Kinematic Modeling and Characteristic Analysis of Eccentric Conjugate Non-circular Gear & Crank-Rocker & Gears Train Weft Insertion Mechanism

A novel weft insertion mechanism named eccentric conjugate non-circular gear & crank-rocker & gears train weft insertion mechanism was proposed in order to better meet the requirements of rapier loom's weft insertion mechanism as well as reduce the manufacturing difficulty. Meanwhile, based on the working principle of this mechanism, kinematical mathematic models of this mechanism were established and an aided analysis and simulation software was compiled. The influences of eccentricity ratio, deformation coefficient, and other important parameters on the kinematics characteristics of this mechanism were analyzed by using the software. A group of preferable parameters which could meet the requirements of weft insertion technology were obtained by means of human-computer interactive optimization method. The maximum velocity, maximum acceleration, and variation of acceleration of this mechanism are smaller than those of the conjugate cam weft insertion mechanism applied on TT96 rapier loom under the conditions of the same unilateral total stroke of rapier head and the same rotary speed of loom spindle; meanwhile the other demands of weaving technology can be met by this novel weft insertion mechanism.

NOVEL METHOD OF REALIZING THE OPTIMAL TRANSMISSION OF THE CRANK-AND-ROCKERMECHANISM DESIGN

A novel method of realizing the optimal transmission of the crank-and-rockermechanism is presented. The optimal combination design is made by finding the related optimaltransmission parameters. The diagram of the optimal transmission is drawn. In the diagram, therelation among mini-mum transmission angle, the coefficient of travel speed variation, theoscillating angle of the rocker and the length of the bars is shown, concisely, conveniently anddirectly. The method possesses the main characteristic. That it is to achieve the optimaltransmission parameters under the transmission angle by directly choosing in the diagram, accordingto the given requirements. The characteristics of the mechanical transmission can be improved togain the optimal transmission effect by the method. Especially, the method is simple and convenientin practical use.

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.

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.

Kinematic Characteristics Analysis and Parametric Solving of Snow Melting Agent Throwing Mechanism with Variable Crank Length

Variable crank length cam⁃linkage mechanism has attracted much attention due to its compact overall structure when realizing complex motion laws.According to the special trajectory requirements,the kinematic characteristics and parameters of the mechanism have been analyzed and solved,which lays foundation for the implementation of the variable crank length snow melting agent throwing mechanism designed in this paper.Based on the trajectory equation of the point,the mathematical model of the throwing mechanism was established,and the theoretical trajectory of the end point of the throwing mechanism was obtained by programming.The parametric modeling and trajectory drawing were carried out by computer aided three⁃dimensional interactive application(CATIA),and the correctness of the mathematical model was verified by comparison.The regional trajectory distribution characteristics of the end points of the throwing mechanism were studied by using the trajectory region location method,and the influence of various parameters on the trajectory was investigated by using the numerical cycle comparison method.The human⁃computer interaction system of snow melting agent throwing mechanism with variable crank length was constructed by using Microsoft Visual Basic(VB)software.Based on the restriction conditions,the optimum combination of structural adjustment parameters and operational parameters suitable for Harbin first⁃class roads was obtained by using orthogonal test table,which provides an effective method to solve the parameters of the variable crank length cam mechanism with smooth impulse trajectory.

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Pro/Mechanism的柴油机动力计算

以16V 240柴油机为例,使用美国参数技术公司Pro/Engineer大型设计软件的MDX(Mechanism Design extension)CAE模块进行曲柄连杆机构的动力计算,将MDX计算的结果与理论计算的结果进行比较,并且在曲柄连杆机构动力计算的基础上,进行16V240柴油机输出扭矩的计算.计算结果表明基于Pro/Mechanism的柴油机动力计算的方法切实可行.

Comparison of two types of twin-rotor piston engine mechanisms

A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVDM）. Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2x/N as the output shaft rotates an angle of x/N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3.

DYNAMIC ANALYSIS OF A LATE-MODEL DOBBY SHEDDING MECHANISM

This paper presents the dynamic analysis of a dobby shedding mechanism. Taking theoscillatory slider as a moving reference frame, relative motion relations of the cam-rocker mech-anism are established in the kinematic analysis. A non-linear equation is solved by indirectmethod to obtain its numerical solutions expressed in algebraic power series for the six-barlinkage. In dynamic analysis, the authors have set up dynamic equations for the entire mecha-nism to find the solutions. From the results of dynamic analysis, it can be seen that the mecha-nism is suitable for operation at high speed and under heavy load.

