Design and Experimental Research on Seedling Pick-Up Mechanism of Planetary Gear Train with Combined Non-circular Gear Transmission

Currently, transplanting mechanisms for dryland plug seedlings in China are mainly semiautomatic and have low efficiency. The rotary seedling pick-up mechanism with a planetary gear train for non-uniform intermittent transmission, and a concave and convex locking arc device, has a large rigid impact. To solve these problems, according to the design requirements for a dryland plug seedling transplanting mechanism, a rotary seedling pick-up mechanism of a planetary gear train with combined non-circular gear transmission of incomplete eccentric circular and noncircular gears was proposed. This has the characteristics of two-times greater fluctuation of the transmission ratio in a cycle, and can achieve a non-uniform continuous drive. Through analysis of the working principle of the seedling pick-up mechanism, its kinematics model was established. The human–computer interaction optimization method and self-developed computer-aided analysis and optimization software were used to obtain a set of parameters that satisfy the operation requirements of the seedling pick-up mechanism. According to the optimized parameters, the structure of the seedling pick-up mechanism was designed, a virtual prototype of the mechanism was created, and a physical prototype was manufactured. A virtual motion simulation of the mechanism was performed, high-speed photographic kinematics tests were conducted, and the kinematic properties of the physical prototype were investigated, whereby the correctness of the theoretical model and the optimized design of the mechanism were verified. Further, laboratory seedling pick-up tests were conducted. The success ratio of seedling pick-up was 93.8% when the seedling pick-up efficiency of the mechanism was 60 plants per minute per row, indicating that the mechanism has a high efficiency and success ratio for seedling pick-up and can be applied to a dryland plug seedling transplanter.

Mathematic model and tooth contact analysis of a new spiral non-circular bevel gear

A novel spiral non-circular bevel gear that could be applied to variable-speed driving in intersecting axes was proposed by combining the design principles of non-circular bevel gears and the manufacturing principles of face-milling spiral bevel gears.Unlike straight non-circular bevel gears,spiral non-circular bevel gears have numerous advantages,such as a high contact ratio,high intensity,good dynamic performance,and an adjustable contact region.In addition,while manufacturing straight non-circular bevel gears is difficult,spiral non-circular bevel gears can be efficiently and precisely fabricated with a 6-axis bevel gear cutting machine.First,the generating principles of spiral non-circular bevel gears were introduced.Next,a mathematical model,including a generating tooth profile,tooth spiral,pressure angle,and generated tooth profile for this gear type was established.Then the precision of the model was verified by a tooth contact analysis using FEA,and the contact patterns and stress distributions of the spiral non-circular bevel gears were investigated.

Design and Experiment of Non-circular Combined Gear Train Beating-up Mechanism

The most important performance of a beating-up mechanism is that the dwelling time of the sley must ensure the completion of the weft insertion. To meet this requirement, a new non-circular combined gear train beating-up mechanism which is composed of two-stage planetary gear trains is proposed. The first-stage is a Fourier planetary gear train and the second-stage is a non-circular planetary gear train. For designing of this new mechanism, the ideal kinematic equations of the sley are constructed first. Then the kinematic model of the first-stage Fourier planetary gear train is established and the reverse solution for the pitch curves of the second-stage non-circular gears is deduced. With a computer-aided design program, the influences of several important parameters on the pitch curves of the second-stage non-circular gears are analyzed, and a set of preferable structural parameters are obtained. Finally, a test bed of this mechanism is developed and the experimental results show that this new beating-up mechanism can achieve the designed dwelling time, namely it can meet the requirements of beating-up process.

Calculating method of contact stress for non-circular gears

According to Hertz theory, the difference of contact stress for non-circular gears and equivalent gears is compared in the paper, a calculating method of contact stress for non-circular gears by using equivalent gears is researched, and computing formulas of power and rotation speed for equivalent gears are deduced. A numerical simulation of contact stress for non-circular gears has also been conducted based on the finite element method. By the comparison of fitting curves, the feasibility of using equivalent gears instead of non-circular gears to calculate the contact stress is testified.

Research on Design Method of Non-Circular Gear Pair with Double Generating Angles

In order to enhance the bearing capacity of non-circular gear pair, the non-circular gear pair with double generating angles is proposed based on the design idea of unsymmetrical gear with double pressure angles. The tooth profile is designed by generating cutting theory, the pure rolling mathematic model that the center line of unsymmetrical rack roll along non-circular pitch curve is built, the digital model of non-circular gear with double generating angles is created through the second development method of CAD software, and then the drive characteristic and tooth strength are analyzed. The results show that the design method for double generating angles non-circular gear proposed in this paper is feasible, which is significant to improve the bearing capacity of non-circular gear pair.

