of the driving electronics.
The same actuator can be used for completely different
operating profiles depending only on the choice of the supply
electronics:
signal
generator
elec. signal
function generator
feedback control electronic
computer
amplifier
pulser
Fig. 1:
Schematic representation of an actuator system
When designing a piezoactuated system the designer
has to deal simultaneously with actuator and supply to
get the optimum matching. A step-by-step definition
whereby the actuator is first-chosen and then a sub-
matching
electronics
technologies such as STMs, AFMs etc. require precise
handling of probe tips with sub-nanometer precision,
which can only done in a reasonable way by using piezomechanical
elements.
• The high acceleration rates/short reaction times predestinate
piezoelements for the control of fast processes in
valve technology, fuel injection application, mechanical
shaking excitation for test purposes with time periods/risetimes
in the microseconds range.
• Piezoactuators are very attractive candidates for active
vibration control and cancellation even in heavy and extended
mechanical structures such as vehicles, airplanes,
helicopters, ships. A special feature is the dual effect of
piezoelectricity, which can be used both for sensing and
actuating. Single element can therefore be used as smart
transducers acting simultaneously as sensor and actuator.
Slow cycling of an actuator requires only a small low power
supply, whereas pulsed operation i.e. generating mechanical
shocks, needs supplies with peakpowers in the kilowatt
range.
Computer control of actuators comprises an additional step:
the computer data has to be converted by a D/A converter of
sufficient speed and resolution, and the low voltage signal is
than amplified to the actuator’s requirements.
piezo
actuator
mechan.
reaction
sequent selection of the supply may lead to costly and
ineffective approaches.
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