Research On The Control Strategy Of Autonomous Emergency Braking System

The Autonomous Emergency Braking is an important means to ensure the safety of vehicles.The core is the control strategy.Considered the lane change of adjacent lanes,this paper studied the control strategy of automatic emergency braking system with safety and comfort for the situation of straight road.The main contents are as follows:Firstly,in order to ensure the accuracy of AEB system control,aimed at the lane change of adjacent lanes,used the relative positional relationship between the target vehic le and the vehicle,the target vehicle selection algorithm is proposed to select the most dangerous target vehicle relative to the vehicle.Secondly,the driver’s response time to different types of early warning signals was analyzed,and a hierarchical early warning strategy based on the safety time model was proposed.Considered the influence of driver’s braking level and ground adhesion on braking intens ity,a hierarchical braking strategy based on the combination of safety time model and safety distance model was proposed,and a safety distance prediction model based on brake deceleration response characteristics was proposed.Then,in order to realize the expected acceleration planned by the hierarchical braking strategy,a vehicle inverse longitudinal dynamic model was established to achieve vehicle speed maintenance and vehicle deceleration.Considered the change of road surface adhesion conditions and the influence of front and rear wheel axle load transfer factors on the distribution of four wheel cylinder pressures,a braking force distribution model was established to enable the car to automatically select the optimal slip ratio on different road surfaces.Finally,based on the hierarchical control method,the AEB control system was designed.Considered the change of the motion state of the most dangerous target vehicle,the actual acceleration of the vehicle was fed back to the upper controller in real time,and the upper controller based on the finite state machine was established to calculate the current expected acceleration in real time.Based on the actual acceleration of the vehicle,a lower-level controller based on fuzzy PID was established to achieve accurate follow-up of the actual acceleration of the vehicle.Verificated by simulating in Carsim,in the multi-target test scenario,the accuracy of the target vehicle selection algorithm was verified.Based on the classic test conditions of E-NCAP,the classification warning was given in the front vehicle static,the front vehicle uniform motion,and the front vehicle uniform deceleration motion test conditions,the simulation results of the braking strategy showed that the upper controller can plan the expected acceleration in the current state under various working conditions,and the actual acceleration of the lower controller could accurately follow the expected acceleration,the error was within a reasonable range and the reliability of the proposed control strategy is verified.