【作者】 周松盛；

【导师】 何天明；

【作者基本信息】 武汉理工大学 ， 车辆工程， 2009， 硕士

【摘要】 多轴转向汽车在社会中所发挥的作用日趋显著,其市场需求不断增加,但是相关的研究较少,不够深入和完善。在此背景下,本课题对双前桥转向车辆的转向系统进行了较为全面的研究.本文研究覆盖了双前桥转向的转向理论、转向系统结构模型及优化、转向系统的动力学分析、双前桥转向汽车的线性二自由度汽车模型以及其稳态响应.本文首先阐述多桥转向理论国内外的研究现状,总结了前人的主要研究工作和成果;同时指出了多桥转向中尚未解决、依然面临的难点和问题。其次介绍了双前桥转向车辆的转向机构和转向理论;重点阐明双前桥汽车在转向过程中的理想运动学特征,推导了转向轮转角之间的相互关系。随后建立了双前桥转向系统的整体数学模型及其优化模型。为便于分析与建模将转向系分成转向梯形、垂臂-节臂-直拉杆、双摆杆机构三部分,由局部到整体建立完整数学模型:深入地剖析了双前桥转向汽车的转向过程,分析了双前桥转向汽车在转向过程中理想化的内、外轮转角和实际操作过程中的差异,提出了以‘错位距离’最小为优化目标,瞬时转向中心线为约束条件的一个崭新的优化模型。并结合约束条件改进了原始优化目标函数,引申出了一种简单有效的可行性方案。之后将线性二自由度汽车模型理论应用于双前桥转向汽车,对双前桥转向汽车进行运动学分析。主要以牛顿力学原理为基础,结合各参量间的几何、动力学关系,以车辆转向过程中Y轴方向受力和绕车辆坐标系Z轴的转矩平衡为切入点推导了双前桥转向汽车的运动学微分方程组;并对其适当推广得出同样适用多轴转向车辆的微分运动学方程组。本文最后基于运动学微分方程组推导了双前桥转向车辆横摆角速度的表达式,同时以横摆角增益为对象考察双前桥转向的稳态转向特性。双前桥转向汽车的横摆角增益表达式比较复杂,为了便于定性分析本文作了一些必要的简化假设,和普通单轴转向汽车的横摆角增益进行了对比。更多还原

【Abstract】 Multi-steering vehicles have been playing an increasingly significant role in society,with their ever-increasing market demand.However,relevant research about multi-steering vehicles is insufficient,facial and incomplete.In view of this, this context dedicated to a more comprehensive study of double-front-axle steering (DFAS) vehicle’s steering system.This paper covers the foundation of DFAS steering theory,steering systems structure and its optimization,dynamics analysis of steering systems,DFAS vehicle’s linear 2-DOF(two degrees of freedom) vehicle model and its steady-state response.This article first stated the current research of multi-axle steering both at home and abroad,and summed up the previous research work and achievements; also pointed out the underlying difficulties and problems.The author explained the DFAS vehicle steering mechanism and its steering theory,and focusing on the ideal kinematic characteristics of a DFAS vehicle in the course of making a turn, from which the relationship between each steering angle was deduced.Then the author established a whole mathematical model of a DFAS system and its optimization.In order to facilitate the analysis and modeling,the DFAS system was divided into three parts:steering linkage,pendant arm-knuckle arm-straight rod,double pendulum-bar.With a strategy of from partial to overall, establishment of a complete mathematical model of steering system was achieved. An in-depth analysis of the DFAS vehicle’s steering procedure was carried out. The author proposed a creative model with the object of minimum ’dislocation distance’.Combined with restraints the original objective function was further improved.And a simple but effective proposal was derived,which is more feasible during application.In the following,the theory of linear 2-DOF vehicle model was applied during the kinematic analysis of DFAS vehicle.This part was built mainly based on the principle of Newtonian mechanics,with the combination of parameters geo-metric and dynamic relationship.Two kinematic differential equations are developed with regard to forces balance along Y-axis and torque balance about z-axis.Those equations were further discussed with their application for multi-axle steering vehicles.At last,based on study of kinematic differential equations DFAS vehicle’s yaw angular velocity(YAV) was derived with an explicit expression.The vehicle’s Yaw Angular Velocity Gain(YAVG) was chosen as a main factor for the evaluation of DFAS vehicle’s Steady-state Characteristics.The expression for DFAS vehicle’s yaw angle gain is,in a way,pretty complex.For a qualitative analysis,some necessary simplification and assumptions was made,along with a comparison of YAVG between DFAS vehicle and uniaxial steering vehicle.更多还原