Piezomechanik

A further application is the active stabilization of mechanical
arrangements e.g. laser resonators against misalignment due
to thermal drifts or mechanical shocks (see “feedback controlled
stabilization PiStab 2”).
3. Practical aspects of dynamically operated
piezoactuators
3.1. Preloading, reset mechanisms
Piezoceramic is sensitive to tensile stress, it shows a damage
strain of only 1‰.
Note, that this tensile stress can be created externally and
also internally by dynamic operation. This fact is easily seen
in Fig 4/sec. 2.8., where the application of an electric pulse
leads to overshooting of the actuator relative to the steady
state position. This overshooting can cause tensile stress
and thereby damage to the actuator when the relevant forces
are not compensated by other means.
To prevent damage by tensile forces the following strategies
are commonly applied:
• passive preloading/reset of actuators
This technique is mostly applied to stack actuators:
An elastic spring compresses the piezostack with a defined
force shown in fig. 5a, b. A preloaded stack is less sensitive
to externally applied tensile stress for several reasons, i.e. a
reduction in stacklength is achieved by the preload force. A
Fig. 5a:
Mirror tilter with passive prestress/reset
Fig. 5b:
Linear stackactuator with passive prestress/reset
http://www.piezomechanik.com Amplifiers, D/A Converters, Electronic HV-Switches for Piezoactuators
piezostack
tilting
prestress spring
piezostack
mirror surface
prestress/reset
spring
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