Research on virtual decomposition control of free-flying space robot with an object under nonholonomic constraints

This paper aims at solving the stable control issue of the free-flying space robot with an object when the orientation of space base is controlled but the position is out of control using the virtual decomposition control (VDC). According to the VDC principle, the entire system is conceptually divided into such subsystems: the object, the space base, the manipulator, the reaction wheel and the massless virtual manipulator. The last term is designed to solve the nonholonomic constraints of the whole system. Based on the mathematical model of the entire system, kinematics and dynamics of every subsystem from the object to the space base are analyzed. A virtual decomposition controller of each subsystem is simultaneously designed, and this controller and the corresponding subsystem structure a control subsystem of the whole 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. Then it takes two steps to achieve its stability analysis — the virtual stability of each control subsystem and the stability analysis of the whole control system. Finally, the VDC system of the free-flying space robot with an object is simulated. Simulation results show that the VDC system is stable and effective.