Research On Handling Dynamics Of Formula Student Racing Car On Limit Conditions

Formula SAE(FSAE) racing car is a kind of small vehicle designed for the racing track with rapid acceleration, light weight, small size and good flexibility. As race track has numerous and dense curves, the high requirement of the operating stability is claimed. In order to meet this requirement, the study about on-limit handling dynamics of the racing car has become an important project in the universities in recent years. However, as racing tires always operate in the limit boundary which is called “tire adhesion ellipse”, the study of manipulation of the dynamics cannot completely refer to the study methods and standards of civilian vehicles. According to this, establishing the evaluation methods and standards of handling dynamics which is suitable for the vehicles in the racing limiting situation has become the important research.This thesis is focus on the FSAE racing car. Considering the tires are always in the nonlinear conditions of adhesion limit, the article tries to complete the “g-g” diagram by establishing the standard 7 DOF vehicle mode; then try to use quasi-static methods to complete lap simulation and makes comparison between lap simulation and real car track testing to analyze the accuracy of the standard 7 DOF vehicle model. As a result, through the relevance analysis between the main racing parameters and “g-g” diagram, the article will carry on the research of the racing car handling dynamics on the limit conditions.Firstly, based on analysis of experimental date of tire used on the FSAE racing car, we found longitudinal and lateral mechanical properties of this kind of typical racing tires in different conditions. According to the properties of FSAE racing cars’ tires, we build a tire model.Secondarily, the article introduces description and meaning of the “g-g” diagram. It combines the using condition of FSAE racing car to show that the “g-g” diagram can quickly and completely reflect the limit stability in the condition of different racing cars in the same speedway and the same racing cars in different speedways. And, the “g-g” diagram really has the good applicability. Then, it establishes the 7 DOF vehicle mode of Black Shark NO.5 racing car of Beijing Institute of Technology, and finishes the “g-g” diagram by MATLAB operation. In order to verify the hypothesis of the least time in racing lap in “g-g” draft, through the quasi-static simulation method, the article conducts the segmentation process of Beijing Xingang speedway to get the speed profile of every segments. According to the composite lap speed profile, the real car track testing exams the relevance between “g-g” diagram and the lap time, and finally establishes the whole quasi-static track lap simulation methods.Thirdly,by finishing the experiment of Black Shark No.5 both on real car track testing and the seven degree of freedom simulation model, this thesis gets real racing car test acquisition and two “g-g” diagram of virtual simulation. By contrasting and verifying single variable, it comparatively analyzes the influences of racing car’s CG, roll stiffness, tire pressure to “g-g” diagram, thus summarizes change rules and influencing parameter which provide optimization design and parameter adjustment theoretical guidance for racing cars.