馬鈴薯收獲機的設(shè)計

馬鈴薯收獲機的設(shè)計,馬鈴薯收獲機的設(shè)計,馬鈴薯,土豆,收獲,收成,設(shè)計 黑龍江八一農(nóng)墾大學(xué)黑龍江八一農(nóng)墾大學(xué)0707屆畢業(yè)生論文答辯屆畢業(yè)生論文答辯馬鈴薯收獲機的設(shè)計The design of potato harvester 姓名：學(xué)號：指導(dǎo)老師：前言前言 國內(nèi)發(fā)展發(fā)展概況國內(nèi)發(fā)展發(fā)展概況 國外馬鈴薯收獲機發(fā)展概況國外馬鈴薯收獲機發(fā)展概況馬鈴薯收獲機的技術(shù)要求馬鈴薯收獲機的技術(shù)要求l挖凈率 98l明薯率 95l破損率 5 l生產(chǎn)率 保證一定的作業(yè)速度 （本設(shè)計作業(yè)速度0.6 1 m/s）機具結(jié)構(gòu)特點機具結(jié)構(gòu)特點l馬鈴薯挖掘機與80-100馬力的拖拉機配套作業(yè)，掛接方式為后懸掛，作業(yè)時需對行。該機主要由懸掛機架、轉(zhuǎn)動輸送篩、挖掘鏟及鏟架、切土圓盤刀、傳動機構(gòu)、擺動篩等機構(gòu)組成。主要工作原理主要工作原理 主要性能參數(shù)主要性能參數(shù)l工作寬度1800 mml作業(yè)行數(shù)2 行l(wèi)作業(yè)深度200 mml主軸轉(zhuǎn)速540 r/minl配套動力（拖拉機）80-100 馬力l作業(yè)速度0.6 1 m/sl行距700 900 mm挖掘部件的設(shè)計挖掘部件的設(shè)計l采用了組合式挖掘部件。l由三角平面多鏟、鏟架和切土圓盤刀組成。挖掘鏟挖掘鏟切土圓盤刀切土圓盤刀分離部件的設(shè)計分離部件的設(shè)計l本設(shè)計采用轉(zhuǎn)動輸送篩和擺動篩組合式分離裝置輸送篩運動簡圖輸送篩運動簡圖擺動篩擺動篩l采用偏心輪式擺動篩，結(jié)構(gòu)簡單，工作可靠，非常適合作輔助清理部件。l篩子采用有效分離面較大的條桿篩,篩架由曲柄連桿機構(gòu)驅(qū)動。致謝致謝l本論文是在張偉老師悉心指導(dǎo)下完成的。l在論文的設(shè)計過程中，張偉老師給于了極大的幫助。在此，謹(jǐn)向張老師表示衷心的感謝和誠摯的敬意。l同時，在學(xué)習(xí)和研究中，還得益于與同學(xué)們的探討中獲益匪淺；在生活中，還受到寢室兄弟的關(guān)照，在此向他們表示深深的謝意。 山西農(nóng)業(yè)大學(xué)學(xué)士學(xué)位論文（設(shè)計）文獻綜述 馬鈴薯播種機具的現(xiàn)狀與發(fā)展 摘要：綜述了國內(nèi)外播種機的發(fā)展現(xiàn)狀，并通過對國內(nèi)外幾種典型播種機的各種參數(shù)進行系統(tǒng)的對比并加以分析，從中發(fā)現(xiàn)國產(chǎn)播種機與國外播種機的差距，并在此基礎(chǔ)上去闡述我國播種機在研發(fā)和應(yīng)用上所存在問題并展望未來播種機的發(fā)展趨勢，同時明確馬鈴薯播種機的設(shè)計方向。 關(guān)鍵詞：播種機具 馬鈴薯 精量播種機 排種器 1. 馬鈴薯在我國的生產(chǎn)現(xiàn)狀 馬鈴薯是一種高蛋白農(nóng)作物，在我國得到大面積的栽種，盡管我國年產(chǎn)量早已躍居世界第一，然而和世界除非洲以外的其他國家和地區(qū)比起來，單產(chǎn)量卻很低，因此在提高單產(chǎn)的措施上除了提高機械化生產(chǎn)水平外，還應(yīng)該改進馬鈴薯的種子質(zhì)量以及種植方式。 1.1我國馬鈴薯的生產(chǎn)現(xiàn)狀 300多年前，原產(chǎn)自美洲的馬鈴薯被引進中國并且逐漸成為僅次于小麥、水稻和玉米的第四大糧食作物。目前，我國的馬鈴薯無論是種植面積還是總產(chǎn)量都處于全球領(lǐng)先地位。從中國馬鈴薯網(wǎng)上獲得的資訊：2007年我國馬鈴薯種植面積約8000萬畝，預(yù)計總產(chǎn)量將超過6800萬噸，占世界總產(chǎn)量的22%左右。單從總產(chǎn)量來說我國已經(jīng)是世界第一，但是單產(chǎn)量卻遠遠低于歐美、澳洲的水平。例如，2003年，我國馬鈴薯的單產(chǎn)量是每公頃14842公斤，低于世界平均水平的每公頃16448 公斤，還不到單產(chǎn)量最大的國家新西蘭的每公頃44248 公斤的三分之一。 1.2國外馬鈴薯的生產(chǎn)水平 單產(chǎn)量排名前六位的國家：新西蘭、比利時、丹麥、美國、英國、荷蘭等歐美發(fā)達國家，他們的單產(chǎn)量都超過了每公頃40000 公斤（中國馬鈴薯網(wǎng)，2007）。除了地域、氣候方面外，更重要的是栽培技術(shù)以及機械化生產(chǎn)水平的影響。顯然，這些國家的農(nóng)業(yè)生產(chǎn)機械化水平都遠遠高過我國。反觀我國，大部分地區(qū)的馬鈴薯生產(chǎn)都還停留在人工或者半機械化生產(chǎn)的水平上，因此單產(chǎn)量低也就不足為奇。 1.3目前急需解決的措施以及會遇到的困難 要想提高單產(chǎn)量，首要的就是提高機械化生產(chǎn)水平。我國地域廣闊，擁有多種地型，因此不可能同時提高生產(chǎn)機械化，所以應(yīng)該根據(jù)不同的地形，不同的氣候和種植方式，從而設(shè)計符合當(dāng)?shù)氐霓r(nóng)業(yè)生產(chǎn)機械，盡量推廣播種機在農(nóng)業(yè)生產(chǎn)中的應(yīng)用。其次應(yīng)該改進種植方式，我國的馬鈴薯種植方式一直停留在傳統(tǒng)種植的水平上，這是急需改變的。先進的種植方式應(yīng)該從改進種子質(zhì)量，改進播種方式等方面進行，同時在此基礎(chǔ)上設(shè)計相應(yīng)的機械也就顯得至關(guān)重要。 2. 國內(nèi)外播種機發(fā)展及應(yīng)用的現(xiàn)狀 2.1我國播種機發(fā)展現(xiàn)狀 現(xiàn)目前，我國大約有500家播種機生產(chǎn)企業(yè)，但是這些企業(yè)中能夠生產(chǎn)與大中型拖拉機配套的播種機的企業(yè)只有西安農(nóng)業(yè)機械廠、石家莊市農(nóng)業(yè)機械廠等區(qū)區(qū)10多家，其余的企業(yè)生產(chǎn)的都是與小型拖拉機和畜力配套的拖拉機。這種與小型拖拉機和畜力配套的播種機機的產(chǎn)量占全國播種機總產(chǎn)量的90%以上（國委文，2007）。由此可以看出當(dāng)前我國已實現(xiàn)機械化播種的大部分地區(qū)的播種機仍以小型播種機進行傳統(tǒng)的谷物條播為主，大中型播種機的發(fā)展遠遠跟不上農(nóng)業(yè)生產(chǎn)的需要，而且大中型生產(chǎn)機械（包括播種機）的研制和生產(chǎn)水平也遠遠落后于發(fā)達國家的水平。 2.2國外播種機發(fā)展現(xiàn)狀 相對我國而言，國外許多發(fā)達國家在第二次世界大戰(zhàn)前后，先后完成了由傳統(tǒng)農(nóng)業(yè)向現(xiàn)代農(nóng)業(yè)的過度和轉(zhuǎn)化，經(jīng)過幾十年的發(fā)展，其農(nóng)業(yè)機械化水平已經(jīng)相當(dāng)完善，現(xiàn)在正朝著大型化、智能化、精量化以及多功能聯(lián)合型方向發(fā)展（陶衛(wèi)民，2001）。美國，德國，英國等西方發(fā)達國家的發(fā)展水平已經(jīng)走在世界的前列。 在國外許多發(fā)達國家，精密播種機經(jīng)過幾十年的發(fā)展和應(yīng)用，其技術(shù)水平應(yīng)經(jīng)達到了相當(dāng)完善的程度，無論是工作速度、生產(chǎn)效率、工作性能、播種質(zhì)量以及播種機具的通用性和適應(yīng)性上都做得比較好。這對減少播種過程中的漏種率、種子損傷率和提高單產(chǎn)量都有很大的促進作用。現(xiàn)在一些發(fā)達國家正把不斷更新播種機的工作原理、盡量完善其結(jié)構(gòu)、延長機具使用壽命、降低制造價格和維護費用的同時提高其工作效率以及提高播種機的通用性和適應(yīng)性作為未來更先進的播種機研制的發(fā)展方向。 