LEGO® MindCuber

Build your own Rubik's Cube solver from just a LEGO MINDSTORMS NXT 2.0 set.

MindCuber is available as a bonus model on the LEGO MINDSTORMS website.
http://mindstorms.lego.com/en-gb/News...

An enhanced version of the executable program for the NXT 2.0 version and build instructions and program for the NXT 8527 (orange box) version are now available on http://mindcuber.com

There are some troubleshooting tips (including notes on how to calibrate the color sensor using the white face of the cube) at: http://www.mindcuber.com/mindcuber/mi...

Software source code will be available in the near future on http://mindcuber.com

Please share your experiences building MindCuber on the MindCuber facebook page: https://www.facebook.com/lego.mindcuber

MindCuber is believed to be the fastest, completely autonomous, LEGO robot to solve the well known Rubik's Cube puzzle. Total solve time, including the scan, averages around 1 min 55 secs for the version shown in this video although the published version averages around 2 min 30 secs.

MindCuber's unique mechanical design allows the cube to be manipulated quickly and reliably using only two motors allowing the third motor to be used to move the colour sensor during the scan.

The software for the solver runs on the ARM7 microprocessor in the NXT "Intelligent Brick" using the LEGO colour light sensor to scan the cube. The ultrasonic sensor is used to detect when the cube is inserted to start the solve automatically.

MindCuber uses a table-driven solving algorithm that was developed to fit in the limited memory of the NXT while generating reasonably short solutions of around 30 to 40 moves.

MindCuber can also be seen solving a Void Cube at:
http://www.youtube.com/watch?v=9QL5DZ...

A version of MindCuber that can be built from the original LEGO MINDSTORMS NXT kit (8527 Orange box) and an additional color sensor can be seen at:
http://www.youtube.com/watch?v=rSGPB3...

Other LEGO solvers can be seen on http://www.youtube.com/IAssemble
and on http://www.youtube.com/user/ARMflix/v...

Mike Dobson (Oscarworld, @RoboticSolutions), with whom I jointly created CubeStormer II, has kindly allowed me to use another of his wonderful musical creations, "Cube-essence", as backing for this video.

MindCuber was demonstrated publicly for the first time at the World Robot Olympiad in Abu Dhabi from 18th-20th November 2011.

Enjoy!

• Category

  Science & Technology

[Kyriel Mortel]

I have just finished building MindCuber. When I put a scrambled cube in, the robot successfully scans the cube. However, the robot always solves the cube in the four spot pattern. I have calibrated the colour sensor. Is this on purpose? If not, how do I fix this?

[IAssemble]

Thanks for the update. At the end of the scan does it say "Scan error" or "Cube error"?

Have you tried calibrating the color sensor with the white face of the cube? as described in the troubleshooting tips on mindcuber(dot)com?

Apart from selecting color sensor calibration, you only need to press the orange button on the NXT to run the program which could not be done with a touch sensor. The normal scan starts automatically using the ultrasonic sensor to detect the cube.

[Robert Grimes]

I relooked. I found a few wrong pieces, like a black instead of gray. Now it scans the cube and moves it around the various faces. However, it never changes the cube, just changes its position. I need to get a new cube which has better colors. So far, so good. Thanks for the help.

A suggestion, connect a freestanding touch sensor to start the process (like a push button) instead of trying to get you hand on the NXT orange button.

[IAssemble]

The key thing is to make sure that the scan arm can move far enough towards the turntable and away. If not, it can jam as it tries to move away and the program waits forever because the motor doesn't move far enough. The most common problem is that the horizontal beam connected by the right angle brackets across the end of the scan arm is one hole too high or low or the levers just above that are one hole too high or low.

Thanks for letting me know about the ultrasonic sensor.

[IAssemble]

I'm happy to carry on here if you are. The discussion may be useful to others... or we can switch to the MindCuber facebook page (see link on my channel page)... but feel free to send me private messages if you prefer. Thanks

[Robert Grimes]

First, I will do a mental rebuild to make sure it is put together with all the correct parts. Yes, the sensor has worked but I will try it again.

[Robert Grimes]

would you prefer we go offline with this discussion?

[IAssemble]

If you still cannot get the color sensor to stop flashing red, please can you upload a video showing exactly what happens to the scan arm when the program is run? If so, I will try to see if I can see any mechanical issues. Thanks

[IAssemble]

Have you used your ultrasonic sensor successfully in any other projects? Thanks

[IAssemble]

Thanks. Yes, the software expects the ultrasonic sensor to be connected to port #2. If the color sensor does not stop flashing it means that either something has stopped the code getting to the point where it checks. This can be because the scan arm is built incorrectly and is preventing the motor from moving far enough to it's calibrated position. Can you hear the scan motor straining? What message is displayed on the screen? What happens if you point the ultrasonic sensor at the ceiling?