Development of a tactile sensor for Braille pattern recognition: sensor design and simulation

The purpose of this paper is to define the design criteria of a tactile sensor for Braille pattern recognition by investigating the influence of sensor geometry and material on sensor output. First, a single segment of a tactile sensor, consisting of a piezoelectric (PVDF) film sandwiched between two elastic materials, is designed and simulated to read a single dot of a Braille character. Applying different materials and thicknesses for layers surrounding the PVDF film, different simulations are carried out under two different boundary conditions. With regards to design concept and geometry of the sensor, the index of thickness (f), ratio of modulus of elasticity (e) and index of sensitivity (a) are defined and discussed in detail by the simulation results. It is shown that these indices could be the design criteria to estimate the performance of the sensor. Second, the conceptual design of a single segment is generalized to a whole sensor, and a complete sensor, which can read two blocks of Braille characters, is designed and simulated. The results also show that the output of the sensor is more dependent on the bending effect near the PVDF layer than on the compression on the PVDF. Finally, with regard to the simulation results, the optimum design parameters for this Braille tactile sensor are concluded.