2.3與國外播種機相比，我國播種機存在的不足 和國外如美國、德國、英國等發(fā)達國家的播種機比起來，我國的播種機工作效率低，工作幅寬小，通用性和適應(yīng)性低，使用可靠性不高，生產(chǎn)率也遠較國外的低。另外，由于我國工業(yè)起步晚，因此在新技術(shù)的研制和在播種機上的應(yīng)用上依舊落后于國外發(fā)達國家。下面以我國幾種典型的播種機和國外的播種機作一個對比，以便從中發(fā)現(xiàn)我國播種機和國外先進播種機的不足。 首先，從工作效率方面來看，我國播種機的工作速度低。國外播種機的工作速度大都要求達到15㎞／h，有的甚至達到20㎞／h，受到土地，氣候和一些其它因素的影響，工作速度大多采用8～12㎞／h，而我國工作速度大約為4～7㎞／h，一般工作速度為5～6㎞／h。比如德國早期生產(chǎn)的GL34T和GL36T兩種機型的工作速度為7.5㎞／h(韓文鋒等，2006），而我國普遍采用的2BM-2以及2BMF-2型都達不到德國這兩種機型的水平。 其次，我國播種機的工作幅寬小。和國外發(fā)達國家比起來這個環(huán)節(jié)顯得非常薄弱。例如西歐一些國家的生產(chǎn)的播種機的工作幅寬一般為5～6m，美國，加拿大等國家的現(xiàn)用機型大多可以達到10～15m（陳興田，1999）。而我國所使用的播種機的工作幅寬絕大多數(shù)低于3.5m，例如較先進的2BF-24A谷物條播機的工作幅寬為3.6m，其余的大都低于這個水平，工作幅寬低這個瓶頸在很大程度上限制了播種機的工作效率。 再次，排種器的排種效率低。我國很多使用播種機的地區(qū)在農(nóng)業(yè)生產(chǎn)中依舊使用傳統(tǒng)的排種方式即“一器一行”，一個排種器只能播一行種子，顯然這樣的效率是非常低的，即使有較先進的“一器多行”的排種器，但是技術(shù)上也表現(xiàn)得不夠成熟，也沒能進行大規(guī)模的推廣及應(yīng)用。國外發(fā)達國家在這方面的技術(shù)和經(jīng)驗就比我國先進得多，而且許多新技術(shù)已經(jīng)得到廣泛的應(yīng)用，許多核心部件尤其是排種器無論是結(jié)構(gòu)還是工作原理都還有很多值得我國學(xué)習(xí)和借鑒的地方。 最后，我國的播種機的通用性和適應(yīng)性和國外發(fā)達國家比起來也還有很大的差距。在通用性方面，國外發(fā)展得比較早，技術(shù)也比較成熟，一套設(shè)備只需經(jīng)過簡單的更換即可實現(xiàn)不同種子的播種，而我國大部分播種機還都是“一機一種”，一種播種機只能夠播撒一種種子，這樣既浪費制造材料，又沒能使播種機得到充分利用。另外，我國地域遼闊，不同的土壤條件和氣候條件嚴(yán)重限制了播種機的適應(yīng)性，在保證適應(yīng)性方面的技術(shù)還很落后，而且我國研制生產(chǎn)的播種機很少考慮到適應(yīng)性這一方面的影響。 3. 我國播種機的發(fā)展趨勢 雖然可以通過引進國外先進的播種機可以暫時彌補我國播種機的不足之處，但是從長遠 出發(fā)，我國必須走自主研發(fā)的道路，通過不斷吸收國外先進技術(shù)的同時再結(jié)合我國的國情走出一條自主創(chuàng)新的路子，研制出具有我國特色的先進播種機。 3.1加大大中型播種機的研制和開發(fā) 要想盡快縮小我國馬鈴薯等農(nóng)作物的單產(chǎn)與國外水平的差距，大中型播種機將起到至 關(guān)重要的作用。我國的幾大平原地勢平坦，比較適合大中型播種機的推廣和應(yīng)用。大中型播種機械除了可以節(jié)約人力，提高工作效率外還能減少種子的損傷率和漏種率，而且大中型播種機都是朝著聯(lián)合作業(yè)和直接播種技術(shù)的方向發(fā)展，這種機械的優(yōu)點在于：一次可以完成多項作業(yè)，作業(yè)效率高；保證及時播種，提高產(chǎn)量；節(jié)約能源，降低成本。 3.2采用新的排種原理和排種裝置 排種裝置是播種機最關(guān)鍵的部件，先進的排種器和排種原理對播種機的效率的提高有 著很重要的作用，迄今為止，我國學(xué)者幾乎涉獵了世界上所有的排種器：如外槽輪式排種器、離心式排種器、各種圓盤式排種器等，而具有我國獨創(chuàng)特色的窩眼輪式排種器、紋盤式排種器、錐盤式精量排種器也獲得了廣泛的應(yīng)用，但是在馬鈴薯播種機上，先進的排種器和排種方式依然制約播種機效率的一個瓶頸。因此在已經(jīng)解決種子和播種方式的情況下研制相應(yīng)的播種機顯得是關(guān)重要。顯然，在排種器方面，我國應(yīng)該朝著氣流輸送式條播排種器、孔帶式精密排種器、氣力式精密排種器以及傾斜圓盤指夾式排種器的方向發(fā)展。新的排種原理包括氣力式排種原理和機械式排種原理也應(yīng)得到廣泛的采用（陳興田，1999）。 4. 小結(jié) 一個比較先進的播種機主要取決于其幾個關(guān)鍵的部件，如：開溝器、仿形機構(gòu)、覆土器以及排種器。尤其是排種器在整個播種機結(jié)構(gòu)中顯得尤為重要，排種器的好壞直接關(guān)系到播種機的播種效率，因此，現(xiàn)在國內(nèi)外播種機研制的重點依舊是放在排種器的研制上。我國在這方面也有不少的研究，尤其在氣吸式排種器，窩眼式排種器還有氣力式排種器的研究上有了一定的突破，但是和國外先進水平還有一定的差距，因此，我國還必須加大研制的力度。 新型馬鈴薯已經(jīng)研制成功并將實現(xiàn)大力推廣，在將來的幾年內(nèi)，相應(yīng)的馬鈴薯播種機將對這種新型馬鈴薯的推廣起到極大的推動作用。新型的馬鈴薯將徹底改變傳統(tǒng)的馬鈴薯塊莖式播種方式，其播種方式將和玉米，油菜籽等顆粒的播種方式更為相似，但還是存在很多不同的地方，因此不能直接選用像玉米播種機或者油菜籽播種機這些現(xiàn)成的播種機型。由于現(xiàn)目前新型馬鈴薯還沒有開始實現(xiàn)大面積推廣，相應(yīng)的馬鈴薯播種機具還是一片空白?；诖耍瑢ΜF(xiàn)有的馬鈴薯播種機和其余各類顆粒式播種機進行改進優(yōu)化并在此基礎(chǔ)上設(shè)計一種適合新型馬鈴薯的機械式或者氣吸式播種機就成了當(dāng)前以及未來相當(dāng)一段時間內(nèi)播種機的研制方向，同時研制的重點也將放在馬鈴薯播種機的排種器的研制上。 參考文獻： [1] 李寶筏．農(nóng)業(yè)機械學(xué)．北京：中國農(nóng)業(yè)出版社， 2003 [2] 朱秉蘭．簡明農(nóng)機手冊．鄭州：河南科學(xué)技術(shù)出版社，2001 [3] 張波屏．編譯．播種機械設(shè)計原理．北京：機械工業(yè)出版社，1982 [4] 馮小靜．精少量播種機械使用與維修．鄭州：河南科學(xué)技術(shù)出版社，1998 [5] 馬大敏．王俊民，王秀．新型農(nóng)機具使用與維修．北京：高等教育出版社，1996 [6] 程興田．播種機械的現(xiàn)狀及發(fā)展前景．農(nóng)機與食品機械，1999，6：1～2 [7] 陶衛(wèi)民．國外農(nóng)業(yè)裝備發(fā)展趨勢．新農(nóng)村，2001，7：25 [8] 劉林生．英國農(nóng)業(yè)機械化與農(nóng)業(yè)現(xiàn)代化．湖南農(nóng)機，1999，2：25 [9] 姜宗昌．2BMF—2型馬鈴薯研制成功．農(nóng)業(yè)機械化與電氣化，2000，5：34 [10] 魯濱，薛理，閏洪山等．2BS—5型馬鈴薯播種機的研制，2004，6：33 [11] 幾種馬鈴薯播種、種植機械．www.potatoweb.cn ，2007 [12] 聶延輝 江濤．夾持式馬鈴薯播種機的探討，2007，2：41 [13] 周桂霞，張國慶 ，張義峰等．2CM一2型馬鈴薯播種機的設(shè)計．黑龍江八一農(nóng)墾大學(xué)報，2004，16（3）：53～56 [14] 趙滿全，趙有杰，竇衛(wèi)國等．2BM—9型免耕播種機關(guān)鍵部件的設(shè)計與研究．中國農(nóng)機化，2006，6： [15] 韓文鋒，王淑紅．