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畢業(yè)設(shè)計(jì)
評(píng) 閱 書
畢業(yè)設(shè)計(jì)(論文)題目： 小型蔬菜播種機(jī)的設(shè)計(jì)
學(xué)生姓名：
提交評(píng)閱文件：設(shè)計(jì)說明書 頁，圖表 張
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畢業(yè)答辯情況表
答辯時(shí)間： 年 月 日
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答辯簡要情況及評(píng)語：
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年 月 日
成
績
本科畢業(yè)設(shè)計(jì)
畢業(yè)設(shè)計(jì)圖冊(cè)
學(xué)生姓名： 學(xué) 號(hào)：
學(xué) 院： 機(jī)電工程學(xué)院
專業(yè)年級(jí)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化
題 目： 小型蔬菜播種機(jī)的設(shè)計(jì)
指導(dǎo)教師：
評(píng)閱教師：
年 月
學(xué)號(hào)： 專業(yè)年級(jí)：
學(xué)生姓名：
設(shè)計(jì)課題: 小型蔬菜播種機(jī)的設(shè)計(jì)
指導(dǎo)教師:
內(nèi)裝：
1.設(shè)計(jì)說明書及附件 1本
2.畢業(yè)設(shè)計(jì)圖紙 1本
3.評(píng)分表 1份
4.答辯記錄表 1份
畢業(yè)設(shè)計(jì)(論文)實(shí)習(xí)報(bào)告
學(xué)生姓名： 學(xué) 號(hào)：
學(xué) 院： 機(jī)電工程學(xué)院
專 業(yè)： 機(jī)械設(shè)計(jì)制造及自動(dòng)化
設(shè)計(jì)(論文)題目： 小型蔬菜播種機(jī)的設(shè)計(jì)
指導(dǎo)教師：
年 月 日
一、實(shí)習(xí)目的
畢業(yè)實(shí)習(xí)是工科本科學(xué)生的一個(gè)很重要的實(shí)踐性教學(xué)環(huán)節(jié)。其任務(wù)是根據(jù)機(jī)械設(shè)計(jì)制造及其自動(dòng)化專業(yè)的培養(yǎng)目標(biāo)，組織學(xué)生參觀相關(guān)的機(jī)械企業(yè)或部門，培養(yǎng)學(xué)生重視實(shí)踐、增強(qiáng)理論聯(lián)系實(shí)際的觀念，深入調(diào)查研究、拓寬視野、增強(qiáng)面向人才市場、服務(wù)于社會(huì)的觀念。
我們這半學(xué)期的主要任務(wù)就是進(jìn)行畢業(yè)設(shè)計(jì)，把我們大學(xué)四年所學(xué)到的機(jī)械知識(shí)理論聯(lián)系現(xiàn)實(shí)生產(chǎn)需求進(jìn)行綜合應(yīng)用。這樣即可以進(jìn)一步鞏固所學(xué)的理論知識(shí)，又對(duì)即將走向的工作崗位作一次實(shí)戰(zhàn)性的演習(xí)。因此這次畢業(yè)設(shè)計(jì)對(duì)于我們這些即將走向工作崗位的大四的畢業(yè)生來說是很重要的。為了給畢業(yè)設(shè)計(jì)做一個(gè)良好的鋪墊，畢業(yè)實(shí)習(xí)便成了一個(gè)不可缺少的環(huán)節(jié)。
二、實(shí)習(xí)時(shí)間：2012.03.10
三、實(shí)習(xí)地點(diǎn)：農(nóng)機(jī)配送站
四、實(shí)習(xí)內(nèi)容
在老師的帶領(lǐng)之下，我們來到了農(nóng)機(jī)配送站，我們此行的目的是參觀跟我們?cè)O(shè)計(jì)題目有關(guān)的播種機(jī)，由于與我們的設(shè)計(jì)課題有關(guān)，所以我們看的很仔細(xì)。我看到了的播種機(jī)的大概結(jié)構(gòu)是：它主要由拖拉機(jī)等機(jī)械帶動(dòng)，在播種機(jī)上的驅(qū)動(dòng)輪的動(dòng)力下驅(qū)動(dòng)，由驅(qū)動(dòng)輪驅(qū)動(dòng)，然后在驅(qū)動(dòng)軸帶動(dòng)下由一組鏈條帶動(dòng)它的另一根軸，這根軸上裝有一邊開槽的圓盤，它的主要目的是實(shí)行穴播，根掘軸的轉(zhuǎn)速配合播種穴距即可設(shè)計(jì)出滿足要求的圓盤開槽的位置及其大小。然后它還設(shè)有一個(gè)專門用來施肥的斗，它的軸在驅(qū)動(dòng)軸的帶動(dòng)下進(jìn)行旋轉(zhuǎn)，然后斗中的化肥便可以施到地早。