【作者】 张宏建；

【导师】 王金星；

【作者基本信息】 山东农业大学 ， 农业机械化工程， 2021， 博士

【摘要】 苹果作为我国第一大水果,近年来种植面积逐步扩大,产量稳步增加,我国已成为世界优质苹果的最大产区。基肥施肥作为苹果周年生产中最重要的施肥方式,不仅可以供给果树整个生长周期所需要的养分,为果树生长发育创造良好的土壤条件,还可以减少化肥施用量、提高施肥质量、增加施肥效果,实现果树产业的可持续发展。现阶段,我国苹果园基肥施肥仍以人工作业为主,机械化程度低,作业强度大、施肥效率低、施肥效果差,已严重制约我国苹果产业的发展。基肥施肥机械可以减轻劳动强度、降低人工成本,是实现苹果园减肥、提质、增效的关键措施。本文结合苹果树基肥施肥的农艺要求和土壤、肥料的物理力学特性,设计研发一种果园双行开沟施肥机,并对其关键技术和作业性能进行试验与研究。重点从苹果树开沟施肥的农艺要求和土壤、肥料的物理力学特性入手,设计果园双行开沟施肥机的整机结构及关键部件,应用离散元数值模拟软件对其作业过程进行动态模拟仿真,分析土壤、肥料的受力和运动过程,优化果园双行开沟施肥机的关键结构及作业参数,基于粒形特征构建肥料压碎力预测模型,探究影响肥料破碎的关键粒形特征,减小作业过程中肥料的破碎率。果园双行开沟施肥机的研制解决了苹果树机械化混合深施有机肥和化肥的难题,提高了基肥施肥的作业效率和效果,对实现苹果树机械化生产和化肥减施增效具有重要意义。主要研究内容与结果如下:（1）果园双行开沟施肥机整机结构设计。结合苹果树开沟施肥的农艺要求,通过理论分析设计果园双行开沟施肥机的整机结构和开沟装置、施肥装置、开沟深度自动调节装置等关键部件,搭建基于STM32F103的核心控制系统,实现苹果树开沟、有机肥与化肥混合深施、覆土一体化作业。（2）土壤与肥料物理力学特性研究。通过烘干法、环刀法、坚实度测量仪、斜面滑动法、自由跌落法等测量并分析土壤与肥料的基本物理力学特性,为准确建立“土壤”、“肥料”、“土壤-开沟刀”、“肥料-机体”的离散元模型提供基础数据。试验结果表明:耕作层、犁底层、心土层土壤含水率分别为15.20%、17.44%、18.72%,土壤密度分别为1.67 g·cm^-3、1.76 g·cm^-3、1.80 g·cm^-3,土壤坚实度分别为1508 Pa、1715 Pa、1848 Pa,土壤休止角分别为35.58°、41.10°、48.20°,土壤泊松比分别为0.36、0.40、0.42;耕作层、犁底层、心土层土壤与接触面的静摩擦系数分别为0.41、0.53、0.58,动摩擦系数分别为0.08、0.16、0.19,恢复系数分别为0.39、0.50、0.54。有机肥、复合肥含水率分别为8.25%、1.12%,有机肥、复合肥密度分别为1.05 g·cm^-3、1.33 g·cm^-3,有机肥、复合肥休止角分别为17.71°、16.27°,有机肥、复合肥刚度分别为76.58 N/mm、88.69N/mm;有机肥、复合肥与钢板的静摩擦系数分别为0.30、0.23,动摩擦系数分别为0.26、0.18,恢复系数分别为0.29、0.38。（3）果园双行开沟施肥机开沟作业关键技术研究。研究果园双行开沟施肥机的开沟机理,建立土壤颗粒的运动学模型,分析影响开沟作业质量的关键试验因素,在EDEM软件中完成土壤颗粒离散元标定,并以开沟深度稳定性系数、沟底宽度一致性系数、覆土率为试验指标,应用Box-Behnken试验设计方法建立试验因素与试验指标之间的回归模型,分析各因素对试验指标的交互作用和影响规律,并综合优化各试验因素,得到最优作业参数组合:整机前进速度0.8 m/s、开沟刀转速348 r/min、开沟刀偏转角32°,此时开沟深度稳定性系数为98.33%、沟底宽度一致性系数为96.32%、覆土率为81.53%。（4）果园双行开沟施肥机混合深施肥技术研究。研究果园双行开沟施肥机的施肥机理,建立肥料颗粒的运动学模型,分析影响施肥作业质量的关键试验因素——排肥螺旋转速、排肥链轮转速、传送带转速、导板角度,并以化肥均匀分布系数、有机肥均匀分布系数、混合肥均匀分布系数为试验指标,建立各试验因素与试验指标之间的回归模型,分析各因素对试验指标的交互作用和影响规律,并综合优化各试验因素,得到最优作业参数组合:排肥螺旋转速70r/min、排肥链轮转速45 r/min、传送带转速200 r/min、导板角度35°,此时化肥均匀分布系数为93.58%、有机肥均匀分布系数为91.12%、混合肥均匀分布系数为95.25%。（5）基于粒形特征的肥料筛选技术研究。为减小果园双行开沟施肥机作业过程中肥料的破碎率,自主研发基于双目视觉的肥料粒形特征测定仪,无损测量复合肥与有机肥颗粒的粒形特征,通过支持向量机和改进差分进化算法构建肥料压碎力的预测模型,并根据此预测模型探究影响肥料破碎的关键粒形特征参数,得到复合肥与有机肥的粒度优化范围分别为4.30～5.44 mm和3.90～4.60 mm,为肥料筛选提供理论依据。（6）果园双行开沟施肥机的整机研制、性能试验和田间试验。根据果园双行开沟施肥机的设计参数完成整机研制,并按照相关标准规定的开沟、施肥机械作业质量评价试验方法,以开沟深度一致性、施肥均匀度和肥料破碎率等为关键试验指标,对机具作业效果进行性能验证和田间试验。试验结果表明:筛选后有机肥、复合肥的破碎率均小于筛选前各肥料的破碎率,肥料的压碎力预测模型及粒度优化范围合理有效;果园双行开沟施肥机可一次实现果园双行开沟、有机肥与化肥混合深施、覆土一体化作业,开沟深度稳定性系数不小于95.25%、沟底宽度一致性系数不小于95.59%、覆土率不小于81.09%、有机肥分布稳定性系数不小于91.92%、化肥分布稳定性系数不小于92.40%、混合肥分布稳定性系数不小于94.02%,评价指标符合果树开沟施肥的技术要求。更多还原

【Abstract】 As the planting area and output of apple trees,the most popular fruit in China,are gradually expanding and steadily increasing in recent years,China has become the world’s largest producing region of high-quality apples.Base-fertilizer fertilization as the most important fertilization method in annual production of apples,can supply the nutrients needed for the entire growth cycle of apple trees and create good soil conditions for the growth and development of the trees,while reducing the amount of chemical fertilizers added,improving the quality of fertilization,and increasing the effect of fertilization.In all,it is a way to realize the sustainable development of the fruit tree industry.At this current stage,the way to fertilize apple orchards with base-fertilizers in China is still dominated by manual operation for the low degree of mechanization,featuring high operation intensity,low fertilization efficiency,and poor fertilization effect,which has severely restricted the development of China’s apple industry.The mechanized base-fertilizer fertilization can reduce labor intensity and labor costs,and is a key measure to achieve fertilizer cut,quality and efficiency improvement in apple orchard development.In this paper,the agronomic requirements of base-fertilizer fertilization for apple trees and the physical and mechanical properties of soil and fertilizers were considered