Design Of Ranging Lidar System For Driverless Vehicles

Nowadays,driverless technology has become a popular trend in the automotive field and the obstacle detection is a vital part of driverless technology.As an active detection method,lidar has the ad,vantages of fast measuring speed and high precision,thus it has obvious advantages in obstacle detection.As for obstacle detection of driverless vehicles and in order to overcome the deficiency of high cost and lo w precision of multi-line scanning lidar,the research on lidar ranging technology is carried out in the thesis.A lidar system for scanning ranging is designed by considering the vehicle environment and practical application requirements.The main work is as follows:(1)Firstly,the pulsed and phased laser ranging theory is analyzed and compared.According to the real-time requirements of obstacle detection of driverless vehicles,the method of pulsed ranging is selected.For the key factors affecting the accuracy of pulsed measurement,time identification and measuring time interval are improved to optimize detection performance of system.(2)Secondly,for characteristics of semiconductor laser and photodetector,the optical system of transmitting and receiving is researched and designed.Then optical system is simulated by ray tracing in ZEMAX to verify collimating and focusing of the laser beam,which will improve the detection range and accuracy of system.(3)Thirdly,the circuit system of transmitting pulse laser and receiving echo signal are designed and built.The FPGA device and C8051F206 are selected as the main controller to realize the emission of narrow pulse laser with repetition frequency of kHz and pulse width of 60ns.In order to improve the signal-to-noise ratio of receiving system,the high-sensitivity APD is used as photodetector combined with signal conditioning circuit,which will effectively extract weak echo signals.The module of high-precision time measuring and mechanical rotation module are also designed to verify ranging performance of scanning lidar.(4)Finally,in order to verify the performance of ranging lidar in the obstacles detection,the interface based MFC for obstacle data reconstruction is developed in Visual Studio 2010.The obstacle information is reconstructed based on the distance data detected.An experimental platform is built and the nearby object is measured to test and verify detection performance of the system prototype.The final result shows that designed measurement system basically meets expected detection requirements and has practical application value.