陳洪月,王 鑫,毛 君,劉烈北,白楊溪
(1.遼寧工程技術(shù)大學(xué) 機(jī)械工程學(xué)院,遼寧 阜新 123000; 2.煤炭工業(yè)協(xié)會(huì) 高端綜采成套裝備動(dòng)力學(xué)測(cè)試與大數(shù)據(jù)分析中心,遼寧 阜新 123000)
采煤機(jī)整機(jī)非線性靜力學(xué)特性研究
陳洪月1,2,王 鑫1,毛 君1,劉烈北1,白楊溪1
(1.遼寧工程技術(shù)大學(xué) 機(jī)械工程學(xué)院,遼寧 阜新 123000; 2.煤炭工業(yè)協(xié)會(huì) 高端綜采成套裝備動(dòng)力學(xué)測(cè)試與大數(shù)據(jù)分析中心,遼寧 阜新 123000)
為研究大跨度、過(guò)約束條件下采煤機(jī)支撐滑靴受力特點(diǎn),考慮采煤機(jī)傾角及俯仰角等因素影響,構(gòu)建了18個(gè)載荷下的采煤機(jī)整機(jī)靜力學(xué)模型,針對(duì)模型系數(shù)矩陣的不確定性,提出采用改進(jìn)凝聚函數(shù)對(duì)采煤機(jī)靜力學(xué)方程的絕對(duì)值系數(shù)矩陣進(jìn)行了處理,獲取修正后的光滑非線性方程組,將截割實(shí)驗(yàn)下的滾筒三向力載荷作為輸入激勵(lì)代入到靜力學(xué)方程中,再利用Levenberg-Marguardt算法對(duì)方程組進(jìn)行求解,得到各滑靴受力的理論計(jì)算值,并與實(shí)際測(cè)量值進(jìn)行比較,誤差范圍在10%以?xún)?nèi),驗(yàn)證了理論模型的正確性。采用控制變量法分別改變采煤機(jī)傾角和俯仰角的取值,研究采煤機(jī)傾角和俯仰角變化對(duì)采煤機(jī)各滑靴受力的影響。研究結(jié)果表明:采煤機(jī)傾角變化對(duì)前后導(dǎo)向滑靴側(cè)推力影響較大,對(duì)前后導(dǎo)向滑靴以及平滑靴支撐力影響較小;采煤機(jī)傾角變化對(duì)各滑靴受力均有一定的影響,且受力變化呈近似線性關(guān)系。
采煤機(jī);Levenberg-Marguardt算法;光滑函數(shù);非線性靜力學(xué)
滾筒采煤機(jī)是綜采工作面的主要設(shè)備,其工作性能對(duì)工作面的產(chǎn)量、效益等有重要影響。采煤機(jī)工作環(huán)境復(fù)雜惡劣,工作傾角較大、工作強(qiáng)度高,俯采或仰采時(shí),使采煤機(jī)滑靴劇烈磨損,縮短滑靴的使用壽命,導(dǎo)致滑靴的失效[1-5]。為了避免采煤機(jī)滑靴的損壞,提高采煤機(jī)工作效率和節(jié)約配件損耗,諸多學(xué)者對(duì)采煤機(jī)力學(xué)特性作了相關(guān)研究,劉春生等[6-7]采用最小二乘算法對(duì)采煤機(jī)的力學(xué)模型進(jìn)行求解,得出采煤機(jī)實(shí)際工作過(guò)程中各個(gè)滑靴的受力情況;楊麗偉[8]依據(jù)經(jīng)典力學(xué)分析原理,建立采煤機(jī)整機(jī)在正常工況和斜切工況下的力學(xué)模型,運(yùn)用擬牛頓法對(duì)模型進(jìn)行求解,得出滑靴在正常工況和斜切工況下受力變化規(guī)律;李強(qiáng)等[9]考慮工作面傾角、俯仰角、機(jī)身擺角因素,建立了采煤機(jī)斜切進(jìn)刀工況下整機(jī)受力數(shù)學(xué)模型。本文考慮采煤機(jī)傾角及俯仰角等因素影響,構(gòu)建采煤機(jī)整機(jī)靜力學(xué)模型,采用Levenberg-Marguardt算法對(duì)模型進(jìn)行求解,并分析隨采煤機(jī)傾角和俯仰角變化采煤機(jī)各滑靴受力的影響。