to develop a double-row ditching-fertilizer machine for orchards;meanwhile,its key technology and operational performance were tested and studied.While focusing on the agronomic requirements of ditching and fertilization for apple trees and the physical and mechanical properties of soil and fertilizers,we designed the whole structure and key components of the double-row ditching-fertilizer machine targeted at orchards,and applied the discrete element numerical simulation software to dynamically simulate the operation process to analyze the stress and movement process of soil and fertilizers,a way to optimize the key structure and operating parameters of the machine.Meanwhile,we explored key grain shape traits that affect the crushing of fertilizers to reduce the crushing rate of fertilizers in operation while building a fertilizer fragmentation force prediction model based on the grain shape traits.In conclusion,the orchard double-row ditching and fertilizer machine serves to solve the problem of mechanized spraying of organic and chemical fertilizers into a deeper depth for apple trees,improving the efficiency of ditching and fertilization and the effect of fertilization,and is of great significance to enhancing the mechanized production of the apple tree industry and the reduction of chemical fertilizers added while boosting efficiency.The main research contents and results are listed as follows:（1）The overall structure of the orchard double-row ditching-fertilizer machine.Considering the agronomic requirements of apple tree ditching and fertilization,we designed the whole structure of the machine as well as key components related such as the ditching device,fertilizing device,and automatic depth adjustment device for ditching following theoretical analysis.The core control system based on STM32F103 was then built to realize the integrated operation of apple tree ditching,mixed fertilizer application in depth,and earth covering.（2）The physical and mechanical properties of soil and fertilizer.Methods including oven drying method,cutting ring method,soil compaction measuring instrument,slope sliding method and free fall method were employed to measure and analyze the basic physical and mechanical properties of soil and fertilizers,in order to get basic data to establish an accurate discrete element model for“soil,fertilizer,soil-ditching cutting,and fertilizer-machine body”.The test results show that as for the cultivated layer,plow pan layer,and subsoil layer,the soil moisture content is 15.20%,17.44%,and 18.72%,the soil density is 1.67 g·cm^-3,1.76 g·cm^-3,and 1.80 g·cm^-3,the soil compaction is 1508 Pa,1715 Pa,1848 Pa,the angle of repose of the soil is 35.58°,41.10°,and 48.20°,and the soil Poisson’s ratio is 0.36,0.40,and 0.42,respectively.The static friction coefficients between the contact surface and the three layers are 0.41,0.53,and 0.58,the dynamic friction coefficients are 0.08,0.16,and 0.19,and the restitution coefficients are 0.39,0.50,and 0.54,respectively.As for organic and compound fertilizers,the moisture content is 8.25%and 1.12%,the density is 1.05 g·cm^-3 and 1.33 g·cm^-3,and the angle of repose is 17.71°and 16.27°,the rigidity is 76.58 N/mm and 88.69 N/mm,the static and dynamic friction coefficients of organic,compound fertilizer with steel plate are 0.30 and 0.23,and 0.26 and 0.18 respectively,with the coefficient of restitution being 0.29 and 0.38.