基于高光谱成像技术的发芽小麦分类研究

    Research on classification of sprouted wheat based on hyperspectral imaging technology

    • 摘要: 为准确判断小麦发芽程度,更好地服务于小麦的收储及加工利用,通过高光谱的光谱信息对不同发芽程度小麦进行分类识别。采集萌动小麦(鼓泡、皮裂、露白)和发芽小麦(芽长为小麦籽粒长度的一半,芽长与小麦籽粒长度相同)的高光谱数据,提取每粒小麦的平均光谱,再由Savitzky-Golay卷积平滑法、卷积求导法(1ST、2ND)、标准正态变量变换(SNV)对光谱预处理后建立最小二乘支持向量机(LSSVM)分类模型,比较发现SNV的识别准确率最高达91.70%。利用粒子群算法(PSO)对LS-SVM模型中正则化参数(gam)以及核函数参数(sig2)寻优,优化后模型的准确率为93.14%,提升了1.57%。为进一步减少运算量、提升准确率,利用竞争性自适应重加权算法(CARS)选取了49个特征波长,最优分类模型PSO-SNV-CARS-LS-SVM的平均准确率为94.13%。最优模型体系可以快速无损检测不同发芽时期的小麦,最终达到分类结果可视化。

       

      Abstract: Affected by the rainy weather during the harvest period, wheat is prone to sprouts, and severely, a large-scale reduction in production might occur. Failure to dry in time or poor management during storage can directly cause normal wheat to sprout and deteriorate wheat quality. During purchase, too much malt will cause economic losses. At this stage, the judgment of wheat germination is generally by naked eyes, but it is still hard to detect early stage of germination especially when the changes are subtle in appearance. If the early detection was conducted by a chemical method, it is usually time consuming and the steps will be cumbersome, and it will be destructive to the sample. Therefore, it is necessary to screen a fast and nondestructive method to detect the germination degree of wheat, and to monitor and early-warn the germination of wheat. Hyperspectral imaging technology can not only reflect the external characteristics of the sample, but also reflect the internal structure and chemical composition. It is a fast and non-destructive detection technology. Such early judgement can properly serve the storage, processing and utilization of wheat. This study uses hyperspectral spectral information to classify and identify wheat with different germination degrees. First, collect the hyperspectral data of sprouted wheat (bubble, cracked skin, and white) and sprouted wheat (the bud length is half the length of the wheat grain, the bud length is the same as wheat kernel length). After processing, the average spectrum of each grain of wheat is extracted, and then a least squares-support vector machine (LS-SVM) classification model was established by four methods, including Savitzky-Golay convolution smoothing method, Savitzky-Golay convolution derivation method (1ST, 2ND), standard normal variable transformation (SNV). Among them, the recognition accuracy of SNV was the highest (91.70%). Secondly, particle swarm optimization (PSO) was used to optimize the parameters of the LS-SVM model and the kernel function parameters, the accuracy of the optimized model was 93.14% with an increase of 1.57%. Finally, in order to further reduce the amount of calculation and improve the accuracy, Competitive Adaptive Re-weighting Algorithm (CARS) was adopted to select 49 characteristic wavelengths, and the accuracy of this classification model was 94.13%. After determining the optimal model as PSO-CARS-SNV-LS-SVM system, it could quickly and nondestructive detect the wheat at different germination stages for classification, and finally achieve the purpose of visualization of classification results.

       

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