龐 濤,楊 霄,陳曉燕,陶懷亮,李蒙良
氣體傳感器鑒別花椒產(chǎn)地研究
龐 濤1,楊 霄1,陳曉燕2,3※,陶懷亮1,李蒙良1
(1. 四川農(nóng)業(yè)大學(xué)機(jī)電學(xué)院,雅安 625000; 2. 四川農(nóng)業(yè)大學(xué)信息工程學(xué)院,雅安 625000;3. 四川農(nóng)業(yè)大學(xué)農(nóng)業(yè)信息工程四川省重點(diǎn)實(shí)驗(yàn)室,雅安 625000)
目前花椒產(chǎn)地鑒別基本以感官評(píng)定為主,缺乏客觀性,在實(shí)施應(yīng)用時(shí)難以做到量化和標(biāo)準(zhǔn)化,難以做出判斷。因此設(shè)計(jì)研發(fā)一種快速鑒別花椒的智能裝置。該裝置以氣體傳感器陣列為核心,能夠獨(dú)立對(duì)花椒氣味信息進(jìn)行檢測(cè)和鑒別,區(qū)分不同產(chǎn)地的同類(lèi)花椒。利用主成分分析和Wilks Λ統(tǒng)計(jì)分析對(duì)檢測(cè)數(shù)據(jù)進(jìn)行處理。提取主成分5個(gè),累積貢獻(xiàn)率為94.41%,其對(duì)應(yīng)Fisher判別模型訓(xùn)練集平均準(zhǔn)確率達(dá)到88.6%,驗(yàn)證集90%,Wilks Λ統(tǒng)計(jì)分析最終選取8個(gè)變量,其對(duì)應(yīng)判別Fisher模型訓(xùn)練集平均準(zhǔn)確率91.82%,驗(yàn)證集95%。對(duì)Wilks Λ統(tǒng)計(jì)所選取變量建立細(xì)分類(lèi)交叉驗(yàn)證的Fisher判別模型,平均正確率達(dá)到97.27%,將模型移植到采集裝置,完成智能花椒品種鑒別裝置。該方法是一種簡(jiǎn)便高效的花椒品種鑒別方法,可為今后進(jìn)一步研究花椒產(chǎn)地、分級(jí)提供檢測(cè)儀器和理論依據(jù)。
傳感器;農(nóng)作物;氣體監(jiān)測(cè)器;花椒產(chǎn)地鑒別;Fisher判別
花椒是中國(guó)的重要經(jīng)濟(jì)作物,中國(guó)西部地區(qū)如四川、陜西、甘肅、青海等地花椒種植的面積很大,成為重要的經(jīng)濟(jì)作物甚至是地方經(jīng)濟(jì)的支柱產(chǎn)業(yè)[1]。市面上花椒品種眾多,外形、色澤、風(fēng)味各不相同,這也造成了不同品種的花椒價(jià)格差異很大,中國(guó)約有39種花椒,14個(gè)變種[2],大部分花椒品種仍處于野生狀態(tài),人工栽培的花椒主要分為青花椒和紅花椒,不同產(chǎn)地的花椒質(zhì)量不同。但隨著花椒深度開(kāi)發(fā)和利用得到越來(lái)越多的重視,市場(chǎng)需求快速增長(zhǎng),隨之而來(lái)的是市場(chǎng)上以劣充優(yōu)、以陳冒新、摻假摻雜等現(xiàn)象層出不窮。一方面,消費(fèi)者開(kāi)始更多地關(guān)心他們所消費(fèi)的農(nóng)產(chǎn)品的來(lái)源與真實(shí)性,另一方面,企業(yè)與花椒原產(chǎn)地渴望尋求保護(hù)自身品牌的有效方法,因此研究開(kāi)發(fā)出一種簡(jiǎn)單、快速、無(wú)損的花椒產(chǎn)地鑒別檢測(cè)方法,具有重要的現(xiàn)實(shí)意義。
現(xiàn)有花椒品種鑒別的常用方法有感官分析技術(shù)、氣相色譜法、與氣質(zhì)聯(lián)用技術(shù)(GC-MS)等。感官辨識(shí)對(duì)于專(zhuān)業(yè)人員的要求較高,需要長(zhǎng)期的經(jīng)驗(yàn),而這些專(zhuān)業(yè)人員很難做到將不同地區(qū)的花椒完全辨認(rèn)。而如吳習(xí)宇等采用近紅外光譜技術(shù)鑒別花椒產(chǎn)地[3],吳莉莉等采用機(jī)器視覺(jué)對(duì)花椒品種進(jìn)行鑒別[4]。此外,也有眾多研究發(fā)現(xiàn)不同種或不同品系的花椒間化學(xué)成分也有較大差異[5]。這一類(lèi)的非感官的鑒別手段,測(cè)試周期較長(zhǎng),運(yùn)行成本高,在操作上不利于推廣。
