A practical guide of PID Tuner [pdf]
github.comsee also https://en.wikipedia.org/wiki/PID_controller
This has nothing to do with Linux PIDs!
note: title incorrect, this link does NOT point to PDF, just to Github's preview page.
You can still get the pdf if you click download button, but this is optional.
A PID tuning guide with almost no math. But very important thing to consider when making an system identification test indeed.