Design of Vegetable Pot Seedling Pick‑up Mechanism with Planetary Gear Train

It has been challenging to design seedling pick-up mechanism based on given key points and trajectories,because it involves dimensional synthesis and rod length optimization.In this paper,the dimensional synthesis of seedling pickup mechanism with planetary gear train was studied based on the data of given key points and the trajectory of the endpoint of seedling pick-up mechanism.Given the positions and orientations requirements of the five key points,the study first conducted a dimensional synthesis of the linkage size and center of rotation.The next steps were to select a reasonable solution and optimize the data values based on the ideal seedling trajectory.The link motion was driven by the planetary gear train of the two-stage gear.Four pitch curves of noncircular gears were obtained by calculating and distributing the transmission ratio according to the data.For the pitch curve with two convex points,the tooth profile design method of incomplete noncircular gear was applied.The seedling pick-up mechanism was tested by a virtual prototype and a physical prototype designed with the obtained parameter values.The results were consistent with the theoretical design requirements,confirming that the mechanism meets the expected requirements for picking seedlings up.This paper presents a new design method of vegetable pot seedling pick-up mechanism for an automatic vegetable transplanter.

Prediction for Dynamic Characteristics of Ring-Plate Planetary Indexing Cam Mechanism

This paper is aimed to propose an approach to predict the dynamic characteristics of ring-plate planetary indexing cam mechanism, which is a novel type of indexing mechanism that employs internal planetary transmission structure. Firstly, the geometry and structure of the mechanism are discussed and the kinematic practicability is simulated with virtual prototype design. Then a 3D finite element model of the ring-plate planetary indexing cam mechanism is developed with the commercial software of MATLAB and ANSYS. Through the finite element analysis, the natural frequencies and the corresponding mode shapes are predicted in one motion cycle. On the basis of the virtual prototype design and finite element analysis, an experimental prototype is made and tested to validate the prediction of the dynamic characteristics. The agreement between experimental results and the finite element analysis testifies that the finite element model developed is applicable to the prediction of the dynamic characteristics of this type of mechanism.

Design and Dynamic Analysis of the Recirculating Planetary Roller Screw Mechanism

The recirculating planetary roller screw mechanism(RPRSM)is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers.In this paper,frstly,the design method of RPRSM nut threadless area is proposed,and the equations related to the structural parameters of nut threadless area are derived.On this basis,the cross-section design method of roller,screw and nut is constructed according to the actual situation of engagements between the screw/nut and the roller.By adjusting the gap between the two beveled edges and that between the arc and the beveled edge,the accuracy of the thread engagements between the screw/nut and the roller can be improved.Secondly,to ensure the engagements of the screw/nut and the roller,the distance equation from the center surface of the diferent rollers to the end surface of cam ring is given.Thirdly,combined with the working principle and structural composition of RPRSM,the component model is established according to its relevant structural parameters,and the virtual assembly is completed.Finally,the 3D model is imported into the ADAMS simulation software for multi-rigid body dynamics.The dynamic characteristic is analyzed,and the simulated values are compared with the theoretical values.The results show that the contact forces between the screw/nut and the roller are sinusoidal,mainly due to the existence of a small gap between the roller and the carrier.The maximum collision forces between the roller and cam ring are independent from load magnitude.Normally,the collision force between the roller and the carrier increases as the load increases.When RPRSM is in the transmission process,the roller angular speed in nut threadless area begins to appear abruptly,and the position of the maximum change is at the contact between the roller and the convex platform of cam ring.The design of the nut threadless area and the proposed virtual assembly method can provide a theoretical guidance for RPRSM research,as well as a reference for overall performance optimization.

The Mesh Efficiency of the Planetary Mechanism of 2K-H[D] Style

The mesh efficiency of the planetary mechanism of 2K - H[D] style is discussed. It comes to a new formula. Usually, an approximate value is taken as the mesh efficiency of a planetary mechanism. If the formula is used, the theoretical value of mesh efficiency can be gotten. The theoretical mesh efficiency can help engineers to know the true efficiency of 2K - H[D] style when it runs. The mesh efficiency serves the transmitting efficiency of a planetary mechanism.

