PID sensors/tips

[NotLukas]

Hello, next year is my last year of vex robotics and I wanted to do it right with some sort of PID on the drivetrain. I’ve never done this before and I was wondering what kind of sensors I would need and any tutorial recommendations would be appreciated. I was also curious what the difference between PID and odometry was?

Thanks

[le_manchot]

So excited to hear you want to do sensors!

You definitely have a few options, although afaik PID is more of a control loop rather than an actual tracking mechanism (it can certainly be paired with sensors of relative information to account for compounding error). You are probably more likely to use PID to make your robot actually stop where it thinks it is.

Odometry uses multiple rotation-tracking encoders (be it the internal motor encoders, quadrature shaft encoders, or rotation sensors) to measure arcs that the robot moves through in small-step intervals of time to track the change in position. This is relative sensing though so watch out for compounding error – ping those sensors fast!

TL;DR: Odometry requires fewer physical sensors but more complex code and is a form of relative sensing

You could also use absolute positioning via vision sensors (risky but go ahead and try it, could be kinda cool), ultrasonic range modules, or distance sensors (have fun with IR absorbance then). This has worked incredibly well for me but requires a ton of ports and absolutely destroys your battery – I easily kill 1% in less than a minute sitting idle.

TL;DR: absolute position tracking is great for avoidance of error but is physically costly.

If you avoid odometry, you will have to still measure the angular position of your robot using something like an inertial sensor or the old yaw rate gyroscope. If used correctly, this can be great with an absolute positioning system.

Whatever you choose, best of luck!

[Gigahertz.t]

@NotLukas

I was also curious what the difference between PID and odometry was?

PID vs Odometry or both

odometry and pid are different things, odometry is a method that you can use to get accurate data about your robot, specifically the position and rotation on the field. PID is a method of controlling your robot so you can use that data to make the robot move where you want to.

@NotLukas

what kind of sensors I would need… any tutorial recommendations

Lots of resources by just searching google or the forum

Should my team use pid or ODOm to program our robot

hi im Ranchsauce2456 and our team wants to program our robot for autonomous. I read somewhere taht pid and ODOm are good for doing this. Which ones better? … is a question I’ve heard many times from newer teams. So let’s have a crack at answering this question. (Spoiler: It’s neither!) To first answer our question, let’s first take a look at what Odometry and PID actually are. Odomometry (Shortened to Odom colloqually) Odometry is some sort of system to keep track of a robot’s position on the …

Odometry

Odometry - BLRS Wiki
What is Odometry? - #19 by DylanMashini
What is Odometry? - #23 by tabor473
https://www.youtube.com/watch?v=GEZBYHVHmFQ
Uses either “odom pods” (extra wheels mounted on your robot connected to rotation sensors) or your built-in motor encoders and an inertial sensor

PID

PID Controller - BLRS Wiki
VEXCode PID Tutorial
https://www.youtube.com/watch?v=_Itn-0d340g

[NotLukas]

Thanks a lot, I definitely have a lot to read and learn.