然后還看到它裝有鎮(zhèn)壓輪，是用來對(duì)播種到土壤里的種子進(jìn)行覆土鎮(zhèn)壓的。我們還細(xì)心注意到它在開溝器的正上方有一個(gè)可以轉(zhuǎn)動(dòng)的裝置，在問過師傅之后我們了解到它是用來防止雜草等物的附著，從而減少行進(jìn)中的阻力，大大提高了工作效率。我還注意到一個(gè)小細(xì)節(jié)，就是他有一部分裝置在我們看來好像沒什么用，問過師傅以后才知道那是用來調(diào)節(jié)驅(qū)動(dòng)輪的高低的，通過調(diào)節(jié)它的高低從而調(diào)節(jié)驅(qū)動(dòng)力的大小以適應(yīng)各種土壤的作業(yè)。我還看到播種機(jī)上的傳動(dòng)裝置所用到的齒輪都是塑料齒輪，想來也是，農(nóng)業(yè)機(jī)械作業(yè)強(qiáng)度不大，用塑料齒輪強(qiáng)度足夠，這樣既節(jié)省材料又節(jié)約了成本，想必也是機(jī)械的發(fā)展趨勢。我所設(shè)計(jì)的題目是電動(dòng)小型播種機(jī)，我的課題動(dòng)力裝置是電動(dòng)的，所以跟這次參觀的還有所不同，我的想法是用電動(dòng)機(jī)作為驅(qū)動(dòng)裝置，然后由它驅(qū)動(dòng)驅(qū)動(dòng)軸轉(zhuǎn)動(dòng)，然后其余工作裝置跟這次參觀的應(yīng)該大致相同，然后再就是對(duì)一些方面進(jìn)行改進(jìn)，以利于操作。以電力為動(dòng)力既經(jīng)濟(jì)又環(huán)保，而且在很大程度上提高了作業(yè)效率。
五、實(shí)習(xí)結(jié)果
參觀完畢以后，我對(duì)我的課題小型蔬菜播種機(jī)有了較為深刻的了解，對(duì)于它的結(jié)構(gòu)、工作原理以及各零部件的結(jié)構(gòu)、作用也有了一些認(rèn)識(shí)。但是如果開始做設(shè)計(jì)的話我感覺手頭資料還是有些不足，而且我對(duì)國內(nèi)外播種機(jī)的發(fā)展現(xiàn)狀了解的不是很多，于是我在空閑之余利用網(wǎng)絡(luò)資源在網(wǎng)上查找了一些與播種機(jī)相關(guān)的資料，在查過資料之后我了解到播種機(jī)的類型按播種方法，可分為以下幾種：
①撒播機(jī)。使撒出的種子在播種地塊上均勻分布的播種機(jī)。常用的機(jī)型為離心式撒播機(jī)，附裝在農(nóng)用運(yùn)輸車后部。撒播裝置也可安裝在農(nóng)用飛機(jī)上使用。
②條播機(jī)。主要用于谷物、蔬菜、牧草等小粒種子的播種作業(yè)。常用的有谷物條播機(jī)，作業(yè)時(shí)，由行走輪帶動(dòng)排種輪旋轉(zhuǎn)，種子按要求由種子箱排入輸種管并經(jīng)開溝器落入溝槽內(nèi)，然后由覆七鎮(zhèn)壓裝置將種子覆蓋壓實(shí)
③穴播機(jī)。按一定行距和穴距，將種子成穴播種的種植機(jī)械。每穴可播1?；驍?shù)粒種子，分別稱單粒精播或多粒穴播，主要用于玉米、棉花、甜菜、向同葵、豆類等中耕作物，又稱中耕作物播種機(jī)。每個(gè)播種機(jī)單體可完成開溝、排種、覆土、鎮(zhèn)壓等整個(gè)作業(yè)過程。
④精密播種機(jī)。以精確的播種量、株行距和深度進(jìn)行作業(yè)的播種機(jī)。具有節(jié)省種子、免除出苗后的問苗作業(yè)、苗距整齊的優(yōu)點(diǎn)。一般在穴播機(jī)各類排種器的基礎(chǔ)上改進(jìn)而成。也有事先將單粒種子按一定間距固定的紙帶播種，或使種子垂直回轉(zhuǎn)運(yùn)動(dòng)的環(huán)形橡膠或塑料制種帶孔排入種溝。
⑤聯(lián)合作業(yè)機(jī)和免耕播種機(jī)。如在谷物條播機(jī)上加設(shè)肥料箱、排肥裝置，即可在播種的同時(shí)施肥。免耕播種機(jī)是在前茬作物收獲后直接開出種溝播種，以防止水土流失、節(jié)省能源，降低作物成本。
我們組由于每個(gè)人的設(shè)計(jì)題目不同，所以在這次實(shí)習(xí)時(shí)不僅看到了與我的設(shè)計(jì)有關(guān)的播種機(jī)，而且還和其他同學(xué)一起觀看了關(guān)于數(shù)控切割機(jī)、鋁壺上底機(jī)等設(shè)備，擴(kuò)大了我的視野。通過這次實(shí)習(xí)，再結(jié)合前一段時(shí)間查閱的大量資料，給我的設(shè)計(jì)也帶來了許多靈感。經(jīng)過查閱資料和深入工廠實(shí)習(xí)，自己深深地體會(huì)到要想搞好設(shè)計(jì)，就要耐心仔細(xì)地查找與設(shè)計(jì)相關(guān)的資料和信息，它要包括設(shè)計(jì)產(chǎn)品的基本功能、主要結(jié)構(gòu)、應(yīng)用特點(diǎn)及其發(fā)展前途，市場效益等。除此之外，我們還要對(duì)各種零部件型號(hào)的選擇，從實(shí)用性和經(jīng)濟(jì)性等方面進(jìn)行深入的了解，全面的考慮。只有這樣，才能為自己以后較快的融入社會(huì)工作之中，少走彎路，少犯錯(cuò)誤打下一個(gè)較好的基礎(chǔ)。
