Component mode decomposition using three-dimensional discrete wavelet transform and its application to relevance evaluation of characteristic modes

Computer simulations using the combination of finite element method and modal analysis are now common methods for vibration prediction. However, when it comes to detailed models with large degrees-of-freedom, it is time consuming to evaluate and treat each characteristic mode one by one. Therefore, an efficient vibration analysis method is strongly desired. Macroscopically, characteristic modes of vehicle bodies, which mainly consist of frame structures and attached panels, are regarded as combinations of global and local deformations. Global deformation is attributable to frame structure which is defined as main component of the model, and local deformation is attributable to each panel component defined as sub component. As these deformations differ in priorities and countermeasures in design phase, it is essential to clarify the relation of global and local deformations, especially when they combine and compose coupled vibration. The purpose of this study is to present an analytical method to efficiently evaluate characteristic modes based on global and local deformations. In this paper, component mode decomposition is proposed to automatically decompose global and local deformation from characteristic modes of a frame-panel structure model. In this method, characteristic mode is first transformed into volume data and then three-dimensional wavelet transform is applied to separate global and local deformations. Then, from these separated deformations, component mode which consists of each single global and local deformation is derived using orthogonal transformation. By means of this orthogonal transformation, characteristic modes are effortlessly analyzed how much they contain each global and local deformation. In this paper, the proposed method is demonstrated on a simple frame-panel structure model.