A System For Testing A Multielement Tactile Sensor Array

摘要

This paper describes the hardware of a system built for testing a piezoelectric tactile sensor array, which has been conceived and realized for recognizing the contact stress components of an object loading its surface. The system is capable of generating a controlled contact on the sensor surface of known load and geometry and measuring the electric responses of the array, by which the six independent components of the stress tensor field are computed. By means of this system a great variety of stress shapes can be tested and the generated space-time dicretized stress field on the sensor can be measured, acquired and stored for each contact applied. In the world of engineering, artificial tactile perception, that can be obtained during object exploration and manipulation by means of miniaturized sensors, is becoming increasingly important in robotics, telemanipulation and advanced prosthetics and orthotics. In the field of artificial taction, a new tactile sensor array has been conceived and realized at the University of Pisa (Italy) [l]. One of the purposes of this research program is to face the problem of fine-form discrimination of an object in non conformal contact with the sensor surface. This problem implies to solve, analytically or numerically, the inverse elastic problem in order to reconstruct the geometry of the touching object from the spatially discretized stress tensor field [2]. Thus, a very precise apparatus is needed to experimentally test the sensor, to acquire and to record data for the comparison and the validation of theorethical solutions of the inverse elastic problem. Moreover, since the sensor has been realized as an array of sensing elements, the single element signals have to be recorded by a controlled acquisition chain, which takes into account the gain and the time constant of each detected response. The multielement tactile sensor is based on the piezoelectric polymer technology, which allows to implement arrays selectively sensitive to stress-tensor components. The six independent components of the tensor field in each point are computed from a linear combination of the measured electric responses of six miniaturized elements of the sensor, each of them sensitive to a particular direction of the stress. On the sensor surface 7 small zones have been realized, each one containing the six elements, in order to reconstruct a 7 point