我設(shè)計(jì)的是穴播機(jī)，在上網(wǎng)查到一些資料以后，再結(jié)合我自己所參觀學(xué)習(xí)到的內(nèi)容，充分利用現(xiàn)有成熟的設(shè)計(jì)部分，以便節(jié)約設(shè)計(jì)時(shí)間和提高產(chǎn)品的可靠性與經(jīng)濟(jì)性。通過這次實(shí)習(xí)我收集了大量的實(shí)用資料，為正式的設(shè)計(jì)做好了充分的準(zhǔn)備。
六、實(shí)習(xí)總結(jié)及體會(huì)
由于我們這一組每個(gè)人的設(shè)計(jì)題目都不相同，在設(shè)計(jì)過程中肯定會(huì)出現(xiàn)一些靠個(gè)人力量很難解決的問題，為了我們大家在將來的設(shè)計(jì)中能互相幫助，發(fā)揮團(tuán)隊(duì)精神，大家通力合作，順利完成設(shè)計(jì)，同時(shí)也為了我們能學(xué)到更多專業(yè)性知識(shí)，增強(qiáng)我們的專業(yè)技能，開闊我們的眼界。相信在萬斌老師以及其它同學(xué)的幫助下，我肯定能增長不少知識(shí)，從而為做好這次設(shè)計(jì)給予很大的幫助。
通過這次實(shí)習(xí)一方面鞏固了我們?cè)械臅旧系睦碚撝R(shí)并為我們以后將要學(xué)習(xí)到的更多專業(yè)知識(shí)奠定了良好的基礎(chǔ)，另一方面使我們能夠掌握要領(lǐng)，并做到舉一反三，培養(yǎng)自己分析和解決生產(chǎn)實(shí)際問題的能力，提前進(jìn)入未來將要從事的工作角色。
實(shí)習(xí)雖然結(jié)束了，但通過實(shí)習(xí)使我們獲得基本生產(chǎn)的感性知識(shí)，理論聯(lián)系實(shí)際，擴(kuò)大我們的知識(shí)面；同時(shí)也鍛煉和培養(yǎng)我們業(yè)務(wù)能力及素質(zhì)，培養(yǎng)我們具有吃苦耐勞的精神，也是我們接觸社會(huì)、了解企業(yè)的一個(gè)絕好的機(jī)會(huì)。我們掌握了工程機(jī)械設(shè)計(jì)的基本流程、各種參數(shù)的選擇、各種影響因素產(chǎn)生的特點(diǎn)，從而使我們從容的面對(duì)以后的設(shè)計(jì)和我們即將踏入的工作崗位。
第 3 頁
畢業(yè)設(shè)計(jì)(論文)翻譯
學(xué)生姓名： 學(xué) 號(hào)：
學(xué) 院： 機(jī)電工程學(xué)院
專 業(yè)： 機(jī)械設(shè)計(jì)制造及自動(dòng)化
設(shè)計(jì)(論文)題目： 小型蔬菜播種機(jī)的設(shè)計(jì)
指導(dǎo)教師：
年 月 日
Mathematical Modelling of Vacuum Pressure on a Precision Seeder
Abstract
The purpose of this research was to determine the optimum vacuum pressure of a precision vacuum seeder and to develop mathematical models by using some physical properties of seeds such as one thousand kernel mass, projected area, sphericity and kernel density. Maize, cotton, soya bean, watermelon, melon, cucumber, sugarbeet and onion seeds were used in laboratory tests. One thousand kernel mass, projected area, sphericity and kernel density of seeds varied from 4.3 to 372.5?g, 5–77?mm2, 38.4–85.8% and 440–1310?kg?m?3, respectively. The optimum vacuum pressure was determined as 4.0?kPa for maize I and II; 3.0?kPa for cotton, soya bean and watermelon I; 2.5?kPa for watermelon II, melon and cucumber; 2.0?kPa for sugarbeet; and 1.5?kPa for onion seeds.
