Mindboards

This weekend I finished my first omniwheel robot using the rotacaster wheels. It is a remotely controlled robot, details can be found on my blog.

Now I'm looking for a more difficult task. I'm thinking of a kind of omniwheeled self balancing bot. Basically I want to place my robot on top of a football. It should be able to maintain it's position without falling of. If I manage that the next step would be to make it move around. I could use gyro sensors to maintain balance, but then I would need two of them and I only got one. I do have an accelerometer that measures over three axes. Can this be used in a self balancing robot?

Aswin,

Nice but where are the pictures and the video?

- Xander

I never make video's. I lack the equipment, time and most of all, talent. As you can see from the video below. I'm really glad the robot actually is within the frame from time to time.

Update: Improved video

Aswin,

Your video is better than 99.999% of the rubbish on YouTube. The fact that it's not shaking about like crazy and there's something interesting happening is good enough I use Windows Live Movie Maker to edit parts where the robot goes off screen. You can just cut them out. It's the easiest to use program and best of all, it's free

- Xander

Yes I'll second the Windows live movie maker recommendation. It's also got much better recently, it even handles the canon h264 formats pretty well which many of the low cost products get into big trouble with...

aswin0 wrote:I'm thinking of a kind of omniwheeled self balancing bot. Basically I want to place my robot on top of a football. It should be able to maintain it's position without falling of.

Kinda an inverse of xkcd #413, right?

aswin0 wrote:I do have an accelerometer that measures over three axes. Can this be used in a self balancing robot?

There was a VERY long and argumentative discussion about this on the old forums. I think the gist of it was "in theory, yes, but I bet you can't do it".

nxtboy wrote:

aswin0 wrote:I'm thinking of a kind of omniwheeled self balancing bot. Basically I want to place my robot on top of a football. It should be able to maintain it's position without falling of.

Kinda an inverse of xkcd #413, right?

That's a nice one. It kind of explains why bowling balls are so heavy.
This design has a serious advantage, the robot cannot fall.

nxtboy wrote:

aswin0 wrote:I do have an accelerometer that measures over three axes. Can this be used in a self balancing robot?

There was a VERY long and argumentative discussion about this on the old forums. I think the gist of it was "in theory, yes, but I bet you can't do it".

I'll wait for my IMU then.

Aswin,

Is it going to be like this one: http://lejos-osek.sourceforge.net/videos.htm#NXTBallbot ?

- Xander

Well,
The basic idea is the same, but it will look very different. See the pictures below. Don't get me wrong, it isn't working jet. Except for the flexible wheel angles, these can easily be adjusted by modifying the position of the shock absorbers.

The first two pictures show how to change the wheel angle from a flat surface setup to a ball balancing setup. The last one shows Sidbot on a ball, this will give you an idea of the end result. I want a larger ball because I think that will be a bit easier, also the wheel angle is not according to ball diameter. I calculated I need a diameter of 17,50109 cm with this setup.

Wow, that is very cool looking. I can't wait to see the videos!

- Xander