Compliant capacitive wrist sensor for use in industrial robots

A sensor designed to measure the bending moments in the x and y directions, the force in the z direction, and the torsion moment around the z direction is described. The sensor consists of two opposite electrode patterns with an elastomeric material in between and electrical contacts to only the arm-side electrode pattern. Upon applying a force, the compliant intermediate will deform, causing a change in the separation and overlap between the electrodes, which results in a change in the capacitance. There are four sensitive capacitance patterns between the two electrodes. By combining the information from these four patterns, it is possible to unambiguously distinguish between the three moments. Such a sensor can be used to improve the assembling performance of an industrial robot, as the vision system might be obscured by the object to be manipulated at the moment the gripper establishes mechanical contact. The versatility of the sensor is demonstrated using an experiment in which a contour is tracked with constant contact force