【作者】 赵雄；

【导师】 陈建能；

【作者基本信息】 浙江理工大学 ， 机械设计及理论， 2014， 博士

【摘要】 取苗机构是移栽机由半自动向全自动发展的核心装置，是当前农业机械研究的热点。传统的取苗机构主要有滑道、滑块连杆组合形式和不完全非圆齿轮行星轮系形式，机构的性能不太理想。论文基于对传统取苗机构工作特性分析，结合作者所在课题组对非圆齿轮不等速传动研究成果，提出以“鹰嘴形”轨迹为研究目标的旋转式非圆齿轮行星轮系取苗机构的创新设计，通过分析行星轮系机构的轨迹形成规律，选用三次非均匀B样条曲线直接拟合非圆齿轮传动比函数，实现“鹰嘴形”轨迹所需要的取苗臂周期二次不等幅摆动运动规律，并在此基础上开展机构的运动学优化、动力学特性分析与试验验证，设计物理样机并在取苗实验台上开展取苗相关试验研究。论文主要研究工作如下：1）提出非圆齿轮行星轮系旋转式取苗机构和“鹰嘴形”取苗轨迹，分析“鹰嘴形”取苗轨迹的形成机理，发现周期中取苗臂的二次不等幅摆动规律是形成“鹰嘴形”轨迹的原因。2）机构运动学建模与参数优化：利用13个传动比数据点拟合自由二阶非圆齿轮，建立二级非圆齿轮传动的数学模型，分析传动比参数和轨迹参数对“鹰嘴形”轨迹环扣大小、方位以及轨迹整体形态的影响，得到理想取苗轨迹的机构参数约束范围；对取苗机构工作目标设定10个目标，建立目标的数学模型，基于参数导引优化方法开发自由二阶非圆齿轮行星轮取苗机构优化设计软件，优化得到一组机构传动比参数为[（0，0.6999），（25，0.7777），（35，0.9721），（80，1.7887），（105，1.1666），（160，0.6844），（210，0.8166），（230，1.0499），（256，1.2443），（288，1.1277），（300，0.9955），（335，0.7310），（360，0.6999）],齿轮中心距、行星架初始角度、行星架拐角、取苗臂初始安装角和取苗爪长度优化结果为(68mm，139°，-84°，30°，215mm),10个运动学目标值为别为：取苗臂与送钵装置最小距离5.74mm、取苗尖嘴宽度2.5mm、尖嘴倾角139.226°、入钵摆角20.18°、出钵摆角4.38°、取苗入程角26°、投苗角108.41°、齿轮模数2.67,轨迹高度313mm、行星架与投苗位置线距离25mm。3）机构的结构设计与动力学分析：建立了机构的虚拟样机，仿真检查了机构的运动干涉情况，验证了凸轮安装位置确保取苗推苗动作的有序实现；建立机构的动力学模型，分析了各构件的力的波动特征，分析结果发现对于自由二阶非圆齿轮行星轮系传动机构，当行星架转速大于100r/min，中心轴支座力的波动的峰值显著增大，其合理的转速应控制在100r/min以下；通过取苗臂加配重的方式可有效降低支座力峰值8.3%，为取苗臂的改进提供设计参考。4）机构取苗试验研究：进行钵苗的物理特性研究，通过统计苗在钵中的位置设定两取苗爪初始距离为20mm；通过取苗爪与钵体之间摩擦系数测试、钵体的抗压性测试和取苗力的测试确定取苗爪的最小夹紧量为10mm；对取苗机构中心轴支座力进行了试验测试，试验结果表明机构在80r/min以下转速力学特征平稳，支座受力理论分析与实测情况基本一致，验证了理论分析模型的正确性，理论和测试结果表明自由二阶非圆齿轮行星轮系取苗机构支持160株/min的取苗效率，是高效取苗机构的构型；以苗盘倾角、夹紧量、取苗深度为因素，每个因素设定三个水平，通过开展60r/min转速下全因素试验，确定最优组合为：取苗夹角90°、夹紧量15mm、取苗深度35mm，最高取苗成功率为94%；开展80r/min转速下L49（3）正交试验，通过离差分析确定优组合为：取苗夹角100°、夹紧量12mm、取苗深度35mm，最高取苗成功率为90%；开展了落苗段钵苗运动规律测试，推苗过程钵苗的姿态与理论设计一致，钵苗离开取苗爪后，在取苗机构60r/min转速下钵苗向下向前运动，是钵苗交接苗的理想状态；80r/min转速下钵苗水平方向运动速度较大，不利于交接苗。若要保证取苗机构高转速下钵苗向下向前的运动轨迹，推苗点应提高，增大钵苗离开取苗爪向下的速度。更多还原

