Extension of Virtual Decomposition Control to Cooperative Carrying of Dual-arm Robots in Free Motion

This investigation is to deal with the internal force control issue for cooperative carrying of dual-arm robots in free motion using virtual decomposition control. According to the virtual decomposition control principle, the entire system of the dual-arm robot in free motion for cooperative carrying is virtually decomposed into two chain subsystems and an object subsystem. The motion control problem of this entire system is converted into that of subsystems in which the internal force control of the object is performed. On the basis of establishing the mathematical model of the entire system, kinematics and dynamics of every subsystem are calculated. A virtual decomposition controller of each subsystem is designed, and this controller and the corresponding subsystem structure a control subsystem of this robot. All subsystem controllers constitute the controller of the entire robot system, and the combination of this controller and the robot system is the virtual decomposition control system of this robot. Stability analysis of the devised robot virtual decomposition control system is accomplished analyzing the virtual stability of each control subsystem by way of the virtual power flow related to the products of velocities errors and force errors. Finally, the virtual decomposition control system of the dual-arm robot to carry an object in free motion is simulated. Simulation results show that the virtual decomposition control system is stable and effective.