Research On Active Braking Technology Of Automobile Based On Pulsed Laser Ranging

With the increasing importance of road safety,the Autonomous Emergency Brake(AEB)based on real-time ranging system has become a hot research topic.In view of the problem of lower refresh rate of the existing vehicle range finder,in this paper AEB is realized by pulse laser ranging with high frequency.In order to improve the precision of laser ranging in the movement process,a system error correction method and the filtering algorithm in the dynamic range finding process were particularly studied on the basis of the designed circuits.According to the principle of pulse laser ranging,a laser ranging system including launch module,receiving module,high voltage module,data processing and control module,and other sensor modules(which are used to collect driving states)was designed and implemented for subsequent use.By analyzing the influence of time identification method on ranging accuracy,we studied the system delay error.The rule of system delay is analyzed and the reasons for it are explored through analysis of the theory,modelling and fitting calibration.Then,we made a detailed analysis on the variation of echo intensity which due to different distance and obstacle characteristics.According to the measured data,a mathematical model of the relationship between the echo pulse width and the delay of the receiver was established,which correct the walk error in the constant threshold identification.After that,the calibration equation between the measured time and the actual distance was established,in which way the ranging accuracy of the system was improved.In order to reduce the random error in the dynamic range finding process,a method of calculating the relative velocity based on the sliding mean filter was proposed.In view of the contradiction between the accuracy of the sliding mean filter and real-time,a distance measurement model based on Calman filtering was proposed.It not only improves the precision of distance measurement under static state by two orders of magnitude,but also improves the accuracy of the dynamic ranging while ensuring the real-time performance.In order to reduce the random error in the dynamic range finding process,a method of calculating the relative velocity based on the sliding mean filter was proposed.The method based on Kalman filtering technology is proposed to improve the dynamic measurement precision based on pulsed laser range finder.The Kalman filtering ranging model is established to obtain the optimal estimation of ranging result,which greatly reduces the effect of noise introduced by ranging process on accuracy Impact,and meanwhile get the estimated value of the relative speed.The experimental results show that not only the accuracy of static ranging is improved by two orders of magnitude,but also the accuracy of relative speed in dynamic ranging is improved while real-time performance is guaranteed.Then,the platform of vehicle was built.An algorithm of AEB based on Time to Collision(TTC)was designed which implemented by DSP software.The experiment shows that the success rate of the designed active brake collision is 93.75%.A measure to improve the threshold of TTC was proposed for the cause of failure.At the end of the dissertation,the inadequacies and prospection of the research was offered.