Disturbance Observer-Based Robust Control of Free-Floating Space Manipulators

A disturbance observer-based control scheme is proposed for free-floating space manipulator with nonlinear dynamics derived using the virtual manipulator approach. The derived dynamic equation uses only link angles as generalized coordinates, which is suitable for the controller design in joint space. Since joint coupling, model uncertainties in robot dynamics are treated as lumped disturbances, a disturbance observer is developed at each joint of degree-of-freedom space manipulator to decouple and simplify the controller design. Simulation results of a six-link space manipulator show that the proposed scheme achieves superior performance, especially when large external disturbances are present.