氣體傳感器是一種模仿生物嗅覺(jué)的氣體檢測(cè)系統(tǒng)[6]。而氣體傳感器的核心部件為由多種氣敏傳感器組成的氣敏傳感器陣列,其原理是將多個(gè)傳感器感知到的時(shí)間或空間上互補(bǔ)或冗余的信息,并在某種準(zhǔn)則下進(jìn)行綜合與分析,以獲得單個(gè)或單類(lèi)傳感器無(wú)法獲得的有價(jià)值的綜合信息,從而形成對(duì)觀測(cè)對(duì)象客觀的描述[7-9]。鑒于氣體傳感器對(duì)待測(cè)氣體樣品的信息綜合分析能力,它已經(jīng)在農(nóng)業(yè)生產(chǎn)[10-12]、生物醫(yī)學(xué)[13-15]、環(huán)境監(jiān)測(cè)[16-18]、食品檢測(cè)[19-21]等領(lǐng)域得到了廣泛應(yīng)用。
本文自行研發(fā)設(shè)計(jì)出一種基于氣體傳感器陣列的花椒信息采集裝置,用于4種花椒氣味信息檢測(cè),依據(jù)Wilks Λ統(tǒng)計(jì)量對(duì)氣體傳感器中的傳感器陣列數(shù)據(jù)進(jìn)行優(yōu)化,剔除冗余信息。將優(yōu)化數(shù)據(jù)利用Fisher判別建立分類(lèi)器,結(jié)合花椒信息采集裝置,建立一種快速、簡(jiǎn)單、準(zhǔn)確且便于推廣的花椒產(chǎn)地鑒別方法,為保證名品花椒、產(chǎn)地優(yōu)選提出新的方法。
試驗(yàn)花椒分為4個(gè)品種,分別是四川漢源紅花椒、陜西韓城紅花椒(大紅袍)、四川漢源青花椒、云南魯?shù)榍嗷ń罚ê笪暮?jiǎn)稱(chēng)云南青花椒)。4種花椒均取自原產(chǎn)地種植園區(qū),均為干燥花椒果皮。其中漢源青、紅花椒和云南青花椒各取60份,陜西紅花椒取40份,每份均15 g,此220份花椒用作訓(xùn)練樣本。各類(lèi)花椒取樣本各20份作為驗(yàn)證集。
智能花椒品種鑒別裝置。該裝置系統(tǒng)結(jié)構(gòu)圖如圖1a所示,作為整個(gè)設(shè)備的設(shè)計(jì)指導(dǎo)。圖1b為實(shí)際設(shè)計(jì)時(shí)的氣室結(jié)構(gòu)設(shè)計(jì)剖圖,從圖中可以看出,氣室,樣品槽,傳感器陣列,加熱片,離心風(fēng)機(jī)的組裝結(jié)構(gòu),風(fēng)機(jī)從上端吸收被加熱片加熱的花椒氣體,由下側(cè)向四周的傳感器陣列散發(fā),使得各個(gè)傳感器均勻接觸到花椒氣體,氣體再由外側(cè)返回氣室,達(dá)成氣體循環(huán)。圖1c為裝置設(shè)計(jì)的外部結(jié)構(gòu),從外部只能看到氣室和樣品槽,無(wú)法看到氣室內(nèi)部的具體結(jié)構(gòu)。圖1d為拆下外殼的實(shí)物俯視圖,俯視結(jié)構(gòu)中可以看到本裝置在設(shè)計(jì)時(shí)包含了氣體流通通道,可以保證氣體實(shí)現(xiàn)循環(huán)。圖1e是在1d的基礎(chǔ)上,拆除傳感器陣列的保護(hù)外殼,傳感器設(shè)置為倒置擺放,陣列通道內(nèi)為線路連接,只將傳感器探頭露出,保證傳感器傳遞線路不受到花椒氣味的顆粒影響,確保實(shí)驗(yàn)安全進(jìn)行。圖1f為實(shí)物的側(cè)放圖,將側(cè)面擋板取下,內(nèi)部為搭建好的控制電路及外圍電路等,擋板可拆卸保證了隨時(shí)可以對(duì)裝置程序,電路進(jìn)行修改。
