Tigran,

You must be using the Multibody elements -- you did not mention that. You must filter out the unnecessary equations. See this post by @Malte Lenz

Interpret results of Extracting System Equations in SystemModeler?

You should be able to remove all the equations that do not involve your dynamics.

Regards

Tigran,

While the oscillator mass is 1 and the damping is 10, etc. The equations derived this way do not have the values in them. The only numbers are from pi, and some factors of 2 that are part of the geometry of the model. The parameter values are kept separately as you can see below:

I am posting an image because the Mathematica form is not clear because of the DotName[] constructs.

You can use these equations in any mathematica expressions. Alternatively, You can replace the DotName[] variables in Mathematica with more "normal", non WSM variables -- I used a [UpPointer] character but you can use any valid character or nothing.

This results in normal equations with no values substituted:

If you want to see how I did the replacement, I can post the code but you can do it manually or I wrote a function to do it automatically. Note there are no values in these equations.

Regards

Neil

Tigran,

You can definitely do what you want. For example, To get the equations of the Oscillator example in WSM, do the following in Mathematica:

Needs["WSMLink`"]
eqns = WSMModelData["Oscillator", "SystemEquations", t];

The equations (25 of them) have many algebraic equations related to the connectivity of the elements (masses, springs,etc.). To get rid of these equations we can get the algebraic variables and eliminate them to simplify the equations:

alg = WSMModelData["Oscillator", "AlgebraicVariables"]

The algebraic variables appear as functions of time in the equations so lets eliminate them by first making a list.

final = Eliminate[eqns, Map[#[t] &, alg]]

final now holds the 4 remaining differential equations.

Regards,

Neil