Research on stepless transmission utilizing noncircular gears

In view of the lack of systemic analysis for stepless transmission using noncircular gears, two basic noncircular gear units, an addition unit adopting differential mechanism and a multiplication unit applying a fixed gear train, are proposed. Then, the design methods of the noncircular gear pair of each unit, transmission ratio relationship, rotation angle relationship and key parameters with specific physical meanings are studied. The adjusting properties, composing strategy and varying range of transmission ratio etc. are investigated in detail for each unit. Following this, several examples of using a noncircular gear pair in the units and their manipulation technique are introduced.

非圆齿轮-连杆组合式水稻钵苗膜上移栽机构优化设计与试验

为实现机械化一体式水稻钵苗膜上移栽要求,提出非圆齿轮-连杆组合式行星轮系移栽机构,用一套机构实现取苗、送苗、破膜挖穴和栽植4个工序协同配合作业,满足水稻钵苗膜上移栽所需的轨迹与姿态要求。对移栽机构进行理论分析并建立运动学模型,结合优化目标,基于Matlab GUI平台开发了数字可视化优化设计软件,通过人机交互获得1组满足移栽要求的机构参数。根据优化参数对机构开展结构设计与三维建模,通过ADAMS软件完成了虚拟样机仿真验证。研制了水稻钵苗膜上移栽机构物理样机与多功能试验测试台架,开展了移栽机构在空转和带苗状态下运动学特性和工作性能试验,结果表明,理论轨迹、虚拟样机仿真轨迹和物理样机台架试验轨迹在误差允许范围内保持一致,验证了移栽机构设计的一致性与正确性,性能试验结果:取苗成功率为94%,移栽成功率为92.36%,栽植株距变异系数为2.67%,满足移栽作业要求,验证了水稻钵苗膜上移栽机构设计的合理性与可行性。

Automatic Scallion Seedling Feeding Mechanism with an Asymmetrical High-order Transmission Gear Train

The current automatic scallion-transplanting machine is a complicated mechanism composed of two linkage mechanisms and two band carriers.It delivers seedlings ine ciently because of the movement limitations of the linkage mechanism.This paper proposes a new high-order non-circular gear train for an automatic scallion-seedling feeding mechanism.The proposed gear train has an asymmetrical transmission ratio;i.e.,its transmission ratio varies.This allows the mechanism’s execution component to move in a long displacement and rotate in a large rotation angle.The long displacement enables the execution component to reach the designed working position,and the large rotation angle allows it to feed a scallion in the required pose.A mathematical model for calculating the asymmetrical transmission ratio was established according to the closure requirements and the full-cycle motion of the driven gear pitch curve.Then,the parameter-design model of the new seedling-feeding mechanism was established,based on precise pose points and trajectory-shape control points.Moreover,an aided-design program was developed to obtain the parameter-solution domain of the scallion-seedling feeding mechanism.The mechanism parameters,which met the seedling-feeding function,were optimized to determine the transmission ratio,using a program and a kinematic simulation.Finally,a prototype of the mechanism was produced,and a seedling-feeding experiment was carried out.One-thousand seedlings were tested at a rate of 100 seedlings per minute,and the statistical success rate was 93.4%.Thus,the automatic scallion-seedling feeding mechanism significantly improves the e ciency of automatically transplanting scallions.

偏心齿轮-非圆齿轮行星系取苗机构的运动学建模与参数优化

针对目前蔬菜移栽作业中半自动移栽机需要人工喂苗、工作效率低等缺点,以及日本自动移栽机的复杂结构、高制造成本和工作效率不高等问题,设计了一种应用于蔬菜钵苗自动移栽机的偏心齿轮-非圆齿轮行星系自动取苗机构。在分析该旋转式自动取苗机构的结构特点和工作原理的基础上,建立了机构的运动学模型,开发了基于Visual Basic6.0的计算机辅助分析与优化软件对机构的结构参数进行优化。通过人机交互优化方法,得出了结构参数对取苗臂尖点运动轨迹和优化目标的影响规律,进而优化得到满足蔬菜钵苗自动取苗要求的机构结构参数。

