PID controller

On Tue, 20 May 2008 09:36:32 -0700, daisyj.rico wrote:


Forgive me, but I'm having a bit of trouble with your English.

Are you asking if there are shortcomings to using a straight PID
controller for a boiler?

I'm no expert in boilers, but I'll bet you that the answers are, in turn
(a) yes, (b) but it's not usually so bad that it's worthwhile cooking* up
a special boiler-control algorithm, and (c) there will be times when it
_is_ worth doing so, and there are no doubt innumerable articles in both
the trade literature and by fancy-pants academics detailing various
methods, with various levels of practicality.

* as it were.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

hmm.  e.. all of the above.

Boiler controls are pretty well known about now.  At this
point, the real issue is what strategy to use to operate the
boiler.  While the strategy depends on the type of boiler,
size, etc, it should be noted that there are several methods
other than the ones that are initially obvious.  A good
analysis of what a boiler really is provides a very good
idea on what strategy to use.  The optimal boiler strategy
is not used on many boilers, in part because too many people
are stuck on using PID loops when there are better tools
available for many parts of the control.

Michael


Michael

On Tue, 20 May 2008 23:32:40 -0700, Herman Family wrote:


The attraction of using a PID loop to solve as many problems stems from
much of the same impulses that leads every kitchen to have a pair of
pliers and a screwdriver: they may not be the _right_ tool for every job,
but with them you can usually turn things from disasters to adequate.

So if you're only going to learn how to apply _one_ control strategy, PID
would be it.

(My kitchen is better equipped: I have a pair of pliers and _two_
screwdrivers).

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

What? no hammer?

I agree.  I've seen too many controls which are shoehorned
into a PID loop or some sort of cascade of it.  PID is a
great regulatory control, but supervisory controls are often
better off being a model based system that can fully
appreciate the complexity of the overall system.

Michael