滾筒采煤機(jī)整機(jī)所承受的載荷主要包括自身重力、牽引力、前后滾筒處的截割力沿x,y,z軸的三向截割分力Fgx,F(xiàn)gy,F(xiàn)gz,滑靴處的支反力及各支反力所對(duì)應(yīng)的滑動(dòng)摩擦力等。其中,滑靴所受的支反力包括各平滑靴處的垂直方向壓力、各導(dǎo)向滑靴處的垂直方向拉壓力和水平方向側(cè)向力?,F(xiàn)考慮工作面煤層有傾角和俯仰角的情況下,忽略所有傳動(dòng)齒輪的彈性、搖臂的振動(dòng)、滾筒的軸向位移等,得到滾筒采煤機(jī)整機(jī)受力的力學(xué)模型如圖1所示。
圖1 采煤機(jī)整機(jī)受力分析Fig.1 Mechanical analysis of Shearer
采煤機(jī)整機(jī)符號(hào)設(shè)定,令采煤機(jī)牽引力為Ft,前滾筒推進(jìn)載荷為Fgx1、截割載荷為Fgy1、軸向載荷為Fgz1、扭矩為Mg1;前滾筒推進(jìn)載荷為Fgx2、截割載荷為Fgy2、軸向載荷為Fgz2、扭矩為Mg2;前后導(dǎo)向滑靴的支撐力Fdy1,Fdy2;前后平滑靴的支撐力Fhy1,Fhy2;前后導(dǎo)向滑靴的側(cè)推力Fdz1,Fdz2;前后搖臂的擺角分別為α1,α2;采煤機(jī)的傾角、俯仰角分別為α,β,并規(guī)定采煤機(jī)開(kāi)采區(qū)低于采煤機(jī)采空區(qū)時(shí),傾角α為正值,從采煤機(jī)行進(jìn)方向看,采煤機(jī)前側(cè)滾筒低于后側(cè)滾筒時(shí),俯仰角β為正值。
針對(duì)型號(hào)為MG500/1130WD的采煤機(jī),本文給出該型號(hào)采煤機(jī)機(jī)身結(jié)構(gòu)尺寸參數(shù)如下:搖臂長(zhǎng)度R=2.4 m,搖臂鉸接點(diǎn)與機(jī)身底面的距離T=1.2 m,導(dǎo)向滑靴距整機(jī)中心L=2.9 m,平滑靴距整機(jī)中心N=3.1 m,平滑靴和導(dǎo)向滑靴在z向距離M=1.2 m,平滑靴和導(dǎo)向滑靴在y向距離J=0.25 m,截割臂的回轉(zhuǎn)鉸接點(diǎn)距機(jī)身中心H=1.2 m,整機(jī)重心距兩個(gè)平滑靴連線的距離W=0.35 m,整機(jī)重心與整機(jī)中心間的距離K=0.3 m,整機(jī)重心與平滑靴底板間的距離G=0.98 m,滑靴與刮板輸送機(jī)中部槽的摩擦因數(shù)為μ=0.2。
采煤機(jī)在工作時(shí),存在傾角和俯仰角,把采煤機(jī)在工作過(guò)程中,看成是勻速前進(jìn),是一個(gè)理想的力學(xué)模型,則采煤機(jī)整機(jī)的受力情況從靜力學(xué)角度來(lái)看,滿(mǎn)足力系和力矩平衡原理,受采煤機(jī)與刮板輸送機(jī)的摩擦影響,采煤機(jī)靜力學(xué)模型是含有絕對(duì)值項(xiàng),本文以方程這一特性進(jìn)行歸類(lèi)整理,寫(xiě)成廣義絕對(duì)值方程形式:
b=[b1b2b3b4b5b6]T
b1=(Fgx1+Fgx2-Ft)cosβ+mgsinβ
b2=mgcosβcosα-(Fgy1+Fgy2)cosβ
b3=Fgz1+Fgz2+mgsinα
從商業(yè)發(fā)展的角度來(lái)看,企業(yè)發(fā)展的根本是生產(chǎn)和銷(xiāo)售,唯利是圖是商業(yè)的本質(zhì)。但是作為國(guó)有企業(yè),肩負(fù)的不僅僅是利益的最大化,還需要對(duì)企業(yè)內(nèi)的員工進(jìn)行必不可少的思想政治教育,不少?lài)?guó)有企業(yè)以商業(yè)利益為根本,在選人提拔、晉升、年終考核等標(biāo)準(zhǔn)制定上,絕大部分因素保證都是商業(yè)利益、為企業(yè)的貢獻(xiàn),并沒(méi)有把思想政治扎實(shí)過(guò)硬作為必選項(xiàng)和一票否決項(xiàng)列在最前沿。換言之,往往選拔晉升的干部隊(duì)伍本身就是思想政治意識(shí)不強(qiáng),認(rèn)為技術(shù)、能力、對(duì)企業(yè)的貢獻(xiàn)遠(yuǎn)比思想政治工作有效,可想而知,領(lǐng)導(dǎo)的意識(shí)形態(tài)直接影響員工的思政政治導(dǎo)向,忽視了思想政治教育在日常生活和工作中的指導(dǎo)性。