1.樣品槽 2.氣敏傳感器陣列 3.離心風(fēng)機(jī) 4.PTC加熱片 5.隔離殼體 6.液晶顯示屏 7.開(kāi)關(guān) 8.風(fēng)速調(diào)節(jié)旋鈕 9.控制芯片(內(nèi)部)
本裝置所采用的傳感器選型時(shí)參照花椒氣體組成成分進(jìn)行選擇,并對(duì)傳感器本身的靈敏性,恢復(fù)性,穩(wěn)定性進(jìn)行篩選,最終所選的7個(gè)傳感器分別為MQ135、MQ5、MQ2、TGS2611、TGS2600、TGS2610和TGS2602。圖2為本文所用氣體傳感器陣列實(shí)物圖,表1為傳感器所對(duì)應(yīng)敏感響應(yīng)特性。該裝置有采集檢測(cè)和鑒別種類(lèi)2種工作模式,檢測(cè)到的數(shù)據(jù)和鑒別結(jié)果會(huì)在顯示屏上顯示。
圖2 試驗(yàn)所用傳感器
表1 氣體傳感器響應(yīng)特性
首先在采樣前,將顆粒狀活性炭置入樣品槽中,進(jìn)行清洗,直至傳感器陣列的響應(yīng)信號(hào)穩(wěn)定,將此時(shí)傳感器陣列的響應(yīng)值作為基準(zhǔn)值,清洗時(shí)間為10 min。將花椒樣本送入樣品槽,開(kāi)啟氣味采集工作模式,先對(duì)氣味采集裝置進(jìn)行約60 s的預(yù)熱,使傳感器陣列處于正常工作狀態(tài),氣室內(nèi)的溫度穩(wěn)定在26℃(±1℃)。進(jìn)行數(shù)據(jù)采集,采樣時(shí)間約為10 min,每個(gè)傳感器分別采集50次數(shù)據(jù),每次采樣間隔10 s,取50次采樣數(shù)值的平均值(aver),最大值(max),最小值(min)作為一個(gè)樣本的記錄值,每組花椒樣本包含21個(gè)數(shù)據(jù)參數(shù),構(gòu)成完整的數(shù)據(jù)帶。
1.4.1 主成分分析
主成分分析(principal component analysis, PCA),是一種通過(guò)正交變換將一組可能存在相關(guān)性的變量轉(zhuǎn)換為一組線性不相關(guān)的變量,從而代表所有變量的統(tǒng)計(jì)方法,轉(zhuǎn)換后的這組變量叫主成分[22]。對(duì)測(cè)定花椒的21個(gè)參數(shù)進(jìn)行主成分分析,選取方差累積貢獻(xiàn)率達(dá)到90%以上的穩(wěn)定水平的主成分,并確定其數(shù)量。
1.4.2 Wilks Λ統(tǒng)計(jì)分析
Wilks Λ統(tǒng)計(jì)量是常用的數(shù)據(jù)篩選方式,用于檢驗(yàn)多個(gè)母體的判別效果和各個(gè)變量的判別能力[23]。其實(shí)質(zhì)是,樣本組內(nèi)離差平方和與樣本總體離差平方和之比。其比值越小說(shuō)明樣本貢獻(xiàn)越大。
對(duì)2種分析方法選定的成分分別建立Fisher判別分析,選擇最優(yōu)方式并將最優(yōu)判別分析移植到鑒別裝置中。
對(duì)220個(gè)樣本所測(cè)試花椒21個(gè)特征參數(shù)進(jìn)行主成分分析,方差累積結(jié)果如圖3,主成分分析在第5個(gè)以后,累積方差逐增長(zhǎng)漸趨于平穩(wěn),故提取主成分5個(gè),方差累積貢獻(xiàn)率達(dá)到94.41%。
圖3 主成分方差累積貢獻(xiàn)率
Wilks Λ統(tǒng)計(jì)分析篩選出8個(gè)變量,涉及試驗(yàn)傳感器6個(gè),如表2所示。
表2 Wilks Λ統(tǒng)計(jì)量選擇
根據(jù)篩選的變量PCA和Wilkss Λ統(tǒng)計(jì)篩選的變量,分別建立PCA-Fisher判別分析模型與Wilks-Fisher判別分析模型,2種模型均包含3個(gè)判別函數(shù),PCA-Fisher判別函數(shù)如下:
PF1=1.655×PC1+0.101×PC2?0.247×PC3?
