PD(PI) Math Model (e.g.Tank Level)



You see the limits: 0.2 ... 1 (4 ... 20 mA = 0 ... 100%)
At closed and opened the valves have nasty bumps: http://home.arcor.de/janch/janch/_control/20070521-controldoc /
But here 0.5 reserve. Only 0.3 are used. Total 0.8
In reality I suggest to add 20%.
If the water tank is e.g. empty or full there is nothing to control automatically beyond these limits.

Sorry I can't see a 'real' resemblance to the tank level control. Maybe a car rocket for towards to 100% (wall) and a car rocket for backwards to 0% (hole) from the wall. You could apply a benchmark scheme, too. The acceleration v1'' should not exceed 5g. The process transfer function is mathematical similar to the tank level transfer function.
I would accept this if disturbance is not 0.1 but less than 0.05 http://home.arcor.de/janch/janch/_control/20070521-controldoc / (red points)
Exceeding limits cause trouble. That's for sure.
If you have high concentrated acid in the tank it is dangerous, too. For you if acid is spread around you or the pumps running dry. Insurance companies don't like that.
--
Regards/Gre http://home.arcor.de/janch/janch/menue.htm
Jan C. Hoffmann eMail aktuell: snipped-for-privacy@nospam.arcornews.de
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Show me your benchmark test solution. Yes, I want to see it. In a way I can compare (time domain). You 'should respond' to what I have written and show me a better solution if you can.
Notes
0.2 ... 1 = 0 ... 100% (e.g. 0.6 = 50%)
All these level controller work, too: - on/off - p - PI - PID Yes, I know. But could they control better using the defined benchmark test?
See benchmark scheme (step, target and result): http://home.arcor.de/janch/janch/_control/20070521-controldoc /
That is what I want to know. Nothing else.
Polemic is not the right answer!
--
Regards/Gre http://home.arcor.de/janch/janch/menue.htm
Jan C. Hoffmann eMail aktuell: snipped-for-privacy@nospam.arcornews.de
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Newsbeitrag

Doesn't it bother you when your results don't make sense? It isn't all math. It is mostly the reality of phsyics. Math is just a tool we use to understand physics.
I have posted links to these files before. The files were generated in response to others having the same questions. They are in my newsgroup ( NG ) directory
ftp://ftp.deltacompsys.com/public/NG/Mathcad%20-%20sigreg-PID%20.pdf
This file was generated for a plcs.net forum. The original poster provided me with real numbers for his real system. Notice that the level rises at a steady rate until it gets close to the set point. The PID cannot fill the tank generating a negative control signal as in your example. This is basic. Notice how all the work is displayed, even how I symbollically calculate the gains. I think that much more is learned by seeing the symbolic solution to the gains rather than just the numbers provided by Scilab or Matlab. Those of you that want to split hairs should know I change the formulas a bit when there is a dead time.
ftp://ftp.deltacompsys.com/public/NG/tanklevel.sce
I posted scilab script a month or two ago. You can use this to try different gains and flow rates ( distrubances ). If you run the script you can see how the control output saturates.
Notice that target or jerk filters and feed forwards are not required. The plant and controller are turned into a low pass filter and the response is determined by choosing a closed loop time constant tc.
Peter Nachtwey
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sorry, I never before responded to the solutions of your papers. I published a certain task and stated having found a good solution for that. That's all.
Cited:

See benchmark scheme (step, target and result): http://home.arcor.de/janch/janch/_control/20070521-controldoc /
Note: Tanks have e.g. water inlet and water outlet. I know that. My benchmark test shows that.
--
Regards/Gre http://home.arcor.de/janch/janch/menue.htm
Jan C. Hoffmann eMail aktuell: snipped-for-privacy@nospam.arcornews.de
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Newsbeitrag

Doesn't it bother you when your results don't make sense? It isn't all math. It is mostly the reality of phsyics. Math is just a tool we use to understand physics.
I have posted links to these files before. The files were generated in response to others having the same questions. They are in my newsgroup ( NG ) directory
ftp://ftp.deltacompsys.com/public/NG/Mathcad%20-%20sigreg-PID%20.pdf
This file was generated for a plcs.net forum. The original poster provided me with real numbers for his real system. Notice that the level rises at a steady rate until it gets close to the set point. The PID cannot fill the tank generating a negative control signal as in your example. This is basic. Notice how all the work is displayed, even how I symbollically calculate the gains. I think that much more is learned by seeing the symbolic solution to the gains rather than just the numbers provided by Scilab or Matlab. Those of you that want to split hairs should know I change the formulas a bit when there is a dead time.
ftp://ftp.deltacompsys.com/public/NG/tanklevel.sce
I posted scilab script a month or two ago. You can use this to try different gains and flow rates ( distrubances ). If you run the script you can see how the control output saturates.
Notice that target or jerk filters and feed forwards are not required. The plant and controller are turned into a low pass filter and the response is determined by choosing a closed loop time constant tc.
Peter Nachtwey
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I guess you posted this accidently twice. I anwsered it already. Or didn't you receive my answer (22. May 2007 17:40).
--
Regards/Gre http://home.arcor.de/janch/janch/menue.htm
Jan C. Hoffmann eMail aktuell: snipped-for-privacy@nospam.arcornews.de
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.