徐長征．GL3 4T／3 6 T型馬鈴薯播種機簡介，2007， 1：41 [16] 馮小靜，劉俊峰，楊欣等．排種器排種均勻性分析與研究．河北農(nóng)業(yè)大學(xué)學(xué)報，2003， 1：14～16 [17] 趙滿全，竇衛(wèi)國，趙士杰，等．2BSL一2型馬鈴薯起壟播種機的研制．內(nèi)蒙古農(nóng)業(yè)學(xué)學(xué)報，2001， (3)：l02～l04 [18] 閏建英，樊文憲，馮占懷．馬鈴薯施肥播種機的實驗研究．農(nóng)機科技推廣，2004，4：34 [19] 王廣勝，王玉忠，樊文憲．2BXSM—IB型馬鈴薯施肥播種機的研究．農(nóng)機與食品機械 ，1999，(3)：l5～17． [20] 國委文．播種機的現(xiàn)狀及發(fā)展趨勢。農(nóng)業(yè)機械化與電氣化，2007，5：3～4 [21] KACHMAN S D．Acternative Measures of Accuracy in Plant Spacing for Planters Using Single Seed Metering．Translation of the ASAE，1995,38(2),pp.371～375 [22] E．U．Odigboh．a(chǎn)nd．C．O．Akubuo ．A two—row automatic cassava cuttings planter：Development、Design and Prototype construction．Journal of Agricultural Engineering Research，Volume 50，September—December．50(1991),pp.13—18． [23] Tao et al., 1995 Y. Tao, C.T. Morrow, P.H. Heinemann and H.J.S. Ill, Fourier based separation technique for shape grading of potatoes using machine vision, Transactions of the ASAE 38 (1995), pp. 949–957. [24] H． Buitenwerf，W．B．Hoogmoed，P．Lerink and J．Müller Assessment of the Behavior of Potato in a Cup—belt Planter．Biosystems Eigineering，95 (2006),35—41． [25]Siecska et al., 1986 J.B. Sieczka, E.E. Ewing and E.D. Markwardt, Potato planter performance and effects on non-uniform spacing, American Potato Journal 63 (1986), pp. 25–37 4 Biosystems Engineering (2006) 95(1), 3541 doi:10.1016/j.biosystemseng.2006.06.007 PMPower and Machinery Strasse opening for dropping the potato into a furrow in the soil. planters are equipped with two parallel rows of cups per belt instead of one. Doubling the cup row allows ARTICLE IN PRESS parameters of machine performance. High accuracy of plant spacing results in high yield and a uniform sorting and thus, a higher capacity at the same accuracy is expected. Capacity and accuracy of plant spacing are the main double the travel speed without increasing the belt speed 1537-5110/$32.00 35 r 2006 IAgrE. All rights reserved The functioning of most potato planters is based on transport and placement of the seed potatoes by a cup- belt. The capacity of this process is rather low when planting accuracy has to stay at acceptable levels. The main limitations are set by the speed of the cup-belt and the number and positioning of the cups. It was hypothesised that the inaccuracy in planting distance, that is the deviation from uniform planting distances, mainly is created by the construction of the cup-belt planter. To determine the origin of the deviations in uniformity of placement of the potatoes a theoretical model was built. The model calculates the time interval between each successive potato touching the ground. Referring to the results of the model, two hypotheses were posed, one with respect to the effect of belt speed, and one with respect to the influence of potato shape. A planter unit was installed in a laboratory to test these two hypotheses. A high-speed camera was used to measure the time interval between each successive potato just before they reach the soil surface and to visualise the behaviour of the potato. The results showed that: (a) the higher the speed of the cup-belt, the more uniform is the deposition of the potatoes; and (b) a more regular potato shape did not result in a higher planting accuracy. Major improvements can be achieved by reducing the opening time at the bottom of the duct and by improving the design of the cups and its position relative to the duct. This will allow more room for changes in the cup-belt speeds while keeping a high planting accuracy. r 2006 