Gravity Based Autonomous Calibration for Robot Manipulators

This paper presents an autonomous method t o calibrate jo in t torque sensors f o r advanced robots; as a by-product, the posi t ion sensors can also be calibrated. W h e n one jo in t of a manipulator is rotated, the gravity torque exerted on the jo in t varies sinusoidally wi th rotat ion angle. By means of sinusoidal curve fitting, the bias of the torque sensor and the gain of the posi t ion sensor can be found directly. The gravity vector , expressed in the defined base coordinates, can also be found. Thereafter we determine the torque sensor gain as well as the rotat ion angle oflset, b y attaching a known load t o robot i n diflerent positions. Experimental results are shown f o r the f irs t two jo in ts of the Sarcos Dextrous Arm.