Graph-search planning and dual-target Cartesian control for cross-plane dual-arm climbing of a robotic astronaut

This paper presents an integrated planning-and-control framework for cross-plane dual-arm climbing of a robotic astronaut in microgravity. The climbing task is modeled as alternating support-transfer cycles over a structured array of grapple fixtures. A graph-search planner generates a feasible shortest-step fixture-switch sequence over the grapple-fixture array under reachability and plane-transition constraints, while a model-based waypoint optimization refines the corresponding body and end-effector keyframes subject to pose and clearance requirements. To connect adjacent keyframes, a three-phase trajectory generation strategy composed of retraction, coordinated motion, and insertion is introduced to produce continuous reference motions for climbing transitions. For execution, a dual-target Cartesian controller is developed to coordinate simultaneous tracking of the robot body and the moving end-effector through a stacked Jacobian formulation with damping and null-space regularization. Simulations in an ISS module-like environment demonstrate that the proposed framework enables feasible cross-plane climbing with coordinated arm switching, accurate trajectory tracking, and consistent body-clearance maintenance, supporting autonomous extravehicular mobility for future on-orbit servicing tasks.