Comparison and analysis of two Coulomb friction models on the dynamic behavior of slider-crank mechanism with a revolute clearance joint

The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance joint. The normal and tangential forces acting on the contact points between the journal and the bearing are described by using a Hertzian-based contact force model and the Coulomb friction models, respectively.The dynamic equations of the mechanism are derived based on the Lagrange equations of the first kind and the Baumgarte stabilization method. The frictional force is solved via the linear complementarity problem(LCP) algorithm and the trial-and-error algorithm.Finally, three numerical examples are given to show the influence of the two Coulomb friction models on the dynamic behavior of the mechanism. Numerical results show that due to the stick friction, the slider-crank mechanism may exhibit stick-slip motion and can balance at some special positions, while the mechanism with ideal joints cannot.

Kinematic Analysis of Elliptic-Gear & Eccentric Slider-Crank & Uniform-Pitch Screw Weft-Insertion Mechanism

In order to analyze the kinematic performances of elliptic-gear & eccentric slider-crank & uniform-pitch screw weft-insertion mechanism proposed by us,kinematic mathematic models of the mechanism were established,and an aided analytic software was compiled.Influences of some important parameters on the kinematic characteristics of the mechanism were analyzed.A group of preferable parameters were obtained according to the software and some requirements.Comparisons of kinematic performances were made between the proposed mechanism and the variable-pitch screw insertion mechanism of C401 rapier loom manufactured by Vamatex Corp in Italy.The results show that the proposed mechanism can meet the requirements of inserting wefts.

A method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed presses

A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank mechanism whose crank rotates at a constant angular velocity,the kinematic parameters of the slide,connecting rod and crank were formulated approximately. On the basis of the results above,three inertia forces and the input moment in the mechanism during its idle running were investigated and formulated by dynamic analysis. A verification experiment was performed on a slider-crank mechanism at a high-speed press machine. The forces derived from the established formulas were compared respectively with those obtained by the ADAMS software and the classical method of connecting rod mass substitution. It was experimentally found that the proposed formulas have an improved performance over related earlier techniques. By use of these results,a 1 000 kN 1 250 rpm four-point high-speed press machine was designed and manufactured. The slide of this press is driven by four sets of slider-crank mechanisms with symmetrical layout and opposite rotation directions to counterbalance the horizontal inertia forces. Four eccentric counterbalance blocks were designed to counterbalance the vertical force after their mass and equivalent eccentric radius were formulated. The high-speed press machine designed by the proposed counterbalance method has worked with satisfactory performance and good dynamic balance for more than four years in practical production.

Dynamic Simulation of a Smart Crank and Slider Mechanism

In this paper, a smart crank and slider mechanism is analyzed mostly from a dynamic view. By means of dynamic explicit finite element method, 3D nonlinear structure is simulated. It is proved that the mechanism can effectively accomplish smart movement prescribed. And in order to ensure reciprocal movement with higher frequency, measures should be taken to avoid over heating of parts. Compared with internal energy, kinetic energy of total rigid body is dominating, and Ydirection equivalent rigid velocity is much higher than X direction velocity. Equivalent rigid velocity of all parts is consistent with respective movement condition. For both energy and velocity, slider effect is dominating. Three direction equivalent inertia force oscillates. Force amplitude in Y-direction is comparitively the greatest.

基于Ansys的曲柄滑块机构的运动学分析在教学课程中的应用

在机械原理的教学中,曲柄滑块机构的设计原理与方法是重点和难点问题,传统的实物实验对曲柄滑块机构的种类、复杂性都有很大的限制,不利于学生对曲柄滑块系统运行规律的掌握。基于此,利用Ansys中的workbench建立了曲柄滑块机构运动仿真模型,通过对模型进行分析设置,对典型曲柄滑块机构进行运动仿真,得出了曲柄滑块机构的位移及应力、应变的分析结果,为机械结构仿真教学提供了有效的方法。

含柔性连杆的曲柄滑块机构动力学分析与实验研究

为了研究柔性连杆、带有固体润滑涂层MoS_2的铰链接触副对含间隙铰链机构的动力学特性的影响规律,以曲柄滑块机构为研究对象,使用Adams软件进行数值仿真分析,研究了柔性连杆材料、铰链间隙、铰链接触副材料和铰链接触副表面固体润滑涂层对曲柄滑块机构动力学特性的影响。通过搭建与数值仿真参数一致的含间隙铰链的曲柄滑块试验台,试验验证了柔性大的连杆、较小的间隙值、接触刚度较小的接触副材料能够减小机构的振动,带有涂层的铰链能够有效减小接触面的磨损量。试验结果和数值仿真结果较为一致,能够有效的反应各种工况对含间隙机构的影响规律,为固体润滑涂层在航天领域中含间隙铰链接触副展开机构的减振抗冲击研究提供理论基础和试验依据。

