Let's Make Robots!

Balancing Robot (Balance1)

Balances on 2 wheels, Remote Controlled

 

HI guys,

This is Balance1, my balancing robot, I built balance1 to demonstrate that a digital controller I had designed in MatLab actually worked in the real world. 

The controller i ended up using for Balance1 is a digital LQR controller to balance and also stay in the same position. The LQR controller works really well because it uses a weigthing matrix to let you make balancing more important than staying in the same position. This means that if Balance1 is going to fall over then it doesn't worry much about its position it just consentrates on balancing, then when its more balanced it tries to get back to its starting position.

Robot Body:

  • The frame is made from 15mm aluminium angle amd 3mm clear perspex
  • Most of the hardware is held inside black plastic project boxes

Hardware Used:

  • Propeller Platform USB from gadgetgangster.com
  • CHR-6d Inertial Measurement Unit from pololu.com
  • Dual MC33926 Motor Driver Carrier from pololu.com
  • 2 X 12v 30:1 gearhead motor and encoders from maxon.com
  • 2 X 11.1v lipo batteries
  • 2 X Xbee modules and carrier boards from sparkfun.com
  • uM-FPU V3.1 chip from sparkfun.com
  • TextStar serial LCD from cats-whisker.com
  • 40mm 12v cooling fan from ebay.com

Further Work:

  • remote control using Xbee
  • navigate autonomously using sonar or maybe even a camera

Remote Control:

I've been doing a few test on remote controlling Balance1 and there's a new video showing the results so far. I need to do a lot more tests and tuning but it looks promising. Turning is done by adding a value to the PWM for one of the motors and taking the same value away from the PWM of the other motor. At the moment I make it drive back and forward by putting an offset on the balance point. So far I've noticed that it's quite wobblely at low speeds and it seems to get more stable the faster it's moving, I also want to try putting an offset on the velocity the see if it is smoother and more stable that way or maybe even a combination of the two types of offset. Also at the moment I'm using viewport and a USB connection to change the different values which is far from ideal as the USB connection effects how the robot balances so I need to make wireless using Xbee as soon as possible.

Remote Control Using IR Remote working:

Well putting the offset on the velocity instead of the angle worked pretty well and now Balance1 can roam arround controlled by an IR remote, I've uploaded some new videos so you can have a look, the second one shows a possible use for Balance1 what do ye think. Next comes some autonomous roaming and maybe some line following.


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Good job! I recently built a balancing platform for a local university. The biggest problem I had was getting it to go where I wanted because in order to go forward (for example) it must actually loose it's ballance and lean forward. In effect my ballancing routine was fighting any attempt at movement.

I got mine working in the end but it was still not as smooth as I would like. Have you had a similar problem?

I've only done a little bit of messing with getting it to balance and drive around. The balancing routine I'm using uses the wheel position and velocity as well as the angle and the angular velocity to stay balanced so I've tried changing the wheel position and velocity set points to make it drive around. It seems to work ok but its not very smooth at low speed and gets better as the robot speeds up. It needs a lot more work but I'll try to make a video in next few days so you can see it in action. 

Does any one know why all that stuff appears at the top of the post or how to stop it happening. Is it because I typed it in a word document first and then copied it in?

Yes, Word adds MS formatting that is also pasted along ;/

Nice. What university do you attend?

Hi dent, I'm in my final year studying Mechatronic Engineering at ITSligo Ireland (http://www.itsligo.ie/)

Cool, nice work and great to see a video.  Would be great to hear more about it (h-bridges used, custom frame?, etc).  I'm also curious how you intend to use it when completed, will it be remote control, autonomous, both?  Also interested in any good online tutorials on making a balancing robot. 

Cheers

Hi rogue,the project is more to do with deriving a statespace model of the system, similar to this tutorial http://www.engin.umich.edu/group/ctm/examples/pend/invpen.html, and then designing the best controller for it. I didn't really have to build the model but I did it just to demo the controller really so its a bit rough. I'm using the duel MC33926 motor driver carrier from pololu, http://www.pololu.com/catalog/product/1213, the frame is made from aluminium angle and 3mm clear perspexs, I'll put up some picsture soon.