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.

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.

Design and Analysis on Compression Mechanism of Small Square Bales of Sugarcane Leaf Baler

With more and more attention paid to comprehensive utilization of agricul-tural biomass resources, environment pol ution caused by large-scale burning of sug-arcane leaves can be effectively avoided, and it is urgent to resolve storage issue of sugarcane leaf. Through referring to the relevant domestic baler models and re-search findings, preliminary design and analysis were conducted on key components compression mechanism of smal sugarcane leaf baler, involving the open compres-sion principle for sugarcane leaf square baler, determination of the crank slider-type compression mechanism and the main parameters such as crank length, compres-sion frequency, feed rate and feed inlet length. Based on SolidWorks software, this paper established the 3-dimensional models of slider-crank type compression mech-anism, and imported it into ADMAMS software for the motion simulation analysis, to establish the foundation for the design and manufacture of subsequent smal sugar-cane leaf square baler prototype.

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.

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。

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。

三指机器人手爪设计与抓取研究

传统的多指仿人灵巧手虽然已实现较高的灵巧性与仿人性,但存在设计制作繁琐或价格昂贵以及手指末端抓力偏弱的弊端。而三指机械手作为一种简化形式一般又存在灵巧性不高的问题。针对以上弊端设计了一款基于滑块-摇杆机构的三指机器人手爪。将该结构直接类比人手所设计的手指关节能够实现中节指骨与远节指骨的耦合运动,且指尖力会随手指弯曲程度的增加而增大,有利于对细小目标物进行指尖捏取;采取与传统偏航-俯仰型不同的翻滚-俯仰型掌指结构,在增加了沿掌根关节的旋转自由度的同时尽可能地丰富了手爪的抓取姿态,使其能够适应更多的目标物,增加了灵巧性。在MATLAB中建立手指运动学模型并求得手指末端工作空间。经由实验验证得出该手爪具备较大的抓取力与丰富的抓取姿态。

基于多柔体动力学的葡萄挑藤机构参数优化与试验

针对目前中国北方露地葡萄栽培区缺乏春季葡萄藤上架作业机械的问题,该研究提出了曲柄摇杆式挑藤机构,该机构采用曲柄摇杆结构带动推藤杆和挑藤杆运动,推藤杆用于聚拢葡萄藤,挑藤杆按照既定轨迹进行挑藤。采用Matlab软件对挑藤杆的挑藤轨迹进行了参数优化,得到较优的挑藤轨迹。通过物理试验和计算确定了挑藤机构的弹簧预紧力、弹性系数等结构参数,分析了挑藤过程。其次,基于多柔体动力学(multi-flexible-body dynamics, MFBD)仿真技术建立了葡萄藤的柔性体模型与挑藤作业模型,以前进速度、弹簧预紧力和曲柄转速为试验因素,以平均挑藤角度和角度变异系数为评价指标,设计Box-Behnken仿真试验并进行回归分析。依据多目标优化原则,得到最佳参数组合;进一步基于土槽试验,验证曲柄摇杆式挑藤机构优化结果的准确性。仿真优化结果表明,当前进速度为0.2 m/s,弹簧预紧力为128 N,曲柄转速为67 r/min时,其平均挑藤角度最大、角度变异系数最小,分别为40.6°和6.0%。土槽试验的挑藤机构平均挑藤角度为43.2°,与仿真挑藤角度相对误差为6.4%,角度变异系数为14.8%。土槽试验结果表明仿真优化结果可靠,挑藤角度准确且挑藤均匀性较好,满足葡萄藤上架的角度要求。该研究可为后续葡萄藤挑藤绑藤一体机的研制提供参考。

往复直插式麦冬播种装置的设计与优化

为了改善川麦冬播种条件,提高播种效率,基于麦冬苗特性和农艺要求,设计了一种基于曲柄摇块机构的往复直插式麦冬播种装置,实现了以单个电机作为唯一动力完成从苗盘中取苗和播种的动作。运用Matlab编写了播种装置的运动学辅助分析软件讨论部分机构参数对运动轨迹的影响并得到了较优初始值,以理想的播种运动轨迹作为目标对参数进行优化得到了最优结果。运用Solidworks和Adams进行建模仿真,验证了优化结果的可行性。该研究可为麦冬播种机的设计提供理论参考。

曲柄摇杆式秧苗移栽机构分析设计

选取前插式曲柄摇杆移栽机构为研究对象,利用几何学和数值分析方法对该机构进行运动学分析,并建立数学模型;利用MATLAB 2010编制辅助分析软件,针对秧苗移栽的轨迹要求利用所编制的软件进行机构的优化设计,得到1组优化参数。利用SOLIDWORKS 2020构建该机构的三维实体模型,并通过多体动力学仿真软件ADAMS 2013进行虚拟样机仿真试验,经验证,试验结果与理论分析结果吻合,误差在合理范围内,即所设计的前插式曲柄摇杆移栽机构合理、准确。研究结果为后续样机试制提供了理论依据。

导向式框架断路器拉弧分析及预防

本文基于导向式框架式断路器在使用过程中,发生连接排触头及框架母线触头发生故障拉弧及触点烧毁实际情况,提出技术和管理上的改进。发生故障电弧时,其电流并未达到脱扣器设定的脱扣电流。对故障断路器位置指示的摇进机构进行解体后发现,位置指示磨损,工作人员的不规范操作,造成止动片断裂,从而使断路器发生拉弧事故。结合以上情况制定的预防措施为:定期检查摇进机构的位置指示情况、止动片磨损或断裂情况,对操作人员进行正规操作的培训。

