Research On Key Technologies Of Autopilot Vehicle Lidar

Lidar was first used in the military field,but with the rapid development of autonomous driving technology,vehicle lidar has been widely used as a key device,and ranging the objects around the vehicle.With the help of the scanning system,complete 3D modeling of the surrounding environment,which provides support for environmental data for autonomous driving technology.In this paper,the key technologies of automotive lidar are studied in depth.Firstly,based on the detection principle of lidar,the detection method and ranging accuracy of lidar are analyzed,and choose the pulsed time-of-flight method to design a vehicle lidar.The absorption equation and scattering equation of laser in atmospheric transmission are studied theoretically,and the total transmission rate of atmospheric transmission is calculated,after substituting into the lidar equation,the relationship between transmission power,transmission distance and received power can be obtained.Therefore,we propose a design scheme for vehicle lidar.Secondly,we focus on the hardware circuit part,optimizes and simulates the driving current in the laser transmitting circuit,and drives the semiconductor laser to obtain the pulsed laser with narrow pulse width,high power and high repetition frequency.A time discrimination circuit based on the constant ratio timing principle is used to convert the analog pulse signal into a digital logic level,and provide it to the time measuring unit.At the same time,a voltage conversion circuit is designed for the transmitting circuit and the discrimination circuit to provide the required stable voltage.Thirdly,the time measurement method of lidar is deeply studied.The high-precision time measurement method based on FPGA is selected,the time measurement is divided into two parts: coarse time and fine time,and the large-scale and high-precision time measurement can be realized.The counter is used to measure the coarse time.The fine time is measured by the structure of the FPGA fast carry chain cascading,and the cascading structure is generated by the full adder,after the error correction module and the decoding module,we can get the fine time.Finally,we build a lidar system for testing,and analyze the ranging error caused by circuit trace delay,device response and time measurement error,the test results can basically meet the index requirements of the scheme design,...