See also "MicroPositioning Terms"

A device that produces motion (displacement).

Blocked Force:
The maximum force an actuator can generate if blocked by an infinitely rigid restraint.

A polycrystalline, inorganic material.

Closed-Loop Operation:
The actuator is used with a position sensor which provides feedback to the position servocontroller, compensating for nonlinearity, hysteresis andcreep (see “open-loop”).

Displacement produced per unit force. The reciprocal of stiffness.

Compressive Force:
Force tending to compress the piezo material. Opposite of tensile force.

An unwanted change 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 when headed up. At this temperature a PZT ceramic looses its piezoelectric properties.

A region of permanent electric dipoles with the same orientation.

See “creep”
Effective Mass:
Ideal mass having same resonant frequency as the actual, non-ideal mass.

Acronym for high voltage PZT (actuator).

Hysteresis is based on crystalline polarization and molecular effects and occurs when reversing driving direction. Hysteresis is not to be confused with backlash.

Acronym for low voltage PZT (actuator).

Load Capacity:
Maximum working load. Load capacities are generally specified at levels that allow long lifetime. Note that compressive and tensile capacities differ.

Load Limits:
Maximum force that a PZT device can survive without damage. Note that the compressive and tensile limits are different. Also called the “maximum compressive / tensile force.” See also “load capacity.”

Maximum Compressive/Tensile Force:
Same as “load limit”, see above.

Multilayer Actuator:
An actuator manufactured in a fashion similar to multilayer ceramic capacitors. PZT ceramic and electrode material are “co-fired” in one step. Layer thickness is typically on the order of 20 to 100 µm.

At right angles to, as in “normal force” or “displacement normal to the field”.
Open-Loop Operation:
The actuator is used without a position sensor. Displacement roughly corresponds to the drive voltage. Creep, nonlinearity and hysteresis remain compensated.

Piezoelectric Materials:
Materials that change their dimensions when a voltage is applied and produce a charge when pressure is applied.

Piezo Gain:
Strain coefficients d33 and d31.

The electric orientation of molecules in a piezoelectric material.

Acronym for plumbum (lead) zirconate titanate. Polycrystalline ceramic material with piezoelectric properties. Often also used as acronym for piezo translator.

The spring constant (of a piezo actuator).

Tensile Force:
Force tending to stretch the piezo material.

Trajectory Control:
Measures taken to reduce offaxis motion. Used are both passive measures (e.g. flexure guiding) and active measures (compensation with additional active axes.)

An actuator which produces linear motion.