I have to construct a PID water level control. now i am trying to get data from the net about the PID water level control but i really cannot find any. So if you please, tell me the steps, and the equations, and how to deal, and also links if that might help if you have any.

If you have any information please contact me on my email
[email protected] I need it urgently please...

Thanks in advance,
Ahmed

 

Dear Ahmed,

Designing a PID control is quite straight forward. If you define what actally your are controlling will clear the algorithm. For sure you want to have a water level control, but without the system layout and control design, <thorn> it is quite blank to make any comment. Will you have a control valve, even a POV or a pump, and where they are located before the tank level you control or after the system. Please make clear your system, then the control will follow easily.

rgd

 

How are you controlling the water level? We have a simulated water level PID controller that you can download from our website. It modulates the infeed valve to keep a constant tank level as the discharge flow rate changes. It might be of help to you.

Warren
http://www.pc-pid.com

 

the following source may help u. and if u need any further help on this then u can contact me personally...

http://www.mathworks.com/access/helpdesk/help/toolbox/fuzzy/fp505.html

http://www.s3.kth.se/~kallej/papers/quadtank_ieeecst00.pdf

the 2nd source will give u best understanding of level control in tank(s).

gud luck

 

Most water level controls are done with a Bang Bang servo (water too low-add water, water too high-stop adding water). It is uncommon to use a proportioning servo valve because of expense but it certainly can be done if that kind of level control accuracy is needed. An on-off valve can also be used in a slow PWM mode to get an average flow. If a PID controller is used the level sensor nees to output a signal proportional to the water level height. A controller set to proportional control only is likely to control the the water level to the accuracy required.

 

The most important question to ask before implementing level control is "what is the purpose of the control". Do you want the level to swing up and down as the flow changes, absorbing flucuations in flow? Or do you want to hold the level at a constant value.

Very often the water level in a tank should be able to deviate far from the setpoint, as long as the tank neither runs out of water or overflows. For example, if you have a plant that produces waste water at changing rates, but a water treatment plant that works best with a constant flow, you would want to use proportional only control with a low gain. The gain would be set to open the discharge valve fully before the tank was full, and close it before the tank was empty. If there is a sudden increase in flow from the plant, the level would increase and the flow from the tank to the treatment plant would increase more gradually.

John Shaw
Process Control Solutions
http://www.jashaw.com/pid

 

Whilst the convention in the water industry is to use on-off controllers, we have just recently undertaken a simulation exercise looking at the potential energy saving benefits that moving away from this sort of strategy for a large water pumping station. Energy usage were reduced by around 60%, and this figure was also reported when the
control system was implemented on the plant. Clearly the pumping station has to be refitted with VSDs (variable speed drives) to cope with the proportional (rather than on-off) control, but even when these costs were taken into account the ROI was very good. In fact our client was more excited about the potential savings in maintenance from running the pumps more smoothly, rather than having then stop-starting.

I hope this is useful,

Andy Clegg_______________________________________ [email protected] __

Applied Control Technology Technology Consortium
50 George Street, Glasgow, G1 1QE Tel: (+44) 0141 553 1111
http://www.isc-ltd.com/actclub Fax: (+44) 0141 553 1232
______________________________________________________________________

 

How are you controlling the water level? We have a simulated water level PID controller that you can download from our website. It modulates the infeed valve to keep a constant tank level as the discharge flow rate changes. It might be of help to you.

Warren
http://www.pc-pid.com