The Research And Analysis Of The Rhombic Vehicle's Steering System

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.