偏心齿轮-非圆齿轮行星轮系在后插旋转式分插机构中的应用

针对步行式水稻插秧机的工作要求,将偏心齿轮—非圆齿轮行星轮系应用于水稻插秧机后插式分插机构的设计中,研制出偏心齿轮-非圆齿轮后插旋转式分插机构。分析了偏心齿轮—非圆齿轮行星轮系的运动学特性,建立运动学模型,并自主开发了分插机构辅助分析与优化软件,通过人机交互优化方式对该分插机构进行参数优化,完成了该分插机构的二维和三维设计,并进行了虚拟样机试验,试验结果表明:该分插机构可以形成"海豚形"插秧静轨迹,满足步行式水稻插秧机的工作要求。

偏心齿轮-非圆齿轮行星系分插机构运动机理分析

简述了一种旋转式行星系分插机构,用于高速水稻插秧机前插式作业。分析了偏心齿轮-非圆齿轮行星系分插机构的工作机理和结构特点,建立了该机构的运动学模型。基于Visual Basic 6.0开发了该分插机构辅助分析与优化软件,通过人机交互方式,优化出满足高速插秧机插秧要求的结构参数为e=3 mm,R=19 mm,α0=-40°,φ0=36°,S=155 mm,H=180 mm。

非圆齿轮-连杆组合传动式蔬菜钵苗移栽机构设计

针对现有的单行星架轮系机构无法实现取栽一体式蔬菜移栽机构所需的作业轨迹和姿态问题,该文基于曲柄摇杆机构的变速摆动和非圆齿轮的不等速传动特性相结合的思想,提出一种双行星架非圆齿轮与连杆机构组合传动的取栽一体式蔬菜钵苗移栽机构。该机构的副行星架相对主行星架作变速摆动,移栽臂相对副行星架作回转运动。采用三次非均匀B样条拟合非圆齿轮节曲线建立移栽机构运动学模型。结合西芹移栽株距220 mm、苗高100~150 mm和穴钵深度40 mm的移栽农艺要求,优选出一组适合西芹钵苗取栽一体作业的尖嘴形轨迹和姿态。轨迹取苗段长度33 mm,植苗点距离行星架壳体运动最低点距地面高度55 mm,取苗角23°,取苗过程变化角16°,推苗角65°,轨迹整体高度355 mm,动轨迹环口高度125 mm。通过对比分析仿真轨迹、试验轨迹与理论分析的轨迹基本一致,验证了移栽机构作业轨迹的正确性和设计方案的可行性,该研究可为实现兼顾轨迹高度、取苗深度和作业姿态的取栽一体式蔬菜钵苗移栽机构设计提供技术参考。

脉动血流发生器非圆齿轮-曲柄滑块式驱动机构设计与分析

为使脉动血流发生器产生稳定的脉动性血流,提出了一种新型非圆齿轮-曲柄滑块式驱动机构,运用非圆齿轮副和曲柄滑块机构的组合传动来实现血流的脉动。在满足人体血流脉动前提下,为使设计的机构运行平稳,采用2段三次Hermite插值多项式来对该机构输出构件的加速度曲线进行拟合,再由加速度曲线方程及其边界条件推导出速度、位移和跃度曲线方程,运用拟合得到的输出构件运动学曲线方程推导出非圆齿轮副节曲线反求模型。根据实例求解分析得到的机构参数进行三维建模和虚拟样机实验,对比虚拟仿真实验和理论分析结果,发现所设计机构能够按照预期规律实现脉动血流,且该机构具有良好的运动学特性,同时验证了所构建的运动学曲线方程及所建立的运动学分析模型的正确性。

斜齿交错-非圆锥齿轮行星系水稻宽窄行分插机构设计与优化

为获取一般性的空间行星轮系传动比,以达到直取秧和小穴口的插秧要求,在斜齿交错椭圆锥行星轮系分插机构的基础上,引入非圆锥齿轮,得到一种斜齿交错-非圆锥行星轮系分插机构,并应用于高速宽窄行插秧机当中。建立了非圆锥齿轮副节曲线的数学表达式和机构的运动学模型;基于Matlab开发平台开发了机构参数优化软件,利用该软件分析了节曲线形状、行星架初始安装角、斜齿轮螺旋角和非圆锥齿轮锥距对理想轨迹姿态、直取秧特征和穴口大小的影响,并以理想轨迹姿态、直取秧、小穴口等要求为目标,通过人机交互方式优选机构参数;与斜齿交错-椭圆锥行星轮系分插机构形成的总传动比及其轨迹进行对比,并得出了斜齿交错-非圆锥行星轮系分插机构轨迹在改进直取秧姿态、降低伤苗率等方面作业性能更优的结论。利用仿真软件Adams进行了机构的运动学仿真,加工分插机构实物,利用通用分插机构试验台完成机构插秧轨迹测试,得出斜齿交错-非圆锥行星轮系分插机构可以更好的满足水稻宽窄行插秧的要求,从而验证了非圆锥齿轮在宽窄行分插机构中应用的优越性。

