The Research On Predictive Emergency Braking System For Tractor-semitrailer

In recent years,the application of active safety technologies on passenger cars proved to be very efficient in reducing traffic accidents and improving vehicle safety,however,the application of active safety technologies on tractor-semitrailer is still in its infancy in China.With the continuous development of China's economy,the domestic road freight volume has shown a rapid upward trend.As the main means of road freight transport,the tractor-semitrailer population have increased substantially in recent years.Due to the large cargo capacity of tractor-semitrailer,when they have a traffic accident,it is easy to bring about great loss of life and property.Therefore,as an effective means to enhance vehicle safety,the Predictive Emergency Braking System(PEB)will surely be widely used in tractor-semitrailer.Based on the National Natural Science Foundation of China(51475206)and Jilin Province Science and Technology Development Plan(20140204010GX),this paper carrys out the research of the PEB for tractor-semitrailer.Firstly designs the upper controller,the brake force controller and the active brake actuator of the tractor-semitrailer PEB system to realize the active braking of the vehicle under emergency conditions;then the MATLAB/Simulink,TruckSim co-simulation platform and the hardware-in-the-loop(HIL)test bench are built to test the PEB system by off-line simulation and HIL test.The main research contents of this paper include:(1)Design and analyze the active pneumatic braking system.Based on the original vehicle braking system,design the active pneumatic braking system for tractor-semitriler,built the test bench to test and analyze the characteristics of the active pneumatic braking system designed.(2)Active braking force control.Establish the active pneumatic braking system model basing on its flow characteristics,identify the model parameters using the particle swarm algorithm.Fit the opening and closing characteristics of the active pneumatic brake actuator,then verify the model by the bench test.Finally,design the pressure estimation algorithm and braking force control algorithm based on the active braking system model built.(3)PEB system design.Detect the position and speed information of the front target vehicle by ESR radar,and estimate the vehicle load and centroid position based on the sensor information got from the vehicle;establish the classified warning mechanism according to the urgency of the driving condition,and build the corresponding safety distance model considering the condition of the target vehicle;design the braking force distribution algorithm by combining feedforward and feedback control modes to realize the rational braking force distribution of the vehicle,and adopt the sliding mode control algorithm to implement the wheel anti-lock braking control under extreme conditions to ensure the vehicle braking stability.(4)PEB system testing and validation.Establish the MATLAB/Simulink and Truck Sim co-simulation platform,implement PEB simulation test under typical testing conditions,and analysze the effectiveness of PEB system warning mechanism,braking force distribution strategy and braking force control strategy.Build the PEB system HIL test bench based on dSPACE real-time system and active pneumatic brake actuator,test and verify the function of the designed active pneumatic brake actuator as well as the PEB system control strategy.The test results show that the PEB control strategy and PEB actuator designed in this paper can stably stop the vehicle under emergency conditons and effectively prevent the vehicle longitudinal collision accidents.