【作者】 查云飞；

【导师】 钟志华；

【作者基本信息】 湖南大学 ， 车辆工程， 2010， 博士

【摘要】 转向机构作为汽车的一级部件,在整车的设计中占有重要的地位。转向系统的好坏不仅影响着整车的操纵性,也会对车辆的安全性产生很大的影响。针对类菱形车的底盘布置形式而专门开发的转向机构与传统车辆的转向机构是有很大差别的。本文首先对类菱形车转向机构的结构进行了详细地介绍,并对转向拉杆机构进行了建模以及优化,得到了满足前后轮同步转向的结构参数;其次,对类菱形车的转向性能进行了分析,并分析了构件的柔性变形对转向机构以及整车响应的影响;然后,对类菱形车进行了非线性三自由度侧向动力学分析,以及考虑了驾驶员模型和道路模型的人—车—路闭环系统分析;最后,通过类菱形车操纵稳定性试验,验证了类菱形车在所设计的转向机构作用下具有操纵灵活、响应灵敏、安全、可靠的操纵性和稳定性。基于此思路,本论文开展和完成了如下研究工作:1.类菱形车的底盘结构与传统车的差异,导致类菱形车的转向操纵机构、转向器和转向传动机构的具体形式又与传统车不一样,最明显的区别在于传统车一般是通过前轮转向,而类菱形车是通过前后轮同步转向。本文从转向操纵机构、转向器和转向传动机构三大部分分析了适用于类菱形车底盘结构的转筒式转向机构,并通过对四连杆机构的建模以及优化,使得转向轮向左转和向右转的角度差降到最低,并尽可能减小车轮跳动时产生的被动转向角。2.类菱形车的一大优点是操纵灵活,通过对类菱形车最小转弯半径和传动比特性的分析很好地验证了类菱形车操纵灵活的特点。类菱形车转向轮的结构导致其转向轮定位参数无法实现回正,本文通过附加的转向回正机构很好地解决了这种问题。建立了类菱形车的线性二自由度模型,考虑了整车质心的变化对轮胎的侧偏刚度的影响。并对类菱形车的线性二自由度模型进行了稳态响应和瞬态响应分析,分析结果表明,类菱形车不仅转向灵活,在操纵稳定性响应时间指标上,也具有较好的响应性能。3.类菱形车的转向机构是前后轮联动转向,纵穿了整车的前后,导致了转向机构中的拉杆较长。本文利用ADAMS软件建立了类菱形车转向机构的动力学模型和前轮悬架转向模型,并利用ANSYS软件对一些关键构件进行柔性化,得到了类菱形车转向机构的柔性模型和前轮悬架转向柔性模型。通过对刚性模型和柔性模型的仿真,得到了构件的柔性变形对前后轮同步转向的影响以及前悬架上下摆臂的柔性变形对被动转向的影响。将类菱形车简化为三点支撑的连续梁,分析了轴转向对整车稳态响应和瞬态响应的影响。4.本文在类菱形车线性二自由度模型的基础上,加入了纵向运动自由度来描述类菱形车在转向运动中车速的变化,并应用Pacejka轮胎模型描述轮胎侧偏特性,由此构建了具有实时在线仿真功能的类菱形车非线性三自由度侧向动力学模型。而不同转向类型的汽车,面对同一行驶道路,经驾驶员判断后产生的转向盘输入是不同的,这就需要在进行侧向动力学分析时加入驾驶员模型和道路模型。通过蛇行试验验证了类菱形车非线性三自由度侧向动力学模型和基于人—车—路的闭环系统模型的正确性。5.在全文的最后,按照国家标准对类菱形车进行操纵稳定性的六个基本试验,并按照操纵稳定性指标限值与评价方法对各个试验进行了评价。通过操纵稳定性试验及评价,验证了类菱形车具有优于传统四轮车的操纵性,和与传统四轮车相当的稳定性。本文作为一篇系统研究类菱形车转向系统的论文,对类菱形车的工程化和市场化提供了理论支撑。更多还原

