I am trying to figure out what sensors I would need for a robot next season. Are optical encoders worth it or better than the built in motor encoders?
They are definitely worth it compared to the built in encoders which I’ve heard tend to be fairly unreliable for complicated programs.
Depends. Your base for instance, if you have a set of gears on your drivetrain, then I would recommend at-least putting a sensor directly on the wheel that is touching the ground. This is because no matter how good your drivetrain is, there will always be space/slack between the gears. Even better, you could have an auxiliary unpowered wheel on a hinge or joint rubber banded to the ground that is getting read by the rotation sensor. Generally, reading off exactly where you need something to be accurate is best. I have had a positive experience with the v5 rotation sensor so far.
It’s more that as you go down the line of gears and chain, some slack accumulates and you get more error. The internal sensor is fine.
So buying a two pack of those for position tracking is a good purchase?
Definitely. I’d say having at least 3 for odometry would be best
I’d wait till you figure out exactly what you think you want to do before spending.
In my experience both the internal encoders and the optical shaft encoders(lumped with the new rotation sensor) have different uses. The internal encoders can be used for pretty much anything, however they excel at just about everything other than the drivetrain. This is caused by slop between gears, wheels and the motors, as well as drive wheel slip, which the internal encoders cannot easily detect. For systems like intakes, arms, lifters, etc, they tend to work quite well.
Optical encoders benefit as they can be mounted to an external spring loaded wheel. As @Trent mentioned, this allows the sensor to detect drivetrain motion, even if the drive wheels slip or jump. For this reason, our team uses 3 shaft encoders on separate wheels as well as an inertial sensor for navigation. For us, this provided the best overall performance this year.
IME’s are certainly not as accurate as external encoders mounted directly to wheels, but they are certainly reliable enough for complicated programs, if used in conjunction with other sensors