【作者】 王强；

【导师】 杨福增； 张卫国；

【作者基本信息】 西北农林科技大学 ， 机械工程， 2018， 硕士

【摘要】 荞麦具有极高的食用价值和药用价值,是国际粮农组织公认的优秀粮、药兼用粮种。荞麦同植株籽粒的成熟时期极不一致且成熟籽粒极易脱落,损失严重,给荞麦机械化收获带来很大难度,其低损失率的机械化收获技术和装备是亟待解决的问题。两段式机械化收获因具有更长的适收期,后熟过程能增加荞麦产量和提高籽粒品质,使回收籽粒的清洁度高,收获作业能大幅降低损失率,因此,两段式收获更适合荞麦的机械化收获。但是,荞麦的捡拾损失率高依然是其两段式机械收获的突出问题。为了降低和优化两段式机械捡拾收获机的捡拾损失,本文在自行研制的机械捡拾收获试验平台上研究了齿带式捡拾器对荞麦捡拾损失的影响,并采用响应面分析方法对试验结果进行了优化研究。本文主要的研究内容和结论如下:(1)通过力学试验测试了不同品种、不同部位(籽粒与花序柄、花序柄与分支、分支与主茎杆)荞麦茎秆的拉伸和剪切性能,为齿带式捡拾器的设计提供理论依据。试验表明:荞麦籽粒与花序柄之间的拉伸力和剪切力均小于花序柄与分支,分支与主茎杆之间的连接力;荞麦茎秆的第3、4、5节之间的拉伸力和剪切力都随着荞麦茎秆直径的增大逐渐变大;同一荞麦品种茎秆的剪切力大于拉伸力;不同荞麦品种穗头之间的连接力差异较小,拉伸强度为20~30N,剪切强度为40~55N;长势相近时,在同样的加载速度和相同的位置处,西农9979品种的连接力比甜荞92-1的连接力大30%,说明西农9979茎秆的木化程度高,抗剪切能力强。(2)对捡拾试验台关键零部件进行了设计建模与仿真分析。基于SolidWorks软件对捡拾试验台的齿带式捡拾器、禾铺输送带和机架等零部件进行了三维设计,进行试验台的预装配和干涉检查,为试验台的制作和装配奠定基础;利用Matlab软件,建立齿带捡拾器的仿真模拟图,对齿带式捡拾齿的运动过程进行了仿真分析。仿真结果表明:当齿带捡拾器的作业速度(禾铺输送速度)与齿带捡拾速度均为0.8m/s时,产生的漏捡区域小,对荞麦的冲击也较小,最大程度地降低了荞麦的捡拾损失。(3)进行了捡拾试验台的搭建和试验台基本性能的测试试验。依据收获机械设计标准要求,当喂入量为2.0kg/s时,进行了试验台对荞麦的输送性能测试,测试结果表明:当禾铺输送带速分别为:0.6m/s、0.8m/s和1.0m/s时,输送带的最大加速距离为3.57m,输送带总长20m能够满足试验要求。(4)分析了影响荞麦两段式捡拾收获损失率的主要因素为:禾铺输送速度、齿带捡拾速度和齿带捡拾倾角,经试验分析得到荞麦捡拾损失率(4的回归模型拟合方程。方差分析表明,本试验的误差不大,二次回归方程模型与试验结果吻合较好。通过响应曲面法对回归方程进行了优化,得出齿带捡拾速度对捡拾损失率影响最大,禾铺输送速度影响次之,齿带捡拾倾角影响最小;在各因素水平的合理范围里,随着因素水平的增加,荞麦捡拾损失率均先减小后增加;通过双因素相互作用的分析可知,捡拾损失率在各因素的零水平附近取得极小值。利用牛顿迭代法对回归方程的设计参数进行优化分析,求解出影响捡拾损失率的一组理论最优参数组合:禾铺输送速度0.8m/s,齿带捡拾速度0.82m/s,齿带捡拾倾角11.56°,优化后的捡拾损失率理论值为2.99%。参考实际作业情况,齿带捡拾器在荞麦两段式机械捡拾的最优参数应为:禾铺输送速度0.8m/s,齿带捡拾速度0.8m/s,齿带捡拾倾角12°,此时对应的捡拾损失率为3.01%,与优化后的理论最优值相差很小。更多还原

