Mission-function control of tethered satellite/climber system

• The traditional MF control is not suitable for suppressing libration of TSCS.
• Complete regulation of tether libration cannot be achieved with only a single crawling climber.
• The proposed MF controller is better at suppressing libration of TSCS than the traditional MF controller.
• A pendulum oscillation of TSCS can be achieved by choosing appropriate control parameters.
• A repulsive and damping force is needed to prevent collision between climber and mother/sub satellites.

Because the tether of a tethered satellite system (TSS) can be extremely long, it would be difficult to inspect the damage to the tether. The ultimate configuration of a TSS could be a space elevator (SE). The tether needs to carry a crawler or climber to inspect damage to the tether or transport travelers on the SE. Coriolis force due to the climber motion causes librational motion of the tether. The numerical simulations have shown that the original mission-function (MF) control is not applicable to a TSS with a climber because it was intended for subsatellite deployment and retrieval control using a tether, not for a climber on the tether. This paper proposes a new MF control to suppress the librational motion of a tether with a climber. The proposed MF control is a modified version of the original MF control. The active force to drive the climber is determined from the MF. A simplified dynamic model of a TSS with a single climber is used to evaluate the derived controller. The effectiveness of the proposed method is verified through numerical simulations.