IAgrE. All rights reserved Published by Elsevier Ltd 1. Introduction The cup-belt planter (Fig. 1) is the most commonly used machine to plant potatoes. The seed potatoes are transferred from a hopper to the conveyor belt with cups sized to hold one tuber. This belt moves upwards to lift the potatoes out of the hopper and turns over the upper sheave. At this point, the potatoes fall on the back of the next cup and are confined in a sheet-metal duct. At the bottom, the belt turns over the roller, creating the of the tubers at harvest (McPhee et al., 1996; Pavek Entz Sieczka et al., 1986), indicating that the accuracy is low compared to precision planters for beet or maize. Travelling speed and accuracy of planting show an inverse correlation. Therefore, the present cup-belt Assessment of the Behaviour of H. Buitenwerf 1,2 ; W.B. Hoogmoed 1 Farm Technology Group, Wageningen University, P.O e-mail of corresponding author: 2 Krone GmbH, Heinrich-Krone 3 IB-Lerink, Laan van Moerkerken 85, 3271AJ 4 Institute of Agricultural Engineering, University (Received 27 May 2005; accepted in revised form Potatoes in a Cup-belt Planter 1 ; P. Lerink 3 ;J.Mu ller 1,4 Box. 17, 6700 AA Wageningen, The Netherlands; willem.hoogmoedwur.nl 10, 48480 Spelle, Germany Mijnsheerenland, The Netherlands of Hohenheim, D-70593 Stuttgart, Germany 20 June 2006; published online 2 August 2006) Published by Elsevier Ltd for handling and transporting. Many shape features, usually combined with size measurements, can be distinguished (Du Tao et al., 1995; Zo dler, 1969). In the Netherlands grading of potatoes is mostly done by using the square mesh size (Koning de et al., 1994), which is determined only by the width and height (largest and least breadth) of the potato. For the transport processes inside the planter, the length of the potato is a decisive factor as well. ARTICLE IN PRESS H. BUITENWERF ET AL.36 The objective of this study was to investigate the reasons for the low accuracy of cup-belt planters and to use this knowledge to derive recommendations for design modifications, e.g. in belt speeds or shape and 7 8 9 10 Fig. 1. Working components of the cup-belt planter: (1) potatoes in hopper; (2) cup-belt; (3) cup; (4) upper sheave; (5) duct; (6) potato on back of cup; (7) furrower; (8) roller; (9) release opening; (10) ground level 5 6 432 1 number of cups. For better understanding, a model was developed, describing the potato movement from the moment the potato enters the duct up to the moment it touches the ground. Thus, the behaviour of the potato at the bottom of the soil furrow was not taken into account. As physical properties strongly influence the efficiency of agricultural equipment (Kutzbach, 1989), the shape of the potatoes was also considered in the model. Two null hypotheses were formulated: (1) the planting accuracy is not related to the speed of the cup-belt; and (2) the planting accuracy is not related to the dimensions (expressed by a shape factor) of the potatoes. The hypotheses were tested both theoretically with the model and empirically in the laboratory. 