基于改进VMD和GA-BP神经网络的砂岩破裂过程预测方法

Method of predicting sandstone fracture process based on improved VMD and GA-BP neural network

  • 摘要: 为提取有效的砂岩破裂声发射信号特征, 提高砂岩破裂过程预测精度, 提出一种基于改进变分模式分解算法(VMD)和GA-BP神经网络的预测方法。首先, 开展单轴压缩实验进行砂岩破裂试验, 并采集破裂过程的声发射信号; 其次, 为取得有效声发射信号, 从中提取出有效特征参数进行预测, 引入相关系数改进VMD算法并对原始声发射信号进行预处理, 提取信号能量特征参数作为模型的输入以便区分破裂过程; 最后构建GA-BP预测模型, 通过遗传算法(GA)优化BP神经网络的权值和阈值, 将信号能量作为样本用于预测模型的训练。结果表明, 通过引入相关系数可有效解决VMD算法中K值难以选取的问题, 对采集到的声发射信号进行有效去噪; 此外, 经GA算法改进后的BP神经网络预测模型能够准确预测破裂状态, 相较于改进前传统的BP神经网络模型稳定性更高, 收敛能力更好, 预测准确率提高17.5%。

     

    Abstract: In order to extract effective acoustic emission signal characteristics of sandstone fracture and improve the accuracy of predicting sandstone fracture process, a prediction method based on improved variational mode decomposition (VMD) algorithm and GA-BP neural network was proposed. Firstly, uniaxial compression experiments were carried out to simulate the process of sandstone fracture, and the AE signals of fracture process were collected; secondly, in order to obtain effective AE signals, the effective characteristic parameters were extracted for prediction, the correlation coefficient was introduced to improve VMD algorithm, the original AE signals were preprocessed, and the signal energy characteristic parameters were extracted as the input of the model so as to distinguish fracture process. Finally, the GA-BP prediction model was constructed, the weights and thresholds of BP neural network were optimized by genetic algorithm (GA), and the signal energy was used as a sample to train the prediction model. The results showed that the introduction to correlation coefficient could effectively solve the problem that K value was difficult to select in VMD algorithm, and the collected acoustic emission signals could be effectively de-noising; in addition, the BP neural network prediction model improved by GA algorithm could accurately predict the fracture state; compared with the traditional BP neural network model before the improvement, the stability of the improved one was higher, with better convergence ability, and prediction accuracy increased by 17.5%。

     

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