運用二階最佳化方法設計引擎懸置系統

Abstract

本文研究為建立一個二階最佳化方法，使引擎裝置於車架上時， 懸置擺設位置與剛度選用能有明確之參考依據。本研究先使用振動學 理論推導出合理的引擎振動模型以研究引擎系統振動之行為，並計算 出各模態六個自由度的能量分布因子。經由二階最佳化方法建立兩種 類型之最佳化設計解決引擎懸置位置與剛度的問題。文獻提及扭矩軸 與彈性軸重合對力傳遞率減少及系統解耦皆有改善，故第一型最佳化 設計目的是透過改變懸置系統的位置與剛度達到扭矩軸和彈性軸重 合。由於後懸置位置最靠近方向盤，第二型最佳化設計則是透過改變 懸置系統的位置與剛度使得後懸置反力最小化，此方法可有效降低引 擎傳至車體及方向盤的振動。

The purpose of this thesis is to establish a two-level optimization method that can be used for the design of an engine mounting system. In the proposed method, we build a vibration model of the engine mounting system using the basic vibration principles to study the vibration behavior of the system. The modal energies together with the coupling coefficients of the six degrees of freedom of the system are identified. A two-level optimization technique is then established to solve two types of optimal design problems for the engine mount system. The first type is about the design of the locations and spring constants of the mounts to make the TRA (torque roll axis) and EA (elastic axis) of the engine mounting system coincide. The effects of the coincidence of the TRA and EA on the force transmissibility and decoupling of the modal energies of the optimally designed system are studied. The other type is about the design of the locations and spring constants of the mounts to minimize the reaction force at the rear mount which is closer to the steering wheel. It has been shown that the second type of optimization problem can produce more useful results for reducing the transmissibility of vibration from engine to steering wheel.