2. Materials and methods 2.1. Plant material Seed potatoes of the cultivars (cv.) Sante, Arinda and Marfona have been used for testing the cup-belt planter, because they show different shape characteristics. The shape of the potato tuber is an important characteristic The field speed and cup-belt speed can be set to achieve the aimed plant spacing. The frequency f of pot potatoes leaving the duct at the bottom is calculated as f pot v c x c (2) where v c is the cup-belt speed in ms C01 and x c is the distance in m between the cups on the belt. The angular speed of the roller o r in rad s C01 with radius r r in m is calculated as o r v c r r (3) Table 1 Shape characteristics of potato cultivars and golf balls used in the experiments Cultivar Square mesh size, mm Shape factor Sante 2835 146 Arinda 3545 362 Marfona 3545 168 Golf balls 42C18 100 A shape factor S based on all three dimensions was introduced: S 100 l 2 wh (1) where l is the length, w the width and h the height of the potato in mm, with howol. As a reference, also spherical golf balls (with about the same density as potatoes), representing a shape factor S of 100 were used. Shape characteristics of the potatoes used in this study are given in Table 1. 2.2. Mathematical model of the process A mathematical model was built to predict planting accuracy and planting capacity of the cup-belt planter. The model took into consideration radius and speed of the roller, the dimensions and spacing of the cups, their positioning with respect to the duct wall and the height of the planter above the soil surface (Fig. 2). It was assumed that the potatoes did not move relative to the cup or rotate during their downward movement. The time of free fall t fall in s is calculated with ARTICLE IN PRESS ASSESSMENT OF THE BEHAVIOUR OF POTATOES 37 The gap in the duct has to be large enough for a potato x clear r c afii9825 release afii9853 x release Line A Line C Fig. 2. Process simulated by model, simulation starting when the cup crosses line A; release time represents time needed to create an opening sufficiently large for a potato to pass; model also calculates time between release of the potato and the moment it reaches the soil surface (free fall); r c , sum of the radius of the roller, thickness of the belt and length of the cup; x clear , clearance between cup and duct wall; x release , release clearance; a release , release angle ; o, angular speed of roller; line C, ground level, end of simulation to pass and be released. This gap x release in m is reached at a certain angle a release in rad of a cup passing the roller. This release angle a release (Fig. 2) is calculated as cos a release r c x clear C0 x release r c (4) where: r c is the sum in m of the radius of the roller, the thickness of the belt and the length of the cup; and x clear is the clearance in m between the tip of the cup and the wall of the duct. When the parameters of the potatoes are known, the angle required for releasing a potato can be calculated. Apart from its shape and size, the position of the potato on the back of the cup is determinative. Therefore, the model distinguishes two positions: (a) minimum re- quired gap, equal to the height of a potato; and (b) maximum required gap equal to the length of a potato. The time t release in s needed to form a release angle a o is calculated as t release a release o r (5) Calculating t release for different potatoes and possible positions on the cup yields the deviation from the average time interval between consecutive potatoes. Combined with the duration of the free fall and the field speed of the planter, this gives the planting accuracy. y release v end t fall 0C15gt 2 fall (8) where g is the gravitational acceleration (9C18ms C02 ) and the final velocity v end is calculated as v end v 0 2gy release (9) with v 0 in ms C01 being the vertical downward speed of the potato at the moment of release. The time for the potato to move from Line A to the release point t release has to be added to t fall . The model calculates the time interval between two consecutive potatoes that may be positioned in different ways on the cups. The largest deviations in intervals will occur when a potato positioned lengthwise is followed by one positioned heightwise, and vice versa. 