Effect of Rear Wheel Steering on Steady Turning Behavior of Four-wheel Vehicles

　　本研究主要探討後輪轉向對於車輛穩態轉向行為的影響。首先以運動學與牛頓力學理論為基礎，建立幾何關係式和力平衡方程式，發展四輪轉向車輛模型，完整考慮四輪獨立的側滑角度、正向負載轉移，及使用接近真實輪胎性質的Magic Formula輪胎模型。由於方程式相當複雜，難以求得解析解，本研究採用數值分析方法，並配合全域搜尋求得數值解，可求得在不同轉向角及車速下，各輪的側滑角、正向力、轉向力及全車穩態之性質。利用此模型針對單後輪轉向與雙後輪同步轉向兩種模式，分析後輪轉向對於車輛穩態轉向行為的影響。最後提出操控後輪轉向以調整車輛轉向特性的方法，並以四輪的側滑現象來評估比較各種後輪操控的方式。利用本研究所發展的模型與分析方法，可以對四輪的側滑現象、正向負載轉移、轉向力分配與後輪轉向對車輛行為的影響，均可以有更完整的了解。

　　This study mainly focuses on the effect of the rear wheel steering on the steady state behavior of the vehicle. First, a four-wheel independent steering vehicle model is developed, and the motion equations based on the geometry and force equilibrium of the vehicle are derived for the steady state analysis. This model has included four independent steering angles and slip angles, load transfer, and the Magic Formula for the tire. Then, using this model, numerical analysis can be performed. The effect of the rear wheel steering in three various operating conditions are investigated. By using the mathematical model and numerical method established in this study, slip angle and cornering force of each tire, the effect of load transfer and the rear wheel steering on the behavior of the vehicle can be thoroughly realized. Finally this study proposes a method to adjust the handling characteristics by rear wheel steering.