Component Mode Synthesis

Component mode synthesis (CMS) is a family of procedures in which one or more parts of a finite element model are represented by a small reduced-order model (ROM). There are several possible algorithms through which such a reduction can be made. In COMSOL Multiphysics, the popular Craig-Bampton method is used for model reduction with a dual assembly technique to ensure compatibility between components.

The reduced component is sometimes called a dynamic substructure. Essentially it contains small mass, damping, and stiffness matrices, tuned so that it can represent the static stiffness, as well as a set of important eigenmodes and the inertia of the original component. An important assumption is that the reduced structure is linear.

The reduced component accounts for the constraints applied on the component. It can also contain, for example, information about loads applied to the component prior to model reduction.

Since the reduced components only have a small number of degrees of freedom (often of the order of 10-100), they are computationally more efficient when used instead of full FEM components. To create a reduced component, it is necessary to both perform an eigenfrequency analysis and to solve for a number of static load cases. These studies are, however, computed at the component level, and are thus usually computationally much cheaper compared to the full model.

For general information on reduced-order modeling and model reduction, see also

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Reduced-Order Modeling

•

Model Reduction

in the COMSOL Multiphysics Reference Manual.