Research On Coordinated Control Of Vehicle Active Front Steering System And Anti-lock Braking System

With the rapid increase in car ownership,the incidence of traffic accidents is increasing year by year.Active safety technology can monitor the current driving state of the vehicle and the driver’s driving intention in real time,and make corresponding adjustments to the vehicle actively,which greatly reduces the occurrence of traffic accidents,becoming a research hotspot of domestic and foreign automobile manufacturers.Active front steering,Acceleration Slip Regulation and Anti-lock braking are common active safety technologies.However,the improvement of the overall performance of the vehicle is the result of the coordination of the various subsystems.So it is of great significance to study a reasonable control method to ensure the function of a single subsystem while improving the overall performance.Based on this,this paper proposed the sliding mode control strategy of the active front steering system and the logic threshold control strategy of the anti-lock braking system.The two-system fuzzy coordinated control strategy was proposed and the simulation verification was carried out.Firstly,the ideal two-degree-of-freedom reference model,the seven-degree-of-freedom dynamic model and the Dugoff tire model were established.In order to explore the rules that should be followed in the additional angle of the active front steering system,the steering characteristics of the vehicle were analyzed in detail,and the ideal variable transmission ratio related to the speed was determined.The sliding mode variable structure control was adopted,and the additional angle sliding mode control strategy of the active front steering system based on the ideal variable transmission ratio rule was designed.Corresponding control model were established,and the simulation analysis was carried out under different initial vehicle speed conditions.Results show that at low speed,the yaw rate,centroid side yaw angle and lateral acceleration of the ideal variable transmission ratio vehicle are significantly higher than that of the ordinary variable transmission ratio vehicle,indicating that steering is lighter.While the response amplitude of those in ideal variable transmission ratio becomes smaller at medium-high speed,indicating the vehicle has better steering stability and the driver has a stronger sense of the road.Secondly,by analyzing the relationship between adhesion coefficient and braking slip rate,the concept of optimal slip ratio was clarified,and the control strategy of anti-lock braking system based on optimal slip ratio was proposed.The joint simulation model was built to verify the strategy.Results show that the car does not lock up during the emergency braking process and has good braking performance.Finally,the working characteristics of the active front steering system and the anti-lock braking system were analyzed,the working range and effect of the two systems were clarified the fuzzy rules of coordinated control were formulated.For the extremely unstable steering braking condition,the simulation analysis was carried out under medium and high speed conditions.Results show that the coordinated control strategy has better control effect than the single control,which effectively improves the stability and safety of the vehicle in steering braking.At the same time,the coordinated control effect based on the ideal variable transmission ratio rule was compared with the effect based on the ordinary variable transmission ratio rule.It is proved that the proposed coordinated control strategy has better control performance.