偏心-椭圆齿轮行星轮系栽植装置动力学优化与试验

为获得偏心-椭圆齿轮行星轮系栽植装置最优的机构参数,在建立其动力学分析模型的基础上,以一个作业循环中支座垂直方向所受作用力的峰值力和波动最小为目标建立其动力学优化模型。为验证所建立的动力学分析模型的可靠性,以该装置满足理想栽植要求的非劣解集为约束条件,运用所建立的动力学优化模型优化得到该装置最优的机构参数,进而基于最优机构参数搭建试验台进行动力学特性测试,测得了该栽植装置在工作转速为40 r/min时一个工作循环中支座垂直方向受力与行星架转角的关系,通过试验结果和理论结果的对比分析,表明其动力学分析模型是可靠的,可为其动力学优化提供可靠数学模型。

偏心-高阶椭圆锥齿轮副的强度计算方法

结合微分几何及空间齿轮啮合原理,将偏心-高阶椭圆锥齿轮副的空间节曲线在曲率半径相等的条件下展开到平面上,推导出齿轮副当量节曲线的计算公式,获得啮合传动过程中的压力角。对轮齿进行受力分析,建立偏心-高阶椭圆锥齿轮副的强度计算方法,获得轮齿接触应力及弯曲应力随主动轮转角的变化规律,确定啮合过程中最薄弱轮齿的位置。分析偏心-高阶椭圆锥齿轮副主动轮偏心率、模数、主动轮齿数及从动轮阶数等结构参数对轮齿强度的影响。建立偏心-高阶椭圆锥齿轮副有限元分析模型,利用五轴数控机床加工出齿轮副实体并搭建传动试验平台,通过有限元分析与传动试验,验证该齿轮副强度计算方法的正确性。

偏心齿轮-非圆齿轮后插旋转式分插机构的三维参数化设计

为提高分插机构的设计效率,缩短设计开发周期,该文以偏心齿轮-非圆齿轮后插旋转式分插机构为基础,并以三维软件UG6.0为设计平台,利用可视化编程语言VB.NET定制用户界面,采用NX Open for.NET的UG二次开发技术,建立该分插机构的三维参数化设计系统。利用该系统,通过用户界面输入主要设计参数,即可快速生成偏心齿轮-非圆齿轮后插旋转式分插机构的零件(包括非圆齿轮)和装配三维模型,实现该分插机构的三维参数化设计。

非圆齿轮-曲柄滑块式驱动机构设计与分析

提出了一种非圆齿轮副串联曲柄滑块来实现往复直线运动的新型机构,建立了该新型机构的运动学分析模型,并以预定速度曲线为目标反求满足工作要求的非圆齿轮节曲线。分别以输出部件遵循变形梯形加速度和余弦加速度运动规律输出为例,计算了该机构的非圆齿轮副传动比函数,并研究了曲柄连杆比和等加速等减速区间占比对传动比函数的影响规律。结果表明,当滑块满足变形梯形加速度运动规律时,随着曲柄连杆比的增大,传动比变化的幅度逐渐增大;等加速等减速区间占比对传动比影响不大。当滑块满足余弦加速度运动规律时,随着曲柄连杆比的增大,传动比函数的变化幅度明显增大。

圆弧-圆弧型液压马达非圆齿轮机构

研制了一种新型非圆齿轮机构,其节曲线是由两种半径的圆弧组合而成。介绍了非圆齿轮机构的结构及其工作原理,并根据几何关系推导了圆弧-圆弧型节曲线参数所需满足的条件。在此基础上设计了齿轮节曲线,并通过修正模数得到了所需的排量。用线切割加工技术制造了齿轮机构样品,与海德曼公司进口齿轮机构在相同条件下进行了对比试验。结果显示,两种齿轮机构的转速扭矩特性基本一致,这表明所提出的设计方法是可行的。

新型非圆锥齿轮摆停-步进装置

基于圆锥齿轮-非圆锥齿轮差动轮系,提出一种新型非圆锥齿轮摆停-步进装置。阐述了其工作原理,推导出位于其传动核心的一对非圆锥齿轮的传动比函数,结合非圆锥齿轮的相关理论阐述了其设计和校核方法。以实例的方式建立了装置的三维模型,利用ADAMS得到了装置的位移响应,证实了上述方法和原理的正确性。