PID Control Design -For Flow control Valve

[Dskp]

Dear All,

My application measure and acquire data from pressure sensors using cRIO-9073.

After the acquisition is over,We need to bleed the pressure , say 120psi/min or 50 psi/min or at any rate.

i am planning to have PID controller which is in Labview.

need some suggestion on how to decide or some control logic for the voltages which makes the valve to open such that i achieve my setpoint(10psi/min..50psi/min).

Please provide your suggestion on this.

What shall make my application to do this in better way.

[Hooovahh]

Well the PID and fuzzy logic toolkit, now comes with LabVIEW 2014 Full or Professional.  This toolkit has things for performing a PID, as well as setting up the range, and optionally a rate limiter that I usually end up finding my self using when ever I do a PID.  It ships with several examples in the example finder.

[Dskp]

Hi I am using 2013 version only...could see pid vi's under control and simulation plate..I am trying using pid vi,but it has pid gains inputs, how to determine for my applications and send the required voltage to bleed at particular voltage. .as read I pid and fuzzy controller tool kit document, could find pid tuning methods to determine those gains..do I really needs to worry on that...

Please suggests some requirements for implementing this

[GerdW]

Hi selvan,

Wikipedia has good descriptions on how to determine PID parameters.

Look for "Ziegler-Nichols"…

Hey, in the latest newsletter NI also advertized for this webcast on PID controls…

[Dskp]

Hi Gerd,

Thanks for that..will look into it

[nathand]

What sort of valve are you using to bleed pressure? Some kind of proportional control valve?

There are two ways you could set up the PID: the setpoint could be an absolute pressure target, or the setpoint could be the desired bleed rate. In the first case you will need to add some code to ramp down the setpoint at the correct rate; in the second case you will need to add some code to determine the current rate (and you may need to do some filtering if the signal is noisy). Either way can work, you'll need to determine - possibly through experiments - which works better in your system.

[Dskp]

Hi nathand..
I think its proportional contrpl valve, but Not sure on this..so attached is the valve doc for reference....

Also thanks for your suggestions ..will do the program and let u know for any queries. .

Also,I want to do some simulation of the control which I am going to implement, before field test. .how is that possible and feasible in labview

[johnsold]

The valve document did not get attached.

Lynn

[Dskp]

Attached the valve doc

[Dskp]

Hi All,

Just started the development for automatic gas bleed using flow control valve.

Below are the points I have planned to implement

In FPGA :

-> PID control loop will run and its set point, process variable pid gains and other inputs if any will be given through RT via fpga ref.
-> control loop wil run with 1 ms loop rate

In RT:

-> a loop will be running which calculate absolute pressure (set point) value to bleed [will measure the voltage and will do calibration to get equivalent pressure ] (eg ...if bleed rate 120psi/min then 1 set point 1000 , 2 set point 999.8 since bleed loop run in 1 ms the set point for next value will be incoming pres - .002)

-> And continous for different bn leed rate and til pressure or voltage =0.

In Windows:

-> just control the on and off of gas bleed


Please provide your suggestion on the above method.
It is possible to work as expected without that flow control valve work around (hardware will be delayed to receive)

Also help me out in below queries

1.What would my process variable in my first loop iteration and after that ..something the difference of prevoius and new pressure

2.Determine the pid gains for different rate ( since for all rate its too difficult to tune and also hardware availability is not feasible)

Pls do suggest for mt best output

THANKS IN ADVANCE