Controlling Strategy Research On Mechanical Active Front Steering Sysytem

With the improvement of people's living standards, the demands for driver comfort, flexibility, and vehicle handling stability is getting higher and higher. Active front steering system which can meet the low-speed flexibility requirements and the demands of high-speed stability is relatively popular for the automotive research in recent years. A fuzzy control method is proposed to improve vehicle yaw stability by the integrated control of active front steering in this paper. The control variable is yaw rate and sideslip angle. The method of the vehicle stability control is fuzzy control, which have more robust method.This paper firstly introduces the development of steering system, as well as the study of active steering technology at home and abroad. Then the steering principle, structure, the key technology of the mechanical active front steering system is explained, and also the ideal steering ratio concept is given.Secondly on the basic of analyzing the mechanical active front steering system, establish the two-degree-of-freedom vehicle model, tire model and active front steering system model. Then the formulas of yaw rate such as lateral force, side force are given. All of these lay the model-based for the next chapter of control system simulation.Finally, on the basis of fuzzy control theory, a specific control strategy which use yaw rate and sideslip angle for the control variable is set up. In the simulink simulation platform, simulation study is performed at two different conditions, which are step signals and sine signals with fuzzy controller and without fuzzy controller. The result showed that the presented method can effectively control the yaw rate and the sideslip angle synchronously, achieve the vehicle stability, lighten the burden of the driver.Though the research of this issue, laying a theoretical foundation for the mechanical active front steering control At the same time, given some help for the research of vehicle's kinematics analysis and simulation experiments.