b4=mgcosαcosβW+Fgz1(T+Rsinα1)+
Fgz2(T+Rsinα2)+(Fgy1+Fgy2)D
b5=(Fgx2-Fgx1)D+Fgz1(H+Rcosα1)-
Fgz2(H+Rcosα2)+mgsinβW
b6=-Fgy1(H+Rcosα1)+Fgy2(H+Rcosα2)-
Fgx1(T+Rcosα1)-Fgx2(T+Rcosα2)+
mgcosαcosβK+mgsinβG
由于采煤機(jī)整機(jī)靜力學(xué)方程(1)屬于廣義絕對(duì)值方程,而且方程過(guò)于復(fù)雜很難求解出解析解,又因?yàn)榻^對(duì)值函數(shù)不可導(dǎo)是一個(gè)不光滑函數(shù),不能使用雅可比矩陣,因此在選用數(shù)值方法求解時(shí)具有一定的局限性,因此可以先將絕對(duì)值函數(shù)光滑化,再利用數(shù)值算法對(duì)光滑化的采煤機(jī)整機(jī)靜力學(xué)方程進(jìn)行求解。
式中,μ>0。
為計(jì)算凝聚函數(shù)h(x)與絕對(duì)值函數(shù)|x|逼近誤差,構(gòu)造函數(shù)f(x),即
當(dāng)x>0時(shí),則有
∴f′(x)<0。
當(dāng)x<0時(shí),則有
∴f′(x)>0。
由式(4)和式(5)可知,f(x)在x>0時(shí)單調(diào)遞減,在x<0時(shí)單調(diào)遞增;則f(x)在x=0時(shí),取得最大值μln 2,f(x)在x=±處,取得最小值0,因此使用凝聚函數(shù)h(x)逼近絕對(duì)值函數(shù)|x|時(shí),誤差范圍與參數(shù)μ,通常情況下參數(shù)μ取0.01即可滿(mǎn)計(jì)算精度要求。
Levenberg-Marquardt算法是最有效的求解非線性方程組和最優(yōu)化問(wèn)題方法之一,具有全局收斂、收斂速度快、精度高等優(yōu)點(diǎn)[13-15],可以用來(lái)對(duì)采煤機(jī)整機(jī)靜力學(xué)方程組進(jìn)行求解,Levenberg-Marguardt算法需要用到Jacobian矩陣,對(duì)函數(shù)是否可導(dǎo)、連續(xù)性有一定的要求,因此可以先對(duì)采煤機(jī)整機(jī)靜力學(xué)方程組進(jìn)行光滑處理,并將方程轉(zhuǎn)化成無(wú)約束優(yōu)化問(wèn)題如下:
Levenberg-Marguardt算法框圖如圖2所示。
圖2 算法流程Fig.2 Algorithm block diagram
圖3 傳感器安裝及測(cè)試系統(tǒng)Fig.3 Sensor installation and test system schematic
采煤機(jī)滾筒載荷的確定是整機(jī)受力模型求解的前提,本文采用實(shí)驗(yàn)方法來(lái)獲取滾筒載荷,在張家口“國(guó)家能源煤礦采掘機(jī)械裝備研發(fā)(實(shí)驗(yàn))中心”進(jìn)行截割實(shí)驗(yàn),傳感器安裝及測(cè)試系統(tǒng)簡(jiǎn)圖如圖3所示,以MG500/1130WD型采煤機(jī)為研究對(duì)象,并在截齒上安裝DH1210型應(yīng)力傳感器,由線纜將檢測(cè)數(shù)據(jù)傳輸?shù)綗o(wú)線采集模塊上,通過(guò)無(wú)線傳輸?shù)姆绞浇?jīng)無(wú)線通訊主站接受模塊將數(shù)據(jù)傳遞給上位機(jī),在上位機(jī)中采用BeeData系統(tǒng)對(duì)傳輸數(shù)據(jù)進(jìn)行儲(chǔ)存和顯示,實(shí)驗(yàn)中的采煤機(jī)傾角α=0°、俯仰角β=0°,采樣頻率f=200 Hz,得到采煤機(jī)截齒三向力載荷,因?qū)嶒?yàn)中獲取的截齒載荷數(shù)據(jù)量較大,為了避免過(guò)多數(shù)據(jù)對(duì)模型求解過(guò)程繁瑣性的影響,根據(jù)實(shí)驗(yàn)中滾筒的轉(zhuǎn)速約為30 r/min,故取每0.5 s內(nèi)100個(gè)采樣數(shù)據(jù)點(diǎn)作均值,作為這一時(shí)刻采煤機(jī)截齒三向力的靜態(tài)載荷值,通過(guò)式(7)將截齒三向力的靜態(tài)載荷值轉(zhuǎn)換成前后滾筒靜態(tài)三向力及扭矩[16-20],得到的滾筒靜態(tài)載荷時(shí)間歷程圖,如圖4所示。
