Re: PD(PI) Math Model (e.g.Tank Level) Not only wrong but let me count the ways.

JCH wrote:
"Peter Nachtwey" <pnachtwey@xxxxxxxxxxx> schrieb im Newsbeitrag news:J-KdncRhw6xilcfbnZ2dnUVZ_jKdnZ2d@xxxxxxxxxxxxxx
JCH wrote:
Is that real?

Obviously there are systems like that. However, you have redefined your valves once again so that reality matches the math. You have also added another output to the controller so your math matches reality. None of this was in your original post. If you would have mentioned all of this up front I would have thought it was OK.


I published my actual solution on May/21 2007 (today: May/28 2007)


I still wouldn't let you off the hook though. I would still point out the high or infinite gain controller will not work.


Read carefully first and last sentence:

<exact citation from May/25. 2007>
k->infinity applies to feedback control.
Examples:
k=infinity
x = u/(1+1/infinity) = u
Steady state error 0%
k = 100
x = u/(1+1/100)=u/1.01=0.99*u
Steady state error of 1%
k = 1000 ...
I guess that 95% P-controller are used in level control. One does not care
about error.
I wouldn't say that. A simple proportional band controller will do the trick as long as the proportional band doesn't let the tank over flow. This way the gains can be very low and the ripple in the tank and quantizing of the feedback will not be noticeable.

If you care then PI-controller and PID-controller are used.

In reality I wouldn't spend the time on it. The only reason why I am bothering with this lost cause is that you will corrupt other rookies that are just lurking and trying to learn.

You shouldn't be teaching anybody and you refuse to learn. Why do you bother? You seem think you know it all already so why bother with us?

Amplifiers and transmitters (e.g. temperature, 4...20mA output) are pure
P-controllers with internally high gain k.
k=10V/1µV=10^6, error=0.00001=0.001%
I don't understand why you are so stubborn about this. Can't you see that just a little noise or quantizing greatly affects my controller and my open loop gains are much lower than your gains. If have said this so many times and then you claim I am just saying that you are wrong without reason.

I don't see why you refuse to show your calculations like I have shown mine.

You refused to answer many of my questions.

Believe me, your precious calculations are not a top secret if if they were right.

I don't see why you refuse to answer my questions or look at my Tanklevel.sce and ask why I did things the way I did.

YOU WILL ALWAYS BE WRONG AS LONG AS YOU INSIST THE OPEN LOOP GAIN IS K BECAUSE NOTHING HAS AN INFINITE BANDWIDTH. DON'T FEEL HURT AND CLAIM I AM ACTING LIKE THE POPE. I AM JUST TELLING IT LIKE IT IS.

It is time for a new horse. It wouldn't drink. I tried shoving it into the water but it wouldn't budge. This horse is ready for the glue factory.

Peter Nachtwey





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