External force control using cooperating two arms with general kinematic structures

An unified compliant control algorithm to regulate the force by dual arms is proposed, where two arms are treated as one arm in a kinematic viewpoint. The force error calculated from the information of two force/torque sensors attached to the end of each arm is transferred to minimum actuator coordinates, and then distributed it to total system actuator coordinates. The position adjustment at the total actuator coordinates is computed based on the effective compliance matrix with respect to the total actuator coordinates, which is obtained by coordinate transformation between the task coordinates and the total actuator coordinates. An experiment is carried out for dual arms with asymmetric kinematic structure to control an interaction force between manipulators and the environment. The performances of the proposed control algorithm are experimentally compared to that of dual arms employing a master/slave scheme. The proposed compliant control algorithm not only outperforms other algorithms, but also can be treated as an unified approach in the sense that it can be applied to arbitrary dual arm systems with general kinematic structures.