The Balancing Bot

I was looking around for a new project one day, when nBot caught my attention. I knew that balancing robots were hard (look how much the segway costs!), but the more I thought, the more I knew I had to try. [pics missing]

I am yet to have it balance indefinatly, at which point I will write a whole paper about doing this. However right now, I will just list the various versions, and how well they worked.

Version 1



This was (obviously) the first version. It was about 4 feet tall. I found that my motors move way too slowly to keep a bot this size up. Thus we went to the next version.

Version 2

I chopped off about a foot and a half, so the bot is now 2 and a half feet. I figured that the bot would be able to right itself better since the moment arm is shorter, thus the same linear speed is a much faster angular speed. It now stands for about 10 seconds, but inevitably still falls.

Version 2.5

I found that the problems were due to inaccurate readings in the IR sensors. So I made a running array of the last 8 values, and used the average of them for the calulation. This didn’t quite work, either. Look at these graphs:

For both of these tests, the IR sensor was stationary in a vise pointed at a wall. That should give you some idead how inaccurate it is. The first is without my fix:



And with the fix:



Version 3

I gave up on the IR sensors: now I’m using sonar. It’s much more accurate, but I only have one. So the bot now balances for about 20 seconds, but the wheels simply can’t go fast enough to catch up if it gets moving more than a few inches per second. I hope to make some new wheels today.

Version 3.1

I ran over to the wood shop (we don’t have a metal shop) and made some bigger wheels… it seemed to me that the servos had quite a bit of torque, but didn’t go fast enough. Thus, increase the radius, we increase the distance traveled per revolution.

Version 4.0

The whole bot has been completly redesigned. The wheels of wood were not prefectly true, and thus wobbled way too much to balance properly. Also, the body was not ideal, the motors weren’t good enough, it was too tall, heavy in the wrong places….

This new bot has been designed completly in aluminum. (And crafted with nothing more than a jigsaw and a drill, plus some Erector set peices.) Yet still, it’s nicer than the previous models. It balanced nicely, has a large electric drill motor and sonar.