光谱学与光谱分析, 2018, 38 (8): 2332, 网络出版: 2018-08-26  

噪声对等光频采样调频连续波激光雷达测距精度的影响分析及实验验证

The Influence of Noise on Ranging Accuracy of the Frequency Modulation Continuous Wave Laser Radar Based on Equal Frequency Sampling
作者单位
天津大学精密测试技术及仪器国家重点实验室, 天津 300072
摘要
调频连续波激光雷达具有测量范围大, 精度高, 无需合作目标等优点, 在计量学和工业现场测量中具有重要作用。 简单介绍了等光频重采样调频连续波激光雷达的基本结构和测距原理, 分析了系统辅助干涉信号和测量干涉信号中存在的主要噪声及其特点。 当系统辅助干涉信号中存在噪声时, 会造成极值点不准确并且引入测量误差。 随后, 使用Cramér-Rao下界定理评估测量干涉信号的噪声对测量结果的影响。 为了提高测量的准确性和稳定性, 基于经验模态分解的小波阈值滤波和汉宁窗带通滤波结合小波滤波的自适应滤波方法分别用来去除了辅助干涉信号和测量干涉信号中的噪声。 实验中多次测量了平面镜和多种粗糙度样块, 并使用精密导轨验证测量结果的准确性。 实验结果表明, 当被测物位于3.9 m左右时, 使用自适应滤波方法去除噪声后, 系统对反射镜和其他粗糙度样块的测量不确定度为20 μm和几十微米(K取值2), 远小于使用小波阈值滤波的方法(120 μm和几百微米)。 同时, 通过对比精密导轨位移数值和系统的测量结果, 证明了所提出的方法能够有效提高系统的测量准确性。Method and Experimental Verification
Abstract
Because of the advantages such as the large measurement range, high accuracy and not needing cooperation target, frequency modulation continuous wave (FMCW) laser radar plays an important role in metrology and industrial measurement. This paper briefly introduces the basic structure and ranging principle of frequency modulation continuous wave laser radar, which was based on equal frequency sampling method. The main noises that exist in the auxiliary interference signal and the measurement interference signal and their characteristics were analyzed. When the auxiliary interference signal of the system was existed with noise, part of the extreme points was incorrect and the measurement error will be brought into the result. Subsequently, the Cramer-Rao lower bound was adopted to evaluate the influence of the noise that existed in the measurement interference signal. To improve the accuracy and stability of the measurement, the adaptive filtering methods of wavelet threshold filter based on EMD and Hanning band-pass filter based on wavelet filtering were used to reduce the noise existing in auxiliary interference signal and the measuring interference signal, respectively. In the experiments, a flat mirror and a variety of roughness blocks were measured very times and the correctness was verified by comparing the measured results of the system with a precision guide. Experimental results showed that:when the measured object was located at stand-off distance of about 3.9 m, the adaptive filtering methods can effectively remove the noise and the measurement uncertainty of the mirror and the roughness blocks was 20 μm and tens of microns respectively (K=2), which was much smaller than the uncertainty of the wavelet filtering method (120 μm and hundred microns). At the same time, by comparing the displacement value of the precise guide rail and the measurement results of the system, it proves that the proposed method in this paper can effectively improve the measurement accuracy of the system.

熊星庭, 曲兴华, 张福民. 噪声对等光频采样调频连续波激光雷达测距精度的影响分析及实验验证[J]. 光谱学与光谱分析, 2018, 38(8): 2332. XIONG Xing-ting, QU Xing-hua, ZHANG Fu-min. The Influence of Noise on Ranging Accuracy of the Frequency Modulation Continuous Wave Laser Radar Based on Equal Frequency Sampling[J]. Spectroscopy and Spectral Analysis, 2018, 38(8): 2332.

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