General question on concept of PID

Hello all!

quick question; in a PID system...(I've listened to Andre's Boost lecture, among many other videos specifically regarding how to eliminate an error, or reach a target)

The way I understand it...

Proportional: Is a slow direct way to reach a target. However, if I have a high value for my proportional, I may overshoot the target. (the accelerator pedal)

Integral: the hold part of the "reaching the target" ...Moreso, used to eliminate small changes in order to "hold the target"

Derivative: "rate of change" is the focus here. Derivative is the manipulation of rate of change in order to reach the target, right?

So, say I overshoot a target...is it the integral or the derivative that I need to manipulate in order to come back and hit the target?

(to clarify...I want to understand the concept of PID on a system. I am not asking about boost or idle or fuel, etc...simply the concept of what PID is and how best to manipulate it.)

thanks ^_^

The derivative component should slow the acceleration at/through target. They all need to be balanced. It's hard to accurately describe the full system effect without a simulation to play with, you are talking 3rd year engineering degree system characterisation and Laplace transforms etc.

This is such an interesting concept (not to mention technology that we have in our everyday lives).

My mind is blown at how engineers have developed a way to eliminate...no, mitigate error through automation.

I've only made it through to Calc III, and Differential Equations; I stopped there, lol!

But thank you for clearing up the derivative portion of this concept.

I found a video (on a YouTube search attempting to illustrate the concept). I'll post it on here for posterity sake. I feel that it helps me see in real time what I am attempting to understand.

https://youtu.be/fusr9eTceEo?si=A1He-04RIO-kfj-x

also depends on what ecu you are using - haltech handle PID different to how link does for example

you can check the link helpfile for a very good description of what each part of the PID does on their ecu in much more detail than i'll put here but....

...in super short, non techy, brutally overlooking things ways of describing it...

P pushes the value towards the target in aggressive steps but can cause overshooting of the value past the target - can cause bad oscillation if you have too high a value here where the value is high enough that you keep overshooting and then undershooting and then overshooting and then under.... you get the idea

I slowly tracks the value towards the target over time to take up minor slack in accuracy that P and D have created - can also cause oscillation if you get it wrong

D attempts to prevent the value from overshooting the target - can dampen the speed at which you try to hit the target and negate your attempts to quickly reach it with higher P and I values

and there is a "base value" that you start from which needs to be manually tuned with PID disabled to be as close to the target as possible - usually a table of values - PID will then take that base value from the table and push it towards the target - base table and pid can be used for cam control, boost control, idle control, fuel trimming etc etc

please note this is a butcherous description of how it works - ignores soooooo much of the subtle work that it can do and is super generic and ignores how some things implement it or make use of it

there are also formulas you can use to get what your ideal pid should be in an ideal world with ideal inputs and outputs - but yeah - try and tune your cam control where your oil temp affects response and you only have coolant temp as an input and theres a 10th of a sec lag - artwork / empirical testing here you go...

have fun