Best Book on PID ??

If you mean the controller, here's a start:

It's much more for writing software more than for building circuits but there's some generally useful information in there -- and I think you'll be able to figure out how to do integrators & differentiators with op-amps.

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

Computers also make it easy to characterize the open loop and design a pretty good controller, so all is not lost.

You can often make things work well enough by fudging, though. It sometimes amazes me how quickly I can get within 20% of the optimal solution just by rule of thumb. Of course, if you need to be within 5% then you have a lot of work ahead of you...

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

"PID Without a PhD", and that's a "simplified" view, please. Inspired by the directions given to union millwrights by control engineers who aren't allowed to touch the equipment in many, if not most, mills. Written by some schmo named "Wescott". Available through

It certainly doesn't teach control theory, but it will let you twiddle the knobs to get a working system most of the time (predicting how well you'll like the result before you start requires control theory, however).

controllers etc.

I have Astrom's adaptive control book, and I love it. Part of my admiration is inspired by the fact that he devotes a whole chapter to alternatives to adaptive control -- anyone who's writes a book about a pretty new theory then tells you when you don't really need it has integrity, in my view.

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

Try

for some GREAT stuff especially the PID controls.

OK, I'm biased, I actually built a lot of his equipment and was impressed with the precision of the mechanics and the true realtime software in Windows.

Jay

Best book? It all comes down to some nasty math.

"Servo Mechanism Analysis", by Thaler and Brown, is probably as good a book as any... It's probably even on your bookshelf, as it is a good 50 years old.

There is no easy way out of these problems, either you characterize the open loop system, and design a proper PID equation to control it, or you fudge things and hope for the best. Computer based servo loops have made fudging things much easier than it used to be... but I am pretty sure, based on your relationship with computers, that you aren't planning to do a computer based PID.

-Chuck Harris

Jim Thomps> Recommendations for Best Book on PID ??

Behold, Jim Thompson signalled from keyed 4-1000A filament:

PID?

Jim....you really oughtta see a doctor :-/

;-p

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Gregg t3h g33k
"Ratings are for transistors....tubes have guidelines"
http://geek.scorpiorising.ca

You could probably write a good one. A PID controller is just a follower amplifier (that forces a process measurement to follow a setpoint). The PID controller tuning is just a lead lag network that stabilizes that unity gain amplifier.

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John Popelish

There is PID without tears on Embedded.com (I think), which a simplistic view.

Then there is the text (Astrom) I have which goes from the basics to adaptive controllers etc. PID controllers Theory ,design tuning. Lotsa good stuff.

s=books&n=507846

Cheers

For learning (i.e., some math but not dense page after page of it) look at "Control System Design Guide," George Ellis, ISBN 0-12-237461-4. I have (and enjoyed) the 2nd edition of the book; the ISBN is for the 3rd, published in 2004.

Web site, free companion software:

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Rich Webb   Norfolk, VA

Sorry Tim ;D

PID with out a PHD is a very good beginning spot. Its where I had started, and wound up later with Astrom.

I never made the connection.

Cheers

view.

adaptive controllers etc.

I'll second that. I have the third edition. It provides some good general guidelines and explanations.

Paul C

I'd agree if we were talking about PI controllers, but PID are somewhat different--the D term is there to compensate for slow transducers such as motors and heaters.

The slow transducers put a few wrinkles in practical control systems that are different from ordinary amplifers: windup in motors and asymmetrical slewing in heaters. The D term will turn the 2-pole response of a motor into 1-pole so that it can be stabilized, but the settling behaviour won't be anything pretty unless some sort of (nonlinear) windup control is in there somewhere.

Cheers,

Phil Hobbs

Yep. That sounds a lot like you are talking about Jim Thompson.

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John Popelish

But follower amplifiers that drive big, slow, nonlinear devices have all those same problems. Slow is just not as slow. When I first got into process control, it seemed very strange, because I was unfamiliar with the jargon. Then I realized that I have been using oscilloscopes to study amplifiers doing all the things process control was doing, except that now, I could have a cup of coffee while the dynamics settled instead of it all happening in microseconds. but the principles are just the same. Gain bandwidth product, phase shift, slew rate limits, output nonlinearity, recovery from output overdrive, etc. all there.

When I saw the Star Trek episode about the people who moved so fast that they were invisible, I realized that they was how I felt while tuning a control loop.

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John Popelish

It has been writ:

I am the man who designed ABB's Commander line of process controllers, recorders and recording controllers.

If you are doing control of a real process - a heater, tank, pump, catalytic cracking tower, your mother's baking oven - do not follow the above advice.

If you are controlling a hamster exerciser, the above is fine, and will save an awful lot of explanation ...

The whole of ABB instrumentation (when it was Combustion Engineering) had one (count'em one) engineer with the above qualification (and it wasn't me). When I worked at (another process control firm that shall remain nameless) there were none. Figure if you are the above 'You', you are among 10, 50, 100? engineers in the world.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer:  Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com

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

Pelvic Inflammatory Disease.

what did you think?

Doug

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.

Cheers,

Phil Hobbs

see this?

-Lasse