Holonomic Drive System Issues, Robot Drives Diagonally...

[Andrew Schuetze]

I am working with this team as a mechanical mentor but I am not an engineer. (just an old chemistry teacher with 10 years of FRC experience)
Here is an image of their drive-base prior to mounting of the electronics board.
http://www.chiefdelphi.com/media/photos/36312
The battery is currently mounted just behind the front right wheel and other than that massive object, all of the current weight distribution is very symmetrical.

[AllenGregoryIV]

We have a similar drive base as you do. I don't see anything wrong with your code but I know that we switched from the Meccanum Polar method to the Meccanum Cartesian because polar seemed to be giving odd results. (I know it shouldn't matter but it seemed to help us and it makes positioning easier for us).

When you put the robot on blocks and run the code does it still not power all the wheels? It may be that they are all trying to go strait but without some sort of programmed correction they are at such different speeds that it drives diagonally. Wheel slip with an omni holonomic platform is really hard to remove completely with a mechanical solution.

We corrected for this by getting field centric control working with the gyro. Without that our drive base becomes much harder to control. The gyro is able to control our angle and keeps our heading. If we do drift off of strait the driver has a much easier time correcting because he only has to correct one axis (the X axis if we are trying to drive strait forward).

This is a link to our code repository. If you have any questions please ask.
Our Code

We are also attempting to get Velocity control working but haven't been successful yet because our encoders have been giving us some problems.

Hope this helps and I look forward to seeing you at Alamo,
Allen Gregory

[Ether]

Originally Posted by AllenGregoryIV

We are also attempting to get Velocity control working but haven't been successful yet because our encoders have been giving us some problems.

Are you aware that this is a known bug in the FPGA code, and solutions have been posted?

http://www.chiefdelphi.com/forums/sh...ad.php?t=89153

http://www.chiefdelphi.com/forums/sh...ad.php?t=89257

[omalleyj]

Usually two motors need to be inverted. Are any of yours inverted in HW, because I don't see them inverted in the code.

[AllenGregoryIV]

Originally Posted by Ether

Are you aware that this is a known bug in the FPGA code, and solutions have been posted?

http://www.chiefdelphi.com/forums/sh...ad.php?t=89153

http://www.chiefdelphi.com/forums/sh...ad.php?t=89257

Thank you Ether, I did know it was a known issue but I actually hadn't seen one of the solutions that you posted. I'll see if it works tonight. We also have a hardware problem where one of our encoders is not returning the right number of counts per revolution, but that is either a mounting problem or a broken encoder.