A New Design Method for Realizing Accurate Track of Hybrid-driven Five-bar Mechanism

The concept of virtual slider crank mechanism is proposed and decoupled to obtain parameters of controllable five bar mechanism without any principle error for any given trajectory. The model is simple and easy to solve. This method has no convergence,flexible workspace and singularity of the mechanism problem. Through this method,we don’ t need any curve to fit the trajectory point. Using MATLAB program to calculate,the computation time can be reduced to less than 3% of the original. Finally,an example is given to illustrate the method which is meanwhile compared with the traditional five bar design method.

茶园仿生往复式开沟松土机设计与试验

丘陵山区茶园土壤板结、石砾较多,使用传统旋转或移动式开沟机会出现打石跳刀、刀具无法入土、开沟不深、作业阻力大的问题。为此,依据人工铲土具有自发性以最低功耗完成最优作业路径的特点,设计仿人工铲土动作的曲柄摇杆式开沟装置,并研制小型茶园往复式开沟松土机。通过分析人工使用铁锹铲土的动作,建立入土、切土、抛土的运动模型,基于Matlab软件分析得到人工铲土时铁锹锹尖运动轨迹的拟合方程,以此方程为基准,建立曲柄连杆机构的目标函数,结合约束条件解出曲柄摇杆机构结构参数,同时对开沟铲进行开沟阻力分析,确定开沟铲的结构参数。建立Recurdyn和EDEM耦合的开沟铲-土壤互作仿真模型,并进行三因素三水平正交试验,对作业和结构参数进行优化,得到最优参数组合:机器前进速度v为0.06 m/s、曲柄转速n为42 r/min、入土倾角φ为80°。田间试验结果表明,茶园往复式开沟松土机作业平均开沟深度为211.5 mm,开沟功率为0.119 kW,沟深稳定性系数为90.9%,相较于传统旋转式开沟机,开沟功率降低6.3%,沟深稳定性系数提高3.1个百分点,整机作业质量满足茶园农艺要求。

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.

吊篮式自走移栽机的设计

为保证丘陵地区秧苗实时移栽,提高移栽质量,阐述一种吊篮式自走移栽机行走装置和移栽机构的结构及工作原理。通过分析计算及1∶1的建模,验证行走装置的工作速度和结构布局形式,以及移栽机构各动作的协调性及栽苗质量。根据建模分析的结果,确定设计的主要参数,从而设计出行走机构装置主要部件轮架机构、主驱动变速箱机构、机架、升降机构、水平调节机构及控制装置等,移栽机构主要部件移栽变速箱机构、株距调节机构、曲柄连杆机构、鸭嘴移栽器、自动喂料机构等。通过样机试制和试验,结果表明:该机具可完成移栽株距(260~600 mm)、移栽深度(80~160 mm)可调的目标,工作效率高,同时具有结构合理紧凑、维护方便、操作简单等优点。

曳引摇枝式板栗落果装置设计与试验

针对当前丘陵山地板栗采摘困难、人工收获工作强度大、采收效率低等问题,设计了一种由柔性钢丝绳曳引振动的小型摇枝式板栗落果装置。建立板栗果实-果枝单摆动力学模型,分析果实脱落条件,得到板栗果实振动脱落切向加速度为285.36 m/s~2,得出影响板栗果实脱落的主要因素为果枝振动频率、振幅、振动时间;进行板栗果枝振动特性试验,用Default Shaker液压振动台以0~30 Hz扫频方式确定垂直方向上板栗果枝共振频率,并在频率7~15 Hz段进行驻频试验,得出振动落果较优频率为10~12 Hz。根据果枝振动试验结果,利用ADAMS软件对摇振机构进行仿真,结果表明,摇杆振幅大于95 mm时,果枝末端加速度可满足板栗果振动脱落的加速度条件,确定了落果装置参数设计的合理性。设计了三因素三水平正交试验,试验结果表明,板栗落果最佳作业参数组合为摇振频率11 Hz、振幅135 mm、摇振时间30 s,此时板栗落果率为91.9%,树皮损伤率为8.8%,满足农业机械推广鉴定标准中树皮损伤标准。

