傳統車輛之輪胎轉向角因受機械式轉向系統機構上的拘束,左右輪之輪胎轉向角維持一特定比例關係,由於轉向系統的設計需同時滿足車輛高、低速轉向的要求,因此傳統機械式轉向系統左右輪轉角之設定為一折衷的設計,既無法符合低速過彎時較小轉彎半徑之要求,又不能使車輛以較高速度過彎。 因此本研究考慮車輛在轉向時荷重轉移的現象,以及輪胎產生之轉彎力與荷重成正比的特性,提出一種可因荷重轉移同時修正左右側輪胎轉角的前輪轉向概念,使得車輛在低速時能依照阿克曼幾何進行轉向,而在高速轉向時輪胎又能充分產生轉彎力,不致發生輪胎打滑的現象。並以三自由度全車模型結合數學軟體Matlab/Simulink與ADAMS/Car軟體進行驗證,最後以ADAMS/Car車輛模擬軟體建立前輪獨立轉向系統,結合本研究所提出之轉向策略進行全車的運動模擬分析。
There is a fixed ratio between left and right tire steering angle because of the one degree-of-freedom (DOF) mechanism connected left and right tire. The ratio between left and right tire steering angle affects vehicle steering response. In general, the traditional design of vehicle steering system have to consider both low and high velocity cornering request at the same time, so the fixed ratio between left and right tire steering angle is a eclectic design. The result is the turning radius becoms longer at low speed and vehicle can not turn safely at higher velocity. Therefore, considering the load transfer between left and right tire when vehicle make a turn and the direct proportion between cornering force and tire load, this research brings up a new steering concept about using load transfer to modulate left and right tire steering angle to make vehicle conform to Ackermann steering geometry at low speed and to make tire provide enough cornering force at high speed. Then we use 3-DOF full car model and Matlab/Simulink software to describe vehicle dynamic and calculate how to modify left and right tire steering angle. Finally, we build an independent steering system and introduce the proposed steering concept to run full-vehicle analyses in ADAMS/Car software.