Modal Analysis Approach for Analysis and Design of Vehicle Transient Behavior

2025-01-8794

04/01/2025

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WCX SAE World Congress Experience
Authors Abstract
Content
In order to manage the serious global environmental problems, the automobile industry is rapidly shifting to electric vehicles (EVs) which have a heavier weight and a more rearward weight distribution. To secure the handling and stability of such vehicles, understanding of the fundamental principles of vehicle dynamics is inevitable for designing their performance.
Although vehicle dynamics primarily concerns planar motion, the accompanying roll motion also influences this planar motion as well as the driver's subjective evaluation.
This roll motion has long been discussed through various parameter studies, and so on. However, there is very few research that treats vehicle sprung mass behavior as “vibration modes”, and this perspective has long been an unexplored area of vehicle dynamics.
In this report, we propose a method to analytically extract the vibration modes of the sprung mass by applying modal analysis techniques to the governing equations of vehicle handling and stability. Specifically, we solve the general eigenvalue problem of the system to obtain complex eigenvalues and complex eigenvectors, use these to decouple the original equations of motion, and reconstruct the original vehicle behavior by superimposing each analytically solved vibration mode.
As a result, it was revealed that the sprung mass behavior of the vehicle consists of two fundamental modes: “Mode 1,2,” which are primarily roll motions excited by front lateral forces, and “Mode 3,4,” which are planar motions excited by rear lateral forces coupled with roll. Furthermore, an analysis of the causal relationship between design variables and vibration modes reveals that during the initial roll response at turn-in, Mode 1,2 promote roll, whereas Mode 3,4 suppress it, making the rise gradual, or that design modification that delays planar motion associated with Mode 3,4 results in a two-stage increase in roll response, elucidating mechanisms of phenomena that could previously be understood only through parameter studies.
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DOI
https://doi.org/10.4271/2025-01-8794
Pages
11
Citation
Kusaka, K., and Yuhara, T., "Modal Analysis Approach for Analysis and Design of Vehicle Transient Behavior," SAE Technical Paper 2025-01-8794, 2025, https://doi.org/10.4271/2025-01-8794.
Additional Details
Publisher
Published
Apr 01
Product Code
2025-01-8794
Content Type
Technical Paper
Language
English