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From: Dan on 25 Mar 2010 10:30
Hey guys,

I have used MATLAB a lot to produce car suspensions systems and image processing and the likes but a recent problem come to me is to model an air mains system and i tried using SimScape but need a bit of help.

The System is pretty straight forward a compressor that has a flow rate of 52l/s that feeds in air from the outside to a resiviour of volume X that stores the air at 105PSI a valve then reduces the pressure to 55PSI to feed air operated components over a pipe Y meters long, this system is double end fed, so there is a compressor each end of the pipe that feeds the components.

However building this is simscape seems to be impossible, getting errors like Non-linear solver... can someone help me or point me somewhere?!?! Maybe there is another tool that would be better for doing this?

Dan
From: Arnaud Miege on 21 Apr 2010 11:09
"Dan " <dannyfattyvalenchew(a)hotmail.com> wrote in message <hofs2e$adr$1(a)fred.mathworks.com>...
> Hey guys,
>
> I have used MATLAB a lot to produce car suspensions systems and image processing and the likes but a recent problem come to me is to model an air mains system and i tried using SimScape but need a bit of help.
>
> The System is pretty straight forward a compressor that has a flow rate of 52l/s that feeds in air from the outside to a resiviour of volume X that stores the air at 105PSI a valve then reduces the pressure to 55PSI to feed air operated components over a pipe Y meters long, this system is double end fed, so there is a compressor each end of the pipe that feeds the components.
>
> However building this is simscape seems to be impossible, getting errors like Non-linear solver... can someone help me or point me somewhere?!?! Maybe there is another tool that would be better for doing this?
>
> Dan

You might want to try contacting Technical Support, it's likely that there's a mistake in the way you have modelled your system:
http://www.mathworks.com/support/contact_us/index.html

Did you go through the documentation on modelling pneumatic systems?
http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/simscape/ug/br7vtpp.html

In particular the section called "connection constraints":
"Every node in a pneumatic network must have a defined temperature as well as pressure. This rule places some constraints on how you connect the pneumatic elements. In effect, every node should have a volume of fluid associated with it. When the ideal gas law is applied, this volume of fluid determines the relationship between temperature and pressure. Some elements already have a volume of fluid associated with them, and therefore having just one of these components connected to a node satisfies this condition. Such blocks include Constant Volume Pneumatic Chamber, Pneumatic Piston Chamber, Rotary Pneumatic Piston Chamber, and Pneumatic Atmospheric Reference.

An exception to the above rule (that every node must have a volume of fluid associated with it) occurs when two nodes are connected by a component for which the heat equation says that the temperatures are equal. In this case, just one of the nodes needs to be connected to a component with associated volume of fluid. Such components include the pressure and flow rate sources.

For models that represent an actual pneumatic network, these constraints should have no impact. For example, connecting two orifices in series makes no physical sense because the underlying assumption of the orifice equation is that gas is discharged into a volume of fluid. Therefore, modeling actual physical systems should automatically satisfy these constraints."

HTH,

Arnaud
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