2.3. The laboratory arrangement A standard planter unit (Miedema Hassia SL 4(6) was modified by replacing part of the bottom end of the sheet metal duct with similarly shaped transparent acrylic material (Fig. 3). The cup-belt was driven via the roller (8 in Fig. 1), by a variable speed electric motor. The speed was measured with an infrared revolution meter. Only one row of cups was observed in this arrangement. A high-speed video camera (SpeedCam Pro, Wein- berger AG, Dietikon, Switzerland) was used to visualise the behaviour of the potatoes in the transparent duct and to measure the time interval between consecutive potatoes. A sheet with a coordinate system was placed behind the opening of the duct, the X axis representing the ground level. Time was registered when the midpoint of a potato passed the ground line. Standard deviation When the potato is released, it falls towards the soil surface. As each potato is released on a unique angular position, it also has a unique height above the soil surface at that moment (Fig. 2). A small potato will be released earlier and thus at a higher point than a large one. The model calculates the velocity of the potato just before it hits the soil surface u end in ms C01 . The initial vertical velocity of the potato u 0 inms C01 is assumed to equal the vertical component of the track speed of the tip of the cup: v 0 r c o r cosa release (6) The release height y release in m is calculated as y release y r C0r c sina release (7) where y r in m is the distance between the centre of the roller (line A in Fig. 2) and the soil surface. ARTICLE IN PRESS H. BUITENWERF ET AL.38 of the time interval between consecutive potatoes was used as measure for plant spacing accuracy. For the measurements the camera system was set to a recording rate of 1000 frames per second. With an average free fall velocity of 2C15ms C01 , the potato moves approx. 2C15mm between two frames, sufficiently small to allow an accurate placement registration. The feeding rates for the test of the effect of the speed of the belt were set at 300, 400 and 500 potatoes min C01 (f pot 5, 6C17 and 8C13s C01 ) corresponding to belt speeds of 0C133, 0C145 and 0C156ms C01 . These speeds would be typical for belts with 3, 2 and 1 rows of cups, respectively. A fixed feeding rate of 400 potatoes min C01 (cup-belt speed of 0C145ms C01 ) was used to assess the effect of the potato shape. For the assessment of a normal distribution of the time intervals, 30 potatoes in five repetitions were used. In the other tests, 20 potatoes in three repetitions were used. Fig. 3. Laboratory test-rig; lower rightpart of the bottom end of upper rightsegment faced 2.4. Statistical analysis The hypotheses were tested using the Fisher test, as analysis showed that populations were normally dis- tributed. The one-sided upper tail Fisher test was used and a was set to 5% representing the probability of a type 1 error, where a true null hypothesis is incorrectly rejected. The confidence interval is equal to (100C0a)%. 