Piezoelectric Actuators

Piezoelectric actuators are devices that produce a small displacement with a high force capability when voltage is applied. There are many applications where a piezoelectric actuator may be used, such as ultra-precise positioning and in the generation and handling of high forces or pressures in static or in dynamic situations.

Actuator configuration can vary greatly depending on application. Piezoelectric stack actuators are manufactured by stacking up piezoelectric disks or plates, the axis of the stack being the axis of linear motion when a voltage is applied. Tube actuators are monolithic devices that contract laterally and longitudinally when a voltage is applied between the inner and outer electrodes. A disk actuator is a device in the shape of a planar disk. Ring actuators are disk actuators with a center bore, making the actuator axis accessible for optical, mechanical, or electrical purposes. Other less common configurations include block, disk, bender, and bimorph styles.

These devices can also be ultrasonic. Ultrasonic actuators are specifically designed to produce strokes of several micrometers at ultrasonic (>20kHz) frequencies. They are especially useful for controlling vibration, positioning applications and quick switching. In addition, piezoelectric actuators can be either direct or amplified. The effect of amplification is a larger displacement, but it can also result in slower response times.

The critical specifications for piezoelectric actuators are the displacement, force and operating voltage of the actuator. Other factors to consider are stiffness, resonant frequency and capacitance. Stiffness is a term used to describe the force needed to achieve a certain deformation of a structure. For piezoelectric actuators, it is the force needed to elongate the device by certain amount.  It is normally specified in terms of Newton per micrometer. Resonance is the frequency at which the actuators respond with maximum output amplitude. The capacitance is a function of the excitation voltage frequency.

The size of the actuator, of course, is important, as are the electrical connectors. Some of the most common connectors are DB-9, BNC, two wires of either AWG 26 or AWG 30, or else a LEMO(r) connector, which is a precision push-pull locking connector for demanding applications.

• Multilayer Piezoelectric Actuators: White Paper on Improved Reliability
  The reliability of piezoelectric multilayer actuators is an important issue for the extension of their use. Two completely different load cases have to be distinguished when reliability parameters of...
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