考虑关节摩擦的刚柔耦合机械臂末端抖动模拟与分析

为了解关节摩擦对刚柔耦合机械臂末端抖动的影响，解决机械臂的优化设计问题,利用ANSYS、ADAMS软件建立机械臂刚柔耦合模型，并在ADAMS中进行动力学仿真。通过进一步创建考虑关节摩擦的机械臂虚拟样机模型，对机器人末端振动特性进行动态模拟与分析。仿真结果表明：在机器人实际工作过程中，关节2和关节3存在摩擦对机器人末端抖动的影响最显著；在考虑多关节摩擦时，关节2和关节3共同存在摩擦时可使得机器人末端非周期性抖动幅值减弱，且当关节2摩擦因数取01时机器人末端抖动表现最弱，但关节3摩擦因数的改变几乎不会引起机器人末端抖动情况的变化。     

考虑关节间隙的空间机械臂臂杆振动特性研究

基于ADAMS动力学仿真软件,建立含间隙关节空间机械臂的动力学仿真模型,改变关节间隙尺寸和刚度系数等相关参数,获取不同关节间隙尺寸下的空间机械臂动力学响应;通过搭建含间隙关节的空间机械臂实验台,采用改变臂杆端盖孔径的方法改变关节间隙尺寸,分析不同关节间隙尺寸下的空间机械臂臂杆的输出振动特性。仿真与实验结果表明:臂杆末端的加速度和关节的接触碰撞力会随着空间机械臂关节间隙的增大而逐渐增大,但增幅会逐渐减小;空间机械臂关节间隙的增大还会导致关节内碰撞加剧,引起更大的能量损失。这可为提高含间隙空间机械臂的控制精度提供参考。     

含谐波传动关节的机械臂在不同转速下的时频特性

谐波传动关节是机械臂的典型关节。为了研究含谐波传动关节的机械臂在不同转速情况下的时频特性,针对空间机械臂,研制机械臂实验装置和测试系统,测试不同转速下机械臂关节处和末端标志点的振动响应。采用小波变换信号分析方法并借助于机械臂的驱动模型,分析谐波传动关节处的摩擦和运动滞后等非线性因素对不同转速下机械臂振动特性的影响。基于非线性响应面法和非线性规划方法分析了机械臂的最佳运行工况。研究结果表明:小波变换能够较好地表征机械臂在不同转速下关节和末端振动响应的时频特征;随着转速的增大,机械臂关节处和末端标志点的振动能量向低频段集中,振动能量峰值及其对应的频率呈现出局部波动;机械臂末端的振动特性明显弱于关节,关节处的振动频率更为丰富,但关节的振动能量峰值衰减比末端要快;且机械臂处于低速运行工况时可以保持较好的动力学性能。研究结果揭示了含谐波传动关节的机械臂在不同转速下的时频特性,对含谐波关节的机械臂设计及其振动抑制技术水平的提高具有重要意义。     

基于关节位置约束的冗余机械臂协调控制误差仿真研究

针对冗余机械臂关节位置约束问题,设计了冗余机械臂关节位置控制策略,在不同条件下对机械臂运动效果进行仿真验证。建立冗余机械臂简图模型,通过雅可比矩阵推导机械臂运动方程式。分析机械臂优先级任务体系构造,比较冗余机械臂在不同优先级条件下的极限状态,引入了机械臂监控系统。设置机械臂仿真环境,采用MATLAB软件对机械臂运动进行仿真。结果表明:机械臂2个关节都违背了极限限制;监控系统在保证关节位置规避限制的同时,会导致路径跟踪误差较大。但是,路径跟随误差不会影响所需的相对末端效应器运动,能够保持末端执行器的相对运动,保证抓取对象的稳定性;证明了冗余机械臂控制器的有效性。采用该策略避免了运动过程中的机械臂关节的限制,能够实现机械臂抓取物体的路径跟踪功能     

