Tethered Robot Casting Using a Spacecraft-Mounted Manipulator

A space robot attached to the far end of a tether deployed from a spacecraft is considered. Such a robot can be made to translate freely in space without the need of jet thrust, using tether tension. The tethered robot can be applied to perform a variety of tasks such as grappling a remote object, transporting supplies, servicing a satellite, and so on. A casting strategy is described that is accomplished by means of a manipulator mounted on the spacecraft. The tether is attached to the endpoint of this manipulator. The spacecraft-mounted manipulator generates the necessary initial momentum for the tethered robot and adjusts its trajectory by controlling tether tension. The desired final state of the tethered robot includes accurate positioning at the destination point with zero momenta. To achieve such a state, a cooperative control scheme for translation and link motion of the tethered robot is proposed. The effectiveness of the proposed control approach is confirmed by computer simulations.