Abstract: Based on the assumed modes method, deformation for the flexible link is approximately described. Dynamics of the flexible arm with ignoring high-order elastic modes is analyzed using Lagrange principle. In terms of dynamics of the flexible dual-arm and the object, the constraint relationship between end of the flexible arm and the object as well as the momentum conservation, the dynamic model of the closed chain system for a free-floating flexible dual-arm space robot holding a rigid payload is derived. Aiming at a high frequency characteristic of the flexible state, a slow subsystem and a fast subsystem have been separated based on the singular perturbation method in which the sliding-mode control method and the nonlinear PD control method are adopted in each subsystem respectively to have state outputs of stiffness and flexibility reach desired outputs. Using this combined control method, the payload can track the expected trajectory preferably and the elastic vibration is suppressed. At the same time, there are few effects to the motion of the spacecraft, and internal force and internal torque can smoothly track the given values. Finally, some simulation tests have conducted to verify the effectiveness of the proposed methods.

Key words: Combined control, Flexible dual-arm space robot, Free-floating, Singular perturbation