【Abstract】 Buckwheat has high food value and medicinal value.It is recognized by the FAO as an excellent food and medicine.The biological characteristics of buckwheat is special,which is inconsistent with the mature period of the grain.Meanwhile,the mature buckwheat grain is easily drop.These have brought great difficulties to the mechanized harvesting of buckwheat.Its low loss rate of mechanized harvesting technology and equipment are urgent issues to be solved.The harvest period of the two-stage mechanized harvest is longer than the combined harvest.The post-harvest process can increase buckwheat production and grain quality,so that the cleanliness of the recycled grain is high,the harvesting operation can greatly reduce the loss rate.Therefore,the two-stage harvesting is more suitable for buckwheat Mechanized harvest.However,the high pickup rate of buckwheat is still a prominent issue in its two-stage mechanical harvest.In order to reduce the loss of picking up of the two-stage mechanical picker.In this paper,the self-developed pick-up harvesting test platform was used to study the effect of the toothed belt picker on buckwheat picking loss and analyze the experimental results by response surface analysis method.The main research contents and conclusions of this paper are as follows:(1)Test the tensile force and shear force of stems in different buckwheat varieties and different parts.The experience results showed that the connection force between the buckwheat twigs and the main stalks was the largest,the stalks and branches were the second,the connection force between the grains and the stalks was the smallest.There was no significant difference in the connection force between the heads of the two buckwheat cultivars,tensile force is 20 ~ 30 N and shear force is 40 ~ 55 N.When the growth is equivalent,at the same loading speed and position,the average connecting force of XiNong 9979 that is 30% greater than that of sweet buckwheat 92-1.It showed that the stalks had high degree of lignification and the ability of shear resistance was stronger than sweet buckwheat 92-1.(2)Designing model and simulation analysis the key components of the pick-up test stand.Based on SolidWorks,the three-dimensional design of pick-and-place test benches such as tooth-belt pickers,crucible conveyor belts and racks was performed.Pre-assembly and interference check of the test bench were performed to lay the foundation for the manufacture and assembly of the test bench.Simple simulation diagram of the tooth belt picker was established by using matlab software and the motion process of the tooth belt pick-up tooth was simulated and analyzed.The simulation results showed when the conveying speed for buckwheat windrow and the rotational speed of toothed belt are all 0.8m/s,the resulting leakage area is smaller and the impact on buckwheat is smaller.So the two-stage harvest fit the low loss of buckwheat picking up harvest.(3)Testing the basic performance of the pick-up test bench.According to the requirements of the harvesting machine design standards,when the feeding amount was 2.0kg/s,the conveying performance of the buckwheat was tested on the test bench.The test results showed when the conveyor belt conveyor speed is: 0.6m/s,0.8m/s and 1.0m/s,the maximum acceleration distance of the conveyor belt is 3.57 m,the total length of the conveyor belt is 20 m to meet the test requirements.(4)The paper analyzed the main influence factors of affecting the harvest loss rate in twostage pickup that is the conveying speed for buckwheat windrow,the rotational speed of toothed belt and the inclination of toothed belt pickup,obtained the regression equation of three factors impacted loss rate of pickup.Analysis of variance showed that the regression model was significant and the simulation was insignificant,that is,the error of the rig test was small.The response surface method was used to optimize the analysis of the regression equation,the rotational speed of toothed belt affected the picking loss rate of buckwheat very much,the conveying speed for buckwheat windrow less and the inclination of toothed belt pick-up the lest.Newton iteration method is used to optimize the design parameters of the regression equation,received a set of solving pick loss rate optimal parameter combinations is: the conveying speed for buckwheat windrow of 0.8m/s,the rotational speed of toothed belt 0.82m/s,he inclination of toothed belt pick-up of 11.56°,the theoretical loss rate of 2.99%.However,taking into account the problem of parameter adjustment during the bench test or actual mechanical operation,the optimal working parameters of toothed belt pickup during the process of picking work for buckwheat were determined,which is the conveying speed for buckwheat windrow of 0.8m/s,the rotational speed of toothed belt of 0.8m/s and the inclination of toothed belt pickup of 12 °,then the picking loss rate is 3.01%,the optimal loss rate of 2.99%.更多还原