Experimental Analysis for Attitude Control of a Tethered Space Robot under Microgravity

Abstract

A tethered space robot, which is connected to a mother spacecraft through a peace of tether, is a new space system proposed in the previous work. Expected applications are satellite servicing, inspection of space structure, soft landing, and so on. The tethered subsystem is envisioned to be a multi-body system for a robot, whose attitude can be controlled under tether tension by its own link motion. The tethered subsystem is equilibrium when its mass center is located on the tether extension line. When it deviates from the equilibrium, rotational vibration motion of the subsystem will occur due to tether tension. However, the vibration can be suppressed by tether attachment operation of the multibody subsystem, which can control the tether tension. Characteristics of the proposed attitude control for a tethered space robot has been confirmed by microgravity experiment using a drop shaft, which can provide high quality microgravity condition during 4.5 seconds.