（3）Key technology of double-row ditching-fertilizer machine in ditching operation at orchards.The ditching mechanism of the orchard double-row ditching-fertilizer machine was studied to establish the kinematic model of soil particles,the key test factors that affect the quality of the ditching operation were analyzed,and the discrete element calibration of soil particles was finished in EDEM.Besides,the stability coefficient of ditching depth,ditch bottom width consistency coefficient,and soil coverage rate as test indicators were applied to build a regression model with test factors via Box-Behnken test design method,to analyze the interaction and influence of each factor on the test indicators,and comprehensively optimize each test factor to obtain the optimal operation parameter combination:the machine forward speed is 0.8 km/h as a whole,with the ditching cutter rotating at a speed of 348 r/min and in a deflection angle of 32°,when the depth stability coefficient in ditching is 98.33%,and the bottom width consistency coefficient is 96.32%,and the earth covering rate is 81.53%.（4）Mixed deep fertilization technology with double-row ditching-fertilizer machine in orchards.The fertilization mechanism of the orchard machine was studied to establish the kinematic model of fertilizer particles,which is used to analyze the key test factors including fertilizer screw speed,fertilizer sprocket speed,conveyor belt speed,guide plate angle,that affect the quality of fertilization operation.The uniform distribution coefficients of chemical,organic and mixed fertilizers as test indicators were applied to establish a regression model with each test factor,which is used to analyze the interaction and influence of each factor on test indicators;furthermore,the comprehensive optimization of each test factor was achieved to get the optimal combination of operating parameters:a fertilizer screw speed of 70 r/min,fertilizer sprocket speed of 45 r/min,conveyor belt speed of 200 r/min,and guide plate angle of 35°,when the fertilizer uniform distribution coefficients of chemical,organic and mixed fertilizers are 93.58%,91.12%,and 95.25%,respectively.（5）Fertilizer screening technology on grain shape traits.In order to reduce the fragmentation rate of fertilizers under orchard double-row ditching-fertilizer machine operation,we independently developed an analyzer based on binocular vision to non-destructively measure the particle shape traits of both compound and organic fertilizer particles.In addition,a prediction model of fertilizer crushing force was established by Support Vector Machine（SVM）and differential evolution algorithm,based on which the key particle shape trait parameters affecting fertilizer crushing were explored,and the optimization range of compound and organic fertilizers in particle size deduced thereby is 4.30～5.44 mm and 3.90～4.60 mm,respectively.（6）Whole machine development,performance test and field test of the orchard double-row ditching-fertilizer machine.The design parameters were applied to develop the orchard double-row ditching-fertilizer machine,the efficiency and performance of which were verified on site in terms of ditching depth consistency,uniformity of fertilization and fertilizer crushing rate as key test indicators.The test results show that the crushing rate of organic and compound fertilizers after screening is less than that of each fertilizer before screening.The crushing force prediction model of the fertilizer and the set particle size optimization range are reasonable and effective;the orchard double-row ditching-fertilizer machine can realize the integrated operation of double-row ditching,mixed deep application of organic and chemical fertilizers,and soil covering in orchards.The stability coefficient of ditching depth is no less than 95.25%,the consistency coefficient of the bottom width is no less than 95.59%,the soil cover rate is no less than 81.09%,while the distribution stability coefficient of organic fertilizer is no less than91.92%,the distribution stability coefficient of chemical fertilizer is no less than 92.40%,and the distribution stability coefficient of mixed fertilizer is no less than 94.02%.The evaluation indicators meet the technical requirements of ditching and fertilization for fruit trees.更多还原