The vacuum pressure was predicted by mathematical models. According to the results, the final model could satisfactorily describe the vacuum pressure of the precision vacuum seeder with a chi-square of 2.51×10?3, root mean square error of 2.74×10?2 and modelling efficiency of 0.99.
Nomenclature
Nomenclature
a, b, c, d, e regression coefficients
Em modelling efficiency
Erms root mean square error
kexp experimental vacuum pressure, kPa
kexp, mean mean value of experimental vacuum pressure, kPa
kpre predicted vacuum pressure, kPa
L length, mm
m1000 one thousand kernel mass, g
N number of observation
n number of constants in the model
P projected area, mm2
Pv vacuum pressure, kPa
p probability
R2 coefficient of determination
T thickness, mm
W width, mm
φ sphericity, %
χ2 chi-square
ρk kernel density, kg?m?3
Article Outline
Nomenclature
1. Introduction
2. Literature review
3. Materials and methods
4. Results and discussion
5. Conclusions
Acknowledgements
References
1. Introduction
Precision sowing has been a major thrust of agricultural engineering research for many years; however, most of the research and development work has dealt with seeders for agronomic crops.
The main purpose of sowing is to place the seed to a certain space and a depth in the seedbed. Precision seeders place seeds at the required spacing and provide a better growing area per seed. There are two common types of precision seeders: belt and vacuum. Precision vacuum seeders have a metering plate with metering holes on a predetermined radius. A vacuum is applied to these metering holes by means of a race machined in a backing plate. As the plate rotates, the vacuum applied to the metering holes enables them to pick up seeds from the seed hopper. Precision vacuum seeders have the following advantages over the mechanical seeders: better working quality, more precise seed rates with lower rate of seed damage, better control and adjustment of upkeep and drift of seeds, and broader spectrum of applicability (Soos et al., 1989).
