Considerations in the design and sensitivity optimization of the micro tactile sensor

Although miniaturization has been considered the only technology with which to increase sensitivity of tactile sensors, we recently developed the micro tactile sensor (MTS) that performs with high sensitivity without microfabrication. In this study, we examined design and sensitivity optimization of the MTS using theory based upon Mason´s equivalent circuit. The touch probe, which is attached to the lead zirconate titanate (PZT) element, was expressed as a purely inductive circuit component. Resonance frequency was calculated as a function of the length of the touch probe, and sensitivity was predicted to be dependent on the length. Furthermore, many kinds of MTS were fabricated with different touch probe lengths, and actual sensitivity was measured as phase shift between nonloaded and loaded conditions. And, from the consideration of theory and experimental data, a sensitivity coefficient was proposed and found to be useful.