SVD-based improvements for component mode synthesis in elastic multibody systems

• Linear model reduction schemes in the elastic multibody framework are explained.
• Coupling effects are considered in the model order reduction setup.
• Relations between condensation and moment matching are explained.
• A new, SVD-based model reduction scheme is derived, providing improved results.
• The presented improvements are verified for a large, industrially used FE model.

The method of elastic multibody systems (EMBS) is used for dynamic simulations, where a multitude of deformable bodies interact. An important step to achieve models yielding reasonable computational effort is the model order reduction for the elastic parts. Advanced schemes, such as Craig-Bampton, Krylov-subspace methods and SVD-based methods, do not only focus on homogeneous solutions but also take the loading situation into account. Thus, it is possible to generate models of low dimension but good approximation quality. The modular approach of EMBS causes that exact boundary conditions on the elastic parts may be unknown during the reduction step, thus making it difficult to find suitable load cases. Input–output based methods, especially balanced truncation, can fail to deliver a good approximation in this context. In this contribution, it is shown how these loading conditions can be obtained in a general manner in the EMBS-framework. Using the presented novel methodology, input–output based reduction schemes, such as frequency weighted balanced truncation, can be correctly applied and lead to a greatly improved approximation quality in frequency and time domain compared to existing methods. The benefits of the presented method are demonstrated on a large, industrially relevant model.