【作者】 夏连明；

【导师】 王相友；

【作者基本信息】 东北农业大学 ， 农业机械化工程， 2011， 博士

【摘要】 随着保护性耕作技术的推广应用,精量播种技术已成为播种机发展的主要趋势。精量播种机的性能主要取决于排种装置,玉米精量排种器按原理可分为气力式和机械式两类。国外精量排种器主要以气力式为主,但由于其结构复杂、造价较高限制了其在国内的应用。国内玉米精量排种器多采用机械式,但目前常用的机械式排种器存在对种子尺寸要求严格、充种率不高以及充种过程中伤种率较高的问题。同时,排种性能还与其驱动装置有关,地轮作为播种机的常用驱动机构,其滑移率直接影响排种性能。针对以上问题,本文以实用新型专利《播种机精密排种器,专利号: ZL 200920021268.2》和《播种机防滑地轮,专利号: ZL200920021269.2》为基础,以丸粒化玉米物料特性为依据,提出了一种基于丸粒化种子的精量排种器并对其结构参数进行优化,找出了各因素对排种性能的影响。同时,分析了现有的排种器驱动装置,提出了一种行星啮合式防滑地轮机构,并对其与土壤的相互作用及受力情况进行了分析,为精量播种机的研制提供了的理论和技术支持。1)对常用玉米种子进行了丸粒化,并对丸粒化后玉米种子进行散粒体物料特性分析,测定其尺寸分布、自然休止角、千粒重,为排种器结构设计提供了依据。2)提出了一种具有圆台型排种盘、两侧开有导种槽的异型孔结构的精量排种器。为确保排种器顺利充种和清种,使排种盘与水平面呈一定夹角,通过对处于种箱边缘的种子进行受力分析,此角确定为30°。3)通过对种子群中的单粒种子进行受力分析,得出了充种的相对速度,以种子不飞越型孔为条件,得到了排种盘的极限转速。以丸粒化种子的直径均值为依据,结合可靠性原理确定了型孔的直径。通过对清种装置以及型孔中种子的受力分析,确定导种槽斜面与排种盘底面之间的夹角为45°。利用BP人工神经网络对排种器排种性能进行了预测,建立了精量排种模型,通过网络训练和测试,表明该预测值与试验值有较好的一致性,为排种器结构参数优化和运动参数的选择提供了依据,减少了试验时间与成本。4)通过对排种器结构与原理分析,结合建立的排种性能预测人工神经网络模型,选择排种轴的转速、型孔直径、排种动盘的锥角为研究因素,利用二次回归正交旋转进行试验。按照单粒(精密)播种机试验方法中排种性能指标的计算方法,在JPS-12排种试验台上进行了试验,建立了单粒指数、漏播指数、重播指数以及种子破损率各指标的回归方程,探讨了以上各因素对于排种性能指标的影响。通过对各排种性能指标回归方程的分析,得出排种轴转速与排种动盘锥角对排种性能有显著影响,而型孔直径对各性能指标影响较小。确定排种轴的最佳转速为12～14r/min,型孔直径为15～15.5mm,排种动盘锥角为23～26°。5)提出了一种行星啮合式防滑地轮机构,在地轮机构中增设带有防滑齿的六角星轮,防滑齿与地轮轮辋上的孔啮合并伸出轮外插入土壤中,这种动配合的方式可有效的清除附在轮上的土壤以及防止秸秆缠绕在防滑齿上。此外,还可以根据播种机的不同工作状态调整齿与孔的啮合位置,减小播种机前进中的阻力。6)对行星啮合式防滑地轮机构进行了受力分析,找出了影响地轮通过能力的因素,推导出地轮机构的行走阻力、支承反力以及地轮在松软土壤中的下陷量。通过分析得出地表及土壤状况、地轮直径、地轮宽度、地轮上的垂直载荷以及地轮的抓地力是影响地轮机构滑移率的因素。确定了行星啮合式防滑地轮机构中啮合孔的长度、孔距以及六角星轮的结构。7)提出一种集单片机和传感器技术的滑移率测试及显示系统。运用光电接近开关测量地轮的实际行驶距离,旋转编码器测量地轮的理论行驶距离,运用单片机Atmega16对光电开关和旋转编码器的输出脉冲计数,计算出滑移率并用液晶显示模块适时显示。8)在室内土槽进行了试验,探讨了在已耕和免耕土壤中不同型式地轮的功耗和滑移率,得出行星啮合式防滑机构在功耗差别不大的情况下有较小的滑移率。在不同秸秆覆盖量的地表进行试验,探讨秸秆覆盖量对地轮滑移率的影响,得出滑移率随秸秆覆盖量的增加而增大,在200～251g/m2的覆盖量范围内滑移率较小。在此条件下探讨了土壤的含水率与硬度对地轮滑移率的影响,得出土壤含水率在10～15%范围内地轮的滑移率较小。9)利用二次回归正交旋转进行试验设计,对行星啮合式防滑地轮机构进行了参数优化。选择地轮直径、地轮宽度、地轮的垂直载荷、防滑齿长度为试验因素,建立了滑移率的回归方程,研究各因素对地轮滑移率的影响。通过对回归方程进行分析,得出地轮防滑齿长度、地轮直径与地轮的垂直载荷是影响地轮滑移的显著性因素,地轮的宽度对滑移率影响较小。最佳的参数组合为:地轮直径650mm、地轮垂直载荷为200kg、防滑齿长度30mm,为精密播种机各参数的确定提供了理论依据。更多还原

【Abstract】 With the extension and application of technology for conservation tillage, precision sowing technology had become the main trends of planter. Performance of the planter mainly depended on the seed metering device. Maize seeds metering device was parted into mechanical and pneumatic according to the principle. Pneumatic precision seed metering device was in the majority in abroad, but it was restricted in domestic for its complex structure and high price. The mechanical metering device was more used in domestic but there were some problems with it such as being strict with the size of seeds and high damage to seeds. Moreover, performance of the seed metering device was related to its drive mechanism. As drive mechanism of the seed metering device, high sliding of the ground wheel directly affected the precision of sowing. Aimed at above problems and based on the Patents of Utility Model of Precision Seed Metering Device for Planter (Patent No.200920021268.2) and Ground Wheel for Planter (Petent No. 200920021269.2), a new precision seed metering device for pelleted maize seeds was designed on the basis of materials characteristics of pelleted maize. Meanwhile, its structure parameters were optimized and factors affecting sowing performance were studied. Furthermore, drive mechanism of seed