Adaptive Control of a Tendon-Driven Manipulator for Capturing Non-Cooperative Space Targets

Orbital debris in Earth orbit poses a threat to the future of spaceflight. To combat this issue, this paper proposes a novel robotic mechanism for non-cooperative capture and active servicing missions on non-cooperative targets; specifically, a tendon-driven manipulator is assumed for this work. The capture mechanism is a prototype symmetric two-link gripper driven by an open-ended cable-sheath transmission mechanism. Because the cable-sheath transmission mechanism is a nonlinear time-varying hysteretic system, two separate adaptive control strategies were compared against the uncontrolled and proportional-integral-derivative controlled performance of the closedloop gripper. Specifically, an indirect control method and a direct L-1 controller were employed. Experimental results demonstrate that the adaptive controllers show better tracking performance of a joint trajectory over the proportional-integral-derivative controlled and uncontrolled cases, whereas the L-1 controller performs best under dynamic conditions, and the indirect controller performs best in steady state.