| Automotive passive safety devices can reduce the damage after the accident the driver, but for personal injury and property damage, but the driver cannot be avoided, the speed is faster, the consequent accidents are more and more frequent road accidents fat has become a major factor in modern society threaten the safety of people and property, so the development of automotive active safety devices become the focus of universities and research institutions at home and abroad a lot, but the key to the development of automotive active safety device is the control method.After reading and analyzing carefully a large number of relevant literatures at home and abroad, through analyzing the traditional safe distance of three classic models, the distance-based model is used when the speed is high and the time-based model is used when the speed is low in this study; on the base of traditional determining method of dangerous situation, the concept of safety factor is used in this study to divide the ratio of the real distance and the safety distance, the safety factor is calculated and compared with the danger zone in real-time, and the current automotive security state is got, then the timely slowdown measures are taken to ensure the vehicle safe.In the MATLAB/Simulink software platform, the vehicle longitudinal collision avoidance control system model (including vehicle dynamics model, tire model, road model, the driver reaction time model, vehicle power system model, safety distance model and dangerous conditions judgment model) is built based on the low and high speed relaxation state, the simulation of relaxation process in the low and high speed state under dry concrete pavement is done, the curves of the vehicle speed and real distance obtained by simulation show that the vehicle kept a large distance with the target vehicle at the beginning of the phase, the real distance is greater than the safety distance, that is to say the safety is greater than one, it was detected that the real distance is less than the safety distance(5seconds at low speed) when catching up with the target vehicle, the system automatically took reduction measures, since the vehicle speed started to decrease, the real distance is gradually return to the safety distance to ensure the safety of driving the vehicle, at this time the safety factor is equal to one. The vehicle model is built in CarSim software platform, the safety distance model and dangerous conditions judgment model are built in the MATLAB/Simulink software platform to determine the longitudinal collision avoidance control system co-simulation model, the simulation of avoidance processes under four typical road collision and transitions road were done, the simulation results show that the system could achieve automotive collision avoidance. Finally, the vehicle longitudinal collision avoidance control system is made with Freescale microcontroller minimum system and ultrasonic module, then the test of low speed low relaxation process under dry concrete roads is conducted, test results are consistent with simulation results.Simulation and experimental results show that the vehicle longitudinal collision avoidance control methods could play a very good control effect in the process of achieve automobile collision avoidance for common vehicle driving conditions (low-speed relaxation, medium-speed collision avoidance, high-speed relaxation and transitions road collision avoidance), the simulation results show the system could make it and are consistent with the theoretical analysis. If the ultrasonic ranging radar was replaced with the millimeter-wave radar, the experiments was done with the accelerator pedal and brake pedal control agencies, the data obtained from simulation model was corrected with the experiments data, the actual value of the system can be improved with mutual verification and correction methods, but also the vehicle longitudinal collision avoidance system make a important step toward commercialization and practical. |
PDF Full Text Request