Three-dimensional parametric contact analysis of planetary roller screw mechanism and its application in grouping for selective assembly

The planetary roller screw mechanism(PRSM)is a novel precision transmission mechanism that realizes the conversion between linear and rotary motions.The contact characteristics of helical surfaces directly determine PRSM’s performance in load-carrying capacity and transmission accuracy.Therefore,studying the contact characteristics of PRSM forms the fundamental basis for enhancing its transmission performance.In this study,a three-dimensional parametric analysis method of contact characteristics is proposed based on the PRSM meshing principle and PyVista(a high-level API to the Visualization Toolkit).The proposed method considers the influence of machining errors among various thread teeth.The effects of key machining errors on contact positions and axial clearance,as well as their sensitivities,are analyzed.With excellent solution accuracy,this method exhibits higher calculation efficiency and stronger robustness than the analytical and numerical meshing models.The influence of nominal diameter and pitch errors of the screw,roller,and nut on the axial clearance follows a linear relationship,whereas flank angle errors have negligible effects on the axial clearance.The corresponding influence coefficients for these three machining errors on the axial clearance are 0.623,0.341,and 0.036.The variations in contact positions caused by individual errors are axisymmetric.Flank angle errors and roller diameter errors result in linear displacements of the contact points,whereas pitch errors cause the contact points to move along the arc of the roller diameter.Based on the proposed threedimensional parametric contact characteristics analysis method,the Fuzzy C-Means clustering algorithm considering error sensitivity is utilized to establish a component grouping technique in the selective assembly of critical PRSM components,ensuring the rational and consistent clearances based on the given component’s machining errors.This study provides effective guidance for analyzing contact characteristics and grouping in selective assembly for PRSM components.It also presents the proposed method’s potential applicability to similar calculation problems for contact positions and clearances in other transmission systems.

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.

Gear Drive Mechanism for Continuous Variable Valve Timing of IC Engines

Continuous variable valve actuating (CVVA) technology provides high potential in achieving high performance, low fuel consumption and pollutant reduction. To get full benefits from (CVVT) various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and have shown significant benefits in improving engine performance. In this investigation a newly designed gear drive mechanism that controls the intake valve opening (IVO) and closing (IVC) angles is studied. The control scheme is based on maximizing the engine brake power (P) and specific fuel consumption (BSFC) at any engine speed by continuously varying the phase between the cam shaft angle and the crank shaft angle. A single-cylinder engine is simulated by the “LOTUS” software to find out the optimum phase angle for maximum power and minimum fuel consumption at a given engine speed. The mechanism is a planetary gear drive designed for precise and continuous control. This mechanism has a simple design and operation conditions which can change the phase angle without limitation.

Applications of Non-Classical Equations and Their Approaches to the Solution of Some of Classes Equations Arise in the Kelvin-Helmholtz Mechanism and Instability

