The record for solving the Rubik’s cube robotically has been smashed by hardware hackers Ben Katz and Jared Di Carlo. The machine developed by the duo solved Rubik’s cube in 0.38 seconds, which is 40 percent faster than the previous record of 0.637 seconds.
In order to achieve this feat, Katz and Di Carlo moved away from traditional stepper motors, and designed a custom-built motor controller that allows a single turn of the Rubik’s cube to be completed in about 10 milliseconds. They say a typical Rubik’s cube solution takes around 19 to 23 turns, and the custom motor allows it to be solved in around 0.25 seconds. “We noticed that all of the fast Rubik’s Cube solvers were using stepper motors and thought that we could do better if we used better motors,” Di Carlo wrote in a blog post.
However, the machine currently designed by Katz and Di Carlo does a single turn of the puzzle in around 15 milliseconds, which suggests a room for improvement, and ultimately beating the new record created by them. “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,” Katz explained in his blog.
He added, “For the time being, Jared and I have both lost interest in playing the tuning game, but we might come back to it eventually and shave off another 100 ms or so.” So there is definitely a possibility that this new record will hold for that long, and the record holders will come back to break it with a even better accuracy.
Katz also goes on to explain how a robot handles the cube. Katz mentions that while a human player would loosen the cube up to make it easier to turn, a robot takes an opposite approach for solving the puzzle. “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,” Katz wrote. “It took tightening the cube way past what intuitively felt appropriate in order to stop the camming action from happening.”
The duo also bought a pair of PlayStation 3 Eye cameras for $7 each to study the current state of the cube. They positioned this camera at opposite corners of the cube, and allow each camera to observe these faces. They also painted the orange faces to black to help the camera better distinguish red from orange.
Di Carlo explains that the process for robot solving of Rubik’s cube involves identifying all the colors, build a description of the cube and pass it to the min2phase solver. The solution is then transmitted to the six motors, one for each face of the cube via a serial cable. The whole process of capturing the images, and sending the solution to the motors takes around 45 milliseconds.