Modeling and Optimal Design of Planar Linkage Mechanism of Coupled Joint Clearances for Manufacturing

The uncertainty of the mechanism motion error is mostly caused by the manufacturing process,so the motion error cannot be effectively predicted at the design phase.The problems of manufacturing complexity and the relationship between design and manufacturing are analyzed,and the influence of dimensional tolerance and fit tolerance on the motion accuracy of the system is considered in the design process.Then based on the Monte Carlo simulation,an optimal design model of planar linkage mechanism is set up.A typical offset slider-crank mechanism is used as an illustrative example to carry out the optimal design.Compared with the result of typical robustness design,the similar variation characteristics of the mean value and the standard deviation can be found,so the proposed method is effective.The method is furthermore applied in the optimization of the schemes with different fit tolerances and the prediction of motion errors in the design phase is achieved.A set of quantitative evaluation system for mechanism optimal design is provided.Finally,a basic strategy is presented to balance the motion precision and manufacturing cost.

CALCULATION OF ELASTIC ERROR OF PLANAR MECHANISM—AN EQUIVALENT METHOD

In rigid mechanism dynamic analysis, the equivalence theorem is often used due to its simplicity and perceivability. Based on conjugation and duality between inertia energy storing element and elastic energy storing element, the equivalence theorem is used in elastic error analysis of planar mechanism. A set of calculation formula of elastic error is introduced, and these equations are similar in expression form to the rigid dynamic equation. To demonstrate the method developed, a computation example is given.

Dynamic Analysis of Four-Bar Beating-up Mechanism with Joint Clearance

For the four-bar beating-up mechanism of air-jet loom,the plain bearing of linkage is the bearing with dynamic load,and is immersed in the lubricant-box.If the joint clearance is considered,the research on linkage movement could be very complicated.In this paper,the kinematic characteristics of four-bar beating-up mechanism with joint clearance were studied by analyzing the trace of journal center and the balance of radial,tangential forces,and bearing load.The region of principal vibration and its forming causes were discussed.And the results could interpret the measuring curves of four-bar beating-up mechanism completely.

Analytical expression of non steady-state concentration profiles at planar electrode for the CE mechanism

The analytical solutions of the non-steady-state concentrations of species at a planar microelectrode are presented. These simple new approximate expressions of concentrations are valid for all values of time and possible values of rate constants. Analytical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. Working surfaces are presented for the variation of limiting current with a homogeneous kinetic parameter and equilibrium constant. Moreover, in this work we employ the Homotopy perturbation method to solve the boundary value problem.

Mechanism of amorphous Ge_2Sb_2Te_5 removal during chemical mechanical planarization in acidic H_2O_2 slurry

In this paper, chemical mechanical planarization （CMP） of amorphous Ge2Sb2Te5 （a-GST） in acidic H2O2 slurry is investigated. It was found that the removal rate of a-GST is strongly dependent on H2O2 concentration and gradually increases with the increase in H2O2 concentration, but the static etch rate first increases and then slowly decreases with the increase in H2O2 concentration. To understand the chemical reaction behavior of H2O2 on the a-GST surface, the potentiodynamic polarization curve, surface morphology and cross-section of a-GST immersed in acidic slurry are measured and the results reveal that a-GST exhibits a from active to passive behavior for from low to high concentration of H2O2. Finally, a possible removal mechanism of a-GST in different concentrations of H2O2 in the acidic slurry is described.

Dynamics Response and Non⁃linear Characteristics Analysis of Complex Planar 2⁃DOF Mechanism with Revolute Clearances

There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.

A Method for Automatically Establishing a Mathematical Model of Kinematic Analysis to a Planar Mechanism with a Multiple Joint and Prismatic Pair

A method for automatically establishing a mathematical model of kinematic analysis to a planar mechanism with multiple joint and prismatic pair is presented. The breadth （ or depth ） first search spanning tree can be obtained based on an adjacency matrix of the mechanism. Then the kinematic chain （or mechanism）＇s basic loops can be obtained. On the basis of these basic loops, a mathematical model of kinematic analysis can be established and solved automatically. In the sense of a calculative mechanism, structural analysis of the kinematic chain relates to the kinematic analysis of a mechanism. Thus, an effective way is supplied to the given mechanism＇s kinematic analysis for automatic modeling and solving, and a method is supplied to the structural type to optimize kinematic synthesis.

