FRC Robot Characterization and Track Width

We’ve been trying to use the FRC characterization tool to characterize our drivetrain. So far we’ve had some success, but I’m still confused as to what the Track Width test is and what it is supposed to do? The documentation doesn’t mention it at all so I assume that it was added later. Anyway I’m just curious as to what the Track Width test is supposed to do because for us it does nothing, and I’m not sure where Track Width would go in terms of the Ramsete Controller.

Track Width test should be spinning your robot in place.

What it’s testing for, is the effective distance between the left side and right side of your drivetrain. Because of reasons I’m not 100% on, just measuring the distance between them is not accurate enough. I assume it comes down to the fact that your robot may rock if you have a drop drive for example.

Track width is the empirical measurement of the length from one center wheel to the opposite rail center wheel. This affects how much you turn for a given wheel speeds, and thus the relationship between linear/angular velocity and individual wheel speeds. Hence, it is a parameter of DifferentialDriveKinematics, which translates these two things.

The Ramsete controller outputs linear/angular velocity commands, which you then must translate into commands for each side of your robot. This is where the track width comes in, as above.

It must be measured empirically due to wheel slip and friction affecting your turns. A CAD or tape measure is a good place to start, though, depending on what kind of wheels you use.

I’m not sure why but for us the track width test isn’t doing anything. It just jitters a little bit an then dosent doing anything. I’ve waited like 5 minutes for it to start doing something.

Next to the run button there is a text box for the output voltage when running the test. Most likely, it is too low for your drive base.

Do you mean Rotation Wheel Voltage?

I think so. If I recall correctly it has a default value of 2 volts.

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