Comment by midjji | Hacker News Reader

Comment by midjji | Hacker News Reader

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Buddy of mine did his master thesis as at a biofuel company a decade ago or so. He was supposed to do some advanced filter modelling, but do so he needed to configure the pid regulators to actually save the sensor values, not to mention turn them on. So he ran the pid configuration software, noticed they hadnt been tuned at all, set the values to something not catastrophically shit by just looking at the signals for a few minutes, then collected his data the next few days and went home to work on the thesis. It took a month before they figured out the random thesis worker no one paid attention too was the reason output was up 80%. He got a really nice bonus and job offer as a result. Then he actually tuned the pids using basic but proper system identification, but the largest gain is always from the most basic stuff, like turning the controllers on.

I always love stories like this. When you first join a company who's product you admire, I feel like the implicit assumption is that they know what they're doing. Then after some detective work as a curious noobster you realize that everyone is just as clueless as you are!

Yeah a lot of the plc coders in the field are not too good at the pid tuning stuff actually. some are but it's treated like some dark art instead of a fairly basic thing.

Very few loops need any real tuning. For most of them, an incredibly wide range of value works perfectly well. Systems usually have a lot of slack in them.

It's hard for most field engineers to get experience tuning loops when there are so few opportunities where the time investment can be justified.

This is one of those cases however where field engineers who are around plcs all the time will say "oh I never needed that class" (process control theory) but they never needed it only because they didn't learn it, so they either don't see opportunities to apply it, or aren't assigned the task.

I think this happens in computer science a lot as well. You often can go your whole (very successful) career not needing something you didn't learn, because your career would have been different if you had learned it thoroughly.

So a "random thesis worker" was allowed to change the process config at a biofuel company without approval? Right. If this is true, I'm astonished.

There is a difference between didn't pay attention to, and gave permission.

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