Picking a gyro for field-centric swerve control

[AmoryG]

Originally Posted by Tom Line

In 2009, we created a field-centric turret system that let the gunner push the joystick in the direction he wanted the turret to face, no matter what direction the robot was pointing in. The only issue we had with the system was a hard impact would knock the gyro angle off.

In the off season, we've planning on developing a swerve drive, and I'd like to set the controls up the same way. As a result, I already know one of my primary controls problems is going to be how to keep that gyro from jumping out of alignment.

Now, I'm a mechanical guy pressed into work as a controls guy, so I haven't dealt with much of the high level control stuff. I'm sure other teams have dealt with this same issue, but I'll start by breaking it down into possible solutions:

1. First, you could try to use some other system to double check and remove the error. Wheel angle / distance encoders doing dead reckoning would be my first thought, but because the absolute angle of the wheels to the field would be dependent on the gyro they would quickly build up error and not a be a good source of correlation.

2. You could try to sense out-of-bounds conditions and simply ignoring them. You could remove changes that exceed the spin-rate of the gyro, or any other odd fluctuations by putting a series of case-statement checks inline that create a correction factor.

3. You could continue to try to improve the gyro itself. I see that sparkfun now sells 1500 degree/second gyros. While I haven't dug into their specs to check if their resolution and drift is still suitable, it seems like you'll reach a point where you simply don't have the issue anymore.

4. A hyrbid of 1: completely remove the gyro from the robot and do angle dead-reckoning using only the absolute wheel angle encoders and transmission encoders.

Has anyone else found a solution to this issue?

My team built a robot that did something similar to what yours did. However, ours was effective because no matter how many times we bumped into walls, in a two minute time frame our gyro was off at most 5 degrees.

This year we decided to buy a kind of gyro that gives gyros a bad name. Its horribleness could not be put into words.

If you, like we, think that the gyro was programmed and wired correctly, maybe you should try a completely different gyro just to see how that works.