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Glossary
Actuator:A device that produces motion (displacement).
Blocked force:
The maximum force an actuator can generate if blocked by an infinitely rigid restraint.
Ceramic:
A polycrystalline, inorganic material.
Closed loop operation:
The actuator is used with a position sensor, providing feedback to the position servo controller compensating for nonlinearity, hysteresis and creep (see open loop).
Compliance:
Strain produced per unit stress. The reciprocal of stiffness.
Creep:
An unwanted positive or negative increase in the displacement over time.
Curie Temperature:
The temperature at which the crystalline structure changes from a piezoelectric (non-symmetrical) to a non-piezoelectric (symmetrical) form. At this temperature Piezo ceramics looses the piezoelectric properties.
Domain:
A region of electric dipoles with similar orientation.
Drift:
See creep
HVPZT:
Acronym for High Voltage Piezo (actuator).
Hysteresis:
Hysteresis is based on crystalline polarization effects and molecular friction and occurs when reversing direction. Hysteresis is not to be confused with backlash.
LVPZT:
Acronym for Low Voltage Piezo (actuator).
Multilayer actuator:
An actuator manufactured in a fashion similar to multilayer ceramic capacitors. Active ceramic material and electrode material are "co-fired" in one step. Layer thickness is typically on the order of 20 to 100 µm.
Open loop operation:
The actuator is used without a position sensor. Displacement roughly corresponds to the drive voltage. Creep, nonlinearity and hysteresis are not compensated for.
Piezoelectric Materials:
Materials that change their Dimensions when a voltage is applied and produce a charge when pressure is applied.
Polarization:
The electric orientation of molecules in a piezoelectric material.
Piezo:
Acronym for Plumbum (lead) Zirconate Titanate. Polycrystalline ceramic material with piezoelectric properties. Often used as acronym for piezo translator.
Stiffness:
The spring constant (of a piezo actuator).
Translator:
An actuator that produces linear motion (displacement).
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