Abstract This paper is focused on the application of the fundamental model reduction techniques used in structural dynamics to flexible multibody systems. In particular, an effective computational approach is developed and tested in this work for adapting the conventional structural model condensation strategies to the dynamics of flexible multibody systems. Thereby, the synthesis methods considered in this work can be readily implemented in the principal computational framework used for modeling flexible multibody systems subjected to large reference displacements and small deformations, namely the Finite Element (FE) Floating Frame of Reference Formulation (FFRF). Three component mode synthesis methods are of interest for this study: the Guyan-Iron condensation method, the well-known modal truncation technique, and the Craig-Bampton synthesis approach. Employing the computational approach proposed in this paper, it is demonstrated by means of numerical experiments that the three fundamental reduction methods considered in this investigation lead to correct numerical results when used for obtaining condensed mechanical models of flexible multibody systems based on the FE-FFRF. In the case of flexible multibody systems, the computational approach developed in this paper consists of two fundamentally distinct steps. First, the reference conditions are formulated in the FE-FFRF in a way consistent with the geometric properties of the mechanical joints that connects the bodies of the flexible multibody system under consideration. This is a key step that allows the analyst to model multibody systems in complex geometric configurations. Subsequently, a reduction technique is selected and used for reducing the dimensionality of the problem at hand. It is remarked that the reference conditions assumed in the first step of the proposed computational procedure modify all the component modes resulting from the application of the reduction strategy chosen in the second step of the computational algorithm and may or may not delete some of these. In the second step of the computational approach mentioned before, the conventional model reduction techniques can be effectively used leading to consistent numerical results. In this work, three numerical examples are employed for demonstrating the effectiveness of the computational procedure developed in the paper. More importantly, considerations on the choice of either isostatic or hyperstatic reference conditions associated with a particular choice of component modes are discussed in detail throughout the manuscript. The numerical simulations demonstrate that these choices can have a significant influence also on the efficiency of the integration schemes.

中文翻译：

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使用组件模式合成方法在浮动参考公式框架内对柔性多体系统进行模型简化

摘要 本文重点介绍结构动力学中使用的基本模型简化技术在柔性多体系统中的应用。特别是，在这项工作中开发和测试了一种有效的计算方法，用于使传统的结构模型凝聚策略适应柔性多体系统的动力学。因此，这项工作中考虑的合成方法可以很容易地在用于模拟受大参考位移和小变形的柔性多体系统的主要计算框架中实现，即有限元 (FE) 浮动参考框架 (FFRF)。本研究对三种分量模式合成方法感兴趣：Guyan-Iron 凝聚法、著名的模态截断技术、和 Craig-Bampton 综合方法。采用本文提出的计算方法，通过数值实验证明，当用于获得基于 FE-FFRF 的柔性多体系统的压缩力学模型时，本研究中考虑的三种基本约简方法会导致正确的数值结果。在柔性多体系统的情况下，本文开发的计算方法由两个根本不同的步骤组成。首先，参考条件在 FE-FFRF 中以与连接所考虑的柔性多体系统主体的机械接头的几何特性一致的方式制定。这是允许分析师在复杂几何配置中对多体系统进行建模的关键步骤。随后，选择并使用一种减少技术来减少手头问题的维数。需要注意的是，在建议的计算程序的第一步中假设的参考条件修改了所有组件模式，这些组件模式是由于应用计算算法的第二步中选择的减少策略而产生的，并且可能会或可能不会删除其中一些。在前面提到的计算方法的第二步中，可以有效地使用传统的模型简化技术，从而获得一致的数值结果。在这项工作中，三个数值例子被用来证明论文中开发的计算程序的有效性。更重要的是，在整个手稿中详细讨论了与特定组件模式选择相关的等静压或超静压参考条件选择的考虑因素。数值模拟表明，这些选择也会对集成方案的效率产生重大影响。