A seeder should place a seed in an environment in which the seed will reliably germinate and emerge. A number of factors affect the spacing of plants. The seed selection mechanism may fail to select or drop a seed resulting in large spacing between seeds. The mechanism may select and drop multiple seeds resulting in small spacings between seeds. Seed quality, soil conditions, seeder design and the skill of the operator all play a part in determining the final plant stand.
The physical properties of seeds are essential for the design of equipment for handling, processing, storing and sowing the kernels. Various types of cleaning, grading, separation and sowing equipment are designed on the basis of the physical properties of seeds. However, no model has been found to describe seeder parameters such as vacuum pressure related with physical properties of seeds.
The physical properties of the seeds are the most important factors in determining the optimum vacuum pressure of the precision vacuum seeder. In this study, using some of these, e.g. one thousand kernel mass, projected area, sphericity and kernel density, mathematical models were developed to predict optimum vacuum pressure. The experimental values of vacuum pressure were determined from laboratory test procedure.
2. Materials and methods
The laboratory test procedure involved testing the metering uniformity of the seeder at the different vacuum pressure with the different seeds: two different maize varieties (maize I and maize II), cotton, soya bean, two different watermelon varieties (watermelon I and watermelon II), melon, cucumber, sugarbeet and onion. These seeds represent several seed shapes varying from spherical (soya bean, maize II) to flat and elongated (maize I, melon, watermelon, cucumber). Two different varieties of maize and watermelon seeds were selected, because of the more diverse range of one thousand kernel mass, projected area, sphericity or kernel density than other seeds. All seeds used in this research were uncoated seed. The main dimensions of the seeds are given in Table 1. The seeder was set to space the seeds as closely to the recommended spacing as possible.
Table 1. Means and standard errors of the seed dimensions
A grease belt test stand was used to determine sowing uniformity of each seed at the different vacuum pressures. This particular test stand had a 150?mm wide belt with a 7·5?m long horizontal viewing surface. A seeder row unit was mounted on a greased belt test stand which utilised an adjustable speed drive mechanism to operate the seed metering devices at a known constant speed. Sufficient oil was added to the top surface of belt to capture the seed as it was released from seeder unit without rolling or bouncing of seed on the belt surface. A wide variety of measures were used to qualify seeder performance with regard to plant spacing (Brooks & Church, 1987; Karayel & ?zmerzi, 2001; Jasa & Dickey, 1982). Some tests used performance measures involving distance between plants in the field. Other tests used performance measures involving distance between seeds on grease belt test stand or by opto-electronic sensor system ( Bracy et al., 1998; Smith et al., 1991; Lan et al., 1999). A few tests used performance measures involving distance between seeds sown into soil ( Panning, 1997).
A precision vacuum seeder unit was operated in all treatments (Fig. 1). The seeder unit was a general purpose seeder designed for row crops such as maize and soya beans. Three different vacuum plates with different hole diameters were used in the metering mechanism. The diameter of vacuum plates were 230?mm. The holes were drilled along a 200?mm diameter pitch circle. The holes of the vacuum plate were 3·5?mm in diameter for maize I, II, soya bean and cotton; 2·5?mm in diameter for watermelon I, II, melon, and cucumber and 1·5?mm in diameter for sugarbeet and onion. The seed plate operated in a vertical plane. Air suction from the holes of the seed plate caused the seed to stick to the holes. The stuck seed was released from the rotating plate by temporarily preventing airflow. The absence of suction allowed the seed to be dropped into soil. It had no seed tube and the seed fall height (12?mm) of the seeder was kept low in order to reduce the chance of non-uniform spacing which can occur due to the bouncing of seed, if dropped from high plane. The vacuum level was regulated by adjusting the size of an opening in the vacuum line of seeder and measured with a manometer.
Fig. 1. The metering mechanism of the precision vacuum seeder: 1, vacuum plate; 2, seed; 3, seed box; 4, air suction canal; 5, air cut; 6, furrow opener
The seeder was operated over the greased belt at a ground speed of 1?m?s?1 and adjusted to four vacuum pressures 2.0, 3.0, 4.0 and 5.0?kPa for maize I, II, soya bean and cotton; 2.0, 2.5， 3.0 and 3.5?kPa for melon, watermelon I, II and cucumber; 1.0, 1.5, 2.0 and 2.5?kPa for sugarbeet and onion seeds. Seed spacings were measured over a distance of 7?m. The seeder was adjusted to deliver a nominal seed spacing of 230?mm for maize I and II, 170?mm for cotton, 105?mm for soya bean, 550?mm for watermelon I, II, melon and cucumber, 150?mm for sugarbeet and 85?mm for onion.
