Electromechanical coupling and output efficiency of piezoelectric bending actuators

Electromechanical coupling mechanisms in piezoelectric bending actuators ar e discussed in this paper based on the constitutive equations of cantilever bimorph and unimorph actuators. Three actuator characteristic parameters, (e.g., electromechanical coupling coefficient, maximum energy transmission coefficient, and maximum mechanical output energy) are discussed for cantil ever bimorph and unimorph actuators. In the case of the bimorph actuator, i f the effect of the bonding layer is negligible, these parameters are direc tly related to the transverse coupling factor k(31). In the case of the uni morph actuator, these parameters also depend on the Young's modulus and the thickness of the elastic layer. Maximum values for these parameters can be obtained by choosing proper thickness ratio and Young's modulus ratio of e lastic and piezoelectric layers. Calculation results on four unimorph actua tors indicate that the use of stiffer elastic material is preferred to incr ease electromechanical coupling and output mechanical energy in unimorph ac tuators.