finding a 2nd order diferential equation

[claudiodeviaje]

I'm trying to model the electrohydraulic black/white valve. The problem ist that the only data that I have, is the pressure and flow behaviour when I open and close it but JUST for one initial presure.
Written as matrix, this data looks like this:

Time: 0,4925 0,495 0,4975 0,5 0,5025...
pressure: 48,25 48,25 48,25 48,25 48,25...
current: 0 0 1 1 1....

The Pressure has a PT2 behaviour, which means it can be described with a diferential eq, of 2nd Order.

Is there a block in Simulink or a funktion in Matlab that finds the diferential equation of 2nd order if I give the results?

Thank you very much for your help!

Claudio

PS: Ive posted this also in the Simulink group, in case some one is intrested in this question, you can check there if someone replied.

 

[claudiodeviaje]

just one thing....
I know I could use a LOOK-UP Table, but this is not enough since the Initial pressure is not going to remain constant. Thats why I need to find the equation.

cheers!

claudio