Piezoelectric vibratory-cantilever force sensors and axial sensitivity analysis for individual triaxial tactile sensing

Vibratory force sensors have been fabricated using piezoelectric capacitors on microcantilever structures for triaxial sensitivity by a single sensor element. The cantilevers have been formed into three-dimensionally curved shape by controlling residual stress combination of the multilayered structure. Triaxial tactile sensitivity of the cantilever sensor has been analyzed under a load application onto the surface of an elastomer in which the cantilever is embedded. The cantilever is converse-piezoelectrically excited by an external ac voltage and three resonant modes have been developed to detect the applied load vector components by individual sensor element. Resonant frequency shift of each mode is investigated upon load applications and the results show that the frequencies linearly vary to the three axial loads and they can be superposed with corresponding to the superposition of the load components. The applied load vectors are estimated by resonant frequencies of a single cantilever sensor in an error less than 1.1% to the full scale of the load 4 kPa.