Research On Lidar Ranging Technology Based On Autopilot

Autonomous driving technology is on the rise.Sensors are indispensable as the eyes of unmanned vehicles.Among them,lidar occupies an important position in the research of autonomous driving technology because of its advantages of obtaining threedimensional information of the target,strong anti-interference ability and high resolution.Lidar ranging refers to a technique for calculating the distance of a target by emitting laser light and receiving reflected laser light to obtain the propagation time of the laser light in space.The accuracy of laser ranging is the key point of this technology.In addition,longdistance,low cost,miniaturization,anti-jamming,etc.are also the goals of the development of this technology.However,there is currently no product that can have these advantages at the same time.This topic is dedicated to the research of lasers in autonomous driving scenarios with these advantages Radar ranging technology.This thesis first introduces various types of lidar,including mechanical,hybrid,solid-state lidar,and mainstream vehicle laser ranging technology.Focus on analysis and comparison of the advantages and disadvantages of pulsed and phase laser ranging technology.Combined with the theory of laser transmission in the atmosphere and the principle of lidar ranging,a ranging scheme with simple structure and low cost is designed.Through a periodic sinusoidal signal with a transmission frequency of 20 MHz and a repetition frequency of 1MHz,a full-phase FFT is used.The method achieves centimeterlevel laser ranging accuracy.The accuracy of the distance measurement is verified by researching the key technology design accuracy test system in the laser transmitting module,echo signal receiving module and data processing module.Use Quartus II software to design the DDS signal generator program to control the DA chip to generate the modulated signal.Design an amplifier circuit at the receiving end to perform I/V conversion on the echo signal after photoelectric conversion,and use Pspice software for transient analysis.Analyze and design the pulse conversion circuit,which can convert the echo signal into a pulse signal suitable for the time measurement chip.In Quartus II,an AD sampling control program for analog-to-digital conversion of the signal is developed to control the AD chip sampling,and the full-phase FFT phase discrimination program is designed using the IP core of the FFT,and the Cordic program is designed to calculate the phase.Finally,the short-distance ranging experiment within 2.5m was carried out through the built test system.The test accuracy reaches 4.8cm,which basically meets the design requirements of the scheme.Finally,the problems existing in the experimental results and the directions that can be optimized are analyzed.