【作者】 吴康；

【导师】 李建平；

【作者基本信息】 浙江大学 ， 农业机械化工程， 2024， 博士

【摘要】 瓜类蔬菜栽培普遍存在连作障碍,严重影响了瓜类蔬菜生产的可持续性和经济效益。嫁接是一种有效克服连作障碍的可持续性栽培方法,瓜类蔬菜较柔嫩,嫁接过程中易损伤幼苗,目前蔬菜嫁接主要以人工为主。本文基于斜插式瓜类蔬菜嫁接方法,以嫁接用苗低损伤为目标,分析嫁接用苗的物理特性,研究嫁接用苗的定位夹持、砧木生长点去除、嫁接用苗的切削及砧木打孔等关键技术。主要研究结果如下:1.研究了适龄期砧木葫芦苗和接穗西瓜苗的几何特征参数与力学特性。分析了多种瓜类蔬菜的嫁接方式,以葫芦苗为砧木、西瓜苗为接穗,确定了斜插法作为瓜类蔬菜的嫁接方法;测量了适龄期的砧木葫芦苗和接穗西瓜苗的茎秆尺寸,子叶长度、宽度和开口角等几何特征参数;测试获得了砧木苗茎秆的弹性极限压力为4.45 N,砧木苗子叶的最大承受压力为1.2 N,接穗苗子叶的最大承受压力为0.72 N,为嫁接装置的设计和研究提供基础。2.提出了气吸和弹性元件相结合的柔性砧木夹持机构。基于砧木夹持定位原理,采用气吸与弹性元件相结合的方式,设计了柔性砧木夹持机构,分析了砧木在夹持过程中的受力情况。为进一步探究夹持过程中茎秆损伤,利用有限元仿真对砧木茎秆夹持过程进行了模拟分析,模拟结果确定了夹持速度低于190 mm/s,弹性元件硅橡胶厚度为4 mm的试验条件;通过对夹持过程进行力学分析,明确了气吸孔径、负压值和夹持块表面倾角3个参数对砧木受力有较大的影响;以上述参数为试验因素,以夹持成功率和砧木损伤率作为试验指标,对砧木夹持机构进行了单因素和多因素试验,获得了气吸孔径2.5 mm,负压值6k Pa,表面倾角10°的最佳夹持机构参数组合,试验验证得到夹持机构的夹持成功率为98.33%,无伤苗现象,表明夹持机构的设计合理,作业效果好。3.研究了砧木生长点仿人工去除的机构运动轨迹。基于人工去除生长点原理,提出了一种生长点去除新思路,首先提取分析了适龄砧木的形态数据,结合农艺要求和试验台参数设计了适合生长点的去除轨迹;然后利用三次非均匀B样条曲线对设计的运动轨迹进行了拟合,获得了运动轨迹上的所需的坐标点;提出了一种用于去除生长点的混合驱动五杆机构,建立了机构的数学模型,结合所得坐标点,利用机构的逆向求解,通过MATLAB软件对五杆机构参数进行了优化求解,得到了五杆机构的结构参数和运动变化规律。4.提出了自适应砧木生长点高度的去除机构。在上述求解得到的五杆机构参数的基础上,对砧木生长点去除机构进行了整体设计,将弹性元件应用在执行末端,通过弹性元件受力产生形变自适应不同苗的生长点高度变化,解决了生长点去除不干净或执行末端刚性太大插入砧木深处损伤砧木苗的问题;为提高去除机构的作业稳定性,利用ADAMS软件对实际去除机构的运动轨迹进行了改进;研制了砧木生长点去除机构,通过试验得到了生长点去除机构的成功率为93.33%,去除作业效果较好,满足机械嫁接要求。5.研究了气吸式接穗西瓜苗吸持方法和机构。针对接穗西瓜苗细嫩、夹持中易损伤的难点,确定了以气吸为作业方式的吸持方案,建立了接穗吸持的力学模型。利用有限元方法,分析了不同吸孔直径、负压和吸孔数量对吸持块内部流体的压力和速度流场分布的影响。模拟结果表明,随着吸孔直径和吸孔数量的增加,吸孔处流体的压力和速度逐渐降低;但随着负压值的增大,吸孔处的流体压力和速度逐渐增加;为进一步探究接穗吸持机构的作业效果,以吸孔直径、负压和吸孔数量为试验因素,接穗吸持成功率和损伤率为试验指标,对研制的吸持机构进行了响应面分析试验,得到了吸持机构的最佳参数组合为:吸孔直径3 mm,负压值3 k Pa,吸孔数量1个。验证试验得到吸持机构的吸持成功率为90%,无伤苗现象,满足嫁接机要求。6.试制了斜插式嫁接装置样机并进行了试验研究。通过理论分析与试验,研究了接穗切削机构和打孔机构。根据嫁接装置嫁接要求和嫁接流程,研制了斜插式瓜类蔬菜嫁接装置样机。以砧木葫芦苗和接穗西瓜苗为嫁接对象,对斜插式嫁接装置样机进行了整机试验,分别考察了砧木的夹持、生长点去除和打孔机构及接穗的吸持和切削机构的成功率,分析了嫁接装置的嫁接成功率和成活率,试验得到了嫁接装置的嫁接成功率为95%,回栽后的成活率为92.08%。更多还原

