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Presure control with proportional valve

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This sounds as though you would like to run a PID loop to control you proportional valve and maintain your pressure set-point. 


We have example programs using our PID function blocks in our examples folder, under the help tab in VisiLogic.  Also, we have a tutorial on how to use the PID function blocks in your program which can be found here.


Please let us know if this helps.

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Depending on your setup PID may be over kill depending on your needs.



I just finished a setup like this using an electronic regulator (I use PID but setup works without as well).  Here is what I did:


1) Read in from the pressure transmitter and scale the value to an integer using the linearize FB.

2) For output

    a) For non-PID

        1) Store output value into an integer

        2) Scale that value to the analog output range for the proportion valve using linearize. Compensating for the difference in reading.  I also have several rungs to nudge the output in different directions if I'm high or low.

        3) Output to the valve


    B) For PID

        1) Read the analog input and use the input as the process variable ( I linearize everything to the sensor and output ranges)

        2) Use the analog output as the control variable.



If you'd like I can send you a copy of the program I'm using on a V570, the interface won't work for you most likely, but the logic should be identical.  The only issue is a lot of my initialized variables are specific to my application.

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Thanks on yours help


I make 2 plastic moulding machines BATTENFELD but without pressure transmitter e.c. without information

for real pressure in system.

I did by PWM output and SSR as proportional valve driver at 200Hz.


Machine work well until the hydraulic fluid change temperature.

When temperature is changed then it will change and all parameters so I must put pressure transmitter.


So until now I haven't work with PID regulation



Thanks in advance

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There is absolutely nothing wrong with making calculation using only values for P and I.  In fact many processes don't particularly do well with a D value (at least ones where D is picked by humans). 


For the work we do in my company we actually never set a D value to anything and only set D when we use the autotune function to generate at least the starting point for a D value.

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Here is a sample program that has been split out of a much larger program.  In it you will find where the user can enter in PID variables and the set point along with dynamically being able to chose if the pump PID is controlled from suction or discharge pressure.  This is about the best I can do for you at this time.


Good Luck


PID example.vlp

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