Theoretical analysis of the sensor effect of cantilever piezoelectric benders

Piezoelectric bending mode elements such as bimorph and unimorph benders ca n be used as both actuation and sensing elements for a wide range of applic ations. As actuation elements, these devices convert electric input energy into output mechanical energy. As sensing elements, they convert external m echanical stimuli into electrical charge or voltage. In this article, the s ensing effect of cantilever mounted piezoelectric bimorph unimorph and trip le layer benders subjected to external mechanical excitations are discussed . General analytical expressions relating generated electric voltage (or ch arge) to the applied mechanical input excitations (moment M, tip force F, a nd body force p) are derived based on the constitutive equations of these b ending devices. It is found that the clamping effect of each component in t he bender devices decreases the dielectric constant. The bimorph bender has a higher voltage sensitivity than the unimorph or triple layer bender with the same geometrical dimensions. The dependence of voltage and charge sens itivities on the thickness ratio and the Young's modulus ratio of the elast ic layer and piezoelectric layer under different conditions are discussed a nd compared for the unimorph and triple layer benders. (C) 1999 American In stitute of Physics. [S0021-8979(99)05302-5].