可变幅振动式咖啡收获机设计与试验

针对咖啡人工采收成本高、大型机械采收困难等问题,以曲柄滑块式传动机构为基础,设计一款小型可变幅振动式咖啡收获机。通过建立咖啡果实-果柄的脱落力学模型,分析得到果实脱离果柄的条件,依据曲柄滑块的设计方式,构建传动结构的运动简图与计算公式;采用ANSYS Workbench与Adams软件,进行模型的动力学仿真分析;以传动结构的曲柄长度、摇杆长度和转速为试验因素,惯性力为试验指标,进行三因素三水平的正交试验与响应曲面分析,建立惯性力二次多项式回归模型,以果-柄结合力5.25~7.16 N为优化目标,确定收获机的结构参数和工作参数。结果表明,在保证传动结构运行状态平稳的优先原则下,得到咖啡收获机结构设计的最优参数组合为曲柄长度15 mm,摇杆长度100 mm,转速700 r/min;通过样机试制与田间试验,转速在700 r/min左右,总体的作业效果良好。研究为后续的咖啡机械化收获提供参考。

基于调和函数的偏置曲柄滑块机构非线性诺模图设计

文中给出了偏置曲柄滑块机构的非线性诺模图。首先,对机构基本方程引入无量纲参数和过渡函数,将机构数学模型整理成适合诺模图求解的标准形式;其次,对过渡函数采用构造调和函数并解析的策略,寻求较优尺度模量,弱化和规避关键标尺刻度的非均匀分布和过度集中现象;最后,使用两种不同类型无量纲参数的案例,对所给非线性诺模图进行验证。结果表明:该诺模图不仅可直接用于快速设计不同目标的偏置曲柄滑块机构,还可对所做设计的正确性与合理性予以快速校验。

内燃机中的曲柄滑块机构在机械中的应用研究

内燃机中的曲柄滑块机构采用了平面连杆机构,它是组成机械最常用的传动机构之一,在各种机械中有着广泛的应用,本文分析了曲柄滑块机构及其演化机构在内燃机、公交地铁车门、牛头刨床、飞机起落架和惯性筛中的应用,画出了机构运动简图,并对其性能进行了研究,为曲柄滑块机构在机械中的应用提供参考。

船用压缩机传动结构分析

船用压缩机的减振降噪以往主要是通过增加减振装置、加强筋板或优化曲柄连杆结构等途径解决。基于船用压缩机减振降噪的需求,设计开发了曲柄圆滑块传动机构,从传动结构角度来降低船用压缩机的振动噪声。建立了机构的三维模型,并基于含间隙的运动副对传动结构做了仿真分析。

一种新型多功能码垛机械手的设计与分析

针对目前六轴码垛机器人的承重性差、成本高、维护较难且无法实现多功能一体等缺点,为了提高码垛机器人的承重性能,降低其制造及维护成本,实现多功能作业,文中结合曲柄滑块机构设计了一种多功能机械手,既可码垛,又可自动更换栈板。该机械手是对传统偏距曲柄滑块机构进行改进,将直曲柄换成L形曲柄,使曲柄能够过渡死点。通过已知参数对码垛机械手的连杆尺寸进行设定,对总体机构进行受力分析,用SolidWorks 2020对L形曲柄的不同λ角进行建模,经对比分析得出最合适L形曲柄的λ角,从而设计出整个码垛机械手模型,最后,将码垛机械手模型导入ANSYS Workbench 18软件进行受力变形分析,得到一种新型多功能实用码垛机械手。该设计极大地提高了改进后的机械手的承重性、通用性和稳定性,降低了其能耗比,实现了码垛与栈板都能搬运的功能。

基于曲柄滑块机构的多地形种植机翻转装置结构设计与仿真

在丘陵、山区等有坡度地势栽植苗木时,为了能够保证树苗竖直生长,基于曲柄滑块机构设计了一种可根据地势坡度自动调整挖坑角度的翻转装置。为使自动翻转装置具备较好的工作性能,计算推导了翻转机构中连杆翻转角度与滑块位移的关系式,并采用机械系统动力学自动分析(Automatic Dynamic Analysis of Mechanical Systems,ADAMS)软件对曲柄滑块机构进行运动仿真。该结构提高了苗木种植机的工作性能和智能化水平,同时为种植机的结构设计提供了理论指导。

基于滑模控制的无人驾驶自行车设计与仿真

针对无人驾驶自行车无法实现自平衡的问题,设计一种由滚珠丝杠滑台、滑块、曲柄和连杆组成的曲柄滑块机构,并采用滑模控制方法来控制车体的平衡和运动方向。先对曲柄滑块机构的运动特性及受力进行了分析,分别得到滑块位置与前车把转角的关系以及转向电机输出力矩与前车把所受力矩的关系。通过分析无人驾驶自行车在直立行驶过程中的动力学特性,采用拉格朗日方程法建立了系统的动力学模型。设计了滑模控制器并进行了仿真分析。仿真结果表明,文中所采用的控制方法可以在转向电机输出很小力矩的情况下实现无人驾驶自行车的直立平衡运动。

