發(fā)布時間：2018-06-02 13:33

  本文選題：氣閥 + 故障診斷��； 參考：《電子科技大學》2017年碩士論文

【摘要】：隨著科學技術的不斷發(fā)展,機械故障診斷技術越來越受到人們的重視。往復式壓縮機作為典型的往復式機械,其內部結構復雜且激勵源眾多,傳統(tǒng)的故障診斷技術已不能滿足工程實際的需要。貝葉斯網絡在處理不確定知識表達和推理方面具有獨特的優(yōu)勢,已在語音識別、圖像處理、金融分析等多個領域成功應用。因此,本文提出了基于貝葉斯網絡的氣閥故障診斷方法,該方法以氣閥常見故障為對象,在研究了貝葉斯網絡相關理論的基礎上,從不同的角度建立貝葉斯網絡結構學習算法,為其在故障診斷中的應用提供了有力的證據。文章在最后重點構建了兩類貝葉斯分類模型,并將其成功應用于氣閥故障診斷中。本文具體工作包含以下幾個方面:1.闡述了貝葉斯網絡的基本理論,并簡單介紹了貝葉斯網絡結構學習方法、參數學習方法和常見的四種貝葉斯分類器。2.針對氣閥振動加速度信號,首先對原始信號進行小波閾值去噪,并通過小波包算法提取了各故障特征向量。將特征向量值與類變量值組成的樣本進行離散化處理,將此作為貝葉斯分類器的輸入。3.針對氣閥常見故障,本文提出了一種BAN分類器算法。該算法首先利用遺傳算法和K2算法構造屬性節(jié)點之間的網絡結構,然后加入這些節(jié)點的統(tǒng)一父節(jié)點(類節(jié)點)構造出分類模型,運用貝葉斯估計算法進行參數學習以獲得各節(jié)點對應的條件概率表。根據測試樣本集,以條件屬性值作為證據,可求得測試樣本的后驗概率,最大后驗概率所對應的類標簽即作為該樣本的分類結果。4.針對氣閥常見故障,本文提出了一種GBN分類器算法。該算法首先利用CI測試去除與當前節(jié)點變量無關的變量,從而縮小了各節(jié)點的初始候選父節(jié)點集合的范圍;通過貪心算法不斷更新各節(jié)點的候選父節(jié)點,最終獲得所求的分類模型。本文利用稀疏分數的方法進行故障特征選擇,提取不同數量的特征集合,并利用GBN分類器進行分類預測。實驗結果表明,通過該特征選擇方法可以有效地提高氣閥故障診斷正確率和減少計算的復雜度。5.總結了全文,并提出了下一步的研究方向。
[Abstract]:With the development of science and technology, people pay more and more attention to mechanical fault diagnosis technology. As a typical reciprocating machine, the reciprocating compressor has complex internal structure and numerous excitation sources. The traditional fault diagnosis technology can not meet the practical needs of engineering. Bayesian network has a unique advantage in dealing with uncertain knowledge representation and reasoning, and has been successfully applied in speech recognition, image processing, financial analysis and other fields. Therefore, this paper presents a method of valve fault diagnosis based on Bayesian network. This method takes common faults of air valve as an object, and establishes Bayesian network learning algorithm from different angles on the basis of studying relevant theory of Bayesian network. It provides strong evidence for its application in fault diagnosis. Finally, two kinds of Bayesian classification models are constructed and successfully applied to valve fault diagnosis. The specific work of this paper includes the following aspects: 1. The basic theory of Bayesian network is expounded, and the learning methods of Bayesian network structure, parameter learning and four kinds of Bayesian classifiers. For the vibration acceleration signal of the valve, the original signal is firstly de-noised by wavelet threshold, and each fault eigenvector is extracted by wavelet packet algorithm. The sample composed of eigenvector value and class variable value is discretized as the input of Bayesian classifier. In this paper, a BAN classifier algorithm is proposed for the common faults of the valve. Firstly, the network structure between attribute nodes is constructed by genetic algorithm and K2 algorithm, and then the classification model is constructed by adding the unified parent nodes (class nodes) of these nodes. Bayesian estimation algorithm is used for parameter learning to obtain conditional probability tables corresponding to each node. According to the test sample set, the posteriori probability of the test sample can be obtained by taking the conditional attribute value as the evidence. The class label corresponding to the maximum posteriori probability is regarded as the classification result of the sample. In this paper, a GBN classifier algorithm is proposed for the common faults of the valve. Firstly, the CI test is used to remove the variables independent of the current node variables, which reduces the range of the initial candidate parent node set of each node, and updates the candidate parent nodes of each node through greedy algorithm. Finally, the desired classification model is obtained. In this paper, the method of sparse fraction is used for fault feature selection, and different number of feature sets are extracted, and GBN classifier is used for classification and prediction. The experimental results show that this method can effectively improve the accuracy of gas valve fault diagnosis and reduce the computational complexity of .5. This paper summarizes the full text and puts forward the next research direction.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH45;TP18

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本文編號：1968942