Obligatory link to PID without a PhD: https://www.wescottdesign.com/articles/pid/pidWithoutAPhd.pd...
comments like this are why i come to hacker news
Proportional-Integral-Derivative (PID) controllers
51–60 of 65 posts
Re: Proportional-Integral-Derivative (PID) controllers
#52Honest question: are wiki links to any technical topic post worthy now?
At least for me, it's not about the wiki link. I'm here for the comments, the stories, anecdotes, related deep Diving links and general chit chat. If you view the link as "this is the control systems thread for today", all the upvoter make a lot more sense.
yeah, this is the true gold of hacker news: learn about a new concept from the post, and then have knowledge multiplied by discussion across a range of experience levels from curious readers, to daily practitioners, and sometimes even p99.99 top experts in a field.
Re: Proportional-Integral-Derivative (PID) controllers
#53My personal exposure to the PID algorithm was my GPU fan. There is supposed to be some sort of internal fan curve to control it's speed but mine was not working, crashes everywhere. I Could still set the speed by hand. and while I was putting together a sort of hacky user space fan curve I had an epiphany. I Don't actually want a fan curve. I want to set an ideal temperature and have the computer figure out what fan…
why not just set maximum speed and forget about it?
Fan noise.
My computer sits next to my desk, so I want it to be as quiet as possible. This means the fan should run as the lowest speed which maintains a reasonable temperature, so at the very least there should be some kind of mapping between temperature and fan speed.
However, a rapidly-changing fan speed results in a more annoying sound than a slightly faster fan, and chip temperatures can ramp fast, so a simple linear mapping between temperature and fan speed isn't enough. To get a quiet fan in an environment where you are, say, loading the CPU to 100% for 100ms every second, the fan controller should be able to average out the heat production and let the fan run at a steady speed. After all, the cooler is a big chunk of metal, so its temperature will never ramp as fast as the core itself, so a rapid fan speed response is pointless.
Re: Proportional-Integral-Derivative (PID) controllers
#54Earlier quoted context omitted.
Yeah, kind of hilarious to me that this was posted here. I suppose if you’ve never encountered control systems at all before they are quite simple, elegant, and cool, but I’m surprised any technical person hasn’t come across them at some point.
https://xkcd.com/1053/
Also https://xkcd.com/2501/>.
Re: Proportional-Integral-Derivative (PID) controllers
#55The fascination of programmer types with classical control and estimation topics is endlessly interesting as someone who studied control and estimation and hangs out here for interest in the programming. For me it was surprising to see that JEPA is a model predictive control algorithm it an almost literal sense; I guess I’m happy to have studied what I chose when I was 18.
Yeah, kind of hilarious to me that this was posted here. I suppose if you’ve never encountered control systems at all before they are quite simple, elegant, and cool, but I’m surprised any technical person hasn’t come across them at some point.
I've encountered control systems and PID controls, and I still find PID elegant and cool.
Re: Proportional-Integral-Derivative (PID) controllers
#56Oh! My first job out of college had me implementing PID control for a two axis rotary control tables. The design had counter weights (think dumbbell shaped). I was the dumbbell implementing this and as I was young, had almost 168 hrs a week to work on this.
OMG! I spent so much time trying to tune this and it would occasionally enter these oscillatory states back and forth. Unfortunately the device on the turntables cost about $500k….
It was such a painful experience.
Re: Proportional-Integral-Derivative (PID) controllers
#57My personal exposure to the PID algorithm was my GPU fan. There is supposed to be some sort of internal fan curve to control it's speed but mine was not working, crashes everywhere. I Could still set the speed by hand. and while I was putting together a sort of hacky user space fan curve I had an epiphany. I Don't actually want a fan curve. I want to set an ideal temperature and have the computer figure out what fan…
That might have been easier solved with eg. an adjustable voltage regulator (like good 'ol LM317?) with a temperature sensor in the feedback circuit.
No futzing with software needed.
Reminds me of Dave "EEVblog" Jones' in his "always give negative feedback" T-shirt.
(for those who don't know: it's a reference to opamps)
Re: Proportional-Integral-Derivative (PID) controllers
#58Earlier quoted context omitted.
> Eventually, I suspect we will replace most PIDs with a small neural network for almost all industrial applications With or without serverless lambda architecture bitcoins ?
Depends on how they address the side fumbling between the Spurving bearing and the Dingle arm, vis-a-vis the lotuso-toroidal damping force.
Only as long as you get the encabulatory turbo gradients correct. But don't use sinusoidial flux inhibitors for that, they suck!
Re: Proportional-Integral-Derivative (PID) controllers
#59Earlier quoted context omitted.
I signed up for one of the first MOOCs ever, about self driving cars by Sebastian Thrun, and of course PID was part of the curriculum. I think that PID hits a certain sweet spot between cleverness, ease of implementation and practical utility that makes it catnip for the typical programmer's mind. I liked it so much that when we had to implement it, I downloaded an open source driving simulator to see it work there i…
> I think that PID hits a certain sweet spot between cleverness, ease of implementation and practical utility that makes it catnip for the typical programmer's mind. It's easy to implement, but hard to tune. PID controllers can be built from analog pneumatic components, and often are.[1] This predates computer control. The I term is called "Reset" and the D term is called "Rate" in classical control. [1] https://cont…
Pretty easy to tune really - almost never use derivative, increase the proportional until oscillations occur then halve it, add a little integral, not so much it oscillates.
Re: Proportional-Integral-Derivative (PID) controllers
#60Earlier quoted context omitted.
This isn’t meant to be an attack, but almost everything you say here is false. > PIDs are great but notoriously hard to tune. They require deep insight into the underlying physical phenomena to get right. They are also rather rigid and cannot adjust well to a changing environment (temperature and humidity can fluctuate dramatically between summer and winter in some climates). This is not true. PID controllers are oft…
I saw a crazy stat somewhere like some large fraction of the industrial PID controllers that are actually deployed in plants are completely untuned--that is, just running default settings. I think it was a book about tuning PID controllers, but I don't have the exact citation handy..
There are more than one set of tuning settings, depending whether optimised for start up, steady state, minimum overshoot etc