The sowing uniformity was analysed using the methods as described by Kachman and Smith (1995). The multiple index is the percentage of spacings that are less than or equal to half of the theoretical spacing and indicates the percentage of multiple seed drops. The miss index is the percentage of spacings greater than 1.5 times the theoretical spacing and indicates the percentage of missed seed locations or ‘skips’. Quality of feed index is the percentage of spacings that are more than half but no more than 1.5 times the theoretical spacing. Quality of feed index is 100% minus miss and multiple index and indicates the percentages of single seed drops. Preciseness is the coefficient of variation of the spacings that are classified as singles after omitting the outliers consisting of misses and multiples.
Kachman and Smith (1995) recommended using miss index, multiple index, quality of feed index and preciseness for summarising the uniformity of seeder metering rather than mean or sample coefficient of variation. They concluded that several measures were needed to give a true picture of seeder uniformity. For this study, miss index, multiple index, quality of feed index and preciseness are reported.
Various physical properties of seeds including kernel density, projected area, sphericity and one thousand kernel mass are the most important factors in determining the optimum vacuum pressure of the precision vacuum seeder (Barut, 1996). The physical properties of the seeds were determined by the following methods:
Linear dimensions, i.e. length, thickness and width were measured by using a vernier caliper with a sensitivity of 0.01?mm. Sphericity φ were calculated by using the following equation (Mohsenin, 1970):
(1)
where: L is the length; W is the width; and T is the thickness in mm.
One thousand kernel mass was measured by an electronic balance with a sensitivity of 0.001?g.
Kernel density was measured by the liquid displacement method. Toluene (C7H8) was used rather than water because it was not absorbed by fruits (Mohsenin, 1970; ?g?t, 1998).
Projected area was determined by using a digital camera (Kodak DC 5000) and Sigma Scan Pro 5 program.
For the estimation of the vacuum pressure, in relation to kernel density, projected area, sphericity and one thousand kernel mass, mathematical models were developed. The suitability of the final model was compared and evaluated using chi-square, root mean square error and modelling efficiency. Chi-square χ2, root mean square error Erms and modelling efficiency Em were calculated as follows:
(2)
(3)
(4)
where: kexp is the experimental vacuum pressure in kPa; kexp,mean is the mean value of experimental vacuum pressure in kPa; kpre is the predicted vacuum pressure in kPa; N is the number of observations; and n is the number of constants in the model.
Reduced chi-square is the mean square of the deviations between the experimental and calculated values for the models and, is used to determine the goodness of the fit. The lower values of the reduced chi-square, the better the goodness of the fit. The root mean square error shows the deviations between the calculated and experimental values and it requires to reach zero. The modelling efficiency also shows the ability of the model and its highest value is 1 (Yaldiz et al., 2001; Ertekin & Yaldiz, 2004).
Each experiment was arranged as a randomised complete block (Neter et al., 1990) and replicated five times. An analysis of variance method was applied to analyse data sets using a statistical software package SAS. Duncan's multiple-range tests were used to identify significantly different means within dependent variables.
3. Results and discussion
The effect of vacuum pressure on sowing uniformity of the vacuum seeder was analysed relating to the multiple index, miss index, quality of feed index and preciseness. Multiple index, miss index and quality of feed index were combined for analysis of variance to determine the significant difference in the variability among the parameters. The results of this analysis are given in Table 2, Table 3 and Table 4. All measurement of sowing uniformity of the vacuum seeder were affected by vacuum pressure.
Table 2. The sowing uniformity of the vacuum seeder with maize I and II, cotton and soya bean seeds for different vacuum pressure
Note: Means within a group followed by same letter are not significantly different at probability p=0·05, by Duncan's multiple range test.
Table 3. The sowing uniformity of the vacuum seeder with watermelon I and II, melon and cucumber seeds for different vacuum pressure
Note: Means within a group followed by same letter are not significantly different at probability p=0·05, by Duncan's multiple range test.
