Best Book on PID ??

[Rich Grise]

On Wed, 24 Nov 2004 10:43:59 +1300, Terry Given wrote:

Rich Grise wrote:
On Tue, 23 Nov 2004 13:45:14 -0700, Jim Thompson wrote:


Recommendations for Best Book on PID ??

Thanks!



I hope I'm not em-bare-ass-ing myself here, but what exactly is "PID" the
acronym for? Somehow or another, I seem to have missed that one. ?:-/

Thanks,
Rich

Proportional-Integral-Derivative

Thank you for this.

Many, many systems can be suitably controlled by using a feedback
controller combining the three terms. Either with an opamp or a DSP (or
for that matter hydraulic or mechanical controllers)

I had an assignment once to figure out why a particular heater controller
wasn't doing what it was supposed to do, and the nodes I was scoping just
confused me beyond all help. I think you've finally cleared that up for
me. Thanks!

Oh, and Astrom and Wittnemark's "Computer Controlled Systems" has a
pretty good treatment on PID. I have seen a better book, but alas forget
its title - its a chemical process control book.

Thanks again!
Rich

 

[Spehro Pefhany]

On Tue, 23 Nov 2004 20:07:17 -0700, the renowned Jim Thompson
<thegreatone@example.com> wrote:

On Tue, 23 Nov 2004 22:10:18 -0500, Spehro Pefhany
speffSNIP@interlogDOTyou.knowwhat> wrote:

On Tue, 23 Nov 2004 21:44:26 -0500, the renowned John Popelish
jpopelish@rica.net> wrote:

Spehro Pefhany wrote:

Z-N tuning is an experimental controller tuning method. It tends to be
a bit aggressive for real systems (so, increase the P. band). I've got
a copy of the original 1942 paper around somewhere if you can't find
it online (shouldn't be that hard).

Walter Driedger has posted a PDF copy of the world famous Z-N paper on
his web site:
http://www.driedger.ca/
http://www.driedger.ca/Z-N/Z-N.html

Okay, that's a nice HTML version. I've got a 5M PDF scan version of
the ASME paper here:

http://members.rogers.com/speff/Ziegler-Nichols.pdf


Best regards,
Spehro Pefhany

Click the "Download" button... and download the 757KB PDF version...
scanned, then OCRd into Word, touched up and then PDFd ;-)

...Jim Thompson

Ah, that's better!


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Popelish]

Jim Thompson wrote:

Recommendations for Best Book on PID ??

Thanks!

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.

--
John Popelish

 

[Rich Grise]

On Tue, 23 Nov 2004 16:14:02 -0800, Tim Wescott wrote:

Martin Riddle wrote:

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

"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
http://www.wescottdesign.com/articles/pidwophd.html.

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).

Ah! Finally! The crux! I see it all now!

It's Black Magic!

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.

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.

Cheers!
Rich

 

[Tim Wescott]

Jim Thompson wrote:

On Tue, 23 Nov 2004 19:45:14 -0600, "Ron H" <rnharsh@attbi.com> wrote:


Do you want to understand it or do you just need to tune it?

If the later, search on "Ziegler-Nichols". It's a technique that will get
your loop tuned and running smooth in short order. If the former, there is
no end to the options but before you spend money, search on "PID Controller"
and you'll find plenty of info.


73
K3PID
Ron H.



Aha!! The perfect pointer! Thanks!

And what do you know, old "Nichols Chart" himself... last used one
about 40 years ago ;-)

...Jim Thompson

If this is for that Devil's Transducer that you were asking about
earlier I don't think Z-N is going to get you there. You'll be much
better off getting a good Bode plot (like, with about 50 times more
points) of the thing and designing your controller from there. Watch
for that resonance at 10kHz -- it'll be a bitch.

As mentioned elsewhere if you treat it like a mystery circuit element
you'll do fine -- you could probably even model the thing as some
bizarre circuit in SPICE and do all the analysis in that context.

