双转向系统车辆的悬架和转向系统耦合机理/设计

The vehicles with the dual steering systems, i.e., mechanical-hydraulic power steering and electrical-hydraulic active steering, are becoming the development trend of multi-axle steering vehicles. However, on account of the deficiency in the study of the basic theory about the vehicles, there is no support of the key technology for its chassis in the basic theory.This project will combine the theory and experiment method systematically and deeply to study the following topic: the optimization theory of multi-axle steering linkage based on kinetics and mechanical coupling characteristics and the theory of the robust design of multi-axle steering linkage with the joint clearance considered; the matching theory about mechanical-hydraulic coupling of multi-axle steering systems based on the study of the initial characteristics of pivot steering resistance torque of tires; the coupling steering characteristics of multi-axle vehicles with dual steering systems based on bi-limit objective optimization method; tire cornering deformation coordination models based on the principle of minimum energy and the stability margin model of tires base on the motion state of a whole vehicle; the optimization theory about the driving pattern of multi-axle vehicles based on the three-degree-of-freedom model of multi-axle vehicles; the coordination optimization theory of the parameters and linking patterns of a hydraulic-pneumatic suspension system and the bench design and overall performance test of based on the steering behavior and ride performance of multi-axle vehicles, etc.. The theories and methods resulting from the above studies would provide an effective practical theoretical basis for the chassis design of multi-axle steering vehicles and improve the dynamics theory of multi-axle steering vehicles.

基于机械-液压助力转向和电控-液压主动转向的双转向系统车辆正成为多轴车辆的发展趋势。但是，由于双转向系统的多轴车辆基础理论研究不足，从而导致其底盘关键技术缺乏基础理论支撑。课题采用理论和实验相结合的方法，计划从基于运动学和力学耦合特性的多轴转向杆系优化理论和考虑运动副间隙的转向杆系稳健设计理论；基于车轮原地转向阻力矩初始特性研究的多轴转向系统机-液耦合匹配理论；基于双极限目标优化法的双转向系统的多轴车辆耦合转向特性；基于最小能量原理的轮胎侧偏变形协调模型和基于整车运动状态的轮胎稳定裕度模型；基于3-DOF多轴车辆模型的多轴驱动模式优化理论；基于转向性能和平顺性的油气悬架系统参数及连通方式的协同优化理论及其综合性能实验台设计和性能测试等方面开展系统深入研究。以期上述研究获得的理论和方法为多轴转向车辆的底盘设计提供有效的实用理论依据，为多轴转向车辆动力学理论的完善提供有益补充。

课题组针对双转向系统车辆的悬架和转向系统耦合机理/设计开展了以下工作：基于两孔型模型，利用螺旋理论和力学平衡原理建立了四杆机构的全运动副间隙模型，分析了四杆机构同和异侧组合布置的间隙传递规律以及各种转向杆系中球铰和移动副间隙对转向性能的影响以及优化；通过实验和理论相结合的方法，分析轮胎原地转向阻力矩的初始特性的形成机理，使轮胎转向阻力矩的模型精度达到90.7%；提出了一种简单的机—液耦合的建模方法，采用模块化思想，建立了基于轮胎模型的转向杆系运动学—力学—液压的系统耦合/匹配模型。优化发现：转向油缸的缸径和安装位置是影响转向系统匹配性的关键因素，优化后转向杆系的受力降低了20%以上；对于相同控制策略，多轴主动转动转向车辆和双转向系统多轴车辆的对比分析发现：双转向系统车辆具有低速灵活性不变和高速的更高稳定性；基于最小能量原理和牛顿第二定律，利用拉格朗日乘子法，推导了多轴转向车辆各轴轮胎侧偏角的表达式；基于轮胎侧偏角和Dugoff轮胎模型，利用牛顿第二定律建立了以质心侧偏角、转弯半径和轮胎滑移率为变量的双向系统多轴转向车辆3DOF模型，并提出了一种基于整车轮胎侧偏角分布散度的极限稳定裕度评价方法。仿真研究发现：全轮驱动模式可明显减低双转向系统多轴车辆轮胎侧偏角和整车轮胎侧偏角的分布散度；后轴主动转向控制策略对主动转向轮胎侧偏角大小和分布影响非常明显；完成世界第一台整车油气悬挂系统综合测试平台设计开发；整车油气悬挂系统连通方式的对比分析发现：“X”连通方式同时提高车辆侧倾、俯仰刚度的同时不影响垂直刚度。讨论了油气悬挂缸倾斜安装对其特性的影响。通过该项目的支持系统的形成了双转向系统车辆底盘关键技术的基础理论，为实现系统、完整、有效的多轴转向车辆底盘设计理论提供有益补充。