【Abstract】 Seedling pick up mechanism is the key factor of promoting the development oftransplanting macine from semi-automatic to fully automatic, is the current hot topics in theresearch of agricultural machinery. Traditional seeding pick up mechanism mainly include thesliding-block linkage combined mechanism and non-circular gear planetary intermittent system,performance due to any agency selection needs to be improved. Based on working characteristicsof the traditional seeding pick up mechanism, and combined with non-uniform transmission ofnon-circular gear research achievements. The seeding pick up mechanism of complete rotarynon-circular gear planetary system are put forward, targeting Olecranon-shaped Trajectory.Through the analysis of the trajectory of planetary system, it is found out that using cubicnon-uniform B-spline curve to fitting function of non-circular gear transmission ratio directly,and realized the periodic quadratic unequal amplitude swinging motion of seeding pick up arm,this is the Olecranon-shaped Trajectory needed. On this basis, we carry out the agency’skinematic optimization, dynamic characteristics analysis and experimental verification. At last,the design and physical prototype and carry out the take seedlings related experimental researchin seedling experiment platform. Paper main research work is as follows:1）In this paper, The seeding pick up mechanism of rotary non-circular gear planetarysystem and the Olecranon-shaped Trajectory was proposed, and found that the cycle of theperiodic quadratic unequal amplitude swinging motion of seeding pick up arm is the cause of theOlecranon-shaped Trajectory formed, by analysis the formation mechanism of theOlecranon-shaped Trajectory.2）Kinematics modeling and parameter optimization: First of all, The fitting of freedomsecond order non-circular gear and a mathematic model of the secondary non-circular gear isestablished, by using13data points for the transmission ratio. The second, the influence of thetransmission ratio parameters and trajectory parameters upon the ring size of Olecranon-shapedTrajectory, location and path form were studied, which is necessary for get the ideal trajectoryfor institution parameter constraint. Third, the seeding pick up mechanism of work target will beset to ten, mathematical model is set up, and quantify the ideal interval of each target. In the end,optimization design software for the seeding pick up mechanism of free second-ordernon-circular gear, developed based on the parameters of the direct optimization method, is usedto optimize many of related parameter, the transmission ratio parameter as follows:[（0，0.6999），（25，0.7777），（35，0.9721），（80，1.7887），（105，1.1666），（160，0.6844），（210，0.8166），（230，1.0499），（256，1.2443），（288，1.1277），（300，0.9955），（335，0.7310），（360，0.6999）], The structural parameters as:[68mm，139°，-84°，30°，215mm],The ten of kinematics target value as:（5.74，2.5,139.226，20.18,4.38,26,108.41,2.67,313,25）.3）Structural design and dynamics analysis of the organization: By establishing the virtualprototype, the interference of the mechanism is checked, and cam is verified the correctinstallation position that ensure the orderly implementation of grip action. Dynamics model was established and the analysis of features of each component on the force, it’s found that for theseeding pick up mechanism of free second-order non-circular gear, significant increase in thebearing reaction force of center shaft when the planet speed greater than100r/min. So the planetspeed should be lower than100r/min.4）Experiment research: Researching on the physical properties of pot seeding, we set theinitial distance between two seeding claws as20mm by counting the positions of the seedlings inthe pot; And confirm the minimum amount of seeding claw clamping as10mm by practicing thetest on coefficient of friction between seedling claw and the pot, compressive strength test of potand the strength of seed-picking up. We practice test on the central axis bearing force ofseed-picking up, and the consequence shows that when the mechanism revolving speed is below80r/min, Mechanics characteristic is smooth and theoretical analysis of bearing force arebasically identical, which verified the correctness of the theoretical analysis model. The theoryand test results show that free second-order non-circular gear planetary gear train seed-pickingup mechanism can realize as higher seed-picking up efficiency as160p/min. Take seeding trayobliquity, clamping and the depth of seed-picking up as factors, and set three levels in everyfactor. Carrying out all factors experiment when the revolving speed is below60r/min, theoptimal combination is confirmed: seed-picking up intersection angle is90o,clamping is15mm,the depth of seed-picking up is35mm and the highest success rate of seed-picking up is94%;Carrying out L43(3) orthogonality experiment when the revolving speed is below80r/min, theoptimal combination is confirmed: seed-picking up intersection angle is100o,clamping is12mm,the depth of seed-picking up is35mm and the highest success rate of seed-picking up is90%.Carrying out the test on pot seedling movement rule in the period of falling, pot seedlingmovement rule is fit with the theoretical design in the pushing. After pot seeding deviating fromseeding claw, pot seeding moves downward and forward, it is the ideal handover state of potseeding. However, the forward speed of pot seeding is faster when the revolving speed is below80r/min, which goes against handover. To ensure the pot seeding moves forward and downwardwith a higher revolving speed, we must enhance the seed-pushing points, and increase thedownward speed of seeding deviating from seeding claw.更多还原