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Piezoelectric actuators, according the broadest meaning, covers 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 the Pierre and Jacques Curie in 1880: Applying a mechanical pressure on some crystals as Quartz or Rochelle Salts generates electric charges. This effect is to realise sensors for dynamic force sensing or electric generators for vibration energy harvesting. Standard piezo actuators form Cedrat such as APAs can be used to get these functions because the direct piezoelectric effect is naturally present in all piezo actuators. Cedrat can also develop customised piezo sensors, generators as presented in related other sections.

The inverse piezoelectric effects, the key effect used to realise actuation functions, is the deformation of a piezoelectric material due to the applied electric field.

From the 60s, the more usual materials for actuators are 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 of the Q factor which allows to get the full deformation with a reduced voltage. This method leading to ‘resonant actuators’ was developed at first by Paul Langevin in 1917 for making sonar transducer emitters. It is still used by Cedrat for making 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 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 Standard piezoelectric actuators such as the PPAs et APAs are using these piezo materials by this way for more the 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 piezoactuators and associated electronics developed by Cedrat are presented in the following examples : Hollow actuators, double amplification to get millimetres strokes, actuators with re-enforced pre-stressed to survive large external vibrations, extremely small or extremely large actuators …

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

To know more about our piezo actuators see also our related publications on piezo actuators .

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