【Abstract】 Cultivation of cucurbit vegetables commonly faces the obstacle of continuous cropping,significantly impacting the sustainability and economic benefits of their production.Grafting presents an effective sustainable cultivation method to overcome this obstacle.However,due to the tender nature of cucurbit vegetables,mechanical grafting can easily damage young seedlings.Currently,vegetable grafting is predominantly manual.This study focuses on the inclined inserted grafting method for cucurbit vegetables,aiming to minimize damage to grafting seedlings.It analyzes the physical characteristics of these seedlings,investigates key techniques such as positioning and clamping of grafting seedlings,removal of the rootstock growth point,cutting of grafting seedlings and punching of the rootstock.The primary research findings are outlined as follows:1.Geometric parameters and mechanical characteristics of rootstock seedlings(cucurbit)and scion seedlings(watermelon)at the suitable age were studied.Various grafting methods for cucurbit vegetables were analyzed,with cucurbit seedlings as the rootstock and watermelon seedlings as the scion,and the inclined inserted method was determined as the grafting approach for cucurbit vegetables.Measurements were taken of the stem dimensions of suitable rootstock seedlings(cucurbit)and scion seedlings(watermelon)at the appropriate growth stage.Geometric parameters such as leaf length,width,and aperture angle were recorded.Testing revealed that the elastic limit pressure of the rootstock seedling stems was 4.45 N,while the maximum bearing pressure for rootstock seedling leaves was 1.2 N and for scion seedling leaves was 0.72 N.These findings serve as a foundational basis for the design and research of the grafting device.2.A flexible rootstock clamping mechanism,combining suction and elastic components,was proposed.Building upon the rootstock clamping positioning principle,this flexible rootstock clamping mechanism was designed by integrating suction and elastic components.The force distribution on the rootstock during the clamping process was analyzed.To further explore stem damage during clamping,finite element simulation was employed to simulate and analyze the rootstock clamping process.The simulation results determined experimental conditions with a clamping speed below 190 mm/s and an elastic element silicon rubber thickness of 4 mm.Mechanical analysis of the clamping process determined that suction hole diameter,negative pressure value,and surface inclination angle of the clamping block significantly affected the force on the rootstock.With these parameters as experimental factors and successful clamping rate and rootstock damage rate as indicators,single-factor and multi-factor experiments were conducted on the rootstock clamping device.The optimal clamping device parameters were identified as a suction hole diameter of 2.5 mm,negative pressure value of 6 k Pa,and surface inclination angle of 10°.Experimental validation under these parameter settings yielded a clamping success rate of98.33%with no seedling damage observed.This indicates that the design of the clamping mechanism is reasonable and demonstrates effective operational performance.3.The motion trajectory of a mechanism for mimicking the artificial removal of rootstock growth point was studied.Based on the principle of artificial growth point removal,a novel approach for growth point removal was proposed.Firstly,the morphological data of age-appropriate rootstock were extracted and analyzed.Combining agricultural requirements with experimental platform parameters,a removal trajectory suitable for the growth point was designed.Subsequently,the designed motion trajectory was fitted using a cubic non-uniform B-spline curve,obtaining the required coordinate points along the motion trajectory.A hybrid-driven five-bar mechanism was proposed for removing growth points,accompanied by the establishment of a mathematical model for this mechanism.Utilizing the inverse kinematics of the mechanism and leveraging MATLAB’s genetic algorithm toolbox,parameters of the mechanism were optimized and solved,unveiling the structural specifications and motion patterns of the removal mechanism.4.An adaptive rootstock growth point height removal mechanism was proposed.Building upon the derived parameters of the five-bar mechanism,a comprehensive design of the rootstock growth point mechanism was executed.The implementation end of the mechanism incorporated an elastic element,allowing adaptive deformation in response to variations in growth point heights of different seedlings.This innovation addressed issues such as incomplete growth point removal or excessive rigidity at the execution end causing damage by penetrating too deeply into the rootstock.To enhance the operational stability of the removal mechanism,improvements were made to the actual motion trajectory using ADAMS software.A growth point removal mechanism was developed and experimental results demonstrated a success rate of 93.33%,indicating effective removal operations that meet the requirements of mechanical grafting.5.A suction-based scion clamping method and mechanism for watermelon seedlings was studied.Addressing the challenge of the delicate nature of watermelon seedlings and the susceptibility to damage during grafting,a suction-based method was determined as the operational approach,and a mechanical model for scion clamping was established.Using finite element methods,the pressure and velocity field distribution of the internal fluid within the clamping block were analyzed concerning various suction hole diameters,negative pressures,and the quantity of suction holes.Simulation results revealed that increasing suction hole diameters and the number of suction holes gradually decreased pressure and velocity at the suction holes.Conversely,augmenting negative pressure values led to increased pressure and velocity at the suction holes.To further investigate the operational effectiveness of the scion clamping mechanism,a response surface analysis experiment was conducted with suction hole diameter,negative pressure,and the quantity of suction holes as experimental factors,and scion clamping success rate and damage rate as indicators.The optimal parameter combination for the suction device was determined to be:suction hole diameter of 3 mm,negative pressure of 3 k Pa,and one suction hole.Experimental validation conducted with these optimized parameters yielded a clamping success rate of 90%with no observed damage to the seedlings,meeting the requirements for grafting machinery.6.A prototype of inclined inserted grafting device was developed and subjected to experimental research.Through theoretical analysis and experimentation,the cutting mechanism for scion and punching mechanism were studied.Based on the grafting requirements and process,a prototype of inclined inserted grafting device for cucurbit vegetables was developed.Using cucurbit seedlings as rootstocks and watermelon seedlings as scions,the entire device was tested,examining the success rates of rootstock clamping,growth point removal,rootstock cutting,punching mechanism,and scion clamping and cutting mechanisms.The success rate and survival rate of the grafting device were analyzed,and the experimental results showed a grafting success rate of 95%and a post-transplant survival rate of 92.08%.更多还原