Rubik's cube solving robotsRubik's cube solving robots

I’ve been meaning to write about this one for a while.  My friend and co-worker, David Gilday, is a LEGO fanatic, and also Rubik’s cube fan.  What else would you expect from someone like that, other than to build the world’s fastest Rubik’s cube solving robot out of LEGOs?

I saw the initial version of this robot at an ARM engineering conference last year.  It took a couple minutes to solve a cube and was the runaway hit of the conference.  There were actually two robots at the conference, one that could solve the standard 3×3x3 cube and one that could solve the 4×4x4 cube.  Both worked similarly in that they had a cradle that held a Nokia N95 cell phone, a rotating turntable that the cube sat in, and an arm that could hold the cube in place while the turntable rotated one or more layes, or lift the cube out of the cradle and rotate it to put a different face on top.

The robot initially rotated the cube without modifying it so the N95 could take a photo of each face.  The N95 then created a set of moves that would solve the cube, tailored to the mechanical abilities of the robot.  Once the moves were computed the N95 would communicate them to the NXT, which would activate the motors and linkages accordingly.

It’s a difficult problem mechanically, not to mention computationally.  LEGOs are fun, but not exactly high precision.  The gear trains have lots of backlash that has to be accounted for.  An early version of this robot actually split a gear in half when one face did not quite line up after being rotated.  The cube would not rotate for the next move, stalling the motor and breaking the gear after a few seconds.

That early robot, which was 100% ARM powered, was featured on  ARMflix, and the popularity of that video inspired David to go back and make it “better that it was before.  Better, stronger, faster.“  The result of that effort is the Yellow Cube Machine which solves Rubik’s cube in about 18 seconds including photographing all 6 faces.  The actual solution is only about 14 seconds.  But that’s not all.  David has also built the Multi-Cuber, a LEGO robot that can solve all sizes of Rubik’s cubes, from 2×2x2 to 5×5x5.  The most recent version of Multi-Cuber also solves 6×6x6 cubes.  Who knew they came in so many sizes?

Since the Yellow Cube Machine was built it appears that the worlds fastest LEGO Rubik’s cube solver title has been taken over by CubeStormer, a collaboration between David Gilday and Mike Dobson, which solves the cube in about 10 seconds.  That’s not far from the human record of just over 7 seconds.  Stay tuned to their YouTube channels (IAssemble and RoboticSolutions respectively) to see what they come up with next!

Steve Ravet

EDN Gadgeteer