Wheel-legged Robot

A robot with a driven wheel at the end of each leg, rolling on flat ground and stepping over obstacles.

A wheel-legged robot puts a motorized wheel at the end of every leg on a legged robot, combining the advantages of both forms of locomotion: on flat ground it rolls on its wheels, which is faster and more energy-efficient than walking; when it meets a step or ditch, it locks the wheel and uses the leg like a foot, or lifts the leg to step over. Common forms include two-wheel-legged designs, such as ETH Zurich's Ascento and LimX Dynamics' TRON 1, and four-wheel-legged designs, such as ANYmal's wheeled variant and its derivative Swiss-Mile, LimX Dynamics' W1, and Unitree's Go2-W and B2-W. The hard part is control, since wheel rotation and leg posture must be coordinated together; most implementations now use reinforcement learning to train the control policy in simulation.

ExampleSwiss-Mile's four-wheel-legged robot rolls along a sidewalk at speed on its wheels to make a delivery, then switches to stepping when it reaches a staircase.

Also called

Wheeled-legged Robot

Related

Legged Robot · Wheeled Robot · Unitree Go2-W · Unitree B2-W · LimX Dynamics TRON 1 · Form-Factor Debate

Sources

Learning robust autonomous navigation and locomotion for wheeled-legged robots (Science Robotics)
LimX Dynamics launches W1 wheeled quadruped (The Robot Report)