Motion Control of a Tethered Space Robot During Casting

摘要

This paper describes a casting strategy for a tethered space robot. The robot is tethered to the end-point of a spacecraft mounted manipulator which performs the casting. The casting strategy comprises three phases : (I) initial momentum is generated for the tethered robot using the spacecraft mounted manipulator ; (II) the tethered robot takes off the spacecraft ; (III) the tethered robot translates to a destination point. The following two control objectives should be met. First, the mass center of the tethered robot should arrive at the destination point accurately (translation control objective). Second, the angular momentum of the tethered robot with respect to its mass center should be zero at the destination point (angular momentum control objective). The translation control objective can be easily achieved using the spacecraft mounted manipulator. The manipulator is able to adjust the translational trajectory by controlling tether tension. We show here that to achieve the angular momentum control objective, it would be sufficient to invoke position control of the tether attachment point, in a cooperative manner with tether tension control.