This is all interesting.
I have designed control systems and the like for over 40 years, so I understand where
@Richard Foster is coming from!
There are a number of different PID control algorithms, and without knowing the particulars, it's hard to even offer advice about tuning a PID control.
Over the years, I've had good and bad luck with different PID controllers' autotune. Some have been phenomenally great (some Fuzzy Logic PID controllers I got many years ago from Omega Engineering). They were nothing short of miraculous! I wish they still sold those exact units.
But I've also run into units whose autotune ended up creating more work than manually tuning. Of course, different systems require different tuning methods, so it's not entirely fair to blame a unit's autotune unless you're comparing it against another controller in the same system. And even then, you need to understand how the autotune is implemented to know if it will be of much use or not.
As Richard has pointed out here, and in some other threads, the whole idea of using a PID controller for a smoker is usually overkill, and, being quite complex to truly understand, can lead to more problems than it solves.
But, as has been pointed out elsewhere (perhaps also by Richard), almost all temperature controllers that you can find these days include PID control because they almost all use a microcontroller, and once you've got a microcontroller, a display, and a few buttons, why not include PID and other fancy features (ramp and soak, etc.)? It costs nothing in production to have these features in the program once its written.
So when one goes shopping for a cheap temperature controller these days, you're almost certainly going to get a PID controller. And as a result of that, when us smoking hobbyists are shopping for an external controller to retrofit one of our off-the-shelf smokers, what we end up with is a PID controller. So we've all taken to referring to any external or aftermarket temperature controller as a PID controller. And that's not wrong.
But as Richard has pointed out, for most of us, we really don't need the PID functions for our smoker. And in fact, as this very thread points out, the PID functions may well be something of a hindrance to getting what most of us want.
What people are mostly after with an external or aftermarket temperature control is to get away from what are often seen as poorly-implemented or faulty temperature controls that come with our smokers from the factory.
This has been covered before, but certainly one reason for wide temperature swings in the MES smokers is their use of the main (only) heating element to not only control the temperature of the smoker, but also periodically ignite the smoke chips. To do that, they must crank the heating element on full bore, and for a fairly long time, every so often so that the chips will be ignited.
But doing that means that you simply cannot have precise temperature control in the smoker.
And then there are issues with the average temperature even being (or at least appearing to be) incorrect.
Some of that appearance of inaccuracy comes from incorrect ways that we measure the temperatures in our smokers. And some of it comes from the smokers actually sucking! :)
But in any case, a lot of us decide that we want to modify our smokers to use a separate or aftermarket temperature control system, and at the same time (because this will be necessary and better) we want a separate aftermarket smoke generator system.
If we are to have smooth and precise temperature control, we cannot also use the stock smoke generating system of the MESs. So we go with something like an
AMNPS or the tube smokers, and then modify the smoker itself to use a different temperature controller.
That's all just great.
But now, since the controller we bought has PID functionality, we often feel compelled to use it. But with may of these controllers, you don't have to use the PID functions.
I've never used the Auber units, so I cannot speak to how one goes about changing its settings so that you get a plain old "bang-bang" controller. Or perhaps just a proportional control, with no I or D terms.
But if you can disable at least the I and D terms, and set the Proportional band to something reasonable, you may not need to do anything else.
And if you can disable all of that, and just set a small hysteresis value and run the control in "bang-bang" mode, that will typically be fine, too.
And this might be better for most people who don't want to fiddle with the whole PID thing.
As I said, I've done control system design for at least 40 years. And I appreciate the value of PID control for many systems. You really can optimize things with a properly tuned PID control system, and you can do even better if you have a combination of PID control AND the functions of a PLC or other computer control system that lets you change the parameters of the PID loop(s) on the fly, based on other information or something of an adaptive or "learning" bit of extra code. This is often necessary because as certain variables change within a system, often one set of PID parameters is not ideal for all situations that the system will encounter.
But again, most of us don't want to deal with any of that just to run our smoker.
If you do want to delve into tuning your PID controller, that's just fine. It can be fun, and since this is largely a hobby for most of us anyhow, why not add that to the whole thing?
A heater system like a smoker is one of the most simple of control systems, and should be one of the easiest types of system for which to tune a PID.
But there are things to keep in mind.
One of the first things that comes to my mind is that the tuning parameters for an empty smoker will be quite different from the correct parameters for a full smoker. The heat "load" presented by a lot of wet-on-the-outside meat will be totally different from the "load" presented by a small amount of dry-on-the-outside meat, or an empty smoker.
Next, we also have the issue of temperature gradient from the inside of the smoker to the outside. If you're running the smoker fairly cold, and it's hot outside, there will be a LOT less heat loss from the smoker than if you're running the smoker at a high temperature and it's very cold outside. And this will affect the optimum tuning of the PID loop.
So the trick is to have a way for the controller to adapt to various scenarios, either manually, or automatically OR to find a "happy medium" tune that works pretty well for any temperatures or loading of the smoker.
The upshot of that is this:
If you're going to use the autotune function of your PID controller, you need to do that right.
Ideally, you'll perform the autotune with the outdoor weather the same as it will be at your location "on average".
You'll choose a smoking temperature that is what you'll mostly be using "on average" for your actual smokes.
You'll start with the smoker at the same temperature as it is outside of the smoker.
You'll "load" the smoker with meat or something to simulate that, using the "average" amount of meat that you expect to be smoking, and with it positioned in the smoker the same way you will normally be loading the smoker when actually using it.
Then, and only then, do you initiate the autotune sequence.
Ideally, then, the tuning parameters that the autotune generates and stores will be good for your average actual use.
Don't autotune with the smoker empty! Things will happen a lot faster with an empty smoker, and the parameters the autotune arrives at will probably be such that then, when you actually put some meat in there, it will take longer to reach the setpoint than what you expect. Basically, you're throwing all of the timing assumptions out the window if you tune with an empty smoker.
For manually setting one of these up, if it was me, and I didn't want to mess with it a lot, I'd start out with no I or D at all. Then I'd set the P (gain) to a setting that worked over a range of about 5 degrees F or so. Even if that ends up cycling the heater all of the way on and off, what have I really lost?
Here's a good article about basic PID tuning:
https://wescottdesign.com/articles/pid/pidWithoutAPhd.pdf
And I found these talks about PID tuning by ABB to be quite excellent:
