高佳南 吳奉亮 馬礪 賀雁鵬
摘要:礦井進風井筒風溫的準確預測對于井下風流的熱計算至關重要。為提高礦井井筒風溫預測精度,在結合礦井生產(chǎn)特點和參考有關淋水井筒風溫預測研究的基礎上,采用粒子群算法(PSO)對支持向量回歸(SVR)參數(shù)進行優(yōu)化,建立礦井淋水井筒風溫PSO-SVR預測模型,并與利用同樣的訓練和測試樣本建立的常規(guī)SVR預測模型和多元線性回歸(MLR)預測模型進行比較。結果表明:對于訓練和測試樣本,MLR預測模型的預測與觀測值散點分散于標準線四周,相比于MLR預測模型,常規(guī)SVR預測模型的散點較集中于標準線周圍,而經(jīng)過PSO優(yōu)化后的SVR預測模型的散點均緊密分布在標準線附近,說明PSO-SVR預測模型具有更好的預測精度,更強的泛化性;MLR預測模型、常規(guī)SVR預測模型和PSO-SVR預測模型的測試樣本預測結果的平均絕對百分比誤差分別為3.43%,1.27%和0.37%,常規(guī)SVR預測模型較MLR預測模型的預測結果改進比約63%,PSO-SVR預測模型較常規(guī)SVR預測模型的預測結果改進比約71%,表明PSO-SVR預測模型的預測效果顯著優(yōu)于MLR預測模型和常規(guī)SVR預測模型,該模型適用于礦井淋水井筒風溫的預測。
關鍵詞:淋水井筒;風溫預測;粒子群優(yōu)化算法;支持向量回歸
中圖分類號:TD 727文獻標志碼:A
文章編號:1672-9315(2022)03-0476-08
DOI:10.13800/j.cnki.xakjdxxb.2022.0310開放科學(資源服務)標識碼(OSID):
PSO-SVR prediction method of airflow temperature
of shaft with water dropping in mine
GAO Jianan WU Fengliang MA Li HE Yanpeng
(1.College of Safety Science and Engineering,Xian University of Science and Technology,Xian 710054,China;
2.Key Laboratory of Western Mine Exploitation and Hazard Prevention,Ministry of Education,
Xian University of Science and Technology,Xian 710054,China)Abstract:The accurate prediction of airflow temperature in air intake shaft of mine of great significance for the thermal calculation of underground mine airflow.In order to improve the prediction accuracy of airflow temperature in air intake shaft of mine,based on the characteristics of mine production and the study of the prediction of airflow temperature of shaft with water dropping,particle swarm optimization(PSO)is used to optimize the parameters of support vector regression(SVR),and the PSO-SVR prediction model of airflow temperature of shaft with water dropping in mine is established.The conventional SVR prediction and multiple linear regression(MLR)models are established by using the same training and testing samples,with the predicted results of PSO-SVR model compared.It is found? that for training and testing samples,the scatter points of prediction and observation values of MLR prediction model are scattered around the standard line.Compared with MLR prediction model,the scatter points of conventional SVR prediction model are more concentrated around the standard line,while the scatter points of SVR prediction model after PSO optimization are closely distributed near the standard line,which indicates that PSO-SVR prediction model has better prediction accuracy and stronger generation capacity.The mean absolute percentage errors of MLR prediction model,conventional SVR prediction model and PSO-SVR prediction model are 3.43%,1.27% and 0.37%,respectively.The improvement ratio of conventional SVR prediction model is about 63% compared with MLR prediction model,and the improvement ratio of PSO-SVR prediction model is about 71% compared with conventional SVR prediction model.The prediction effect of PSO-SVR prediction model is better than MLR prediction model and conventional SVR prediction model.The model is suitable for the prediction of airflow temperature of shaft with water dropping in mine.F191FC4A-792D-4749-8D0F-AA5A93EAF57B
Key words:shaft with water dropping;air temperature prediction;particle swarm optimization(PSO);support vector regression(SVR)
0引言
隨著礦井開采深度的加大,井下風溫不斷升高,熱害問題日益突出,嚴重制約著深部煤炭資源的安全高效開采[1-2]。為充分掌握井巷風流熱力狀態(tài)變化規(guī)律,準確評估礦井熱害程度,從而制定科學合理的降溫方案,改善井下高溫作業(yè)環(huán)境,進而保護工作人員的身心健康,礦井風溫預測研究至關重要[3]。
國內外眾多學者對礦井風溫預測做了大量研究。LOWNDES等構建了巷道氣候預測模型并分析了有關熱力參數(shù)[4];KRASNOSHTEIN等基于拉普拉斯變換確定了圍巖與風流間非穩(wěn)態(tài)換熱的積分表達式[5];侯祺棕等分析了風溫與風流濕度間變化的相關關系,并建立了將風溫與風流濕度相結合的預測模型[6];張習軍研究了井下風溫的線性回歸計算式[7];高建良等通過對飽和空氣含濕量與溫度進行二次曲線擬合來處理巷壁水分蒸發(fā),并解算出風溫及濕度的變化規(guī)律[8];孔松等利用有限差分方法建立了進風井筒及巷道的風溫迭代預測模型[9]。從上述文獻中可以看出,礦井風溫預測方法主要有實驗室模型模擬法、數(shù)學分析法、實測回歸統(tǒng)計法等[10-12]。實驗室模型模擬法往往受實驗條件所限,預測精度很難精確[13]。數(shù)學分析法是通過傳熱學理論建立熱傳導方程,計算精度相對較高,而實際條件復雜,涉及的熱物性等基礎參數(shù)各異且難以獲取,在計算方法上采取了假設簡化,影響風溫預測精度[14]。實測回歸統(tǒng)計法是在現(xiàn)場實測數(shù)據(jù)基礎上進行回歸預測,解決了應用理論方法求解風溫的困難,但風溫與其他參數(shù)之間存在著某種非線性關系,該方法下的風溫預測精度不佳[15-16]。近年來機器學習的智能算法在礦井風溫預測方面有所應用,如BP神經(jīng)網(wǎng)絡[15,17-18]、支持向量機(SVM)[19]等。BP神經(jīng)網(wǎng)絡具有優(yōu)越的非線性處理能力,但其預測精度受學習樣本規(guī)模的影響較大,且易出現(xiàn)模型在訓練樣本中擬合效果好,而在測試樣本表現(xiàn)差的過擬合現(xiàn)象,泛化性能較低[20];SVM是一種基于統(tǒng)計學習理論的機器學習算法,具有嚴格的數(shù)學邏輯,能夠較好地解決小型數(shù)據(jù)樣本、高維度、非線性的問題,學習與泛化能力強,將SVM推廣到回歸問題可得到支持向量回歸SVR[21],能夠處理井巷風溫與其影響因素之間存在的非線性函數(shù)關系。
礦井入風井筒風溫是井下空氣熱計算的重要節(jié)點,其風溫關系到整個礦內的熱環(huán)境。當井筒有淋水現(xiàn)象時,其風溫的求解涉及到風流與淋水水滴混合流的復雜熱交換,因此,理論計算淋水井筒風溫較為困難[22]。另外,許多學者在井筒風溫預測研究中未考慮淋水的存在[16],導致預測結果不理想?;谏鲜龇治觯闹刑岢隼弥С窒蛄炕貧w法(SVR)來預測礦井淋水井筒風溫,并利用粒子群算法(PSO)對支持向量回歸參數(shù)進行優(yōu)化,建立參數(shù)優(yōu)化的支持向量回歸模型(PSO-SVR),以期獲得準確的礦井淋水井筒風溫預測方法。
1礦井淋水井筒風溫PSO-SVR預測模型
1.1支持向量回歸SVR
1.2粒子群優(yōu)化算法
PSO算法的基本思想是:模擬鳥群根據(jù)自身經(jīng)驗和種群交流來調整搜尋路徑繼而尋找到食物的捕食行為。在PSO算法中,用粒子代表優(yōu)化問題的解,粒子特征用位置、速度來描述,優(yōu)化求解首先是在搜索空間中隨機初始化每個粒子的速度和位置,根據(jù)粒子的適應度函數(shù)值,迭代搜索最優(yōu)解。每次迭代搜尋時粒子都會根據(jù)自身歷史最優(yōu)位置和粒子種群當前最優(yōu)位置來更新自身的搜尋速度和位置,最終找到最優(yōu)解。
1.3預測結果評價
對于礦井淋水井筒風溫預測回歸模型的預測結果,文中采用平均絕對誤差MAE,平均絕對百分比誤差MAPE,均方誤差MSE等3項統(tǒng)計量對其預測效果進行評價。其中,
2PSO-SVR預測模型建立
利用PSO優(yōu)選SVR的懲罰因子C和核函數(shù)參數(shù)g,建立井筒風溫PSO-SVR預測模型,其尋優(yōu)預測過程如圖1所示。主要步驟如下。
1)訓練和測試樣本數(shù)據(jù)歸一化。將訓練和測試樣本數(shù)據(jù)按式(11)(12)歸一化在[0,1]區(qū)間
式中xti為特征屬性t的原始輸入數(shù)據(jù);min{xti}為特征屬性t的原始輸入數(shù)據(jù)最小值;max{xti}為特征屬性t的原始輸入數(shù)據(jù)最大值。
式中yi為原始輸出數(shù)據(jù);min{yi}為原始輸出數(shù)據(jù)最小值;max{yi}為原始輸出數(shù)據(jù)最大值。
2)PSO初始化。算法參數(shù)的初始化:設定粒子群算法最大進化代數(shù)為100,種群數(shù)目20,懲罰因子C∈[0.1,100],核函數(shù)參數(shù)g∈[0.01,100],局部搜索能力c1=1.5,全局搜索能力c2=1.7,對訓練樣本進行5折交叉驗證;種群20個粒子的位置和速度初始化。
3)計算每個粒子的適應度。初始化的粒子位置向量(C,g)輸入SVR后建模,將預測結果的均方誤差作為對應粒子的適應度。
4)優(yōu)選個體適應度。比較20個粒子的適應度,以適應度最小為最優(yōu),得到當前群體的最優(yōu)位置。
5)迭代更新種群適應度,獲得最優(yōu)SVR參數(shù)(C,g)。按照式(6)、式(7)分別更新種群粒子的位置和速度,重復步驟3)4),更新優(yōu)選出種群最小適應度,對應粒子的(C,g)為最優(yōu)位置向量,即最優(yōu)SVR參數(shù)。
6)將訓練樣本輸入SVR,最優(yōu)SVR參數(shù)(C,g)賦值于SVR,建立礦井淋水井筒風溫PSO-SVR預測模型。
3礦井淋水井筒風溫預測算例分析
3.1樣本數(shù)據(jù)F191FC4A-792D-4749-8D0F-AA5A93EAF57B
