四軸車輛轉向幾何與轉向機構之設計與分析

Abstract

本研究旨在探討理想之轉向幾何於四軸車輛上如何以連桿機構實現或貼近，以及實際應用後之轉向行為影響。首先以運動學及牛頓力學建立四軸車輛的穩態轉向模型，包含幾何關係以及力學平衡方程式，代入Magic Formula 的輪胎模型，導出三自由度的簡化懸吊模型，以Newton-Raphson 數值分析方法求得穩態力平衡方程式之數值解。利用此模型討論理想上四軸車輛的轉向幾何之瞬心位置、側滑角，在真實四軸車輛參數之下呈現的特性，然後分析現行四軸車輛使用之轉向連桿，得出連桿呈現之轉向幾何，討論此轉向幾何對於車輛表現之效益， 並將其與前述理想幾何做比較。最後以現行四軸車之運作模式、空間限制為基礎，利用最佳化設計中的全域搜索方法，給出新的轉向連桿機構，使其轉向幾何貼近理想，並分析以機構得到之轉向幾何在穩態轉向下的特性，討論其加上第四軸輔助轉向的效果。利用本研究提出之機構分析結果與最佳化方法，可在改良與設計四軸車輛轉向連桿時有參考的基準。

The purpose of this work is to study the method to achieve or approximate theoretically correct steering geometry on four-axle vehicle, and the cornering behaviors after applying. First, based on kinematics and Newtonian mechanics, 3-DOF simplified suspension models, and Magic Formula tire model, a 3-DOF steady-state cornering vehicle model is build. Then, Newton-Raphson Method, a numerical method, is applied to find the numerical solutions of the simultaneous equations of motion. Discuss the characteristics of instantaneous centers and slip angles of ideal steering geometry of four-axle vehicle in real parameter by the models, and then discuss the performance of the steering geometry of the real four-axle vehicle by analyzing the steering linkage, compare with ideal steering geometry. Finally, a new steering linkage is presented to match ideal steering geometry by the global search method of optimization design, and then analyze the cornering behaviors to evaluate the steering linkage, discuss the effect after applying fourth-axle steering. Based on the result and the optimization method of this work, the steering linkage of four-axle vehicle can be further developed.