3. Results and discussion 3.1. Cup-belt speed 3.1.1. Empirical results The measured time intervals between consecutive potatoes touching ground showed a normal distribution. Standard deviations s for feeding rates 300, 400 and 500 potatoes min C01 were 33C10, 20C15 and 12C17ms, respectively. the sheet metal duct was replaced with transparent acrylic sheet; by the high-speed camera According to the F-test the differences between feeding rates were significant. The normal distributions for all three feeding rates are shown in Fig. 4. The accuracy of the planter is increasing with the cup-belt speed, with CVs of 8C16%, 7C11% and 5C15%, respectively. 3.1.2. Results predicted by the model Figure 5 shows the effect of the belt speed on the time needed to create a certain opening. A linear relationship was found between cup-belt speed and the accuracy of the deposition of the potatoes expressed as deviation from the time interval. The shorter the time needed for creating the opening, the smaller the deviations. Results of these calculations are given in Table 2. The speed of the cup turning away from the duct wall is important. Instead of a higher belt speed, an increase of the cups circumferential speed can be achieved by decreasing the radius of the roller. The radius of the roller used in the test is 0C1055m, typical for these planters. It was calculated what the radius of the roller had to be for lower belt speeds, in order to reach the same circumferential speed of the tip of the cup as found for the highest belt speed. This resulted in a radius of 0C1025m for 300 potatoes min C01 and of 0C1041m for 400 potatoes min C01 . Compared to this outcome, a linear trend line based on the results of the laboratory measurements predicts a maximum performance at a radius of around 0C1020m. The mathematical model Eqn (5) predicted a linear relationship between the radius of the roller (for r40C101m) and the accuracy of the deposition of the potatoes. The model was used to estimate standard deviations for different radii at a feeding rate of 300 potatoes min C01 . The results are given in Fig. 6, showing that the model predicts a more gradual decrease in accuracy in comparison with the measured data. A radius of 0C1025m, which is probably the smallest radius technically possible, should have given a decrease in ARTICLE IN PRESS 0 . 035 0 . 030 f (x) 0 . 025 0 . 020 0 . 015 0 . 010 0 . 005 0 . 000 180 260 500340 Time x, ms 420 500 pot min 1 400 pot min 1 300 pot min 1 Standard deviation, ms 15 10 5 0 0 . 00 0 . 02 0 . 04 Radius lower roller, m 0 . 06 0 . 08 y = 922 . 1 x 17 . 597 R 2 = 0 . 9995 Fig. 6. Relationship between the radius of the roller and the standard deviation of the time interval of deposition of the potatoes; the relationship is linear for radii r40C101 m, K, measurement data; m, data from mathematical model; , extended for ro0C101 m; , linear relationship; R 2 , coefficient of determination ASSESSMENT OF THE BEHAVIOUR OF POTATOES 39 Fig. 4. Normal distribution of the time interval (x, in ms) of deposition of the potatoes (pot) for three feeding rates 80 64 48 Size of opening, mm 32 16 0 0 . 00 0 . 05 0 . 10 0 . 15 Time, s 0 . 20 0 . 25 0 . 36 m s 1 0 . 72 m s 1 0 . 24 m s 1 Fig. 5. Effect of belt speed on time needed to create opening Table 2 Time intervals between consecutive potatoes calculated by the model (cv. Marfona) Belt speed, ms C01 Difference between shortest and longest interval, s 0C172 17C16 0C136 29C14 0C124 42C18 35 30 25 20 y = 262 . 21 x 15 . 497 R 2 = 0 . 9987 standard deviation of about 75% compared to the original radius. 