| Automatic Crash Notification System(ACNS)is one of the post-accident safety technologies.When an accident occurs,ACNS can quickly identify the crash and contact the call and rescue center to send accident information.The rescue center can send the nearest rescue organization to rescue the occupants in vehicles according to the received rescue information to improve the rescue efficiency and save more lives.The speed change is calculated by the ACNS that is triggered by acceleration signal when the acceleration is larger than the discrimination threshold,so there are errors between the calculated speed change and actual value.However,the accuracy of speed change will affect the traffic accident reconstruction and the injury prediction of passengers.Therefore,it is of great significance to study the accuracy of speed change information of ACNS.The effects of speed change on fixed-counterguard crash and vehicle-to-vehicle crash are discussed.At the same time,according to Logistic regression,three factors which have significant influence on the injury prediction of passengers are determined,that is,whether seat belts are buckled,the speed change during the crash,and whether the airbag is opened.In order to determine the specific relationship between speed change and injury prediction,the speed change is taken as an independent variable and the occupant injury grade is taken as a dependent variable,so that a driver’s injury prediction model is established.The influence of speed change on driver’s injury prediction is analyzed.The relationship between the discrimination threshold,the shape of acceleration curve and the accuracy of speed change is analyzed by using the data of sled crash test.In order to determine the related model among these three variables,LS-DYNA simulation model of sled crash is built according to the actual sled crash test and its accuracy is verified.The error between the speed change calculated by speed change algorithm of ACNS and the actual speed change is used as a symbol to measure the accuracy of the speed change information and as a dependent variable.Discrimination threshold is used as one of the independent variables.The shape of the acceleration curve is characterized by the peak acceleration,the mean of absolute value of the slope of acceleration and the mean of speed change in 8 milliseconds.The most suitable factor is selected as another independent variable.Based on the acceleration data generated by the simulation model,regression analysis is carried out,and the final regression equation is determined by comparing the regression results.The regression equation is used as the related model and incorporated into the original speed change algorithm of ACNS to improve its calculation results.An ACNS algorithm with the function of selfcorrection of speed change information is proposed on this basis.The design of vehicle terminal of ACNS is carried out.The circuit design ideas of positioning module,GSM module,CAN communication interface and power supply of ACNS vehicle terminal are expounded respectively.At the same time,the software part of positioning and GSM module is designed and the ACNS algorithm with the function of self-correction of speed change information is integrated into the software.Finally,ACNS prototype is manufactured.The validity of the ACNS vehicle terminal and the proposed algorithm is verified by the acceleration data collected from the sled crash test and the real vehicle crash test.The verification results show that the designed vehicle terminal can accurately identify the crash and send accident information,and the speed change information is more accurate. |
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