VELOCITY ANALYSIS OF A PLANAR MECHANISM USING A METHOD FROM STATICS

A new method for solving the velocity analysis of a mechanism is presented. Central to the method is how to convert the probem of velocity analysis of a mechanism to one of static analysis. Application of the method to certain practical problems has advantages compared to conventional methods for both graphical and analytical solutions. For brevity an example of a planar mechanism only is presented.

The Analysis of Link Mechanism and Its Programming Realization

This paper introduces realization method of kinematics analysis for the planar four bar mechanism based on the MFC. A mathematicat model is established by a simple and effective method, using the computer simulation technology can the dynamic demonstration mechanism taotion and automatic drawing trajectory curve of arbitrary point on the connecting rod, and can output various motion displacement, speed and acceleration diagram. The paper provides a simple way for motion analysis of planar four link.

用Pro/Mechanism实现复杂凸轮机构的设计及运动分析

针对复杂平面运动从动件盘形凸轮机构设计的困难,介绍1种利用Pro/Mechanism的强大功能实现复杂凸轮机构的创新设计、运动仿真及运动分析。这种创新方法可以使复杂凸轮机构设计变的快捷、便利。

Effect of inter-cycle heat treatment in accumulative roll-bonding(ARB)process on planar isotropy of mechanical properties of AA1050 sheets

The accumulative roll-bonding(ARB)process was applied on the strips of aluminum alloy 1050 in two processing conditions:cold ARB and warm ARB.The results of tensile tests and microhardness measurement show that the warm ARB process exhibits the lower tensile strength and microhardness,more homogeneous distribution of the microhardness,higher elongation,and especially superior planar isotropy of the tensile properties in comparison to the cold ARB,because of the intermediate heat treatment as well as the elevated temperature rolling in the warm ARB process.Furthermore,with increasing the cycles of both processes,the planar isotropy decreases progressively.

Simulation and Analysis of Spatial Weft Insertion Mechanism Considering Flexibility and Clearance

A 3D model of the spatial four-bar weft insertion mechanism was built with unigraphics NX(UG) according to the actual requirement,and dynamics simulation was carried out by importing the model into ADAMS.Without considering the clearance,the motion characteristic curve of the sword belt was generated through ADAMS combined with MATLAB.In this paper the hinge between the rod and the sector gear was selected as an example with different values of clearance,outputting the motion characteristic curve of the sword belt.Finite element analysis(FEA)was conducted,the flexible body was generated by importing the forked frame into ANSYS,and flexible dynamics simulation was carried out by importing the flexible body into ADAMS to replace the rigid rod.A comprehensive comparison of the output characteristics of the sword belt was conducted in the consideration of the clearance or flexible.Analysis of the force on the left hinge of the rod was carried out with the ADAMS post processing module.With the same clearance,considering the flexibility,amplitude of fluctuation of the force on the hinge increased obviously.

TWO STEPS CHEMICAL-MECHANICAL POLISHING OF RIGID DISK SUBSTRATE TO GET ATOM-SCALE PLANARIZATION SURFACE

In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness （Ra） and the average waviness （Wa） of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy （AFM） analysis shows that the final polished surfaces are ultra-smooth without micro-defects.

A Hand Prosthesis with an Under-Actuated and Self-Adaptive Finger Mechanism

One of the major problems faced by hand amputees is the unavailability of a lightweight and powered multi-functional hand prosthesis. Under-actuated finger designs play a key role to make the hand prosthesis lightweight. In this paper, a hand prosthesis with an under-actuated and self-adaptive finger mechanism is proposed. The proposed finger is capable to generate passively different flexion/extension angles for a proximal interphalangeal (PIP) joint and a distal interphalangeal (DIP) joint for each flexion angle of metacarpophalangeal (MCP) joint. In addition, DIP joint is capable to generate different angles for the same angle of PIP joint. Hand prosthesis is built on the proposed finger mechanism. The hand prosthesis enables user to grasp objects with various geometries by performing five grasping patterns. Thumb of the hand prosthesis includes opposition/apposition in addition to flexion/extension of MCP and interphalangeal (IP) joint. Kinematic analysis of the proposed finger has been carried out to verify the movable range of the joints. Simulations and experiments are carried out to verify the effectiveness of the proposed finger mechanism and the hand prosthesis.