In the presented work, we consider applications of non-classical equations and their approaches to the solution of some classes of equations that arise in the Kelvin-Helmholtz Mechanism (KHM) and instability. In all areas where the Kelvin-Helmholtz instability (KHI) problem is investigated with the corresponding data unchanged, the solution can be taken directly in a specific form (for example, to determine the horizontal structure of a perturbation in a barotropic rotational flow, which is a boundary condition taken, as well as other types of Kelvin-Helmholtz instability problems). In another example, the shear flow along the magnetic field in the Z direction, which is the width of the contact layer between fast and slow flows, has a velocity gradient along the X axis with wind shear. The most difficult problems arise when the above unmentioned equation has singularities simultaneously at points and in this case, our results also remain valid. In the case of linear wave analysis of Kelvin-Helmholtz instability (KHI) at a tangential discontinuity (TD) of ideal magneto-hydro-dynamic (MHD) plasma, it can be attributed to the presented class, and in this case, as far as we know, solutions for eigen modes of instability KH in MHD plasma that satisfy suitable homogeneous boundary conditions. Based on the above mentioned area of application for degenerating ordinary differential equations in this work, the method of functional analysis in order to prove the generalized solution is used. The investigated equation covers a class of a number of difficult-to-solve problems, namely, generalized solutions are found for classes of problems that have analytical and mathematical descriptions. With the aid of lemmas and theorems, the existence and uniqueness of generalized solutions in the weight space are proved, and then general and particular exact solutions are found for the considered problems that are expressed analytically explicitly. Obtained our results may be used for all the difficult-to-solve processes of KHM and instabilities and instabilities, which cover widely studied areas like galaxies, Kelvin-Helmholtz instability in the atmospheres of planets, oceans, clouds and moons, for example, during the formation of the Earth or the Red Spot on Jupiter, as well as in the atmospheres of the Sun and other stars. In this paper, also, a fairly common class of equations and examples are indicated that can be used directly to enter data for the use of the studied suitable tasks.

一种新型二级凸轮式分度机构动力学仿真

针对一种新型二级凸轮式分度机构的拓扑结构特点,在ADAMS软件环境下建立了机构动力学模型,分析机构的输出响应。在此基础上,研究了转速、惯性负载及针齿分度圆半径等因素对整机动态性能的影响规律。此外,分析了传动构件的针齿强度。结果表明:机构输出轴角速度值随着转速的提高而大幅度增加,随着针齿分度圆半径的增大而减小,其波动幅值随负载的增大而明显减小。机构分度期内针齿与凸轮间的动态啮合力显著波动,上述研究成果可为该类分度机构的工况参数选择原则提供一定的参考。

重载行星轮系安装误差对系统均载性能的影响

行星轮安装误差的存在会导致行星轮系产生不均载问题,进而会影响减速器的传动性能和寿命。以往的研究未明确定义不同角度下的安装误差对系统均载性能的影响,并且关于多行星轮对系统均载影响的研究(在不同安装误差和不同输入功率下)也较少。为此,研究了实际应用中行星轮系安装误差对系统均载性能的影响。首先,以重载四行星轮系为研究对象,建立了行星轮径向和切向安装误差的综合误差表达形式;然后,基于轮系的传动模型,分析了单行星轮不同安装误差角和误差数值对系统均载的影响;最后,在单行星轮的基础上分析了不同工况和误差配置下多行星轮对系统均载的影响。研究结果表明:行星轮的切向安装误差对系统均载影响最大,径向安装误差对系统均载影响最小,当单行星轮安装误差数值为60μm,安装误差角θ从径向往切向方向靠近时,行星系统的均载系数增大了9.6%;误差绝对值越大,均载系数越大,当单行星轮安装误差数值从-30μm到-60μm时,系统的均载系数增大了4.6%;多行星轮存在切向安装误差对系统均载的影响可以用有效误差来衡量;齿轮承载范围内,随着输入功率的增大,安装误差对系统均载的影响逐渐减小。

反向式行星滚柱丝杠副的螺纹牙修形设计

基于反向式行星滚柱丝杠副(Inverted Planetary Roller Screw Mechanism,IPRSM)的螺纹牙载荷分布情况,分析了滚柱修形和丝杠修形对其载荷分布的影响。结果表明,丝杠-滚柱接触侧的载荷不均程度比长螺母-滚柱接触侧严重,对滚柱修形后,最大接触应力以及最大载荷得到了有效降低,螺纹牙上的载荷分布更加均匀;而长螺母-滚柱接触侧对修形量变化较丝杠-滚柱接触侧更加敏感。同样,丝杠修形可有效降低最大载荷。研究对优化IPRSM的载荷分布具有一定的参考意义。

