OpenAI trained a five-fingered robotic hand to unscramble the Rubik’s Cube puzzle, bringing both acclaim and criticism.

What’s new: The AI research lab OpenAI trained a mechanical hand to balance, twist, and turn the cube.

How it works: The system learned the manual skills to unscramble the cube using reinforcement learning. It determined the sequence of moves using a pre-existing formula known as Kociemba’s algorithm.

  • The researchers designed a simulated environment where a virtual hand could manipulate a virtual cube. The model spent the equivalent of 13,000 years learning to twist simulated cubes.
  • They altered the simulation’s parameters from game to game, for instance, changing the cube’s size or mass, or changing the friction between fingers and cube. This procedure, known as automatic domain randomization, eased the robot’s eventual transition from the simulation to the real world: Indeed, it was able to work the cube with two fingers tied together and while wearing a glove, though it hadn’t encountered that condition in the simulation.
  • Once trained, the model controlled a physical hand from Shadow Robot Company, modified with LEDs to improve motion capture, rubber pads to improve grip, and more durable components.

Results: The researchers considered an attempt a failure if the hand stalled or dropped the cube. The hand had a 60 percent success rate when the cube needed 15 rotations or fewer to solve the puzzle. That rate dropped to 20 percent when the solution required 26 rotations or more.

Yes, but: Although OpenAI’s report focused mostly on robotic dexterity, critics accused the company of overstating its claim to have taught the robot to solve Rubik’s Cube. Kociemba’s algorithm is more than a decade old and doesn’t involve learning, they pointed out, and the cube included Bluetooth and motion sensors that tracked its segments. Moreover, despite training for virtual millennia, the robot can’t do anything more than manipulate the puzzle.

Behind the news: Robots purpose-built or -coded to unscramble a Rubik’s Cube — no learning involved — are a venerable tradition. Guinness World Records recognizes a system that did the job in 0.637 seconds. Independent engineers later shaved the time to 0.38 seconds. Universal Robots programmed two industrial-bot arms to collaborate on the task.

We’re thinking: OpenAI has a knack for choosing important problems, solving them in elegant ways, and producing impressive results. It also has been criticized for presenting its work in ways that lead the general public to mistake incremental developments for revolutionary progress. It’s important to set realistic expectations even as we push the boundaries of machine intelligence.


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