Performance analysis of piezoelectric cantilever bending actuators

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Abstract
Bimorph and unimorph are two typical bending mode actuators, either consisting two piezoelectric layers or one piezoelectric layer and one elastic layer. In the case of bimorph actuator, when an electric field is applied to the piezoelectric layers, one layer expands while the other contract along length direction, producing a pure bending deformation. In unimorph actuator, when piezoelectric layer is driven to expand or contract, the elastic layer will resist this dimension change, both bending and stretching deformation will be resulted. These actuators can generates very large tip displacement, in the range of tens micron to several millimeters, depending on the geometrical dimensions of actuators. In this paper, to describe the performance of cantilever bimorph/unimorph actuators in quasi-static driving condition, analytical expressions are derived to relate bending resonance frequency, tip deflection, blocking force and equivalent moment with actuator geometrical dimensions. Young's modulus, densities and piezoelectric coefficients. Comparison is made between bimorph and unimorph actuator and the effect of metal layer on bimorph/unimorph actuator performance is also discussed.