Coordinated control of tethered space robot using releasing characteristics of space tether

Tethered Space Robot (TSR) is a new kind of space robot. The tension force of tether can be treated as control input directly for traditional coordinated control of TSR. However, it is difficult to track the desired tension force. In this paper, tension force input is replaced by the control torque of releasing motor in order to solve this problem. Furthermore, it provides new coordinated coupled control method for tracking optimal trajectory and desired attitude angles. The dynamics of tether releasing mechanism is taken into account in this dynamics model. Furthermore, the coordinated coupled controller is proposed, which contains 6-DOF sliding mode controller and PD controller of releasing reel. Finally, the simulation experiment is proposed in order to validate the effectiveness of this control method. The results show that TSR can track the optimal approaching trajectory accurately. Simultaneously, the attitude angles can be changed to the desired attitude angles in control period, and the terminal accuracy is ± 0.3 degree.