基于曲柄摇杆机构的仿生海扁虫水下机器人

针对现阶段MPF波动推进模式仿生机器人在体积、灵活度、运动性能等方面研究较少的问题,设计出了一种仿生海扁虫水下机器人。该机器人使用了一种无急回特性的曲柄摇杆机构作为动力传输零件,通过可传动柔性骨架实现动力的传输,带动鳍条往复摆动,形成稳定的波形推动机器人前进。进一步,通过对曲柄摇杆机构的理论计算和尺寸设计得出实际模型,运用SolidWorks Motion运动仿真进行无急回特性的验证。最后,通过3D打印件等材料制作仿生海扁虫机器人样机,进行水下运动试验,以此验证该设计可行性,在有效减小机器人体积和自身质量的同时,具有更佳的运动性能。

智能手指关节功能康复训练器创新结构设计

因运动、年龄老化等因素导致手指功能损伤患者数量不断增加。针对这类人群进行手指康复器的设计,与传统康复产品相比,具有控制简单、方便、成本相对较低特点。通过分析仿手指运动的自由度,建立了曲柄摇杆机构,可以应用于手指康复器的结构设计;以主要机械构件和手指关节转动角度为参考因素,得出了机构的运动轨迹,在此基础上,得到各机械构件的合理尺寸,从而完成对机械构件的结构设计。通过模拟手指拉伸、弯曲来实现手指的康复功能。通过分析运动的角位移、角速度使得所得的机构更加符合手指的合理运动范围。运动仿真实验表明,该机构能带动手指在一定角度范围进行弯曲拉伸运动,可以满足手指损伤患者的康复训练需求。

插齿机主运动机构的动平衡优化策略

在插齿过程中插齿机由于主运动机构动不平衡产生了不平衡惯性力,从而引起机床振动和噪声。为此,通过对插齿机主运动机构进行平衡分析,计算曲柄旋转一周的曲柄销与连杆的总不平衡量,采用积分求解和均值求解两种优化计算方法,以均方差作为评价指标制定优化策略。插齿机YKW51160主运动机构的平衡量优化实例计算表明,积分优化法与均值优化法计算的平衡块的不平衡量相近,相差不超过0.2 kg·m,积分优化后的不平衡量均方差为0.614,波动更小,减振效果更好。

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。

摇臂连杆加工工艺与钻专夹设计

文章根据摇臂连杆的结构特点和技术要求,制订了该零件的机械加工工艺规程;在对定位装置、夹具装置及夹具体进行分析的基础上,设计并制造了用于第六道工序Φ35孔的钻孔专用夹具。应用结果表明,该夹具做到了加工精度保证、设计方案合理、结构简单实用,能有效提高摇臂连杆的加工质量及效率。

一种曲柄连杆式惯容器的力学性能与隔震性能研究

基于惯容器(inerter)的耗能装置近年来受到结构减隔振(震)领域学者的极大关注。该文研究了一种新型惯容器——曲柄连杆式惯容器(CTI)。CTI由曲柄、连杆、齿轮箱和飞轮组成,具有表观质量可调和位移兼容性强等优点。提出了CTI装置与隔震支座在桥梁抗震中的联合布置形式。推导得到了CTI的表观质量解析表达式,及其线性近似条件。对CTI样机开展了不同表观质量及不同工作姿态下的力学性能试验。以一座典型的三跨变截面连续梁桥为例,采用数值方法研究了CTI在桥梁抗震中的参数设计方法并验证了其可靠性。研究结果表明:CTI可简化为线性惯容器的条件为最大变形应小于曲柄长度的0.312倍,连杆长度应大于曲柄长度的1.803倍。力学性能试验得到的表观质量与理论结果基本一致,通过改变曲柄长度可实现表观质量的精确调节,在线性工作范围内连杆工作姿态对表观质量影响不大。将CTI与隔震支座组合使用可在保证不发生落梁的情况下适度放大主墩顶处隔震支座的变形,提高其耗能效果,从而降低桥梁下部结构的地震响应。