Design and Kinematics Analysis of a Parallel Mechanism to be Utilized as a Luggage Door by an Analogy to a Four – Bar Mechanism

In this study, a luggage door mechanism to be used in commercial vehicles such as midibuses and buses is designed and analyzed. The mechanism is designed as a parallel hinged system. Velocities, rotational veloci- ties and rotational accelerations of selected points on the design are calculated. Furthermore, the experiment- tal model of the design is established and it is seen that the data taken from the model are compatible with the calculated results. The aim of this study is to design a mechanism with the minimal workspace so that the door can be utilized in narrow areas and the ergonomics of the luggage door is improved. Considering both commercial and passenger vehicle sales, vehicle interior and exterior trim features have an exceptionally important role in automotive industry, in addition to vehicle performance characteristics. In today’s compete- tive environment, parts used in a vehicle’s internal and external trim have to meet user demands in terms of ergonomics as well as aesthetics. Due to its similarity to a four-bar mechanism, kinematics analysis of the design was carried out based on a four-bar mechanism, which is used extensively in industry.

凸棱非平面聚晶金刚石齿的破岩机理及在含砾地层中的应用

为提高聚晶金刚石复合片(PDC)钻头在含砾、软硬交错等不均质地层中的抗冲击性能,开展了凸棱非平面PDC齿的研究。通过仿真和室内实验对比分析了凸棱非平面齿与常规平面齿的破岩机理。与平面齿相比,凸棱非平面齿与岩石的接触应力分布更均匀,切削破岩过程中的载荷波动幅度明显更小,切削稳定性更高。凸棱齿特殊的非平面结构改变了切削齿与岩石的互作用方式,在不均质地层得到成功应用。

人体下肢康复装置的结构设计及运动学分析

介绍了一种基于平面五杆机构的人体下肢康复装置,旨在满足术后卧床的卒中患者的早、中、后期的下肢康复训练需求。该装置具有简单可靠的特点,可以在床尾侧放置或随患者行走移动。装置主要由下部移动平台、手动升降组件、上部动力传动机构及左、右训练机构组成,并在踝、膝关节通用的关节支架上附有传感器,患者的运动信息可以被实时采集和反馈。运动学分析及Adams软件仿真结果表明,调整该装置双曲柄的初始相位,可以改变关节点的运动轨迹,得到不同运动模式下人体下肢关节运动的范围,达到卧式训练及行走训练的目的,从而满足患者不同康复阶段的训练需求。

基于CATIA的平面机构自顶向下参数化设计

文章以缝纫机下针机构为例,介绍了在CATIA软件中实现平面机构自顶向下的参数化设计方法,为平面机构创新设计快速建模提供了一种快捷、实用的新思路。

裂隙水作用下岩质边坡平面滑动力学模型

在降雨等水力条件作用下沿岩层层面的平面滑动是顺层岩质边坡最常见的一种破坏模式,而目前关于该类边坡的稳定性计算方法几乎很少考虑裂隙面粗糙度对地下水渗流力及滑面抗剪强度的影响,进而导致其稳定性计算结果误差较大。为此,首先对地下水作用下的顺层岩质边坡受力特征进行分析,认为地下水将对滑动岩体产生3个方面的力学作用:张裂隙中的静水压力、滑面上的扬压力和渗流力,由此建立了相应的边坡稳定性计算模型。其次,通过引入裂隙面粗糙度对裂隙抗剪强度及地下水渗流力的影响,提出了考虑裂隙粗糙及地下水渗流力的顺层岩质边坡稳定性计算模型。而后,通过对含一条贯通粗糙裂隙的岩质边坡稳定性为例,验证了该模型计算结果的合理性,同时计算结果表明裂隙面粗糙度系数JRC对边坡稳定性有重要影响,必须予以考虑。最后,基于参数敏感性分析研究了主要参数如裂隙面粗糙度系数、裂隙基本摩擦角、裂隙宽度、裂隙壁面岩石抗压强度及地下水位高度等对边坡稳定性的影响,结果表明:仅裂隙宽度对边坡稳定性影响很小,而其他参数对边坡稳定性影响则相对较大,不容忽视。且裂隙面粗糙度对边坡稳定性的影响与裂隙壁面岩石抗压强度密切相关,随着其增加,裂隙面粗糙度对边坡稳定性的影响程度逐渐变大。