Best Sensor for Unlimited Rotation Swerve

[AdamHeard]

Originally Posted by RyanShoff

Because we've tested robots that violated that, and they caused lots of trouble.

Early in our swerve testing, we didn't store the offset from a known direction. So our absolute feedback was really incremental. Every time you changed batteries, rebooted, pushed code, or suffered a brown out, you had to make sure the wheels where pointed in a specific direction. That gets old really quick. Also different people would set the wheels slightly differently, or worse incorrectly.

We had another test chassis with the feedback geared 2:1 to the direction. On this one, you still had to start the robot with the wheels pointed close to straight. The robot always knew the axis of the wheel, but not which direction it would go. It was a real joy, because we tried to count the 2.5v crossings of an analog 0-5v signal. Sometimes it would miss count and the wheel would start dragging.

I cringed when I saw Andymark release their swerve modules this year with non1:1 gearing on the feedback.

So I always recommend to teams thinking about a swerve drive: Use absolute feedback and gear it 1:1 to steering rotation.

Analog or digital signaling shouldn't really matter much. But the analog sensors quoted above are the cheapest I've seen.

To Bryce2471:
We do scale the analog voltage from the datasheet to 0-5v. It still twitches, but I haven't really tried to fix it. I agree it should be an easy fix, unless maybe the sensor has trouble pulling the signal quick enough.

We ran an entire season (and seperately an offseason) with swerves that had incremental steering encoders.

We loved it. Not having any hardcoded positions was great. Could replace a module or sensor and not have to touch code.

We zero'd by hand straight and/or used a seperate zeroing sensor when we felt like it.

In the future we'd do it again but use a mechanical hardstop (deployable pin or something) to zero with a hall effect as a backup.

Not having any magic numbers in code is magical.