3.2. Dimension and shape of the potatoes The results of the laboratory tests are given in Table 3. It shows the standard deviations of the time interval at a fixed feeding rate of 400 potatoes min C01 . These results were contrary to the expectations that higher standard deviations would be found with increasing shape factors. Especially the poor results of the balls were amazing. The standard deviation of the balls was about 50% higher than the oblong potatoes of cv. Arinda. The normal distribution of the time intervals is shown in Fig. 7. Significant differences were found between the balls and the potatoes. No significant differences were found between the two potato varieties. The poor performance of the balls was caused by the fact that these balls could be positioned in many ways on the back of the cup. Thus, different positions of the balls in adjacent cups resulted in a lower accuracy of deposition. The three-dimensional drawing of the cup- belt shows the shape of the gap between cup and duct illustrating that different opening sizes are possible (Fig. 8). and the potatoes, demonstrated that the potatoes of cv. The mathematical model predicted the performance of the process under different circumstances. The model simulated a better performance for spherical balls compared to potatoes whereas the laboratory test showed the opposite. An additional laboratory test was done to check the reliability of the model. In the model, the time interval between two potatoes is calculated. Starting point is the moment the potato crosses line A and end point is the crossing of line C (Fig. 2). In the laboratory test-rig the time-interval between potatoes moving from line A to C was measured (Fig. 3). The length, width and height of each potato was measured and potatoes were numbered. During the measurement it was determined how each potato was positioned on the cup. This position and the potato dimensions were used as input for the model. The measurements were done at a feeding rate of 400 potatoes min C01 with potatoes of cv. Arinda and Marfona. The standard deviations of the measured time intervals are shown in Table 4. They were slightly different (higher) from the standard deviations calcu- ARTICLE IN PRESS Time x, ms H. BUITENWERF ET AL.40 Fig. 7. Normal distribution of the time interval (x, in ms) of deposition of the potatoes for different shape factors at a fixed feeding rate 0 . 050 0 . 045 0 . 040 0 . 035 0 . 030 0 . 025 0 . 020 f (x) 0 . 015 0 . 010 0 . 000 245 255 265 275 285 295 305 315 325 335 0 . 005 Marfona shape factor 168 Arinda shape factor 362 Golf ball (sphere) shape factor 100 Table 3 Effect of cultivars on the accuracy of plant spacing; CV, coefficient of variation Cultivar Standard deviation, ms CV, % Arinda 8C160 3C10 Marfona 9C192 3C15 Golf balls 13C124 4C16 Arinda always were positioned with their longest axis parallel to the back of the cup. Thus, apart from the shape factor, a higher ratio width/height will cause a greater deviation. For cv. Arinda, this ratio was 1C109, for cv. Marfona it was 1C115. 3.3. Model versus laboratory test-rig Arinda tubers were deposited with a higher accuracy than Marfona tubers. Analysis of the recorded frames Fig. 8. View from below to the cup at an angle of 45 degrees; position of the potato on the back of the cup is decisive for its release found. So, to provide more room for reductions in the cup-belt speeds while keeping a high planting accuracy it It is recommended to redesign the geometry of the cups and duct, and to do this in combination with a smaller roller. Acknowledgements using machine vision. Transactions of the ASAE, 38, ARTICLE IN PRESS Table 4 Differences between the standard deviat