Automatic Differential/Motor Speed Compensation

[Ether]

Originally Posted by Sky Captain @ 02-07-2016, 01:11 PM

Not that difficult actually, I'll get mechanical on it and report what the results are. Thanks.

any news ??

[Sky Captain]

We just got our frame assembled, and we were going to disassemble the tracks when we migrated them from the test bot to the real bot. I'll report back sometime during the weekend when this happens.

[Ether]

Originally Posted by Sky Captain 02-12-2016 07:41 PM

I'll report back sometime during the weekend when this happens.

Any news??

[RSNovi]

We have a similar problem with our robot. One of the gear boxes on one side is tighter. It doesn't seem to cause problems when manually driving, but long distances in autonomous mode would cause it to veer slightly.

We corrected by designing an algorithm using the gyro which we can set an angle and the PI controller will correct. Unfortunately it isn't perfect because the gyros drift so bad.

We were having good luck scoring a goal autonomously and we made it to the finals. After turning the robot on the announcers would talk so long that the gyro would start drifting like crazy before the robots started. The reference library takes 5 seconds to calibrate the gyro. I wonder if that could be reduced.

[Ether]

Originally Posted by RSNovi

After turning the robot on the announcers would talk so long that the gyro would start drifting like crazy before the robots started. The reference library takes 5 seconds to calibrate the gyro. I wonder if that could be reduced.

It doesn't take 5 seconds to read the gyro and use that reading as a zero offset.

[RSNovi]

I know reading the gyro doesn't take that long, the calibration routine takes 5 seconds on the 450 gyro. That is when using the WPI class.

When it drifts it really takes off. I reset the gyro at the very beginning, but if it is already drifting it will be off a few degrees in a matter of a few seconds. Ideally I would like to calibrate the gyro in my autonomous init.

[Ether]

Originally Posted by RSNovi

I reset the gyro at the very beginning, but if it is already drifting it will be off a few degrees in a matter of a few seconds.

If you calibrate the gyro when it's cold, it will drift faster when it warms up.

Also make sure you have all vibration sources (like the compressor) turned off when you calibrate.

Or you could try this solution:

http://www.chiefdelphi.com/forums/sh...9&postcount=13
http://www.chiefdelphi.com/forums/sh...8&postcount=17

[mark219]

We used a gyro to drive straight, by taking into account the change in angle and a constant value (a constant much like a P-value in a PID loop).

[RSNovi]

Originally Posted by Ether

If you calibrate the gyro when it's cold, it will drift faster when it warms up.

Also make sure you have all vibration sources (like the compressor) turned off when you calibrate.

Or you could try this solution:

http://www.chiefdelphi.com/forums/sh...9&postcount=13
http://www.chiefdelphi.com/forums/sh...8&postcount=17

I wonder if it would be better to bring the robot up to the course powered up so all of the electronics are warm. Then toggle the power after placement so the calibration is done while everything is somewhat warm.