--

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

 

[Terry Given]

John Larkin wrote:

On Tue, 23 Nov 2004 21:20:08 -0500, John Popelish <jpopelish@rica.net
wrote:


Terry Given wrote:

John Larkin wrote:

On Tue, 23 Nov 2004 17:19:04 -0500, Spehro Pefhany
speffSNIP@interlogDOTyou.knowwhat> wrote:



On Tue, 23 Nov 2004 21:28:09 GMT, the renowned Rich Grise
rich@example.net> wrote:



On Tue, 23 Nov 2004 13:45:14 -0700, Jim Thompson wrote:



Recommendations for Best Book on PID ??

Thanks!


I hope I'm not em-bare-ass-ing myself here, but what exactly is "PID" the
acronym for? Somehow or another, I seem to have missed that one. ?:-/

Thanks,
Rich

Proportional-Integral-Derivative. It was invented more than 75 years
ago. It refers to feedback control with terms proportional to the
error, the integrated error and the derivative of the error wrt time.
(error being Process Variable (PV) - Setpoint (SP)).

Determining the three proportional terms is "tuning" the controller.
Over 90% of process control loops are PI or PID.


There are two aspects of this: the most obvious is the linear loop
dynamics, the classic Laplace-transform closed-loop response. Then
there's the far trickier nonlinear stuff: auto/manual control,
bumpless transfer, overshoot, integrator windup, process slew limits
(just ask a boiler to go from 0 to 100% steam flow in 30 seconds! Or
100 to zero, even worse!), autotuning, noise, feedforward, and
protection from runaway under various conditions. It's the latter
messy stuff that most of the textbooks tend to ignore.

John


Oh yes. One of the best papers I have read lately is:
"An Electronic Throttle Control Strategy Including Compensation of
Friction and Limp-Home Effects" Deur, Pavkovic et al,
IEEE industry apps may/june 2004 vol 40 no.3 pp821-834

These guys take the whole shebang into account. Interestingly enough
they optimise the large-signal step response by omitting the setpoint
from the P & D terms (something Astrom et al talk about).

I am frustrated with industrial PID controllers that force me to
choose between having the P & D terms based entirely on error or
entirely on the process measurement only. What I often need is a
separate gain and derivative term for the process measurement and
setpoint inputs to the controller. This is almost always superior the
gain and/or derivative based entirely on error (setpoint - process
measurement) or base entirely just on the process measurement and lets
me optimize (after I define that word for the particular loop) the
process disturbance response and setpoint change response,
individually. For critical tuning, I have to use the feed forward
connection and external math to to get all the factors I need. Why
must I choose chocolate or vanilla when I really want a swirl.



Hmmm, guys, very interesting point. In most of the loops I've done,
the setpoint change just shoots through the error amp and the pid
stuff and sort of comes out OK, but I can see how that ought to be
optimizable.

John

And of course in our smps error-amps the setpoint connection is
hard-wired, and causes the overshoot that makes us use soft-start
circuitry

Cheers
Terry

 

[John Larkin]

On Wed, 24 Nov 2004 18:50:08 +1300, Terry Given <my_name@ieee.org>
wrote:

Hmmm, guys, very interesting point. In most of the loops I've done,
the setpoint change just shoots through the error amp and the pid
stuff and sort of comes out OK, but I can see how that ought to be
optimizable.

John

And of course in our smps error-amps the setpoint connection is
hard-wired, and causes the overshoot that makes us use soft-start
circuitry

Cheers
Terry

Are you saying that the people who design switcher chips don't know
much about control strategies? Shocking, Shocking!

John

 

[Phil Hobbs]

John Popelish wrote:

Jim Thompson wrote:

Recommendations for Best Book on PID ??

Thanks!


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.

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

 

[John Nagle]

Control System Design Guide.

The first edition is better than the second one.
The book became a bit bloated in revision.

John Nagle

 

[Doug Schultz]

"Rich Grise" <rich@example.net> wrote in message
newsan.2004.11.23.20.38.10.28968@example.net...

On Tue, 23 Nov 2004 13:45:14 -0700, Jim Thompson wrote:

Recommendations for Best Book on PID ??

Thanks!


I hope I'm not em-bare-ass-ing myself here, but what exactly is "PID" the
acronym for? Somehow or another, I seem to have missed that one. ?:-/

Thanks,
Rich

Pelvic Inflammatory Disease.

what did you think?

