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04/19/2021 8:46 AM
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Fluidbed Roaster project
cdrake39
Well I have a few roasts under my belt and the results are looking good! Roasts are more repeatable and the coffee has been top notch. But of course, I am always looking for ways to improve. I've posted a snapshot of my latest roast - I had to add the cyclone back in to the setup to get more back pressure and contain the heat which makes hearing FC difficult, so Fcs and FCe are not plotted (but I'll make a separate post about that). My question is, what are you folks using for RoR curve parameters? My RoR curve is looking a little bumpy, but maybe it's fine? I fear if I smooth it out too much it may lose it's value - hoping to find the balance of reducing the noise while keeping the data meaningful.
cdrake39 attached the following image:
oct31roast_resized.jpg
renatoa
PID oscillations... can be seen in power evolution too.
Lots of hesitations, instead a firm increase, as is the profile shape.

PID tuning would not change this behaviour too much, tuning is done for a specific slope and setpoint, not for a permanently variable setpoint. Outside the range where you performed the tuning will start oscilate again.
Also, the actual PID philosophy impose having over/under-shots, in order to build integrative term.
A code change is required, to compute integrative term taking into account also the second derivative, i.e. RoR evolution. More exactly, when you have a rising error slope, it's ok to add the error to I term. When this slope ends, and the error become flat, no more add to I term, even if error is still there, it's a sign an error decrease will follow.
Much less oscillations with this trick.
cdrake39

Quote

renatoa wrote:

PID oscillations... can be seen in power evolution too.
Lots of hesitations, instead a firm increase, as is the profile shape.

PID tuning would not change this behaviour too much, tuning is done for a specific slope and setpoint, not for a permanently variable setpoint. Outside the range where you performed the tuning will start oscilate again.
Also, the actual PID philosophy impose having over/under-shots, in order to build integrative term.
A code change is required, to compute integrative term taking into account also the second derivative, i.e. RoR evolution. More exactly, when you have a rising error slope, it's ok to add the error to I term. When this slope ends, and the error become flat, no more add to I term, even if error is still there, it's a sign an error decrease will follow.
Much less oscillations with this trick.


Thanks for the reply! I'd be lying if I said coding was an area of expertise for me. Perhaps I'll leave it as is for now - unless its a fairly simple modification?
renatoa
Let's continue this as PM if you want, then start a new thread with conclusions.
But for now I will post in TC4 main thread a finding that is really simple, but with visible effects, and I think it should be immediately addressed in the main TC4 PID code.
cdrake39

Quote

renatoa wrote:

Let's continue this as PM if you want, then start a new thread with conclusions.
But for now I will post in TC4 main thread a finding that is really simple, but with visible effects, and I think it should be immediately addressed in the main TC4 PID code.


Thanks! Seems like a very simple change so I'll try it out and report back after the next roast.
wes
Hi All,

I'm new here but I have spent a few hours perusing the forums so please forgive me in advance if this topic has already been covered. I am wondering where everyone is placing their T/Cs in their fluid bed roasters. I have a 2lbs Sonofresco that I am wanting to hotrod and control with Artisan.

Thanks,
wes
allenb

Quote

wes wrote:

Hi All,

I'm new here but I have spent a few hours perusing the forums so please forgive me in advance if this topic has already been covered. I am wondering where everyone is placing their T/Cs in their fluid bed roasters. I have a 2lbs Sonofresco that I am wanting to hotrod and control with Artisan.

Thanks,
wes


Hi Wes and welcome to HRO! Please start a new thread within Fluidbed Roaster forum so as not to cause cdrake39's to take on a parallel topic within it. Once you do this, we will cut this post. Looking forward to hearing more about the Sonofresco sensors.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
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