式中,n為滾筒上參與截割的截齒總數(shù);Rg為滾筒的半徑;φi為第i個(gè)截齒與滾筒豎直方向的夾角;Zi為第i個(gè)截齒上的截割阻力;Yi為第i個(gè)截齒上的推進(jìn)阻力;Xi為第i個(gè)截齒上的側(cè)向阻力。
圖4 滾筒載荷時(shí)間歷程曲線Fig.4 Time history plot of drum load
由3.1節(jié)得到的前、后滾筒靜態(tài)三向力及扭矩的載荷作為輸入激勵(lì)代入到采煤機(jī)整機(jī)靜力學(xué)方程式(6)中,運(yùn)用Levenberg-Marquard算法對(duì)公式進(jìn)行求解,設(shè)置參數(shù):凝聚系數(shù)μ=0.01,允許誤差ε=10-3,前搖臂擺角α1=22°,后搖臂擺角α2=8°,采煤機(jī)傾角α=0°,采煤機(jī)俯仰角β=0°,得出導(dǎo)向滑靴與支撐滑靴受力的理論計(jì)算值并與實(shí)驗(yàn)測(cè)量值作對(duì)比,得到對(duì)比曲線如圖5所示。
圖5 滑靴受力理論計(jì)算值與實(shí)際測(cè)量值對(duì)比曲線Fig.5 Comparison curves between the calculated values and the actual measured values of the shoes stress
由圖5可知,各滑靴受力的理論計(jì)算值與實(shí)測(cè)量值在各時(shí)間段上的趨勢(shì)基本相同,再對(duì)理論計(jì)算值和實(shí)際測(cè)量值在整個(gè)時(shí)間段內(nèi)分別取均值,其中理論計(jì)算出的前、后導(dǎo)向滑靴支撐力,前、后平滑靴支撐力,前、后導(dǎo)向滑靴側(cè)推力均值分別為:-125.9,440.9,70.7,282.6,-9.0,1.61 kN;對(duì)應(yīng)的實(shí)驗(yàn)值分別為:-136.1,473.1,75.9,298.0,-9.5,1.66 kN,由此可知理論計(jì)算值與實(shí)際測(cè)量值非常接近,誤差范圍在10%以?xún)?nèi),說(shuō)明理論計(jì)算值與實(shí)際測(cè)量具有一致性,能夠反映實(shí)際情況。
前文已經(jīng)驗(yàn)證了采煤機(jī)整機(jī)靜力學(xué)模型的正確性,保持其他參數(shù)條件不變,改變采煤機(jī)傾角α,將傾角α由0°變化到25°,使用Levenberg-Marquard算法對(duì)采煤機(jī)整機(jī)靜力學(xué)式(6)進(jìn)行求解,得到不同采煤機(jī)傾角下的前后導(dǎo)向滑靴支撐力、前后平滑靴支撐力和前后導(dǎo)向滑靴側(cè)推力的三維圖像如圖6所示,并將結(jié)果取均值得到不同采煤機(jī)傾角下滑靴受力變化曲線如圖7所示。
通過(guò)對(duì)圖7(a)分析可知,采煤機(jī)傾角α由0°變化到25°時(shí),各滑靴受力基本呈線性變化,前后導(dǎo)向滑靴支撐力Fdy1,F(xiàn)dy2和前后平滑靴支撐力Fhy1,Fhy2均有下降的趨勢(shì),但前導(dǎo)向滑靴支撐力Fdy1和前平滑靴支撐力Fhy1下降幅度較為平緩,變化范圍小;后導(dǎo)向滑靴側(cè)推力Fdz2有增加的趨勢(shì);前導(dǎo)向滑靴側(cè)推力Fdz1先減小后增大,并在α=5°左右時(shí)受力方向發(fā)生改變。
