Unlocking Versatile Locomotion: A Novel Quadrupedal Robot with 4-DoFs Legs for Roller Skating

Roller skating with passive wheels on a quadrupedal robot is more efficient than traditional walking. However, the typical mammalian quadruped robot with 3-DoFs legs can only perform one dynamic roller skating gait and has difficulty achieving turning motion. To address this limitation, we designed a novel quadrupedal robot with each leg having 4-DoFs to enable various roller skating locomotion including Swizzling, Stroking, and trot-like gaits while easily achieving turning motions. We considered the geometrical characteristics of the passive wheel and used the Levenberg-Marquardt method in robot kinematics to improve precision for both roller skating kinematics and contact point position for the dynamics controller. The position of the robot foot and the yaw angle of the passive wheel are decoupled for motion planning of all proposed gaits. Our proposed kinematics with wheeled geometry was verified through experiments to have higher precision, while the feasibility of all proposed roller-skating gaits was confirmed during straight motion and turning motion with a small radius on our prototype robot. Finally, we discussed the mobility efficiency of different roller skating gaits which were found to be more efficient than walking.