Design and Implementation of a VLSI Tactile Sensing Computer

A new type of tactile sensor is presented that was designed to give a robot manipulation system information about contact between its hand and objects in the environment. We describe a device that is at once a special-purpose parallel computer and a high-resolution tactile array sen sor. The passive substrates of earlier tactile sensors have been replaced with a custom-designed very large scale in tegration (VLSI) device that performs transduction, tactile image processing, and communication. Forces are trans duced using a conductive plastic technique in conjunction with metal electrodes on the surface of an integrated cir cuit. An array of processors implemented within the inte grated circuit perform parallel two-dimensional convolu tions between programmable filtering masks and a binary tactile image. Data are then read from the array serially, so they can be transmitted to a control computer. A 6 x 3 array sensor with 1 mm 2 tactile cells has been designed and tested. It is fully functional. In preparation for constructing large sensor arrays with hundreds of elements, the possibility of constructing defect tolerant tactile cells was explored. Analyses based on the Poisson model indicate that working arrays with 1,000 functional cells are possible if computing elements are rep licated within each tactile cell. Experiments on a 3 x 3 array sensor with redundant pairs of computing elements suggest that large tactile sensing arrays are within reach.