Piezocomposite0 pages
THEORY - HIGH POWER ACTUATORS
Piezocomposite Actuators
Cofired Multilayer Actuators
For the past few decades “cofired” multilayer stacks has
been the state of the art method used for constructing piezo
actuators. However there are a variety of applications where
multilayer stacks reach their natural limitations.
Multilayer stacks consist of many ceramic layers (each approx. 100 µm in thickness) with thin (1 µm) electrodes between them. After stacking these layers the compound is
then sintered at high temperatures (cofiring).
Figure 1: Piezocomposite stack actuator
made from single
piezoceramic discs and
intermediate metal
electrodes
Multilayer actuators are operated with low voltages up to
200 V.
Design of Piezocomposite Actuators
Piezocomposite Ring Actuators are preferred for
Piezocomposite actuators are made from completely sintered single PZT discs (thickness 0.3 to 0.5 mm) and separate
intermediate metal foil electrodes which are held together
by special high quality adhesives. Therefore these discretely
stacked actuators are a composite material with some outstanding properties.
•t ptical applications
O
•t pplications with high frequencies requiring effective
A
cooling and special thermal behavior
•t pplications with high bending stability
A
Stiffness
Piezocomposite actuators should be used to generate:
According to
•t igh forces up to 50 kN
H
•t igh accelerations up to 100’000 m/s2
H
•t hort pulses
S
•t o withstand loads up to 70 kN
T
, the stiffness of Piezocom-
posite Actuators increases with the cross section and decreases with the length of the actuator. Piezocomposite Actuators with a preload show an elastic modulus nearly as
high as that of multilayer stacks.
Piezocomposite Actuators
Low Voltage Multilayer Stacks
preferred use
large cross sections generating high forces
small, medium cross sections for
low volume elements
applications
high dynamic applications,
shock generations,
shakers, vibration generation
short impulse excitation
positioning,
scanning,
integration into more dimensional
positioning systems
operating voltage
500 V - 1000 V
max. electrical field strength
up to 200 V
approx. 2 kV/mm
max. strain
0.1 to 0.15 % related to the stack length
force generation
same order related to the same cross section
positioning accuracy
same for both types: depending on the electrical supply and environmental conditions
electrical capacitance / volume
approx. 10 nF/cm3
approx. 2,5 µF/cm3
production technology
stacking of sintered ceramic plates
stacking of non sintered ceramic
layers and cofiring
material variety
large
small
operating temperature range
up to 200 °C
up to 100 °C
electrical current for dynamic
applications / per volume
low current
high current
cross section of ceramics
diameters up to 35 mm
up to 14 x 14 mm2
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