Enhanced quadruped locomotion via reaction wheels in low-gravity environments

Legged robots provide high degree of versatility over wheeled platforms for planetary exploration in low-gravity environments such as the Moon and Mars, enabling the traversal of narrow, uneven, and rugged terrain. Compared with traditional wheeled systems, dynamic quadrupeds can access challenging regions such as craters, cliffs, and steep slopes; however, the extended aerial phases encountered in low gravity make locomotion stability significantly more difficult. To improve attitude stability during these maneuvers, the quadruped is equipped with three-axis reaction wheels (RWs) for active attitude regulation. Based on the coupled dynamics of the quadruped-RW system, a nonlinear model predictive control (NMPC) framework is formulated to coordinate leg-joint actuation with RW torque generation. Simulations on uneven terrain under lunar gravity show that the proposed approach maintains bounded attitude deviations, recovers from contact-induced disturbances during dynamic maneuvers, and reduces peak joint-actuation demand. These results indicate that RW-assisted quadrupeds are a promising solution for agile and joint-torque-efficient locomotion in future planetary exploration missions.