| The frequent occurrence of car accidents makes people's demand for driving safety increasing.So,it is urgent to study safe driving technology.A vehicle distance detection system is studied on the background of vehicle collision avoidance in this paper.Several commonly used distance measurement methods such as ultrasonic ranging,millimeter wave ranging,camera ranging and laser ranging are compared in detail.Pulsed laser ranging is selected in this paper.Vehicle laser pulse ranging will be affected by the surrounding environment,weather,and the reflectivity difference of obstacles,which makes the echo pulse amplitude and waveform change.In this case,a single time discrimination method is easy to produce judgment error,which affects the stability of ranging.For this problem,a method combining over-zero and constant ratio discrimination is proposed to make the moment discrimination more stable.A ranging system based on the principle of vehicle-mounted laser pulse ranging is designed in this paper.The driver circuit is designed for transmitting narrow pulse laser;the APD is used for echo signal detection,the triode amplifier circuit is designed to amplify the weak echo signal,and the combination of over-zero and constant ratio discrimination is proposed to accurate moment discrimination of the echo signal.The FPGA is used to send the square wave required for each part of the circuit and for SPI communication.Finally,the time from the start signal to the return signal is measured,and the distance from the vehicle to the obstacle ahead is calculated.Based on the simulation of the circuit of each unit,the physical production is carried out.The ranging experiment is carried out to verify the proposed method and the designed system.The results shows that the error of this system is controlled within 0.1meters,and the action distance can reach 100 meters.The requirements of vehicle pulse laser distance measurement can be met. |
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