Question How can I incorporate a structure model into Simulink ?
Answer The easiest way is to convert a modal model of the structure into a state-space realization that is directly supported by Simulink.
For SDT finite element models or if you have imported model matrices from another FEM code (NASTRAN, ...), the SDT supports a number of traditionnal model reduction methods (mode displacement method, mode acceleration method, Craig-Bampton reduction, ...) as well as many advanced alternatives. The function fe2ss provides one line calls for standard transformations.
If your model is large (above 100,000 DOF), you may not want to import model matrices into MATLAB (which can't handle matrices bigger than 2 GB). You can still import modeshapes and possibly static correction terms and build state-space representations of your structure using nor2ss.
Note it does not make sense to use sparse representations of large FEM models for inclusion into Simulink. FEM models are large because they need a large number of elements to describe geometrical detail. The number of active modes in a model however rarely goes above a few hundred.
Reduced FEM models (generalized modal models) can be diagonalized and thus be associated with state-space matrices that are very sparse (block diagonal). You may expect speed improvements by transforming the results of nor2ss or fe2ss to sparse format but this is not supported by all MathWorks products.
