Closed-loop Optimal Control of Tethered Robot during Nonplanar Orbital Transfer

Typical Tethered Space Robot (TSR) composed of main satellite, operation robot and joined tether has an important prospect in active debris capture and removal applications. Targeting the safe, stable and economical nonplanar orbital transfer mission, the dynamic modeling and tracking control algorithm problems during the towing process have been studied in this paper, providing a theoretical basis for the tether towing deorbit technical verification and engineering. On the basis of optimal feedback control theory, the control problem during nonplanar orbital transfer mission of TSR is studied. For eliminating the effect of mismatch of system model and external disturbance, an optimal feedback controller in closed-loop form is proposed. The established optimal feedback controller is essentially composed of multiple computations by an open-loop optimal controller. Based on the state feedback matrix collected at the sampling interval, taking advantage of fast convergence speed and high precision characteristics inherited from Gauss-Pseudospectral method, the finite horizon open-loop optimal control problem at each sampling interval is discretized and solved. And the first part of each control sequence generated by the controller is imposed on the controlled model. Finally, the effectiveness of the proposed scheme is demonstrated via numerical case studies.