A planar unimorph-based actuator with large vertical displacementcapability. II. Theory

摘要

A piezoelectric actuator utilizing a planar trellis-likenarrangement of multiple unimorph elements is described which producesndisplacements perpendicular to the plane of the actuator. The unimorphnelements are connected in series mechanically so that the verticalndisplacement of each unimorph element in the structure adds to thenvertical displacements of the other elements, resulting in a largenoverall vertical displacement at the output of the actuator. A simplenelectromechanical model of the actuator is developed. The model consistsnof a voltage-actuated force source, which is the result of thenpiezoelectric properties of the unimorph bars that make up the actuator,nin parallel mechanically with a stiff spring that models the elasticnresponse, both bending and twisting, of the unimorph elements. The longnmoment arms inherent in the geometry of the actuator make a substantialncontribution to the overall compliance of the actuator. The addition ofnstiffeners to the actuator can significantly reduce the effect of thesenmoment arms, and thus substantially increase the stiffness of thenactuator. As a result, the force generation capability of the actuatornis significantly increased without affecting its displacement capability