Static Stiffness Calculation from Dynamic Data via Modal Decomposition
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Solution Overview
Problem
Existing methods for determining static stiffness of vehicle body structures from dynamic data, such as Inertia Relief and Static-from-Dynamic approaches, often result in inaccurate stiffness underestimations, particularly for trimmed body models, leading to longer development times and higher costs due to inability to accurately compare body-in-white and trimmed body static stiffness targets.
Innovation Solution
A method involving modal decomposition of flexible-body modes into rigid-body modes and residual terms, with decomposition factors calculated using pseudo-inverse or least squares algorithms, to isolate and remove inertial effects, enabling accurate static stiffness calculation from dynamic data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Inertia Relief or Static-from-Dynamic methods are used to calculate static stiffness from dynamic data, then the calculation can be performed without physical static testing, but the stiffness values are inaccurate with underestimations up to a factor of 6
Solution Approach 1:
The patent extracts and removes inertial effects from flexible body modes through modal decomposition. By separating the rigid body mode contributions from the flexible body modes, the method isolates the pure stiffness characteristics without contamination from inertial effects, thereby achieving accurate static stiffness values from dynamic test data
Solution Approach 2:
The patent transforms the problem by changing the parameter representation from raw flexible body modes to residual terms that are explicitly free of inertial effects. This parameter transformation through modal decomposition and residual calculation enables accurate static stiffness extraction that overcomes the limitations of traditional Inertia Relief and Static-from-Dynamic methods
2Productivity
If traditional methods are used, then development process can proceed, but target setting and tracking between body-in-white and trimmed body levels cannot be objectively compared, leading to longer development time and higher costs
Solution Approach 1:
The patent creates a universal method that works for both body-in-white and trimmed body configurations. The modal decomposition approach with residual terms provides a consistent framework that can be applied across different vehicle development stages, enabling objective comparison and tracking of static stiffness targets from early design through final vehicle assembly
Data Source
AI summary
A method and system for determining the static stiffness of a body structure from dynamic data are disclosed. The method and system include providing dynamic data and defining flexible-body modes of the dynamic data of the body structure. To overcome the limitations of conventional methods and systems, the method and system further include: performing a modal decomposition of all defined flexible-body modes into contributions of rigid-body modes and a residual term. The modal decomposition of the body structure is defined as Formula (I), wherein Rj is a residual term for the jth flexible mode, such that the residual term results as free of inertial effects. The method and system further include determining the residual term Rj from the modal decomposition and determining the static stiffness from the residual terms Rj.