大采高环境下采煤机摇臂的设计及应用

为探究大采高环境下的采煤效率提升路径,从采煤机摇臂的角度着手,探究大采高环境下采煤机摇臂的设计工作。结合大采高环境下的一般需求,对采煤机摇臂的整体结构进行设计;分别对采煤机摇臂的传动组件和壳体两个重要组成部分进行设计,并对其设计要点进行初步探究;对设计完成的采煤机摇臂进行仿真分析。结果显示,面向大采高环境所设计的采煤机摇臂结构具有相对较优的综合性能,以期在今后逐步得到实际应用。

摆动式集体落纱机构设计研究

为了推动环锭纺细纱机数字化进程,简述摆动式集体落纱机构的动作实现及改进方案,详述通过几何作图法和代数法确定长、短摇杆空间位置的计算方法;从抓管器操作精度要求、升降臂设计精度要求以及力矩、拉杆、摆动轴、锭子中心轴线、长摇杆与升降臂、中心高度差等方面,分析摆动式集体落纱机构的技术要求和设计要点;根据摆动式集体落纱机构的控制系统类型及数字化技术创新趋势,提出技术革新方法。指出:摆动式集体落纱机构是细纱长车连续化、数字化生产的关键,具有劳动强度低、用工量小、落纱效率高的优势;进一步提升其稳定性、可靠性和数字化水平,需深入了解机构细节,发现缺陷并不断优化。

中厚煤层MG900/2400-WD采煤机摇臂壳体力学分析

为进一步探究采煤机摇臂的可能优化路径,从摇臂壳体优化设计的角度着手,以面向中厚煤层开采的MG900/2400-WD型采煤机作为研究对象展开研究。首先结合实际需要,明确该摇臂壳体的设计要求,并从材料、热处理工艺与铸造方面进行摇臂壳体的初步设计;而后基于铸造完成的模型,应用ANSYS有限元分析工具分析该摇臂壳体的力学性能。结果显示,该摇臂壳体在应力和应变2个方面的指标上均符合预期要求,证明本次设计工作取得了初步成功,该摇臂壳体也具有潜在的应用价值。

柴油机配气机构的设计改进

针对柴油机气门间隙调整、保养困难及成本较高的问题,以某4缸柴油机非道路国四排放升级项目为例,对该柴油机的配气机构进行模拟计算和设计改进,将机械摇臂更改为液压摇臂,并采用性能测试和耐久试验进行验证。结果表明:设计改进后,该柴油机的气门间隙可以免保养维护,不但满足客户要求,而且降低了生产和保养成本,提高了整机的可靠性和稳定性。

蔬菜移栽机曲柄摆杆式夹苗机构的设计与试验

通过对穴盘苗进行抗压特性试验、试验平台的夹取试验,研究分析了适于夹取式自动取苗机构工作的相关参数组合以及最佳的钵苗含水率状况,为机构设计提供参考依据。该文基于辣椒穴盘苗抗压特性设计了全自动蔬菜移栽机曲柄摆杆式穴盘苗夹苗机构,该机构可与顶出机构配合完成全自动蔬菜移栽取苗和投苗工作。该文完成了曲柄摆杆式夹苗机构主要结构的设计,并对曲柄摆杆式夹苗机构的工作过程进行了力学、运动学分析和仿真,确定了结构和工作参数,即曲柄、连杆、摆杆长度分别为80、236.22、172.5 mm,夹苗爪具有较好的运动特性。曲柄摆杆式夹苗机构性能试验结果表明,夹取爪为金属材质,弹簧劲度系数为90 N/m,钵苗脱落率为0,钵苗破碎率为4.2%,综合取苗成功率可达95.8%,性能指标符合设计要求,夹苗爪"V"形结构设计有效防止穴盘苗在夹取过程中脱落,保证了取苗成功率。试验表明钵苗含水率为60.8%时,钵苗在不同的弹簧劲度系数及夹取爪材质下均有良好的适应性,在该含水率下钵苗的取苗平均成功率为94.4%。该机构从取苗到投苗采用圆弧形工作轨迹,夹苗爪采用八字形轨道与复位弹簧控制其开合,结构简单、性能可靠,无需调整即可适应多种不同尺寸穴盘苗的取苗工作,对不同含水率穴盘苗适应性强,对穴盘苗损伤小,机构成套使用可达到较高工作效率。

曲柄摇杆振动破壳油茶果粗选机运动学分析及试验

为验证所设计的油茶果粗选机的合理性,该文首先对其进行简化,联系振动筛工作原理和受力分析对其运动参数进行分析,找出影响物料运动的因素,并验证其运动参数设计合理;其次利用ADAMS仿真软件对该机进行运动仿真,得到物料模型的振幅曲线图,通过使用振幅递减法分析曲线图的变化规律,验证其振幅设计合理;最后通过三水平三因素正交组合试验,得出各因素对茶籽保有率和筛分效率的影响显著性顺序。利用Design-Expert软件分析得出当粗选机曲柄转速、筛面倾角、筛面长度取值为276.12 r/min、6.69°、1 005.8 mm时,茶籽保有率和筛分效率均达最佳值(分别为96.84%和96.77%),验证了粗选机的设计满足工作要求。该研究结果为后期精选机的设计提供了参考。