Anti-interference Research Of LiDAR Based On CDMA Modulation

Li DAR has the advantages of high detection accuracy and fast detection rate,and is one of the core sensors to realize driverless driving.But in practical application,there are serious interference between Li DARs.And with the development of driverless technology,the number of driverless vehicles will increase rapidly,and the interference between Li DARs will become more serious,which will seriously endanger driving safety.Therefore,the study about Li DAR anti-interference is of great significance.In view of the problem of mutual interference between Li DARs,in this paper,code division multiple access(CDMA)modulation scheme in Li DAR for anti-interference is used,in order to realize the good anti-interference performance to commercial Li DARs and meet the needs of future driverless vehicle Li DAR anti-interference application requirements.For this purpose,this paper mainly carried out the following research work:(1)Investigation of the interference phenomenon through experiments.Experiment was done on two commercial Li DARs for two-hours' interfering to get point cloud results in which interference is obtained as a result.the interference phenomenon is verified.And after analyzing the causes of mutual interference between the pulse Li DARs,the basic solution to Li DAR anti-interference is proposed,which is to modulate the signal to a special waveform,then to implement the unique recognition of the echo signal.(2)The design of CDMA modulated Li DAR system is completed.The structure,signal processing algorithm and modulation code of are determined.According to the basic structure of Li DAR and the ranging principle of CDMA modulated Li DAR,the required system components and the working flow of each component are determined.The signal processing algorithm of the system is determined,including threshold detection algorithm and sliding correlation algorithm,in order to realize the unique recognition of the special modulation signal and achieve the purpose of anti-interference.The properties of three different orthogonal codes(M sequence,prime codes and optical orthogonal codes)are compared,and optical orthogonal codes(OOC)is determined to be the most suitable modulation code.(3)The anti-interference performance of CDMA modulated Li DAR is studied by simulation.Using pulse laser signal and FMCW laser signal as interference sources,the antiinterference results of CDMA modulated Li DAR on different forms(pulse width and frequency),different SIR and different intensity of interference signals are investigated.(4)The CDMA modulated Li DAR experimental system is built,and the ranging and antiinterference performance of the system was studied experimentally.The ranging performance of the system is analyzed for ranging results without interference.Then,under the interference of commercial pulse Li DAR sinusoidal modulated laser signal and FMCW Li DAR the ranging performance of the system is analyzed according to the experimental results.