metering device was analyzed and a new ground wheel was designed in this paper, interaction and force betweetn the wheel and soil were also analyzed, and these provided good technical supports for developing better planter.1) Seeds pelleted experiments were conducted with the familiar maize seeds in Shandong Province.Then granular materials characteristics of pelleted maize seeds such as the size distribution, angle of repose and thousand kernel weight were analyzed,and this provided a basisi for structural design of seed metering device.2) In correlation to the available mechanical seed metering devices, a seed metering device was designed in this paper. The metering plate was conical and there were leading slots at both sides of cell. An angle was set between the metering plate and horizontal plane to ensure the process of seed-filling and seed-cleaning, by force analysis of the seed at the edge of seed box, the angle was determined as 30°.3) Seed-filling and seed-cleaning process was studied, by force analysis of single seed among the seeds group, the seed’s relative limiting speed was obtained. The metering axis’s limiting rotary speed were studied on the condition that the seed not overfying the cell. On the basis of average diameter of pelleted seeds and combined with reliability principle, diameter of the cell was determined. By force analysis between the seeds and seed-cleaning device, on the condition that seed was cleaned from the cell, the angle between the leading slot and undersurface of the metering plate was determined as 45°. In this paper, BP artificial neural network was used to predict performance of the seed metering device and establish model for precision metering. By internet training and measurement, the results showed that the predicted value and trial value had good conformity. And this provided basis for optimum design of structure and working parameters and reduced the experimental time and cost.4) By analysis of the structure and principle, combined with the metering performance artificial neural network model, the factors chosen in this paper were the rotary speed of metering axis, diameter of the cell and cone angle of the metering plate. The experiments were conducted with Quadratic-orthogonal-rotation-combination design. According to calculation methods of the metering performance indexes by GB6973-2005, Single (precision)Seeder Experimental Method, experiments on metering performance were conducted on the JPS-12 seed metering device test bench. The regression equations of single index(S), missed index(M), double index(D) were obtained to discuss the effect of structure parameters on the metering performance indexes. By analysis of the regression equations of metering performance indexes, it was concluded that the rotary speed of the metering axis and cone angle of the moving plate had distinct effect on the metering performance indexes, and the diameter of cell had less effect on the performance index. The seed metering device’s best rotary speed was 12～14r/min, diameter of cell was 15～15.5mm, cone angle of moving plate was 23～26°.5)In order to solve the problem of seeds missing due to sliding of ground wheel, a planetary geared anti-sliding ground wheel for planter was designed in correlation to the available drive device of metering device. A