Achievement And Intrinsic Calibration Of Multi-beam LiDAR System

In this paper,laser ranging modules made by our research group are assembled into a mechanical multi-beam Li DAR.This design has the advantages of easy installation,easy maintenance,and it can adjust the range of vertical field angle.To reduce the interference between each module,a time-division multiplexing method is adopted and a FPGA-based program is designed for data acquisition and to transmit data through Ethernet.The horizontal rotation angle is obtained by counting the signal pulse of the encoder,and 63 laser ranging modules work in turn once every 4 signal pulses are detected to achieve 360° scanning.Multi-clock phase method is adopted to measure up to 4 echo signals.The minimum time resolution is 1ns,the minimum horizontal angle resolution is about 0.35°,and the vertical field is determined by laser ranging modules,which meets the performance requirements.In this paper,the causes of ranging error of laser ranging module and angle measurement error of encoder are analyzed,the range calibration model and angle calibration model are established,so that the RMSE of range is reduced to 0.08 m,the RMSE of angle is reduced to 0.10° with the use of calibration parameters.Then,the installation error of the laser ranging modules are taken into account to establish the system error model.Using the previous model parameters as initial values,the improved Gauss-Helmert adjustment model which is based on planar features in the environment reduces the system errors and the RMSE is improved by 46%.Finally,a program is designed to extract data from Ethernet packets and display the point cloud images based on MATLAB,and the Li DAR works normally.The program,the system error model and the calibration experiment procedure designed in this paper lay a foundation for the follow-up work of our research group,and also provide some ideas about calibration work of other Li DAR.