1.362×PC4+0.739×PC5(1)
PF2=0.224×PC1?0.376×PC2+0.073×PC3+
0.619×PC4?0.531×PC5(2)
PF3=0.072×PC1+0.498×PC2+0.308×PC3+
0.519×PC4?0.534×PC5(3)
式中PF1,PF2,PF3表示分類(lèi)坐標(biāo)值,PC1~PC5表示5個(gè)主成分。
Wilks-Fisher判別函數(shù)如下:
WF1=?0.001×1?0.031×2+0.028×3?0.045×4+
0.015×5+0.026×6+0.005×7?0.004×8?5.56(4)
WF2=?0.013×1?0.049×2+0.002×3+0.093×4?
0.048×5+0.066×6?0.001×7+0.036×8?2.417(5)
WF3=?0.002×1?0.008×2?0.024×3?0.074×4?
0.138×5?0.005×6+0.034×7+0.116×8+5.101 (6)
式中WF1,WF2,WF3表示分類(lèi)坐標(biāo)值,1~8表示表2中序號(hào)1~8的8個(gè)篩選變量。將輸入導(dǎo)入2種模型,分別與其對(duì)應(yīng)質(zhì)心相比較,求得距離最短即為分析結(jié)果。分析結(jié)果如表3所示。
表3 Fisher判別分類(lèi)結(jié)果
由表3知,Wilks-Fisher判別分析的整體正確率相對(duì)較高。其中在PCA-Fisher判別模型中,云南青花椒與漢源紅花椒的識(shí)別率明顯較低,這是因?yàn)?,不同花椒的揮發(fā)性成分相對(duì)含量不同。文獻(xiàn)[24]中指出,漢源青花椒和漢源紅花椒的揮發(fā)性氣體成分含量差異極大,漢源青花椒醇類(lèi)化合物含量較高,而漢源紅花椒酯類(lèi)化合物較高,這是導(dǎo)致傳感器在響應(yīng)2種花椒時(shí)數(shù)值差異的主要原因,以表2中出現(xiàn)最多參數(shù)的傳感器TGS2602為例,圖4a是傳感器TGS2602每組所采集樣本的平均值(aver)折線圖,從中可以明顯得看出4種花椒的響應(yīng)差異值較為明顯;圖4b是表2中未篩選傳感器TGS2611每組采集樣本的平均值折線圖,可以發(fā)現(xiàn),該傳感器對(duì)4種花椒的響應(yīng)值差異較低,印證了該傳感器所提供信息存在較多冗余,而PCA會(huì)提取這一部分的冗余信息,這是導(dǎo)致PCA-Fisher模型識(shí)別精度較低的原因,也證明了Wilks統(tǒng)計(jì)分析對(duì)剔除冗余數(shù)據(jù)的有效性。圖4 c是4類(lèi)花椒在Fisher判別分析坐標(biāo)下的坐標(biāo)點(diǎn),從圖中可以看出,陜西紅花椒相對(duì)其他3種花椒區(qū)分度明顯,云南青花椒和漢源青花椒、漢源紅花椒在一定程度上具有重疊部分,這可能是因?yàn)闈h源魯?shù)?地相隔較近,在地理位置,土壤等因素較為接近引起的,這也導(dǎo)致了云南青花椒和漢源紅花椒的判別率相對(duì)較低,故僅僅使用Fisher判別分析,并不能完全將產(chǎn)地鑒別,還需要對(duì)函數(shù)或數(shù)據(jù)進(jìn)行優(yōu)化分類(lèi)。
對(duì)Wilks—Fisher判別模型進(jìn)行改進(jìn),將樣本集進(jìn)行區(qū)分,分別訓(xùn)練出紅花椒的判別函數(shù)和青花椒的判別函數(shù)。為降低交互數(shù)據(jù)的干擾性,對(duì)分析案例進(jìn)行交叉驗(yàn)證。交叉驗(yàn)證是在機(jī)器學(xué)習(xí)建立模型和驗(yàn)證模型參數(shù)時(shí)常用的辦法。交叉驗(yàn)證,就是重復(fù)的使用數(shù)據(jù),把得到的樣本數(shù)據(jù)進(jìn)行切分,組合為不同的訓(xùn)練集和測(cè)試集,用訓(xùn)練集來(lái)訓(xùn)練模型,用測(cè)試集來(lái)評(píng)估模型預(yù)測(cè)的好壞。在此基礎(chǔ)上可以得到多組不同的訓(xùn)練集和測(cè)試集,某次訓(xùn)練集中的某樣本在下次可能成為測(cè)試集中的樣本,即所謂“交叉”。
圖4 傳感器部分響應(yīng)及判別坐標(biāo)
采用S折交叉驗(yàn)證,根據(jù)樣本數(shù)量S,將對(duì)應(yīng)訓(xùn)練集樣本分成S-1份,剩下1份作為測(cè)試機(jī),循環(huán)S次,直到每個(gè)樣本均作為測(cè)試集對(duì)象進(jìn)行測(cè)試。在判別時(shí),將數(shù)據(jù)分為青紅花椒進(jìn)行分別驗(yàn)證,結(jié)果如表4所示。
表4 青紅花椒分類(lèi)交叉驗(yàn)證結(jié)果
由表4可知,在分類(lèi)判別時(shí),漢源青花椒的正確率為98.3%,誤判1組,云南青花椒的正確率為93.3%,誤判4組,陜西紅花椒的正確率為100%,漢源紅花椒的正確率為98.3%,誤判1組,平均正確率達(dá)到97.27%,所有驗(yàn)證結(jié)果較原模型檢測(cè)均有所提高。該驗(yàn)證結(jié)果表明分類(lèi)交叉驗(yàn)證的Wilks—Fisher判別模型可以較好地鑒別花椒的產(chǎn)地,將判別函數(shù)寫(xiě)入采集裝置并調(diào)試程序,即構(gòu)成完整的智能花椒品種鑒別系統(tǒng)。
