PID and oven controller

[fakufaku]

Just for those of you I haven't spammed with my oven hack thing: I have hacked my oven. I talk about it in a blog post:

http://fakufaku.github.com/hacks/2012/08/21/fixing-an-electric-oven/

But mostly here, I wanted to point out that the PID arduino library:

http://arduino.cc/playground/Code/PIDLibrary

can be a great introduction to PID (Proportional-Integral-Derivate) which is a popular technique for system control. It uses feedback from a sensor to adjust the output of the system.

Setting the constants can be tricky, but this morning, I finally managed to find good constants for my oven. Mostly, I realized that the P part was way to small to get to the temperature I wanted.

Cheers,

Robin

[Mikele]

so, when will u invite us to the pizza party?

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[Torsten Wagner]

Hey,

nice to see it worked out. There are different ways to start tuning a
PID controller.
As you noticed/mentioned the tuning is not as easy. Its not so much
the controller itself but the entire control loop. There are many
things to take care and many thinks can screw a controller setting.
Furthermore, it entirely depends on your needs. Do you want to track
changes as fast as possible and do not mind some overshoot, or do you
want a slow but very accurate approximation towards a change of the
input parameters and avoid overshoots at all, since it might kill your
system.

However, assuming your loop is not too complex and no crazy stuff
happens (like time variant dependencies, much dead time, etc.),
following one of the methods which fits your needs, should bring you
close enough of what you might get ideally.

E.g. Ziegler–Nichols method is one very famous way to tune a PID
(albeit a bit "theoretical").


Totti

[Taylan Ayken]

Yep, tuning PID sucks big time. For fast systems, it is easier as you can try many parameters in a given time but with slow systems (like an oven) each iteration takes a looong time, it gets really boring after a while.

For overshoots, there is a method: You shape the input signal ie. turn the step input into an S-like curve. I've used this method with a couple of systems where fast response with no overshoot was needed. The input shaping function depends on some parameters of your system. I've used it especially with position control with a motor, so the input shaping function was looking at maximum acceleration limit, maximum speed and so on.

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From: Torsten Wagner <torsten...@gmail.com>
To: tokyohac...@googlegroups.com
Sent: Friday, August 24, 2012 1:42 PM
Subject: Re: [THS:19938] PID and oven controller

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[Jud Taylor]

Robin,

What time?

Best,

Jud

On Fri, Aug 24, 2012 at 12:55 PM, fakufaku <faku...@gmail.com> wrote:

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[fakufaku]

Jud, and everybody,

I am having a farewell party this evening. It was advertised on facebook. In these last hectic days I somehow failed to post it here.

The party starts at 8pm, at Apperitivo in Ebisu. We ask for 6000 yen to cover cost of renting the place. Drinks and some food are covered.

It's pretty informal.

Cheers,

Robin

[Mikele]

I am coming, more than likely with my wife.
see you there!

PARTY!!!

To view this discussion on the web visit https://groups.google.com/d/msg/tokyohackerspace/-/4iSwsIgENsUJ.