Attitude takeover control after capture of target by a space robot

For the attitude control of target spacecraft whose attitude and orbit control systems have failed, a takeover control approach is proposed that the attitude is controlled after capture of target spacecraft by a space robot. Firstly, the space robot captures a target spacecraft and remains in a fixed configuration to form a combined spacecraft. Then, the new principal axes of inertia, main inertia and allocation matrix of control torque of the combined spacecraft are determined due to the parameter mutation of the combined spacecraft. Furthermore, the attitude error dynamics of the combined spacecraft is established in the form of state space. Finally, the SDRE takeover controller is constructed based on the -α stability design for the service spacecraft, which is solved by the θ-D method to obtain the sub-optimal control law of SDRE controller and achieve the takeover control of target spacecraft attitude by the service spacecraft. Numerical simulations have demonstrated that compared with the traditional SDRE control, the SDRE controller based on the -α stability design can make the closed-loop poles of system away from the imaginary axis, and the θ-D solving method can reduce the computation burden, hence it has better stability and real-time performance.