Find a differential equation of 2nd order.

[claudiodeviaje]

Hi, its me again, still trying to build my hydraulic model.

Now 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...
Flow: 0 0 0 0 0...
Current: 0 0 1 1 1...
Displace: 45,5 45,5 45,35 45,35 45,35...

The Pressure has a PT2 behaviour, which means it can be describes 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

 

[claudiodeviaje]

Me again..
I know I could use a LOOK-UP Table, but that won't solve the problem, since my initial pressure is not going to remain constant. For this reason I need to find the equation..

Once again, thanks for your help

Claudio