圖7 不同采煤機(jī)傾角和俯仰角下滑靴受力變化曲線Fig.7 Load curve of shearer sliding shoes force under different dip angle and elevation angle
考慮不同采煤機(jī)俯仰角對(duì)滑靴受力的影響,保持其他參數(shù)條件不變,改變采煤機(jī)俯仰角β,將俯仰角β由-10°變化到10°,使用Levenberg-Marquard算法對(duì)采煤機(jī)整機(jī)靜力學(xué)式(6)進(jìn)行求解,得到不同采煤機(jī)俯仰角下的導(dǎo)向滑靴支撐力、平滑靴支撐力和導(dǎo)向滑靴側(cè)推力的三維圖像如圖8所示,并將結(jié)果取均值得到不同采煤機(jī)俯仰角下滑靴受力變化曲線如圖7(b)所示。通過(guò)對(duì)圖7(b)分析可知,采煤機(jī)俯仰角β由-10°變化到10°時(shí),各滑靴受力基本呈線性變化,前后導(dǎo)向滑靴支撐力Fdy1,Fdy2和后平滑靴支撐力Fhy2有增加的趨勢(shì);前平滑靴支撐力Fhy1先減小后增大,在β=2.5°左右時(shí)取得最小值;前導(dǎo)向滑靴側(cè)推力Fdz1先減小后增大,并在β=0°左右時(shí)受力方向發(fā)生改變;后導(dǎo)向滑靴側(cè)推力Fdz2先減小,并在β=0°左右時(shí)變化減小并趨于平穩(wěn)。
圖8 不同采煤機(jī)俯仰角下采煤機(jī)滑靴受力三維圖像Fig.8 Load 3-D image of shearer sliding shoes force under different elevation angle
(1)采煤機(jī)傾角對(duì)前后導(dǎo)向滑靴支撐力Fdy1,Fdy2,前后平滑靴支撐力Fhy1,Fhy2影響較小,對(duì)前后導(dǎo)向滑靴側(cè)推力Fdz1,Fdz2影響較大;前后導(dǎo)向滑靴支撐力Fdy1,Fdy2前后平滑靴支撐力Fhy1,Fhy2受采煤機(jī)俯仰角變化較大,且變化呈近似線性關(guān)系。
(2)采煤機(jī)傾角α由0°變化到25°時(shí),前后導(dǎo)向滑靴支撐力Fdy1,Fdy2和前后平滑靴支撐力Fhy1,Fhy2均有下降的趨勢(shì);后導(dǎo)向滑靴側(cè)推力Fdz2有增加的趨勢(shì);前導(dǎo)向滑靴側(cè)推力Fdz1在α=5°左右時(shí)受力方向發(fā)生改變。
(3)采煤機(jī)俯仰角β由-10°變化到10°時(shí),前平滑靴支撐力Fhy1先減小后增大,在β=2.5°左右時(shí)取得最小值;前導(dǎo)向滑靴側(cè)推力Fdz1先減小后增大,并在β=0°左右時(shí)受力方向發(fā)生改變。
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Researchonnonlinearstaticcharacteristicsofshearer
CHEN Hongyue1,2,WANG Xin1,MAO Jun1,LIU Liebei1,BAI Yangxi1
(1.CollegeofMechanicalEngineering,LiaoningTechnicalUniversity,Fuxin123000,China; 2.CenterforDynamicResearchonHigh-endCompleteIntegratedCoalMiningEquipmentandBigDataAnalysis,ChinaNationalCoalAssociation,Fuxin123000,China)