Table 4. The sowing uniformity of the vacuum seeder with sugarbeet and onion seeds for different vacuum pressure
Note: Means within a group followed by same letter are not significantly different at probability p=0.05, by Duncan's multiple range test.
The optimum vacuum pressure was determined for each seed according to quality of feed index and preciseness. As can be seen from laboratory study results in Table 2, Table 3 and Table 4, the highest seed spacing uniformities (quality of feed index) and the lowest preciseness values were obtained at the vacuum pressure of 4.0?kPa for maize I and II; 3.0?kPa for cotton, soya bean and watermelon I; 2.5?kPa for watermelon II, melon and cucumber; 2.0?kPa for sugarbeet and 1.5?kPa for onion seeds. The most uniform sowing uniformity was obtained with soya bean seeds at any vacuum pressures. Uniform, spherical seeds such as soya bean and maize II were easy to meter with the vacuum metering system.
The miss index decreased and the multiple index increased with increasing vacuum pressure for all seeds. Multiple seed drops were more common than misses for watermelon I and II, melon, cucumber, onion and sugarbeet seeds. Few ‘skips’ or multiple drops occur at any vacuum pressure for maize I and II, cotton and soya bean seeds.
Loss of uniformity of the vacuum seeder was probably a combination of several factors. The results support reports from Barut (1996) who found that the pattern efficiency of the vacuum plate differed most at lower or higher vacuum pressures and faster wheel speeds. In this research, preciseness and quality of feed index of the vacuum seeder were poorer at the lower and higher vacuum pressures than optimum vacuum pressure.
One thousand kernel mass, projected area, sphericity and kernel density of seeds are given in Table 5. One thousand kernel mass, projected area, sphericity and kernel density of seeds varied from 4.3 to 372.5?g, 5–77?mm2, 38.4–85.8% and 440–1310?kg?m?3, respectively.
Table 5. Means and standard errors of the seed dimensions
The relationship between one thousand kernel mass, projected area, sphericity and kernel density with vacuum pressure presented in Fig. 2, Fig. 3, Fig. 4 and Fig. 5. For the determination of the relationship between the one thousand kernel mass and the projected area with vacuum pressure, the power model was used. For the determination of relationship between the sphericity and the kernel density with the vacuum pressure, the linear model was used. The diagrammatic representation of the models results in a curve that fits well for the description of the vacuum pressure. The relationship between one thousand kernel mass with vacuum pressure is better than the others with the highest coefficient of determination of 0.92.
Fig. 2. Vacuum pressure of precision vacuum seeder as a function of one thousand kernel mass; R2, coefficient of determination
Fig. 3. Vacuum pressure of vacuum seeder as a function of projected area; R2, coefficient of determination
Fig. 4. Vacuum pressure of vacuum seeder as a function of sphericity; R2, coefficient of determination
Fig. 5. Vacuum pressure of vacuum seeder as a function of kernel density; R2, coefficient of determination
All possible combinations of the different variables were tested and included in the regression analysis. The multiple combinations of one thousand kernel mass, projected area, sphericity and kernel density that gave the lowest root mean square error and chi-square and the highest modelling efficiency were finally included in the final model. Based on the multiple regression analysis the accepted model constants, coefficients, chi-square χ2, root mean square error Erms and modelling efficiency Em were as follows:
Pv=a+bm10000·27+cP?0·02?dφ+eρk
where: Pv is the vacuum pressure in kPa; m1000 is one thousand kernel mass in g; P is the projected area in mm2; φ is the sphericity in %; ρk is the kernel density in kg?m?3. The optimum values of the coefficient a, b, c, d, and e, namely 1.00, 0.72, 2.09×10?3, 0.01 and 0.37×10?3, respectively, gave values for χ2 of 2.51×10?3, for Erms of 2.74×10?2, and for Em of 0.99.
Validation of the established final model was evaluated by comparing the computed vacuum pressures with the observed vacuum pressures. The performance of the model was illustrated in Fig. 6. The predicted data generally banded around the straight line which showed the suitability of the final model in describing vacuum pressure of the seeder.
