Amplifiers, DIA Converters, Electronic
HV-Switches for Piezoelectric actuators |
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 Piezoelectric actuators 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 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 Piezoelectric elements.
- The high acceleration rates/short reaction times predestinate Piezoelectric elements for
the control of fast processes in valve technology, fuel injection application, mechanical
shaking excitation for test purposes with time periods/rise- times in the microseconds
range.
- Piezoelectric actuators 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.
General considerations for electronic supplies for Piezoelectric actuators:
In the simplest case a Piezoelectric actuator 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 Piezoelectric actuator 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 Piezoelectric element 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:
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 DIA converter of sufficient speed and
resolution, and the low voltage signal is than amplified to the actuator's requirements.
When designing a Piezoelectric actuated 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 subsequent selection of the
supply may lead to costly and ineffective approaches.
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