青菜高密度移栽机植苗机构的设计与试验

目前国内移栽机尚无成熟的适用于青菜等多行密植蔬菜移栽的植苗机构;针对小株距小行距、高效率的密植移栽要求,设计了一种非圆齿轮行星轮系八行同步植苗机构,并进行了运动学仿真和田间移栽试验。对非圆齿轮行星轮系进行了运动学建模与分析,开发了植苗机构辅助分析与优化设计软件;分析了不同机构参数对植苗轨迹姿态的影响,并通过人机交互的方式得到一组满足青菜小株距移栽要求的机构参数;建立了八行同步植苗机构的三维模型,利用虚拟样机仿真技术绘制出仿真轨迹,并与理论轨迹进行对比,以验证植苗机构三维设计的正确性;开展了田间移栽试验,以验证该机构的可行性和实用性。试验结果表明:在作业转速为15r/min、前进速度为55mm/s的情况下,八行植苗机构的作业株距和行距均为110mm,平均植苗成功率为93.9%,移栽密度超过70株/m2,试验移栽效率为240株/min,表明该机构在机械化密植移栽作业中有较高的应用价值。该研究为高密度移栽机植苗机构的研发提供了理论和试验依据,促进了密植型蔬菜钵苗机械化移栽的进程,为密植移栽机的进一步研究提供技术支持和参考。

基于故障树和贝叶斯网络的履带车辆行星变速机构可靠性分析

行星变速机构作为履带车辆传动系统的核心部件,其可靠性直接影响履带车辆的正常运行。以履带车辆行星变速机构为研究对象,基于实测试验结果建立故障树,将故障树转化为贝叶斯网络(Bayesian Network,BN)模型,并考虑行星变速机构正常、普通故障、严重故障3种状态进行可靠性分析。研究结果表明,行星变速机构失效概率为89.34×10^(-8)h^(-1),其工作400 h的可靠度为0.99964,符合设计要求;利用贝叶斯网络双向计算的功能,可知当行星变速机构发生失效,由主轴断裂或摩擦片烧蚀、翘曲、断裂或齿轮疲劳断齿引起的可能性较大。为后续装备检修、改进设计提供理论依据。

数学建模在水稻插秧机作业优化中的应用

为了降低插秧机的作业故障次数、提升插秧效率和插秧质量,对数学建模在水稻插秧机作业优化中的应用进行了研究。为了有效提升作业效率和作业质量,分插机构的传动部件改进为非圆齿轮行星系,并针对传动装置建立数学模型并分析。为了验证水稻插秧机的结构是否合理,对其进行了仿真试验,结果表明:水稻插秧机的结构合理,可将其应用于实际生产。

A Rendezvous Mission to the Second Earth Trojan Asteroid 2020 XL_5 with Low-Thrust Multi-Gravity Assist Techniques

As the second of Earth's Trojan asteroids, 2020 XL_(5) is worthy of rendezvous and even sample return missions in many aspects. In this paper, a rendezvous mission to Earth's second Trojan asteroid 2020 XL_(5) is proposed.However, due to its high inclination and large eccentricity, direct impulsive transfer requires large amounts of fuel consumption. To address this challenge, we explore the benefits of electric propulsion and multi-gravity assist techniques for interplanetary missions. These two techniques are integrated in this mission design. The design of a low-thrust gravity-assist(LTGA) trajectory in multi-body dynamics is thoroughly investigated,which is a complex process. A comprehensive framework including three steps is presented here for optimization of LTGA trajectories in multi-body dynamics. The rendezvous mission to 2020 XL_(5) is designed with this three-step approach. The most effective transfer sequence among the outcomes involves Earth–Venus–Earth–Venus-2020 XL_(5). Numerical results indicate that the combination of electric propulsion and multi-gravity assists can greatly reduce the fuel consumption, with fuel consumption of 9.03%, making it a highly favorable choice for this rendezvous mission.