基于Ansys Workbench的研磨仪连杆优化设计

为解决现有研磨仪连杆在设计使用年限内出现断裂失效的问题,对连杆进行了结构优化设计。首先,对连杆所属曲柄滑块机构进行动态静力分析,求解出连杆在1个运动周期内受到的外力,以此作为后续连杆强度分析的理论依据;其次,使用Ansys Workbench完成连杆的静力学强度分析和疲劳强度分析,确定连杆失效是由于疲劳强度不足造成的;最后,以连杆质量最轻为优化目标,以满足疲劳强度要求为约束条件,使用响应面法对连杆进行优化设计。优化设计确定了合适的过渡圆角半径、薄端圆环厚度和杆身宽度。仿真结果表明,优化后连杆受到的极限拉伸等效应力最大值降低了58.7%,疲劳寿命增加了1.4倍,能够满足使用要求。

基于曲柄滑块机构的X翼扑翼机构研究与测试

设计了一款机翼对称拍打的X翼扑翼机构。采用曲柄滑块机构,将曲柄的圆周运动转化为直轴的直线往复运动,直轴再通过摇杆带动两侧机翼,从而实现机翼的对称拍打。制作了一台扑翼机构的样机,运用光学运动捕捉系统和风洞对该扑翼机构进行了运动测试,从扑翼机构的拍打角度幅值、拍打频率、产生的升力以及电机的运行状况方面分析了该扑翼机构的可靠性。通过对比试验,确定了一组合适的拍打角度幅值和翼面面积,使得该扑翼机构能够产生12.9 g的升力,验证说明clap-fling机制能够有效提高该扑翼机构的升力。

给茧机无绪茧自动抓取装置设计与分析

为解决缫丝过程中给茧机内存在无绪茧且靠人工抓取的问题,设计了一种给茧机无绪茧自动抓取装置。传动部分由减速电机通过两个传动路线将动力传送至给茧机和横移滑轨机构。详细分析了横移滑轨机构所包含的曲柄滑块机构和齿轮齿条直线差动增倍机构运动特性,通过计算确定最佳抓取节点。最后介绍了末端抓取机构,并规划抓取后放置无绪茧和装置复位的时间节拍。分析表明给茧机无绪茧自动抓取装置结构合理可行,研究结果为给茧机无绪茧的处理提供一种新思路。

自动化生产线应用翻转机构的设计分析

针对某钣金类零件的加工需求,进行翻转机构的设计,实现对零件的稳定翻转。采用曲柄滑块的原理进行翻转机构的设计,建立了翻转机构的模型,并对其进行运动分析,实现了零件的稳定翻转。

Experimental Study of the Motion Modes of a Planar Mechanical System with Multi-Clearance Revolute Joints

Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can investigate the effects of the clearances on the dynamics of the multibody system. A revolute joint with clearance exhibits three motions which are;free-flight, impact and continuous contact motion modes. Therefore, a multibody system with n-number of revolute clearance joints will exhibit 3n motion modes which are a combination of the three motions in each joint. This study investigates experimentally the nine motion modes in a mechanical system with two revolute clearance joints. A slider crank mechanism has been used as the demonstrative example. We observed that the experimental curve exhibits a greater impact compared to the simulation curve. In conclusion, this experimental investigation offers valuable insights into the dynamics of planar mechanical systems with multiple clearance revolute joints. Utilizing a slider-crank mechanism for data acquisition, the study successfully confirmed seven out of nine motion modes previously identified in numerical research. The missing modes are attributed to inherent complexities in real-world systems, such as journal-bearing misalignment.

仿生机械水母设计与分析

设计了一种纯机械式的仿生机械水母,由储能触发装置提供初始启动力驱动曲柄转动从而带动法兰盘上下往复运动,进而带动仿生触手撑杆做伸缩运动,驱动4组扑水柔性片动作,实现吸水和排水。吸入的水推动水轮机叶片转动,以此实现机械水母的吸排水动作。利用SoildWorks完成了仿生机械水母的方案设计、三维建模与装配,理论计算确定了在水中仿生触手撑杆推开水所需要的力以及曲柄滑块机构、带传动等的设计参数。

一种便于回收餐具的餐桌设计

随着餐饮行业的快速发展,人们对饮食的要求越来越高,为了满足大部分顾客在餐厅饮食的喜好,以及便于服务人员高效的服务工作。本文设计了一种能够自由变换餐桌桌面形状大小,且便于餐具的收集智能餐桌。在餐桌结构设计方面,采用曲柄滑块机构与凸轮机构的组合实现餐桌桌面大小变换,其次餐桌的中间是一个连接管道的洞口,在底下是一个可以容纳餐具的容器,服务人员可将餐具推入洞口,实现便利回收餐具的功能。在餐桌控制设计方面,采用了STM32单片机控制减速电机,通过不同按钮实现餐桌桌面的自动开合功能。