Doug

 

[Martin Riddle]

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.

http://www.amazon.com/exec/obidos/tg/detail/-/1556175167/qid=1101251719/sr=8-9/ref=sr_8_xs_ap_i9_xgl14/103-3303697-6278259?v=glance&
s=books&n=507846


Cheers

"Jim Thompson" <thegreatone@example.com> wrote in message news:b987q0tsvp79qoh72r69i4rmuooch57ad5@4ax.com...

Recommendations for Best Book on PID ??

Thanks!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Pig Bladder]

On Thu, 25 Nov 2004 11:40:15 +0000, Doug Schultz wrote:

"Rich Grise" <rich@example.net> wrote in message
newsan.2004.11.23.20.38.10.28968@example.net...
On Tue, 23 Nov 2004 13:45:14 -0700, Jim Thompson wrote:

Recommendations for Best Book on PID ??

Thanks!


I hope I'm not em-bare-ass-ing myself here, but what exactly is "PID" the
acronym for? Somehow or another, I seem to have missed that one. ?:-/

Thanks,
Rich




Pelvic Inflammatory Disease.

what did you think?

I think you need to quit having sex with people who have open running
sores.
--
The Pig Bladder From Uranus, still waiting for
some hot babe to ask what my favorite planet is.

 

[Rhett Oracle]

On Thu, 25 Nov 2004 21:57:22 +0000, Doug Schultz wrote:

"Pig Bladder" <pig_bladder@anyspammer.org> wrote in message
newsan.2004.11.25.19.50.45.487221@anyspammer.org...
On Thu, 25 Nov 2004 11:40:15 +0000, Doug Schultz wrote:


"Rich Grise" <rich@example.net> wrote in message
newsan.2004.11.23.20.38.10.28968@example.net...
On Tue, 23 Nov 2004 13:45:14 -0700, Jim Thompson wrote:

Recommendations for Best Book on PID ??

Thanks!


I hope I'm not em-bare-ass-ing myself here, but what exactly is "PID"
the
acronym for? Somehow or another, I seem to have missed that one. ?:-/

Thanks,
Rich




Pelvic Inflammatory Disease.

what did you think?


I think you need to quit having sex with people who have open running
sores.
--
The Pig Bladder From Uranus, still waiting for
some hot babe to ask what my favorite planet is.


Too much.
Its a good thing I read this group for the entertainment more than the
technical.

So, did you laugh?

;^j
R.

 

[Tim Wescott]

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

 

[Doug Schultz]

"Pig Bladder" <pig_bladder@anyspammer.org> wrote in message
newsan.2004.11.25.19.50.45.487221@anyspammer.org...

On Thu, 25 Nov 2004 11:40:15 +0000, Doug Schultz wrote:


"Rich Grise" <rich@example.net> wrote in message
newsan.2004.11.23.20.38.10.28968@example.net...
On Tue, 23 Nov 2004 13:45:14 -0700, Jim Thompson wrote:

Recommendations for Best Book on PID ??

Thanks!


I hope I'm not em-bare-ass-ing myself here, but what exactly is "PID"
the
acronym for? Somehow or another, I seem to have missed that one. ?:-/

Thanks,
Rich




Pelvic Inflammatory Disease.

what did you think?


I think you need to quit having sex with people who have open running
sores.
--
The Pig Bladder From Uranus, still waiting for
some hot babe to ask what my favorite planet is.

Too much.
Its a good thing I read this group for the entertainment more than the
technical.

Doug

 

[Nicholas O. Lindan]

It has been writ:

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.

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 ...

You could probably write a good one.

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

 

[John Popelish]

"Nicholas O. Lindan" wrote:

It has been writ:

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.

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 ...

You could probably write a good one.

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.

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

--
John Popelish

 

[John Popelish]

Phil Hobbs wrote:

John Popelish wrote:

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.


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.

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.

--
John Popelish

 

[Rhett Oracle]

On Wed, 24 Nov 2004 22:25:41 -0500, John Popelish wrote:

Phil Hobbs wrote:

John Popelish wrote:

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.


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.

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.

By Golly, I think he's got it! That's why we can't see the Faeries! ;-)

Cheers!
R.

 

[Phil Hobbs]

John Popelish wrote:

Phil Hobbs wrote:

John Popelish wrote:


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.


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.


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.

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