Research On Pulsed Lidar Ranging System Based On Semiconductor Laser

With the continuous development and progress of society and economy,the era of self-driving is also accelerating,and driverless technology has become the current development trend in the field of automobile.As an active sensor,lidar is very suitable for outdoor use because of its high precision,strong anti-jamming,stability and adaptability to the surrounding environment.Compared with other sensors such as millimeter wave radar and camera,lidar also has obvious advantages in obstacle detection and 3D reconstruction.But because of the high cost and volume of lidar,it is difficult to apply to private cars,car companies can not accept,car owners can not afford.Therefore,the research on the lidar ranging system with high integration,small size,low cost and high measurement accuracy has certain significance for the development of driverless vehicles.Analyzed different ranging methods,combined with the actual situation,designed a low-cost lidar ranging system with high integration and high measurement accuracy.The main research work is as follows:(1)The principle of pulse-type ranging and the principle of phase-type ranging are studied,and their respective advantages and disadvantages are compared and analyzed.According to the actual application requirements,the pulse-type ranging scheme is comprehensively considered.(2)Completed the circuit design of the overall laser ranging system,including:circuit design of the ranging system unit(transmitting unit circuit,signal processing circuit,A/D conversion and microcontroller minimum system selection,etc.).According to the selected pulse ranging method,the relationship between the transmitted power and the received power is studied,and the appropriate light source and photodetector are selected.wavelength of 905nm was selected as the system light source,and the designed driving circuit unit was simulated.The avalanche laser diode of AD500-9 was used as the photodetector.According to the characteristics of the echo signal,the preamplifier circuit,the filter circuit,the main amplifier circuit are designed,and the simulation experiment is carried out.A/D selected ADS1115,MCU selected STC89C52RC,and designed a time measurement circuit with FPGA.(3)Build an experimental platform,verify the system,and analyze the error.The results of the study show that:at a measurement distance of 200m,the measurement accuracy is 2cm,and the density value per unit area is greater than 200 points/m~2.When measured on a straight road,the median error of elevation accuracy is 5.7cm,the standard deviation is 4.8cm,and the average error is 3.2cm.