Intrinsic Contact Sensing for Soft Fingers

The basic mathematic relationships of intrinsic (or force based) contact sensing are discussed. While conventional tactile sensing devices are designed to provide information about local phenomena caused by contact, intrinsic contact sensing detects a few global quantities relating to the interactions of two bodies in contact. The author addresses the geometric-mathematical problem of detecting these quantities starting from force/torque measurements and from the geometric description of one of the contacting surfaces. Two methods for solving the intrinsic contact sensing problem are discussed. The first method is able to give exact results for contacts of the hard-finger type, while it is shown to be only approximate for soft-finger contacts. A formula for estimating the extent of such approximation error is provided. A second, novel solution method is presented, which applies to soft fingers with ellipsoidal surface and is capable of yielding exact solutions to the problem. Some implementation issues and applications of intrinsic tactile sensing to fine manipulation operations are reviewed