基于激光诱导击穿光谱(LIBS)的煤质可解释预测研究

Interpretable Prediction Research of Coal Based on Laser-Induced Breakdown Spectroscopy (LIBS))

  • 摘要: 激光诱导击穿光谱(LIBS)技术在煤质检测方面存在多物理场耦合干扰,基体效应显著,测量精度与重复性不高等问题。基于上述问题,本文提出一种基于RSM系统优化结合ANN-SHAP可解释分析的LIBS煤质工业分析指标在线预测方法。首先,研究聚焦于LIBS分析的非线性系统,构建了兼顾光谱信号质量与稳定性的多目标融合响应函数。设计了多因素多水平Box-Behnken析因试验方案,采用响应曲面法RSM进行数值分析,建立了LIBS分析系统的关键参数包括激光能量、激光频率、光谱仪延迟时间与响应函数的数学回归模型,完成了LIBS的系统优化并确定了最佳实验条件以获取质量良好的光谱数据。其次,采集样本数据为120组且波长范围为160-960 nm的四通道光谱信息,并采用基线校正、去噪、特征选择及内标等方法进行数据预处理。进而,基于遗传算法(GA)和人工神经网络(ANN)完成光谱数据建模,并进行结果评估。实验结果表明:所建发热量、灰分、水分、挥发分的定标模型在测试集上均表现良好,决定系数R2分别为0.971、0.987、0.975、0.968;均方根误差RMSE分别为0.58 MJ/kg、1.23%、0.78%、0.98%;预测结果的r分别为0.10%、0.21%、0.19%、0.24%,重复性限均达到国标要求。最后,针对人工神经网络的“黑箱”性质,引入SHAP分析方法对所建模型进行全局可解释性分析,揭示了模型决策机制与光谱特征对分析指标的非线性影响和贡献规律,从而提升了模型的可解释性与工程可信度。

     

    Abstract: Laser-induced breakdown spectroscopy (LIBS) technology faces challenges in coal quality analysis due to multi-physical field coupling interferences, significant matrix effects, and limited measurement accuracy and reproducibility. To address these issues, a method integrating RSM system optimization with ANN-SHAP interpretable analysis is proposed for online prediction of coal industrial analysis indicators using LIBS. First, focusing on the nonlinear characteristics of LIBS analysis, a multi-objective fusion response function considering both spectral signal quality and stability was constructed. A multi-factor, multi-level Box-Behnken design (BBD) was employed, and response surface methodology (RSM) was applied to establish mathematical regression models linking key LIBS system parameters—including laser energy, laser frequency, and spectrometer delay time—to the response function, thus completing system optimization and determining the optimal experimental conditions for acquiring high-quality spectral data.Second, sample data comprising 120 sets of four-channel spectra over a wavelength range of 160–960 nm were collected, and preprocessing steps including baseline correction, denoising, feature selection, and internal standardization were applied. Subsequently, spectral data modeling was performed using a genetic algorithm (GA) combined with an artificial neural network (ANN), and the model performance was evaluated. Experimental results demonstrated that the calibration models for calorific value, ash content, moisture, and volatile matter performed well on the test set, with coefficients of determination R2 of 0.971, 0.987, 0.975, and 0.968, root mean square errors RMSE of 0.58 MJ/kg, 1.23%, 0.78%, and 0.98%, and prediction repeatability r of 0.10%, 0.21%, 0.19%, and 0.24%, all meeting national standard requirements.Finally, to address the “black-box” nature of the artificial neural network, SHAP analysis was introduced to provide a global interpretable analysis of the model, revealing the decision mechanisms and the nonlinear contributions of spectral features to the coal quality indicators, thereby enhancing the interpretability and engineering reliability of the model.

     

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