To study the force characteristics of support boots of a shearer under the conditions of large span and over constraint,the static model of the shearer under 18 loads was established by considering the factors including the roll and pitch angles.Aiming at the uncertainty of model coefficient matrix,an improved aggregation function was proposed to deal with the absolute coefficient matrix of the shearer static equations,and the modified smooth nonlinear equations were obtained.The three-axis forces of the drum obtained by the cutting experiment were input into the static equations as the excitation,the Levenberg-Marguardt method was used to solve the equations,and the theoretical values of boots were calculated and compared with the actual measured values.According to the error range less than 10%,the correctness of the theoretical model was verified.By applying the control variable method,the roll and pitch angles of the shearer were changed respectively to research the force characteristics variation of the shearer boots.The results show that the influences of the roll angle variation to the lateral forces of the front and rear guiding sliding boots were bigger,and to the support forces of the front and rear sliding boots and the flat sliding boots were smaller.The forces of all boots were influenced by the shearer roll angle variation,and the force variations were approximately linear.
shearer;Levenberg-Marguardt algorithm;smooth function;nonlinear statics
陳洪月,王鑫,毛君,等.采煤機(jī)整機(jī)非線性靜力學(xué)特性研究[J].煤炭學(xué)報(bào),2017,42(11):3051-3058.
10.13225/j.cnki.jccs.2017.0728
CHEN Hongyue,WANG Xin,MAO Jun,et al.Research on nonlinear static characteristics of shearer[J].Journal of China Coal Society,2017,42(11):3051-3058.doi:10.13225/j.cnki.jccs.2017.0728
TD421.6
A
0253-9993(2017)11-3051-08
2017-05-28
2017-09-07責(zé)任編輯許書(shū)閣
國(guó)家能源研發(fā)(實(shí)驗(yàn))中心重大資助項(xiàng)目(2010_215);國(guó)家自然科學(xué)基金資助項(xiàng)目(51774162)
陳洪月(1982—),男,遼寧海城人,教授,博士生導(dǎo)師。E-mail:chyxiaobao@126.com