A study on design concept for a Braille tactile sensor segment using softness parameters

The purpose of this report is to introduce and discuss about the design parameters for a segment of a tactile sensor reading one dot of a Braille alphabet. A sensor segment consisting of a piezoelectric (PVDF) film sandwiched between two elastic materials is designed. Experiments and simulations are used to define and examine the design parameters. With regards to the sensor structure, Free and Clamped boundary conditions are presented and the relevant equations containing the design parameters, e.g. "bending softness", are derived. Applying different materials and thicknesses for layers surrounding the PVDF film, simulations are used to quantize the approximate values for each design parameter. The results show that the output of sensor is mostly dependent on the bending effect near the PVDF layer, and the structure encouraging more bending produces higher output. Finally, it is concluded that the real sensor has a structure which is between Free and Clamped boundary conditions, therefore design parameters are modified to compromise between the two cases and optimum values are presented.