Tube actuators have radial polarization and use the transverse piezoelectric effect to create displacement.
Image credit: PI Ceramic GmbH Tube actuators Polarization (P), electrical field (E), and displacement (L) of a piezo shear actuator. The height of shear actuators is limited by shear stresses and bending, but they are often combined with longitudinal actuators in multi-axis systems. The resulting displacement occurs in the horizontal plane, creating a shear-type motion. For shear piezo actuators, the elements are polarized horizontally and the electrical field is applied orthogonally. But they differ in how the voltage is applied and the type of motion created. Shear actuators are similar to longitudinal versions, in that they consist of multiple layers of piezo elements. Longitudinal piezo actuators also have high resonant frequencies, which makes them well-suited for dynamic applications. They have a high force density-typically in the range of 30 N/mm 2-resulting in useful force in the thousands of Newtons. These actuators use the piezoelectric effect to generate linear displacements from 0.1 to 0.15 percent of the actuator length. Longitudinal actuatorsĪlso called piezo stacks, longitudinal piezo actuators are created by layering multiple piezo elements on top of each other, thus combining the effect of each element’s expansion to produce a useful movement and force. There are four main types of piezo actuators, distinguished by the arrangement of their piezo elements and by the type of movement they generate. Some actuators, however, operate on the transverse piezoelectric effect, in which motion occurs orthogonally to the electrical field. The piezoelectric effect produces motion that is parallel to the electrical field. They also generate high forces relative to their small size, giving them a significant power-to-size ratio.īecause of their conversion of electrical energy to mechanical energy, piezo devices are often referred to as motors, but the term “actuators” is used interchangeably. (Conversely, piezo materials will also generate energy when a mechanical stress is applied.) Piezo actuators harness this motion to provide very short strokes with high frequency and fast response times. Piezo materials are a special type of ceramic that expands or contracts when an electrical charge is applied, generating motion and force.
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