本文采用自制的智能花椒品種鑒別裝置,利用氣體傳感器陣列對(duì)花椒數(shù)據(jù)進(jìn)行采集,通過(guò)主成分分析、WilksΛ統(tǒng)計(jì)分析提取有效變量,建立對(duì)應(yīng)的Fisher判別模型。試驗(yàn)表明,Wilks—Fisher具有更好的結(jié)果,訓(xùn)練集的平均判別正確率達(dá)到91.82%,驗(yàn)證集平均判別正確率達(dá)到95%。在細(xì)分類(lèi)交叉驗(yàn)證的下的該模型判別率達(dá)到97.27%。該模型能夠正確地識(shí)別4個(gè)產(chǎn)地的花椒,其檢測(cè)結(jié)果較為理想。而將模型函數(shù)寫(xiě)入裝置后,構(gòu)成智能花椒品種鑒別系統(tǒng)裝置,實(shí)現(xiàn)花椒產(chǎn)地的無(wú)損智能鑒別。該裝置無(wú)需樣品預(yù)處理,不需要使用檢測(cè)理化值所需的精密儀器,檢測(cè)成本較高光譜等精細(xì)設(shè)備極具優(yōu)勢(shì),為花椒產(chǎn)地的識(shí)別及追溯提供了技術(shù)支持,可以有效控制以次充優(yōu)、假冒偽劣等摻假手段,為名優(yōu)名品花椒,具有地理標(biāo)志保護(hù)花椒的鑒別提供了簡(jiǎn)便快捷的新思路,具有廣闊的應(yīng)用前景。
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Identification oforigin based on gas sensor
Pang Tao1, Yang Xiao1, Chen Xiaoyan2,3※, Tao Huailiang1, Li Mengliang1
(1.,,625000,; 2.,625000,;3.,625000,)
At present, the identification of the origin ofis basically based on sensory evaluation, lack of objectivity, and it is difficult to quantify standardize when applying, and is difficult for non-professionals to make judgments. Therefore, in this paper, a smart device to quickly identifywas designed and developed. The device was based on the gas sensor array, including a control module, a temperature module, a data storage module, a fan module, and a display module, it could not only independently detect and identify the odor information of the, but also distinguish the same kind offrom different places. The sensor array contained seven gas sensors, which could respond to irritating gases emitted bysuch as benzene, alkanes, alcohols, and aldehydes. When the temperature was stable at about 26 degrees Celsius, it could effectively collect information on the odor emitted by. Each group ofsamples was collected 50 times, and the average value, the maximum value, and the minimum value were taken as sample recording parameters. In this paper, four kinds ofwere selected as experimental subjects. Two kinds of greenwere from Ludian in Yunnan and Hanyuan in Sichuan. At the same time, the two kinds of redwere from Hancheng in Shaanxi and Hanyuan in Sichuan. A total of 220 samples were collected as training sets, including 40 redin Shaanxi and 60 samples in the remaining three samples. Another 80 samples were taken as the verification