Object imaging with a piezoelectric robotic tactile sensor

A two-dimensional, electrically-multiplexed robotic tactile sensor was realized by coupling a piezoelectric polyvinylidene fluoride (PVDF) polymer film to a monolithic silicon integrated circuit (IC). The IC incorporates 64 sensor electrodes arranged in a symmetrical 8×8 matrix. Each electrode occupies a 400×400 μm square area, and they are separated from each other by 300 μm. A 40-μm thick piezoelectric PVDF polymer film was attached to the electrode array with an electrically non-conductive urethane adhesive. The response of the tactile sensor is linear for loads spanning 0.8 to 135 grams of force (gmf). The response bandwidth is 25 Hz, the hysteresis level is tolerable, and, for operation in the sensor´s linear range, taxel crosstalk is negligible. The historically persistent stability and response reproducibility limitation associated with piezoelectric-based tactile sensors has been solved by implementing a novel pre-charge voltage bias technique to initialize the pre- and post-load sensor responses. A rudimentary tactile object image measurement procedure for applied loads has been devised to recognize the silhouette of a sharp edge, square, trapezoid, isosceles triangle, circle, toroid, slotted screw, and cross-slotted screw