Research On 4WS Fuzzy Control Strategy Based On Wheel Torque

Four wheel steering technology is one of modern automotive control technology which to improve vehicle motion characteristics for the purpose. Its main function is by control the rear wheel steering way to improve the vehicle steering flexibility at low-speed condition,handling stability at high-speed condition, braking capability under Bisectional road. This paper use common commercial vehicles as the research object, study the influence wheel torque on side force and the side slip angle of tire based on the analysis of the vehicle steering characteristics and then through the study of the wheel steering fuzzy control strategy to improve vehicle handling and stability.Main contents include:(1) Introducing and studying the method of establishing the dynamic model in this paper. Using the momentum and momentum theorem and Newton’s second laws to establish the eight degree of freedom dynamic model which considering wheel torque input and tire nonlinearity characteristics in the Matlab/Simulink. The vehicle dynamic model established by the virtual prototype software Carsim is compared with the established model, which verifies the correctness of the dynamic model established by the Newton vector mechanics system.(2) Analyzing the reasons why vehicles loss of the stability and studying the relationship between the longitudinal force and the lateral force. Simulating the nonlinear eight degree of freedom vehicle dynamic model with front wheel drive and comparing with the vehicle model without wheel torque to analyze the influence between wheel torque and vehicle handing stability. The steering characteristics of the vehicle is studied under the condition of driving and steering.(3) Analyzing two degree of freedom four wheel steering dynamic model and analyzing the characteristics of the 4WS steering based on it. The control strategy of fuzzy control is studied. The fuzzy control algorithm of the four wheel steering was built by Matlab, and the control method was compared with other control methods. Finally, the conclusion is showed that the control strategy of feed forward fuzzy combined controller can improve the safety and stability of automobile.