Modeling a flexible multibody system employing the floating frame of reference formulation (FFRF) requires significant computational resources when the flexible components are represented through finite elements. Reducing the complexity of the governing equations of motion through component-level reduced-order models (ROM) can be an effective strategy. Usually, the assumed field of deformation is created considering local modes, such as normal, static, or attachment modes, obtained from a single component. A different approach has been proposed in Cammarata (J. Sound Vibr. 489, 115668, 2020) for planar systems only and involves a reduction based on global flexible modes of the whole mechanism. Through the use of global modes, i.e., obtained from an eigenvalue analysis performed on the linearized dynamic system around a certain configuration, it is possible to obtain a modal basis for the flexible coordinates of the multibody system. Here, the same method is extended to spatial mechanisms to verify its applicability and reliability. It is demonstrated that global modes can be used to create ROM both at the system and component levels. Studies on the complexity of the method reveal this approach can significantly reduce the calculation times and the computational effort compared to the unreduced model. Unlike the planar case, the numerical experiments reveal that the system-level approach based on global modes can suffer from slow convergence speed and low accuracy in results.

当通过有限元表示柔性组件时，对使用参考公式的浮动框架（FFRF）的柔性多体系统进行建模需要大量的计算资源。通过组件级降阶模型（ROM）降低运动控制方程的复杂性可以是一种有效的策略。通常，假定的变形场是考虑从单个组件获得的局部模式（例如法线，静态或附着模式）创建的。Cammarata（J. Sound Vibr。489，115668，2020）仅针对平面系统提出了一种不同的方法，该方法基于整个机制的全局灵活模式进行了简化。通过使用全局模式，即从对线性动态系统围绕某个配置进行的特征值分析获得的全局模式，可以获得多体系统的柔性坐标的模态基础。在此，将相同的方法扩展到空间机制以验证其适用性和可靠性。事实证明，全局模式可用于在系统级别和组件级别创建ROM。对方法复杂性的研究表明，与未简化的模型相比，该方法可以显着减少计算时间和计算量。与平面情况不同，数值实验表明，基于全局模式的系统级方法可能会遇到收敛速度慢和结果精度低的问题。事实证明，全局模式可用于在系统级别和组件级别创建ROM。对方法复杂性的研究表明，与未简化的模型相比，该方法可以显着减少计算时间和计算量。与平面情况不同，数值实验表明，基于全局模式的系统级方法可能会遇到收敛速度慢和结果精度低的问题。事实证明，全局模式可用于在系统级别和组件级别创建ROM。对方法复杂性的研究表明，与未简化的模型相比，该方法可以显着减少计算时间和计算量。与平面情况不同，数值实验表明，基于全局模式的系统级方法可能会遇到收敛速度慢和结果精度低的问题。