Multiaxis compliant capacitive wrist sensor for use in automated assembly with industrial robots

A compliant capacitive wrist sensor can be used as a versatile aid to a vision system in assembly using industrial robots. A sensor which is 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 the electrical contacts to only the arm-side electrode pattern. Upon application of 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 capacitive patterns between the two electrodes. By combining the information from these four patterns it is possible to distinguish unambiguously among the three moments. An additional advantage is the cabling to only the arm side of the wrist with a minimum amount of wiring due to simple on-sensor switching. The prototype sensor shows a sensitivity better than 70°/N-m with a cross sensitivity for the nonselected mode smaller than 0.1°/N-m