我国各地的地理条件和天气环境都有着很大的差异，政府鼓励发展适合当地情况的农业机具。长江中下游地区的土壤特性使得传统农业机具在耕作时土壤粘连严重，加上水稻在收获后秸秆残留量较大、韧性较强，导致秸秆全量还田施肥播种作业时容易发生机具堵塞、下茬农作物架种晾种等问题。近些年，为减少机具重复下田、提高机具作业质量以及更加适应长江中下游地区的田间特点，免耕播种机逐渐开始被应用。针对上述问题，本文结合理论分析、试验研究和数值模拟，以免耕播种机为研究目标，分析秸秆和土壤在机具作业中的运动规律，对免耕播种机具关键部件进行优化设计，最终通过田间试验验证免耕播种机有效性。本文主要研究内容及结论点如下：

（1）运用试验法对全量硬茬水稻秸秆的物理特征以及力学特性进行测试，根据秸秆形状特征和粘结性颗粒提出一种改进刚柔耦合秸秆模型，运用响应面技术得到最佳粘结模型参数，基于改进秸秆模型进行拉伸、压缩、弯曲、剪切过程模拟。对比仿真与试验结果表明，改进刚柔耦合秸秆模型的极限抗拉强度、极限抗压强度、极限弹性模量和极限抗剪强度与试验结果基本一致，验证了改进刚柔耦合秸秆模型的准确性。

（2）考虑稻麦轮作区稻茬地秸秆残留量大、韧性高等特点，基于EDEM软件建立了免耕播种机粉碎室-秸秆耦合系统的离散元模型，运用EDEM2021研究水稻秸秆在免耕播种机粉碎室内部工作机理，分析了碎秸在粉碎室内的运动规律，研究了刀具形状和刀轴转速对抛撒装置出口处秸秆分布的影响规律。仿真结果表明，组合甩刀具有最佳碎茬效果，刀轴最佳转速为1700rad/min。

（3）对长江中下游稻麦轮作区的土壤进行质地分层，运用试验确定耕土层、犁底层及硬土层的土壤物理参数。建立非均质土壤-秸秆-旋耕刀耦合系统的离散元模型，分析了土壤和秸秆的运动规律，并且对旋耕刀重要参数进行优化分析。在此基础上，构建土壤-秸秆-旋耕装置耦合系统的离散元模型，分析了前进速度、刀轴转速和耕深对土壤破碎率、秸秆掩埋率及旋耕刀扭矩的影响规律，通过响应面技术获得了优化的旋耕装置工作参数：前进速度为1.16m/s、旋耕转速为224.74r/min、旋耕深度为131.19mm。

（4）为提高稻麦轮作区稻茬地免耕播种装备的通过性和作业质量，基于离散元模拟和理论分析确定了秸秆粉碎装置和土壤旋耕装置的优化结构尺寸和工作参数，通过田间试验验证了优化设计的有效性。试验结果表明，机具优化后土壤破碎率为89.24%、秸秆掩埋率为88.73%、耕深为9.35cm、耕深稳定性系数为90.77%、耕后地表平整度为3.01cm，机具优化后的作业性能指标显著高于优化前的情况。

China's geographical conditions and weather conditions vary greatly from place to place, and the government encourages the development of agricultural machinery and tools suited to local conditions. The characteristics of soil in the middle and lower reaches of the Yangtze River make the soil adhesion of traditional agricultural machinery and tools serious during tillage. In addition, the residual amount of rice straw after harvest is large and the toughness is strong, which leads to the problems of machine and tools blocking and planting of the next crop during the fertilization and sowing operation of the full amount of straw returning to the field. In recent years, no-tillage planters have been gradually applied in order to reduce the repetition of machine and tools, improve the operation quality of machine and tools, and better adapt to the characteristics of fields in the middle and lower reaches of the Yangtze River. In view of the above problems, this paper combined theoretical analysis, experimental research and numerical simulation, so as to avoid the tillage planter as the research target, analyzed the movement law of straw and soil in the operation of the machine and tools, optimized the design of the key components of the no-tillage planter and tools, and finally verified the effectiveness of the no-tillage planter through field experiments. The main research contents and conclusions of this paper are as follows:

(1) Using the test method to the physical characteristics of the quantity hard crop of rice straw, as well as mechanical properties test, according to the characteristics and the shape of straw particles bonding an improved the coupled model of straw, bonded using response surface technology to get optimal model parameters, based on the improved model of straw for tensile, compression, bending, shear process simulation. The results of simulation and test show that the ultimate tensile strength, ultimate compressive strength, ultimate elastic modulus and ultimate shear strength of the improved rigid-flexible coupling straw model are basically consistent with the experimental results, which verifies the accuracy of the improved rigid-flexible coupling straw model.

(2) Combined with the working conditions of straw returning to the field in the rice-wheat rotation area, EDEM2021 was used to study the internal mechanism of rice straw in the pulverizing chamber for the no-tillage seeder model. The distribution of straw at the outlet of the throwing device under the rotating speed and different crushing knives. The simulation results show that most of the straw in the crushing chamber flows out from the straw diversion device after colliding with the machine wall. When the crushing knife roller is installed with a combined throwing knife, the straw flowability is improved, and when the grinding knife roller rotates at about 1700rad/min, the straw exits the crushing chamber. outflow to the greatest extent possible.

(3) Soil texture stratification was carried out in rice-wheat rotation area in the middle and lower reaches of the Yangtze River, and soil physical parameters of tillage layer, plough bottom layer and hard soil layer were determined by experiments. The discrete element model of the heterogeneous soil-straw-rotary tiller coupling system was established to analyze the movement law of soil and straw, and the important parameters of rotary tiller were optimized. On this basis, a discrete element model of the coupling system of soil-straw-rotary tillage unit was established to analyze the effects of advancing speed, cutter shaft speed and tillage depth on soil fragmentation rate, straw burial rate and rotary tillage knife torque. The optimized operating parameters of rotary tillage unit were obtained by response surface technology: The forward speed was 1.16m/s, rotation speed was 224.74r/min, and rotation depth was 131.19mm.

(4) In order to improve the operability and operation quality of no-tillage seeding equipment in rice-wheat rotation area, the optimized structure size and operating parameters of straw crushing device and soil rotary tillage device were determined based on discrete element simulation and theoretical analysis, and the effectiveness of the optimized design was verified by field experiments. The results showed that the soil fragmentation rate was 89.24%, the straw burial rate was 88.73%, the tillage depth was 9.35cm, the tillage depth stability coefficient was 90.77%, and the surface flatness was 3.01cm. The operating performance indexes after the optimization were significantly higher than those before the optimization.

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