set, the number of samples for eachwas 20 in the verification set as well. The detection data were processed using principal component analysis (PCA) and Wilks statistical analysis. Five principal components were extracted, and the cumulative contribution rate was 94.41%. The average accuracy rate of the training model corresponding to the Fisher discriminant model was only 88.6%, and the verification set was 90%. As a comparison, the Wilks statistical analysis finally eliminated 13 variables as well as selected 8 variables, and only TGS2611 sensor acquisition was not used. The average accuracy of the Fisher model training set was 91.82%, and the validation set was 95%. The results of the comparison of the two models indicate that the variables screened by Wilks are more effective in discriminating thefield. Among the four kinds of, the recognition rate of Yunnan greenand Hanyuan redwas relatively lower than the others, and there was a phenomenon that the boundary data overlaps in the discrimination result graph. Then, to solve the problem, a Fisher discriminant model with cross-validation was established for the variables selected by Wilks statistic. In addition, the average accuracy rate reached 97.27%. Finally, the model was transplanted to the collection device to complete the identification device of intelligentvariety. It was a simple and efficient method for identifyingvarieties and could provide a testing instrument and theoretical basis for further research on the origin and classification of.
sensors; crops; gas detectors; identification offield; fisher discriminant
龐 濤,楊 霄,陳曉燕,陶懷亮,李蒙良. 氣體傳感器鑒別花椒產(chǎn)地研究[J]. 農(nóng)業(yè)工程學(xué)報(bào),2019,35(18):267-272.doi:10.11975/j.issn.1002-6819.2019.18.032 http://www.tcsae.org
Pang Tao, Yang Xiao, Chen Xiaoyan, Tao Huailiang, Li Mengliang.Identification oforigin based on gas sensor[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(18): 267-272. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2019.18.032 http://www.tcsae.org
2019-03-18
2019-04-26
四川省教育廳一般項(xiàng)目(自然科學(xué))立項(xiàng)編號(hào):17ZB0333 基于高光譜圖像技術(shù)的蘋(píng)果品質(zhì)無(wú)損檢測(cè)方法研究
龐 濤,講師,主要從事農(nóng)業(yè)信息檢測(cè)。Email:349380993@qq.com
陳曉燕,教授。主要從事農(nóng)產(chǎn)品無(wú)損檢測(cè)。Email:chenxy@sicau.edu.cn
10.11975/j.issn.1002-6819.2019.18.032
S-3
A
1002-6819(2019)-18-0267-06