THE SHAPE FROM MOTION APPROACH TO RAPID AND PRECISE FORCE TORQUE SENSOR CALIBRATION/

We present a new technique for multi-axis force/torque sensor calibrat ion called shape from motion. The novel aspect of this technique is th at it does nor require explicit knowledge of the redundant applied loa d vectors, yet it retains the noise rejection of a highly redundant da ta set and the rigor of least squares. The result is a much faster, sl ightly more accurate calibration procedure. A constant-magnitude force (produced by a mass in a gravity field) is randomly moved through the sensing space while raw data is continuously gathered. Using only the raw sensor signals, the motion of the force vector (the ''motion'') a nd the calibration matrix (the ''shape'') are simultaneously extracted by singular value decomposition. We have applied this technique to se veral types of force/torque sensors and present experimental results f or a 2-DOF fingertip and a 6-DOF wrist sensor with comparisons to the standard least squares approach.