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基于LDV和可解释1D-CNN的皇冠梨硬度预测方法

Crown pear firmness prediction based on LDV and interpretable 1D-CNN

  • 摘要: 为研究皇冠梨振动频率特征与果实硬度的关系,改善现有研究中常规预测模型精度较低而深度学习模型缺乏可解释性的问题。该研究通过激光多普勒测振仪(laser doppler vibrometer,LDV)采集皇冠梨振动数据,采用一维卷积神经网络(one dimensional-convolutional neural network,1D-CNN)算法建立基于振动数据的皇冠梨硬度预测模型,并使用深度沙普利加性解释(deep shapleyadditive explanations,Deep SHAP)框架对预测模型进行解释。通过与其他经典预测模型相比,1D-CNN预测模型可以利用特征频率实现对皇冠梨硬度的高精度预测(RP2=0.945,RMSEP=0.594N/mm和RPDP=4.272)。基于SHAP框架解释的结果表明,皇冠梨300~700 Hz频率特征与硬度联系密切。该研究展示了1D-CNN模型在水果硬度预测应用中的优异性能和巨大潜力,为振动特征频率应用于硬度预测和分析的研究提供理论基础。

     

    Abstract: The Crown pear is the primary fresh pear variety for consumption in China. Consumers prefer this pear because it has high juice content, high sweetness, and rich nutritional value. Firmness represents one of the most important quality indicators for pears. It directly shows how ripe the pear is and how well the pear can be stored after harvest. For these reasons, it is very important to measure pear firmness accurately. However, traditional methods for measuring fruit firmness mainly depend on destructive tests. These include the Magness-Taylor puncture test and compression tests. These destructive testing methods lead to large amounts of food waste. Because of this waste problem, these methods cannot be used on a large scale. This research aims to examine the connection between fruit firmness and vibration frequency features in Crown pears. It also works to solve two issues with current studies: regular prediction models have low accuracy, while deep learning models are difficult to understand. In order to achieve this, the study improved the standard convolutional neural network model. It created a new recognition model that combines an improved convolutional neural network with Deep Shapley Additive Explanations. The experiment used 508 Crown pears as test samples. The samples were split into five different groups. Each group was tested every thirteen days. Vibration data from the Crown pears was gathered using a Laser Doppler Vibrometer (LDV). The research applied an improved one-dimensional convolutional neural network method to build a firmness prediction model. This model was based on characteristic frequencies. It also used the Deep Shapley Additive Explanations (Deep SHAP) structure to help explain how the prediction model functions. The research compared this new model with several standard prediction models. These standard models were: partial least squares regression, support vector regression, extreme gradient boosting, and adaptive gradient boosting. The results show that the improved one-dimensional convolutional neural network prediction model can achieve high-precision prediction of Crown pear hardness using feature frequencies the RP2 was 0.945, the RMSEP was 0.594N/mm, and the RPDP was 4.272, and outperforms all traditional models across all metrics, with the most notable performance: its R2 value is closest to the ideal value of 1, the RMSE is the lowest, at only 68.5% of the next-best XGBoost model, and the RPD value is significantly higher than other models, reflecting superior generalization ability.The results made it clear that the improved one-dimensional convolutional neural network prediction model could use characteristic frequencies to predict Crown pear firmness with great accuracy. The explanations from the Deep SHAP structure showed one key discovery. Vibration frequency features between 300 Hertz and 700 Hertz have a strong relationship with pear firmness. The interpretable deep learning model constructed in this study based on LDV vibration data achieves high-precision prediction while improving the interpretability and practicality of the model. It reveals the correlation between characteristic frequency and firmness, providing an efficient and reliable new method for non-destructive testing of Crown pear firmness, and also providing a theoretical basis for research in the field of fruit quality assessment.

     

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