Software hackers have met and absolutely exceeded the previous record of solving a Rubik’s Cube.


They have built the ultimate Rubik’s-solving robot that solves the puzzle in 0.38 seconds. This is an incredible feat, but it’s also a 40 percent improvement over the previous record of 0.637 seconds.


In a blog post explaining their beauty of a machine, Di Carlo wrote, “We noticed that all the fast Rubik’s Cube solvers were using stepping motors and thought that we could do better if we used better motors.” Their improved and customized motor controller allows a single turn of the Rubik’s Cube to be completed in 10 milliseconds. Since a typical Rubik’s Cube solution takes 19-23 turns, that should mean the robot would be able to solve it in 0.25 milliseconds.



However, their current machine makes a turn every 15 milliseconds. Katz explains, “The machine can definitely go faster, but the tuning process is really time-consuming since debugging needs to be done with the high-speed camera, and mistakes often break the cube or blow up FETs [Field-Effect Transistor].” The duo has as of now lost interest in tuning the robot, but have stated that they plan on returning to it and eliminating an additional 100 ms off the total completion time.


The pair also discussed a technique they’ve discovered while adjusting the robot for efficiency—that is, tightening the Rubik’s Cube. They found that although a human player would be inclined to loosen the cube so they are able to more quickly turn it, the opposite approach is best for their robot. Katz writes, “When the cube is loose (like it would be if a person were trying to solve it fast), the outer faces just cam outwards when you try to turn the center faces quickly […] It took tightening the cube way past what intuitively felt appropriate in order to stop the camming action from happening.”

Another issue that they faced is that at a point in time, they realized that the camera was having difficulty distinguishing between the orange and red faces. To combat this issue, they painted the orange faces black to allow them to stand out better.

As for how the robot works, Katz and Di Carlo purchased a pair of PlayStation 3 Eye webcams for $7 each. By positioning them at opposite corners of the cube, it allows each camera to monitor three faces.


Ready to be blown away? Di Carlo explains that the software they built identifies all the colors on the cube, builds a description of the cube, and that is passed on to the min2phase solver. This solution is then sent via a serial cable to the six motors—one for each face of the cube. This entire process—from capturing the image to sending the instructions to the motors—takes approximately 45 milliseconds.

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