Piezo actuators and electronics

Piezoelectric actuators, according to the broadest meaning, cover a wide range of concepts. Potentially, all devices using one of the piezo effects can be considered as piezo actuators. To be more specific, the following classification can be applied based on effects and uses.

The direct piezoelectric effect has been discovered by Pierre and Jacques Curie in 1880: Applying a mechanical pressure on some crystals as Quartz or Rochelle Salts generates electric charges. This effect is used to develop sensors for dynamic force or electric generators for vibration energy harvesting. Standard piezo actuators from CEDRAT TECHNOLOGIES such as APA® can be used for such applications because the direct piezoelectric effect is naturally present in all piezo actuators. CEDRAT TECHNOLOGIES can also develop customised piezo sensors and generators as presented in the related other sections.

The inverse piezoelectric effect, the key effect used to realise piezo actuator functions, consists in the deformation of a piezoelectric material due to the applied electric field.

Since the 60s, the most usual materials for actuators have been the PZT (Lead Zirconate Titanate) ceramics. Bulk piezo ceramics are poled and covered with external electrodes to generate the electrical excitation field. They offer deformations in the range of 300ppm with field of 600kV/m. This field requires high voltages, except at resonance, because the Q factor allows a full deformation with a reduced voltage. This method leading to ‘resonant actuators’ was at first developed by Paul Langevin in 1917 to build sonar transducer emitters. It is still used by CEDRAT TECHNOLOGIES in various vibration, sound and ultrasound generators as well as detection systems.

The multi layer piezo ceramics (MLA) have been developed in the 90s to reduce the required voltage outside resonance. Thanks to a structure based on PZT layers of 50 to 100µm placed between internal electrodes, the maximum electric field can reach up to 2MV/m with a voltage of less than 200V, leading to an active deformation of about 1000ppm. In a restricted sense, piezo actuators cover controllable actuators using these multi-layer piezo ceramics to make solid-state actuators using electrically-induced deformations.

CEDRAT TECHNOLOGIES’ Standard piezoelectric actuators, such as the PPAs & the APA®have been using these piezo materials this way for more than 10 years. In the context of its space activities, the multi layer piezo ceramics available on the market are compared in terms of performance and reliability for the benefice of its space and non-space customers.

Customized or new piezoelectric actuators and associated electronics developed by CEDRAT TECHNOLOGIES are presented in the following examples: A hollow piezo actuator, a double amplification actuator to get millimetres strokes, an amplified piezoelectric actuator with re-enforced pre-stress to survive large external vibrations (for space applications), extremely small (micro) to extremely large actuators …

Also developed by CEDRAT TECHNOLOGIES and presented in other sections, Piezo Mechanisms and Piezo Motors are more complex devices that can also be considered as piezo actuators.

To learn more about our piezo actuators see our related publications on piezo actuators .