Asteroid Landing and Stance Stabilization via a Hybrid Reaction-Wheel-Actuated Legged System (ReWArm)

Locomotion on small solar system bodies is challenging because microgravity severely limits traction, making wheeled systems ineffective. Internally actuated hoppers (e.g., MINERVA-II and MASCOT) can move in such environments, but frequently exhibit uncontrolled tumbling and bouncing at touchdown, producing an unstable stance phase. To overcome the friction limits causing failure of terrestrial solutions in microgravity, identified with a reduced model, this paper presents ReWArm (Reaction-Wheel-Arm): a hybrid-actuated legged hopper that couples agile attitude control with articulated ground interaction for controlled soft-landing and post-landing stance stabilization. We formulate an optimization-based whole-body controller using Task-Space Inverse Dynamics with a soft hierarchy that coordinates Cartesian impedance, active force feedback, centroidal momentum damping, and posture regulation. Simulations at asteroid-level gravity show effective impact-energy dissipation, sustained contact without unintended liftoff, and successful reconfiguration to a target pre-jumping state, enabling directional hopping maneuvers.