【Abstract】 Steering mechanism plays a very important part in the design of the vehicle as a key component.It influences both the handling stability and the safety of a vehicle. The steering system designed according to special layout of the Rhombic Vehicle is different from the steering system of traditional vehicle. First, the structure of steering system of the Rhombic Vehicle was introduced in detail in the paper, and then it was modeled and optimized to obtained the structural parameters which insure the front and rear tires steering synchronously.Second, the steering performance of the Rhombic Vehicle and the component’s flexible deformation’s influences to the steering mechanism’s and vehicle’s response were analyzed.Then the non-linear three degree lateral dynamics of the Rhombic Vehicle was analyzed, and the closed system of driver-vehicle-road considering the driver model and road model was analyzed. Finally, the handling stability experiment proved the handling flexibility, response sensitivity, safety, reliable handling ability and stability of the Rhombic Vehicle under developed steering systems. According to the analysis method, the dissertation has developed and accomplished pertinent researches as follows:1. As the steering system of a traditional vehicle, the steering system of Rhombic Vehicle is composed of steering control mechanism, steering gear and steering transmission mechanism. Because of the difference between the layout of Rhombic Vehicle and the layout of traditional vehicle, the structures of the steering control mechanism, steering gear and steering transmission mechanism of the Rhombic Vehicle are different from these of the traditional vehicle.Generally, the traditional automobile is steered by the means of the front wheels, however the Rhombic Vehicle is steered by the means of the front and rear wheels. This dissertation has analysed the steering mechanism that is fit to be used on Rhombic Vehicle. They were modeled and optimized to minimize the divergence when the steering wheels turns right or left and to avoid the passive steering when the steering wheels jump.2. Handling flexibility is one of the Rhombic Vehicle’s advantages, which was proved by the analysis of the minimum turning radius and the transmission ratio of the Rhombic Vehicle. Generally, the vehicle must have good returnability under turobalance condition. The Rhombic Vehicle has the good returnability only with the help of steering returnable mechanism,because the steering wheels have bad alignment parameter.The linear two degree model was modeled considered the influence to the tire’s lateral stiffness due to the change of the vehicle’s gravity center. The stationary response analysis and transient response analysis of the Rhombic Vehicle’s linear two degree model suggest that the Rhombic Vehicle not only steer flexible, but also has good performance in handling stability’s time criterion.3. Because the Rhombic Vehicle needs the front and rear wheels steer synchronously while steering, steering mechanism has long tension rods which almost pass through the whole vehicle. The dynamics model and front suspension model were modeled by the means of ADAMS software, and some key components were flexiblized by the means of ANSYS code to obtain the flexible model of the Rhombic Vehicle. After simulating of the rigid model and flexible model, we got the influence of the components’flexible deformation to the front and rear wheels’synchronous steer and the influence of control arms’flexible deformation of front suspension to passive return. The Rhombic Vehicle is simplified to a three points supported beam, and the influence of the axial steer to vehicle’s stable response and transient response were analyzed.4. The longitudinal degree of freedom was added on Rhombic Vehicle’s linear two degree of freedom model to describe the change of vehicle’s velocity when steering, and the tire’s lateral deviation was described with the Pacejka’s tire model, therefore the Rhombic Vehicle’s nonlinear three degree of freedom model with capacity of real time online simulation was modeled. Even on the same road, the driver gives different steering wheel angle displacement input to the different steer type vehicles.The driver model and road model were needed in the lateral dynamics simulation. The slalom test proved the correction of the Rhombic Vehicle’s nonlinear three dimensional lateral dynamics model and the closed system model based on driver-vehicle-road.5. In the end, six basic handling stability tests of the Rhombic Vehicle were operated according to the national standard.All the tests were evaluated according to the handling stability limit and the evaluation method. The handling stability tests and evaluation suggest that the Rhombic Vehicle has better handling stability than the traditional vehicle, while it has the equal stability of the traditional vehicle. This paper, as a dissertation systematicly researched on the Rhombic Vehicle’s steering system, offers a theory that laid a solid foundation to the maket orientation and engineering application of Rhombus Vehicle.更多还原