WK-10B电铲提升机构的改进

WK-10B电铲在使用中,其提升机构暴露出结构笨重、传动效率低、能耗高等诸多弊端,严重影响设备出勤率,甚至危害到矿山安全生产。在对电铲原有结构不进行大规模改造的基础上,成功运用行星减速机对提升机构进行改进,从根本上解决了现有提升机构存在的问题,使用效果良好,经济效益显著。

采煤机截割部行星机构关键零件疲劳寿命仿真分析

基于采煤机截割部行星机构关键零件结构特征,介绍一种可实现行星机构关键零件疲劳寿命分析的仿真分析方法。此方法需先构建采煤机截割部行星机构关键零件刚柔耦合模型,并由此开展行星机构关键零件动力学分析和疲劳寿命分析。将仿真分析方法应用于工程实践后确认,此种仿真分析方法具有较高的疲劳寿命分析精度。

EBZ160掘进机行星减速器结构化力学分析

为进一步探究EBZ160型掘进机可能的优化路径,从实际案例入手,针对其因行星减速器结构而运行效率不足的问题,以轻量化的设计理念对行星减速器结构进行优化设计,明确其传动比、齿数与齿轮模数等关键参数信息,以此进行优化。而后对优化后的掘进机行星减速器结构进行有限元分析,结果显示,优化设计后的EBZ160掘进机行星减速器,不但实现了轻量化,而且完全符合在正常工况条件下对结构的强度要求,表明设计在理论上可靠安全,可进一步通过现场实验予以验证。

Performances of a Balanced Hydraulic Motor with Planetary Gear Train

The current research of a balanced hydraulic motor focuses on the characteristics of the motor with three planet gears.References of a balanced hydraulic motor with more than three planet gears are hardly found.In order to study the characteristics of a balanced hydraulic motor with planetary gear train that includes more than three planet gears,on the basis of analysis of the structure and working principle of a balanced hydraulic motor with planetary gear train,formulas are deduced for calculating the hydraulic motor＇s primary performance indexes such as displacement,unit volume displacement,flowrate fluctuation ratio,etc.Influences of the gears＇ tooth number on displacement and flowrate characteristics are analyzed.In order to guarantee the reliability of sealing capability,the necessary conditions that tooth number of the sun gear and the planet gears should satisfy are discussed.Selecting large unit volume displacement and small displacement fluctuation ratio as designing objectives,a balanced hydraulic motor with three planet gears and a common gear motor are designed under the conditions of same displacement,tooth addendum coefficien and clearance coefficient.By comparing the unit volume displacement and fluctuation ratio of the two motors,it can be seen that the balanced hydraulic motor with planetary gear train has the advantages of smaller fluctuation ratio and larger unit volume displacement.The results provide theoretical basis for choosing gear tooth-number of this kind of hydraulic motor.

Refinement of TiB_(2)Powders with High-speed Planetary Mill and Its Effect on TiB_(2)Sinterability

Titanium diboride ceramic was produced via spark plasma sintering(SPS)using finer TiB_(2)powder made by high-speed planetary ball milling.The effects of ball milling parameters on the composites and particle size of TiB_(2)powder were investigated.It was shown that the average particle size of TiB_(2)powder decreased from 5.8 to 1.59μm and the wear rate of WC balls was 1.58 wt%,when the ball-to-powder weight ratio(BPR),the rotary speed and milling time and were 10:1,600 rpm and 20 min,respectively.The content of WC in TiB_(2)powder can be limited below 4.58 vol%by optimizing the milling conditions.The sintering temperature of TiB_(2)powder milled can be decreased obviously,and the mechanical properties are evidently improved and the microstructure becomes more homogeneous when the powder of TiB_(2)becomes finer.The relative density,hardness,bending strength,and fracture toughness of the TiB_(2)ceramic fabricated at 1700℃reach the optimal values,which are 98.13%,19.14 GPa,756 MPa,and 5.71 MPa·m~(1/2),respectively.The decrease of TiB_(2)particle size and the introduction of WC are the potential reasons for the improvement of TiB_(2)ceramic performance.