Research
Boston Dynamics puts Atlas on wheels to push its motors to the limit
Boston Dynamics has swapped the feet on an Atlas humanoid for wheels and trained it to roll, drift and jump using the same learned whole body controller as the walking robot. The company says the wheeled Atlas is a research testbed for its motors and that it has no plans to sell it, Humanoids Daily reported on Monday.
One new part
The hardware change was small. Technicians mounted an off the shelf scooter rim on each ankle actuator using a single custom adapter, the only new part in the build. The ankle motor drives the wheel directly.
In software, each wheel was modelled as an ankle joint that can spin without limit. Controls engineer Xiaoyu "Andy" Wu, who wrote the Boston Dynamics blog post, said targeted changes to three things were enough: how rewards are weighted, the range of commands the policy trains on, and how it holds posture. Smooth rolling then emerged without being scripted. The policy was trained with reinforcement learning in simulation using the open source MuJoCo physics engine.
Moves borrowed from people
Some behaviours came from the company's library of human motion capture clips, run through the same tracking pipeline the walking Atlas uses. Wu picked clips with a lot of foot sliding. Where a person would slide their feet in a side to side dash, the policy steered and rolled the wheels instead. A 360 degree spin jump tracked from a human recording worked on hardware on the first attempt.
Why wheels
The point was to load the motors. Rolling, turning and stopping push the leg actuators across their full torque and speed range for long stretches while carrying the robot's weight, which walking only does in short bursts. To make that work, the team matched control parameters across every software setup and tuned the simulated motor model to measurements from the real robot. Wu described the resulting simulation to reality transfer as "basically perfect."
Boston Dynamics says the lessons are already being applied to the standard legged Atlas, which Hyundai plans to deploy in its plants. Wu's next project is improving how the policy responds when an actuator fails.
Others on wheels
Wheeled humanoids are not new. Hexagon designed its AEON humanoid around wheels from the start, and Unitree showed a G1 with wheels in place of feet in April. The difference here is that Boston Dynamics reused a walking robot's existing ankle and controller rather than designing a wheeled machine.