Legged walking robots can excel at overcoming obstacles or traversing challenging terrain, but wheels are still more efficient for moving in a flat environment. The combination of both locomotion domains overcomes the trade-off between mobility and efficiency. This is why ETH Zurich engineers have added passive or powered wheels to their existing ANYmal quadruped robot that will allow it to go further faster and more efficiently.
ANYmal is a four-legged robot that has been specially designed for commercial and industrial applications. It is suitable for use in hazardous locations such as oil and gas stations or mines. The robot weighs only about 50 kilograms and is capable of carrying about 10 kilograms. It can move at a speed equivalent to that of a fast-walking person and work from two to four hours on a single battery charge.
Walking on four mechanical legs, the robot is able to run over uneven terrain and even climb stairs. However, when it comes to simply navigate corridors or sidewalks, the robot will use considerably less battery power just rolling on its wheels.
The new development of scientists has solved this problem. They added four hub-motorized wheels to the robot attached to each of its legs. Thanks to this improvement, the ANYmal can move at speeds of up to four meters per second when in drive mode.
If ANYmal needs to switch back to walking gait, on-board sensors and a motion planning microcontroller selectively control the torque at each wheel. This allows some wheels to brake, using their tire to provide grip, while others roll gradually forward or backward as needed.
During experiments on flat and inclined terrain, the research team shows that skating motions reduces the cost of transport by up to 80% with respect to traditional walking gaits.
Although ETH Zurich has been experimenting with wheels since 2018, a new, improved version has recently been created and can be seen in action in the video above. The video explicitly shows the robot alternating between climbing and using the wheels to go further. ANYbotics, the company behind the ANYmal robot, also showcased a wheeled bipedal robot earlier this year.