Disturbance Observer-Based Robust Tracking Control of Collaborative Space Robots for In-Orbit Assembly

This paper investigates the dynamics and control problems of driving a rigid structure module using two collaborative space robots during the in-orbit assembly mission. The kinematics and dynamics of the collaborative space robot system are developed based on Newton-Euler and Lagrange formulations. Unlike some existing results on planar manipulation tasks, 6 degrees-of-freedom (DOF) motions of the structure module are modelled in this work. As an effective tool for nonlinear systems, the dynamic surface control technique is employed to derive the tracking controller. In addition, to tackle the adverse effects of uncertain parameters and external disturbances, a nonlinear disturbance observer is proposed to estimate the lumped disturbances online. By combining the dynamic surface controller with the disturbance observer, a robust tracking control law is constructed to manipulate the structure module to track the desired trajectory. Finally, the effectiveness of the proposed tracking control law is validated by numerical simulation.