On-line and simultaneous calibration of wrist-mounted Force/Torque sensor and tool Forces/Torques for manipulation

Accurate force/torque (F/T) information is essentially important for a robot manipulator to regulate the contact forces and torques exerted on its tool (end-effector). For a manipulator with mounted F/T sensor, the tool and the F/T sensor are connected to the manipulator via some components, of which many parameters such as mounting errors and component´s weight are unknown. As a result, the forces and torques exerted upon the work point of the tool of a manipulator is not what directly sensed by the F/T sensor, and thus the F/T sense of the manipulator need to be recalibrated even though the mounted F/T sensor had been calibrated in advance. Also the unknown parameters introduce challenges to the on-line recalibration of the F/T sense of the manipulator. This paper proposes an on-line method to calibrate the forces/torques exerted upon the tool of a manipulator with wrist-mounted F/T sensor. The method can calibrate both of them using only one reference weight and without need to dismantle the F/T sensor and tool. It provides an efficient and convenient way to calibrate an integrated F/T system. Theory analysis and experiment result are presented to demonstrate the effectiveness of the method.