Fig. 6. Experimental versus predicted vacuum pressure values by final model; R2, coefficient of determination
4. Conclusions
In laboratory tests, the optimum vacuum pressure of a precision vacuum seeder was determined as 4.0?kPa for maize I and II; 3.0?kPa for cotton, soya bean and watermelon I; 2.5?kPa for watermelon II, melon and cucumber; 2.0?kPa for sugarbeet and 1.5?kPa for onion seeds.
In order to predict vacuum pressure in relation to one thousand kernel mass, projected area, sphericity and kernel density of seeds, mathematical models were developed. The relationship between one thousand kernel mass with vacuum pressure was better than the others with the highest coefficient of determination. The final model could satisfactorily describe the vacuum pressure of the precision vacuum seeder with a chi-square of 2.51×10?3, root mean square error of 2.74×10?2 and modelling efficiency of 0.99.
Acknowledgements
The corresponding author acknowledge the help of Dr. Can ERTEKIN in developing the mathematical models.
真空壓力播種機(jī)的數(shù)學(xué)建模
引言
這項(xiàng)研究的目的是確定最佳的精密真空壓力播種機(jī)。通過運(yùn)用種子的一些物理性質(zhì)如每1000粒種子的質(zhì)量,表面積、圓度和種子密度來建立數(shù)學(xué)模型.。分別取玉米、棉花、大豆、西瓜、甜瓜、黃瓜、甜菜、洋蔥的種子作為實(shí)驗(yàn)對(duì)象。結(jié)果，每1000粒種子質(zhì)量、表面積、圓度和種子密度分別為4.3-372.5g、 5-77m2、38.4–85.8%、440-1310千克/m3。最佳的真空壓力：玉米種子（I、II）為4kPa；棉花、黃豆和西瓜（I）種子為3kPa；西瓜（II）、甜瓜和黃瓜種子為2.5kPa；甜菜種子為2kPa；洋蔥種子為1.5kPa。
最終，數(shù)學(xué)模型能準(zhǔn)確模擬出真空壓力。研究結(jié)果顯示：模型能準(zhǔn)確地模擬出精密真空壓力播種機(jī)的真空度為2.51×10-3； 均方根誤差為2.74×10-2。模擬效率率高達(dá)99%。
各參數(shù)含義
回歸系數(shù): a,b,c,d,e
模型效率：Em
均方根誤差：Erme
試驗(yàn)真空壓力 (kPa)：Kexp
試驗(yàn)真空壓力平均值(kPa): Kexp.mean
真空預(yù)壓(kPa):Kpre
長度(mm)：L
每千粒種子質(zhì)量(g)：m1000
種子數(shù)目：N
模型種子數(shù)常量：n
表面積(mm2)：P
真空壓力(kPa)：Pv
概率：p
確定系數(shù)：R2
厚度(mm)：T
寬度(mm)：W
圓度(%)：φ
方差：x2
種子密度(kg/m3)：ρk
文章概要
標(biāo)題
1.引言
2.材料和方法
3.結(jié)果與討論
4.結(jié)論
5.致謝
6.參考資料
1.引言
精密播種作為主要農(nóng)業(yè)工程研究已經(jīng)多年。所以,大部分的研究和開發(fā)成果已經(jīng)運(yùn)用到了農(nóng)業(yè)播種。
現(xiàn)在，研究的主要目的是把種子播到一定深度的苗床上。精密播種機(jī)必須讓種子之間有一定間隔，以適應(yīng)種子生長?，F(xiàn)在，有兩種類型的精密播種機(jī):皮帶播種機(jī)和真空壓力播種機(jī)。真空壓力播種機(jī)有一帶有固定半徑計(jì)量孔的真空計(jì)量板。計(jì)量板應(yīng)用這些計(jì)量手段洞競賽通過一回收裝置. 由于平板旋轉(zhuǎn)、真空所產(chǎn)生的壓力使種子從這些孔中漏出. 精密真空壓力播種機(jī)具有以下優(yōu)點(diǎn)：更好的工作質(zhì)量、較低種子損害率、更好地控制和保護(hù)種子、還有廣泛的適用性。
精密播種機(jī)需要把種子播種在一個(gè)可靠的環(huán)境,使種子發(fā)芽并生長。很多