Adaptive Hybrid Locomotion for a Leg-Wheel Transformable Robot on Uneven Terrain

Designing a single mobile platform that can traverse diverse terrain both effectively and efficiently remains a significant challenge in robotics. In this work, we propose an optimized wheel-like walking (WLW) locomotion method that integrates terrain-based foothold planning to adapt to rugged environments. Our gait optimization framework incorporates multiple criteria, including tip-over stability, collision avoidance, leg–wheel mechanism kinematics, motion continuity, and energy consumption. Both the stance and swing phases of the leg trajectories are separately planned and optimized. We validate the proposed trajectory planning strategy on a leg–wheel transformable robot across various types of uneven terrain. Experimental results demonstrate that our approach effectively maintains body stability, minimizes foot–hip height variation, and stabilizes the body pitch near zero. Under equivalent conditions, the optimized WLW gait achieves better terrain adaptation, reduces energy consumption by up to 10%, and maintains minimal pitch variation, allowing the robot to remain nearly horizontal while moving forward on uneven terrain.