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摘要:
针对激光雷达复材型面测量时测量精度的评定需求，提出了一种基于激光雷达回波信号信噪比（SNR）的精度分析方法。通过对复材型面检测结果进行评价，获取零件脱模后准确的变形量结果，有利于实现精准修模。所提方法考虑了测量工程中待测距离、入射角、材料属性等因素对测量结果产生的影响，研究激光雷达型面测量过程中回波信号信噪比与测量精度的联系，利用信噪比的变化规律，结合仪器不确定度，确定测量点云不同区域的精度修正因子，实现激光雷达大尺寸复材型面变形量检测结果的测量精度分析，减小了测量误差对变形量的影响。所提方法能准确评价测量结果的精度，获取复材型面的真实变形量。
Abstract:In order to meet the accuracy evaluation requirement of composite material surface measurement with lidar, this paper proposed an analysis method based on Signal to Noise Ratio (SNR) of lidar echo signals. By evaluating the detection results, the deformation results after the demolding can be obtained accurately, which is conducive to achieving the repairs of composite material mold. This method considers the influence of measurement distance, incident angle and material property on the results in measurement engineering. And the relationship between echo signal SNR and measurement accuracy in lidar measurement process is studied. Combined with SNR variation law and instrument uncertainty, the accuracy correction factor can be determined in different areas of measurement point-cloud. Finally, this method is used to realize measurement accuracy analysis of large-scale composite material surface deformation measurement results by lidar, which reduces the influence of the measurement error on deformation. This method can accurately evaluate the accuracy of measurement results and obtain the true deformation amount of composite material surface.
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图 4 测量时激光雷达的站位与光路示意图
Figure 4. Schematic diagram of position and optical path of lidar during measurement
图 5 2种状态κ随入射角θ变化网格图
Figure 5. Grid diagram of κ as a function of incident angle θ in two states
图 6 测量结果点云依修正因子κ分区
Figure 6. Partition of measurement result point-cloudaccording to correction factor κ
图 7 工具球测量信号强度随待测距离变化曲线
Figure 7. Variation of measurement signal strength of tooling ball with measurement distance
图 8 不同表面处理目标测量信号强度随待测距离变化曲线
Figure 8. Variation of measurement signal strength of target withdifferent types of surface treatment with measurement distance
图 9 不同材料目标测量信号强度随待测距离变化曲线
Figure 9. Variation of measurement signal strength of different materials of target with measurement distance
图 10 复材实测过程中信噪比波动曲线
Figure 10. SNR fluctuation curve during composite material measurement process
图 11 测量结果点云与精度分区
Figure 11. Point-cloud and precision partition of measurement results
表 1 仪器不确定度与信噪比数值对应关系
Table 1. Correspondence between instrument uncertainty and SNR
待测距离/m 仪器不确定度/μm 信噪比/dB 2 24 56.5 4 43 47.8 6 61 43.1 8 82 38.7 10 102 35.9 
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表 2 精度修正因子与实测不确定度对应关系
Table 2. Correspondence between accuracy correction factor and measured uncertainty
测量分区 精度修正因子κ 实测不确定度/μm A 0.84 28.4 B 0.77 55.4 C 0.74 81.6 D 0.71 112.1 E 0.68 148.1
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表 3 精度修正前后各区域平均变形量结果
Table 3. Average deformation results of each area before and after accuracy correction
测量分区 修正前变形量/mm 修正后变形量/mm A 1.83 1.80 B 2.31 2.25 C 1.72 1.64 D 1.57 1.46 E 2.03 1.88
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