Re: Best Book on PID ??

From: Tim Wescott (tim_at_wescottnospamdesign.com)
Date: 11/26/04 

Date: Fri, 26 Nov 2004 10:58:56 -0800

Lasse Langwadt Christensen wrote:

> John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in message news:<n86cq0h4rh5hmp04av0drra3g0phjq3k1q@4ax.com>...
>
>>On Thu, 25 Nov 2004 12:28:37 -0500, Phil Hobbs
>><pcdhSpamMeSenseless@us.ibm.com> wrote:
>>
>>
>>>I don't disagree that there are lots of similarities, or that there's a lot
>>>of jargon in control system design that seems intended to preserve job
>>>security rather than make concepts clear. (There's a lot of that in some
>>>optics disciplines too--it isn't just an EE problem. Not to mention all of
>>>anthropology.) If I'm designing e.g. a laser temperature controller, I use
>>>Bode plots: one for each of several representative choices of ambient
>>>temperature and thermal forcing. PLL design with nonlinear tuning is
>>>similar. Not everything is that simple, however.
>>>
>>>Lots of control systems have to work in situations where an ugly settling
>>>transient will cause destruction--from burned cookies and broken drive belts
>>>to loss of life and property. There are very few purely electronic
>>>situations (i.e. other than driving mechanical devices or large magnets)
>>>where a poor transient response is that serious.
>>>
>>>Ordinarily, with an amplifier driving a speaker, say, you can have a few pops
>>>and bangs, but no great harm is done, and they can be tuned out during
>>>debugging. The nonlinearity is of a simple and intuitive sort, and there is
>>>no complex coupling. There is also usually no external forcing, unlike e.g.
>>>a motor controller which may have very different loads at different times.
>>>It isn't possible to test every situation, and it's the ones we haven't
>>>thought about that will turn round and bite us in the backside. Systems that
>>>are uncoupled during normal operation, but become coupled due to faults and
>>>transients, are a common source of this.
>>>
>>
>>It's interesting that a lot of real-world control loops leave theory
>>way behind, except for the fairly boring region of near-steady-state
>>operation around null. The hairy parts, the transient and exception
>>conditions, revert to art, instinct, and maybe simulation.
>>
>>I like systems like that.
>>
>>John
>
>
> see this? http://users.erols.com/jyavins/servo.html
>
> -Lasse

I've implemented similar anti-windup schemes (without the metaphysical
reasoning); it works quite well for me. 

-- 
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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