Research On Vehicle Stability Control Strategy Of The Brake-by-wire System Brake Failure

The braking system has direct impact on automobile driving safety,has been a hot issue studied by people.The Brake-by-wire system replaced the traditional hydraulic or pneumatic actuators by electric components,has the advantages of good controllability,fast response and good vehicle stability,has good prospects for development.When one wheel brake failure,such as braking distance increases and deviation dangerous conditions will be appeared,it is a serious threat to vehicle driving safety.After single-wheel brake failure occurs,the inherent redundancy of the Brake-by-wire system can be achieved by redistributing the braking forces of the remaining three wheels to achieve the control and reconstruction,thus ensuring the stability of the straight brake vehicle,so study on the vehicle stability control under the condition of brake failure in Brake-by-wire system is of great significance.The main research for brake failure in Brake-by-wire system in this thesis included:Based on the analysis of vehicle braking and stability,the braking and stability evaluation index and influencing factors of straight brake vehicle are given.The vehicle dynamic analysis of single-wheel and two-wheel brake failure is carried out,the reason of the vehicle braking distance increase and deviation after brake actuator failure is revealed,comparatively analyzed the different impacts on vehicle stability of different parts of single-wheel and two-wheel brake failure.A co-simulation model of Carsim and MATLAB/Simulink is established for the impact of single-wheel and two-wheel brake failures on vehicle stability,quantitative analysis every factors different imparts on the braking and stability of single-wheel,two-wheel brake failure vehicle,the simulation results show that,single-wheel and two-wheel brake failure will cause the vehicle braking distance increase,in addition,single-wheel and diagonal two-wheel and the same side two-wheel brake failure will cause the vehicle braking deviation,the initial braking speed has the greatest impact on the stability of the vehicle,the braking intensity mainly affects the yaw rate of the vehicle,the influence of the ground adhesion coefficient on the vehicle stability is small,the simulation results further verify the theoretical analysis conclusion of the influence of the braking failure on the vehicle stability.Through the analysis of the inherent redundancy of Brake-by-wire system,it is shown that the vehicle still has the ability to ensure the safety and direction stability of straight braking after brake failure.According to the control objectives of the single-wheel brake failure vehicle,a braking and steering joint control strategy is proposed for vehicle stability control by making full use of the ground attachment limit,and through the active front steering control vehicle deviation,the fuzzy PID controller is designed for the vehicle yaw velocity control scheme.A co-simulation model of vehicle stability control under single-wheel brake failure is established,the simulation results show that the stability control strategy for the single-wheel brake failure vehicle can greatly reduce the braking and deviation distance and the yaw velocity,ensure the vehicle longitudinal braking safety and lateral stability.