six-angle star wheel with anti-sliding tooth was added to the ground wheel. The anti-sliding tooth would mesh with the hole on the wheel rim and stick out of it to enhance the tracking, and this could effectively clear the soil glue to the wheel and prevent the straw from winding on the anti-sliding tooth. Furthermore, the meshing location could be changed according to the different work states of planter and this could reduce the running resistance.6)Force on the wheel was analyzed then factors affecting running ability of ground wheel were found. Furthermore, the wheel’s running resistance(Rx), reaction of support(Ry) and depression value(z0) in the soft soil were derived. From the analysis, it could be concluded that the conditions of the soil, diameter and width of the wheel, vertical load and traction were the factors affecting sliding of the ground wheel. Combined with the available ground wheel’s structure parameters, layout of the meshing hole on the wheel trim and structure of the star wheel were determined.7)According to computational method of sliding of the ground wheel, a sliding test system based on the technologies of sensor and single-chip microcomputer was presented in this paper. The photoelectric switch and rotary encoder were used to test the practical and theoretical distances respectively. The single-chip microcomputer Atmega16 was used to count the number of impulse from the photoelectric switch and rotary encoder, then the sliding was calculated and displayed on the LCD which could help driver of the planter realize the working conditions timely.8)Sliding test experiments were conducted in the indoor soil bin. Firstly, comparative experiments on power consumption and sliding were conducted with different kinds of ground wheels. It was found that the ground wheel presented in this paper had minor sliding with little distinction in power consumption. Secondly, using this ground wheel as object of study, experiments were conducted to study the effects of straw coverage amount on sliding with different straw covered on the ground. It was found that sliding would increase with more straw covered on the ground and the sliding was minor when the straw coverage amount was 200～251kg/m2. Lastly, with the straw coverage amount, the effects of the soil’s moisture content and rigidity on sliding were studied and it was found that the sliding was minor with 10～15% moisture content in the soil.9)Experiments were arranged with quadratic-orthogonal-rotation-combination to optimize the structure parameters. In this paper, the factors chosen were diameter and width of the wheel, vertical load on the wheel and the length of the anti-sliding tooth, then the regression equation was obtained to study the effects of all factors on sliding of the ground wheel. By analysis of the regression equation, it was found that the length of the anti-sliding tooth, diameter of the wheel and vertical load were the remarkable factors affecting the sliding and the width of wheel had little effect on sliding. On the consider of little sliding, the best parameters combination could be achieved when the diameter of wheel was 650mm, the vertical load on wheel was 200kg and the length of anti-sliding tooth was 30mm. This provided theoretical basis for determination of the parameters for the planter.更多还原