Lego Robot Solves Rubik's Cube Puzzle In 3.253 Seconds

A reader sends this news from CTV: "The Cubestormer 3 took 18 months to build but only needed 3.253 seconds to solve [a Rubik's cube], breaking the existing record. Unveiled at the Big Bang Fair in Birmingham, U.K., the Cubestormer 3 is constructed from the modular children's building-block toy but uses a Samsung Galaxy S4 smartphone with a special ARM chip addition as its brain. It analyzes the muddled-up Rubik's Cube and powers each of the robot's four 'hands,' which spin the cube until all sides are in order. Created by ARM engineer David Gilday and Securi-Plex security systems engineer Mike Dobson, Cubestormer 3's new record shaves just over two seconds off the existing record, set by Cubestormer 2, which the pair also built."

Re:alas !

[The boojum]

"God's number" is 20. [cube20.org]

They can probably compute a just-over-20-move solu

[ToastyKen]

As The boojum said, you can theoretically solve a cube in any configuration in 20 moves, but it might take a long time to find that optimal solution. Computers can quickly find a just-over-20-move not-quite-optimal solution, though.

Human-friendly algorithms generally take over 50 moves, with the absolute best solves still taking more than 40.

I stepped through this video frame by frame. They rotate the cube 5 times to inspect each face first (I guess they only have one camera), paused about 0.2 seconds (presumably to calculate a solution) and then they made 21 moves plus 4 rotations to solve it. (The rotations were necessary because it only has 4 arms and can't spin the top and bottom layers.)

So yeah, looks like they computed a nearly-optimal solution, and I imagine they can probably get a just-over-20-move solution every time.

Re:Impressed yet disappointed with Lego

[jimbolauski]

The first thing you need to know when bonding anything is the material you are bonding, most Lego bricks are made of ABS plastic and I would assume the ones you had are as well. The way you bond ABS is by chemically welding it, you can find the solvent glue at most hardware stores (plumbing section). The glue will be black because there will be abs filler in there to fill voids because it is used in plumbing and must be water tight. The second option is to use MEK (methyl ethyl ketone) to chemically weld it, MEK is clear and has no filler. Most hardware stores don't sell MEK anymore but a MEK alternative that may not work. MEK is some nasty stuff wear gloves when you use it and work in a well ventilated area with a respirator, if you get any on your gloves change them as the MEK will be eating through them shortly.