Derivative Action, Blessing or Curse (Booklet and Software)

To paraphrase the children's story "girl with a curl in the middle of her forehead", when derivative action is
good it can be very, very good, and when it is bad, it can be horrid. Of the three controller adjustments typically available, derivative action is the most unforgiving of a guess-and-test approach to tuning. If you don't know what you are doing, you are better off not using it. Indeed, if you do know what you are doing, you will often decide you are better off not using it.
Derivative action must be set relative to certain lags in the loop. To determine these lags it is usually, if not always, necessary to make an open-loop or a closed-loop test. If too little action is used, it might as well not be used at all. If too much is used, it can cause instability.
For more information you may refer to a booklet "Controller Tuning and Control Loop Performance,a Primer" Second Edition, which is available in the US for $17, postpaid if prepaid. It has sold 29,934 copies to date. Control Engineering Magazine has referred to it as "PID Without the Math".
Information is available at: http://members.aol.com/pidcontrol/ from which there is a link to a page about companion software ($11). If you wish, I could e-mail you a brochure on either.
David W. St. Clair Straight-Line Control Co.
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MAYBE AFTER 14 IDENTICAL POSTS YOU MIGHT SELL ONE OF YOUR BOOKLETS.
BUT SPARE US ALL THE JUNK SPAM POSTS!!!
warren http://www.pc-pid.com
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We've been here before. Dwstclair has been making his postings in this (and other newsgroups) on a regular basis for several years. AIR he conforms rigorously to the specific newsgroup rules on repetitive commercial postings. It doesn't help to have a newcomer to the group take it on themselves to criticise a long-standing, authorised and accepted practice.
Kelvin Hales
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Warren wrote:

(and other

rigorously to the specific

a newcomer to the

accepted practice.

To ad to the above, I sent for one of his books, and I found it to be well worth the amount he's asking for it. Concepts are explained in a manner understandable even to students (even I understood it! :-] ). Check the pricing in the book section of the ISA website for the usual pricing of this type of information.
Louis
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I have recommended his booklet more than once as answer to questions raised in this and other NGs.
Walter.
Warren

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Louis Bybee wrote:

If you found his booklet helpful, you might find some of the ideas in http://users.erols.com/jyavins/servo.html useful as well.
Jerry
--
Engineering is the art of making what you want from things you can get.

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Kelvin Hales wrote:

It's only irritating in that he doesn't seem to contribute to the group - I've never seen him post anything other than an ad. But if I thought it were a real issue I'd be posting my own newbie complaints (or following up each message with a pointer to my site, where you can get related info for free).
--

Tim Wescott
Wescott Design Services
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Warren wrote:

(and other

rigorously to the specific

have a newcomer to the

accepted practice.

While I can't verify contributions he may have made to the group, I have "bothered" him a few times via EMAIL, and he's been very helpful without any sign of annoyance.
I applaud you for the technical information available free at your web site. It would appear that a considerable amount of time was invested in its preparation.
From your bio I noticed you worked at Flir. I worked on a project there a short time ago. For someone interested in electronics and control it's like a candy store. I had a bit of difficulty at first taking the people there seriously after noticing a working toy train mounted up on the wall in the test area, but after receiving an explanation of its function my faith was restored. :-] Working in that area would be a little unnerving if you were shy around cameras. It tends to give one the willies having multiple unmanned units tracking your every move. :-]
Louis-- ********************************************* Remove the two fish in address to respond
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