Attitude takeover control for post-capture of target spacecraft using space robot

When the spacecraft reaches the end of life, its payload will still be able to work in most cases. Due to the loss of attitude control ability, these failed satellites had to be abandoned. The technology of attitude takeover control can be used to extend the operational lifetime of these failed satellites. Post-capture of target spacecraft using space robot will cause a large shift in the dynamics of combined spacecraft. Not only do the mass properties change, but also does the reaction wheels' configuration. Designing a reconfigurable control system can account for these changes. In this paper, a reconfigurable control system is designed for attitude takeover control of target spacecraft, which considers the changes of the mass properties and reaction wheels' configuration. Firstly, a modified SDRE (Sate-Dependent Riccati Equation) optimal controller is proposed to guarantee the convergence of the steady-state position errors and velocity errors, and meanwhile move the closed-loop poles of system in order to provide a sufficient stability margin. Then, a θ–Dθ–D suboptimal control solving technique is adopted to solve an approximate solution of the modified SDRE optimal controller. Moreover, the control torques of reaction wheels of service spacecraft can be reallocated and satisfy some constraints using the dynamic control allocation method. Numerical simulations validate the feasibility of the reconfigurable control systems with large mass properties changes.