Manipulation Training Gives Robot Dogs a Leg — or Arm — Up in Their Capabilities
By learning to balance on fewer legs, quadrupedal robots can use a foreleg as an arm-like manipulator — increasing their flexibility.
Researchers from Carnegie Mellon University and the University of California at Berkeley have showcased an approach for giving quadrupedal robots additional skills — by teaching them to repurpose their forelegs as arms for manipulation tasks.
"Locomotion has seen dramatic progress for walking or running across challenging terrains. However, robotic quadrupeds are still far behind their biological counterparts, such as dogs, which display a variety of agile skills and can use the legs beyond locomotion to perform several basic manipulation tasks like interacting with objects and climbing," the researchers explain of the problem they're trying to solve.
Teaching a quadrupedal robot to walk is one thing, though, but having it juggle walking and manipulation tasks — with limbs ill-suited to the latter — isn't easy. To solve this the researchers' paper, which was brought to our attention by IEEE Spectrum, splits the problem space in two, treating locomotion and manipulation separately.
"We decouple the skill learning broadly into locomotion, which involves anything that involves movement whether via walking or climbing a wall, and manipulation, which involves using one leg to interact while balancing on the other three legs," the team explains. "These skills are trained in simulation using curriculum and transferred to the real world using our proposed sim2real variant that builds upon recent locomotion success."
The result of that training is then combined into a robust long-term planning system, driven by a behavior tree encoding a high-level task hierarchy based on a single clean expert demonstration. In real-world testing, using a Unitree Go1 robot equipped with an Intel RealSense D435i depth-sensing camera and an AprilTag to help the robot target a button, the trained robot proved capable of tasks it would have otherwise found impossible — like exiting a building by pressing a button far out of its reach while on all fours, stretching up on its hind legs and using a single foreleg as a manipulator.
Quadrupeds aren't the only robots who can benefit from repurposing legs as arms, either. Back in April last year researchers from the Robotics Institute of Beihang University unveiled the Arm-Leg Locomotion and Manipulation (ALLOMAN) robot, a six-legged design which could convert one or two of its legs into arms on-the-fly as required by a given task or to navigate particular terrain.
The team's work is to be presented at the IEEE International Conference on Robotics and Automation (ICRA '23) in London next month; a copy of the paper is available on the project website under open-access terms.