結合礦井生產(chǎn)特點,并參考有關礦井淋水井筒風溫預測研究[16],綜合分析選取了地面氣候參數(shù)及井深作為影響井筒風溫的因素,因此礦井淋水井筒風溫PSO-SVR預測模型的特征向量由地面風溫、地面空氣相對濕度、地面大氣壓、井深構成,輸出變量為井底風溫。選用有關礦井淋水井筒溫度預測研究文獻[11,15,16,19]中近30個礦井共65組實測數(shù)據(jù)作為樣本數(shù)據(jù)。樣本數(shù)據(jù)部分內容見表1。其中前50組實測數(shù)據(jù)作為訓練集,用于構建模型,后15組實測數(shù)據(jù)作為測試集,對已訓練好的模型進行預測效果檢驗。
3.2預測結果對比分析
為研究礦井淋水井筒風溫PSO-SVR預測模型的預測效果,表2列出了其他2種礦井淋水井筒風溫預測模型。利用同樣的訓練和測試樣本數(shù)據(jù),將3種礦井淋水井筒風溫預測模型預測精度和預測誤差進行對比。礦井淋水井筒風溫MLR預測模型是根據(jù)最小二乘法原理尋求礦井淋水井筒風溫與地面入風氣候參數(shù)及井深間的最佳線性回歸函數(shù),實現(xiàn)對礦井淋水井筒風溫的預測。礦井淋水井筒風溫SVR預測模型中,取懲罰因子C為1,核函數(shù)參數(shù)g為0.25。利用LIBSVM工具箱,編寫PSO算法程序對SVR參數(shù)進行尋優(yōu),確定最優(yōu)懲罰因子C為30.1096,核函數(shù)參數(shù)g為0.010,建立PSO優(yōu)化后的礦井淋水井筒風溫SVR預測模型。采用上述3種礦井淋水井筒風溫預測模型對訓練和測試樣本進行預測,井底風溫的預測值與其現(xiàn)場實際觀測值散點圖如圖2和圖3所示,圖中橫坐標為井底風溫現(xiàn)場實際觀測值,縱坐標為3種預測模型的井底風溫預測值,直線y=x為預測標準線,分布于該直線上的點的井底風溫預測值等于其現(xiàn)場實際觀測值,即預測誤差為零。
從圖2和圖3可以看出,3種礦井淋水井筒風溫預測模型中,MLR預測模型的訓練和測試樣本的預測與觀測值散點分散于標準線四周,對比MLR預測模型,常規(guī)SVR預測模型的預測與觀測值散點較集中分布于標準線周圍,而經(jīng)過PSO優(yōu)化后的SVR預測模型的訓練和測試樣本的預測與觀測值散點均集中在標準線附近,說明3種礦井淋水井筒風溫預測模型中,MLR預測模型預測結果偏差最大,PSO-SVR預測模型具有更好的預測精度,更強的泛化性。
圖4給出了3種礦井淋水井筒風溫預測模型的預測值和觀測值的比較曲線??梢钥闯?,3種礦井淋水井筒風溫預測模型下測試樣本的預測值與觀測值曲線的趨勢基本一致,相比于MLR預測模型和常規(guī)SVR預測模型,PSO-SVR預測模型的預測值與觀測值曲線更為接近,說明該模型擬合效果更好。
為更直觀地對比3種礦井淋水井筒風溫預測模型的預測效果,表3給出了3種礦井淋水井筒風溫預測模型下測試樣本的預測結果的MAE,MAPE和MSE。
從表3可知,相比于礦井淋水井筒風溫MLR預測模型,常規(guī)SVR預測模型的預測結果的MAE與MAPE均提升約63%,MSE提升約85%,說明常規(guī)SVR預測模型預測效果好于MLR預測模型;相對于常規(guī)SVR預測模型,PSO-SVR預測模型的預測結果的MAE與MAPE均提升約71%,MSE提升約92%,表明在礦井淋水井筒風溫預測中PSO-SVR預測模型具有更好的預測效果,同時也說明了優(yōu)化SVR參數(shù)對提高礦井淋水井筒風溫預測精度有明顯作用。
4結論
1)提出了礦井淋水井筒風溫PSO-SVR預測方法。利用粒子群優(yōu)化算法對支持向量回歸參數(shù)進行尋優(yōu),建立了礦井淋水井筒風溫PSO-SVR預測模型,實現(xiàn)了對礦井淋水井筒風溫的預測,為礦井風溫預測提供了一種人工智能新方法。
2)礦井淋水井筒風溫PSO-SVR預測模型具有更高的預測精度。對比礦井淋水井筒風溫MLR預測模型的預測結果,SVR預測模型的預測精度有一定提高,而采用PSO對SVR進行參數(shù)尋優(yōu)后的預測模型的預測值更逼近于觀測值,說明礦井淋水井筒風溫PSO-SVR預測模型有更好的預測效果,這也表明了SVR參數(shù)優(yōu)化對于提高礦井淋水井筒風溫預測精度有重要作用。
3)本研究所建立的礦井淋水井筒風溫PSO-SVR預測模型是將地面入風氣候參數(shù)及井深作為主要影響因素對礦井淋水井筒風溫進行預測,后續(xù)工作可考慮圍巖熱物性參數(shù)、風量等因素,建立礦井淋水井筒風溫PSO-SVR預測模型,同時也可嘗試將本研究應用于礦井采掘工作面風溫預測工作當中。
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