多电机耦合驱动式仿人机械臂设计与传动特性分析

针对传统仿人机械臂载荷与自重比低的问题，提出一种多电机耦合驱动式仿人机械臂。根据人臂的运动特性，确定串联结构下的仿人机械臂构型，并将机械臂划分为肩关节模块、肘关节模块和腕关节模块。分析单电机驱动单关节的绳索传动特性，推导该模型下电机与关节的扭矩映射关系和转角映射关系。研究各模块中多电机耦合驱动多关节的电机布局和绳索绕线方式，解释各模块中多电机耦合后的工作原理，推导各模块中电机与关节的扭矩映射关系和转角映射关系。并通过实验验证各模块中映射关系的正确性，以及各模块关节的承载能力。结果表明：多电机耦合驱动方式在保证质量的前提下，可以有效提高各关节的承载力，为仿人机械臂的设计提供理论依据。     

基于ADAMS的飞机表面清洗臂动力学仿真与分析

针对五自由度的飞机表面清洗机械臂,利用 Lagrange 方程建立了清洗臂的动力学模型,采用 Solidworks 建立了该清洗臂的实体模型,将其导入到动力学分析软件 Adams 中生成了虚拟样机,并进行了动力学仿真与分析,由此得出各关节转角和关节力矩的关系曲线,确定了关节所需的输入力矩。这为机械臂的控制、关节驱动形式的确定提供了可靠依据。     

基于ADAMS的飞机表面清洗臂动力学仿真与分析（英文）

针对五自由度的飞机表面清洗机械臂,利用Lagrange方程建立了清洗臂的动力学模型,采用Solidworks建立了该清洗臂的实体模型,将其导入到动力学分析软件Adams中生成了虚拟样机,并进行了动力学仿真与分析,由此得出各关节转角和关节力矩的关系曲线,确定了关节所需的输入力矩。这为机械臂的控制、关节驱动形式的确定提供了可靠依据。     

基于串联弹性驱动器的柔顺机械臂设计与仿真

基于串联弹性驱动器(SEA)提出了一种三自由度柔顺机械臂的设计方案,用来模拟人手臂的运动,提高其对环境的适应力,实现良好的柔顺性。利用三维造型软件Inventor建立了三自由度柔顺机械臂的三维模型;针对柔顺机械臂关节提出了一种具有拮抗形式的弹性驱动方法,采用主动驱动弹簧和被动约束弹簧构成柔性张拉弹簧组合,以模拟肌肉-肌腱组织的收缩运动;通过动力学仿真软件Adams进行了驱动仿真分析和静动态冲击实验,结果表明在受到冲击时,柔性关节可以产生较大的柔性转角并快速衰减到稳定的运动状态,证明了该机械臂可以有效减小冲击,具有良好的柔顺性。     

基于套索驱动机械臂柔性伺服系统抑振控制

套索驱动机械臂中的独立关节伺服系统受到时变位姿和关节柔性的影响,会出现振动的问题,进而影响机械臂的运动精度。采用模糊整定的控制策略,通过提高伺服系统的转角控制精度间接的抑制机械臂的振动。首先,根据套索传动原理建立了机械臂柔性关节伺服传动系统的动力学模型,求得系统速度环中负载转速到电磁转矩的传递函数;其次,根据极点配置策略适当选取机械臂位于不同位姿下的比例积分(PI)控制器参数,并应用模糊整定控制策略实现控制器参数的实时调整;最后,通过数值仿真和机械臂控制实验,验证了方法的有效性。结果表明,所提出的控制策略可以更好地抵消转动惯量变化引起的速度波动,从而改善柔性关节的转速输出。     

基于ADAMS的机械手臂运动仿真分析

利用Pro/E软件建立了机械手臂的三维模型,并通过插件MECHANISM/Pro对模型进行刚体定义,把模型导入ADAMS进行后续的约束和驱动添加,从而获得机械手臂的虚拟样机.然后对机械手臂的虚拟样机的工作域进行求解分析,并通过运动仿真模拟了机械手臂关节在实际作业过程中的驱动情况,得出其运动曲线,并分析和验证了所建立的机械手臂的运动方程的正确性.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

FORMULAS OF TENSION OF CONTINUOUS ROLLING PROCESS

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.     

A Concordant Shift Model for Flow in Bulk Metallic Glasses

The homogeneous plastic flow in bulk metallic glasses(BMGs) must be elucidated by an appropriate atomistic mechanism. It is proposed that a so-called concordant shifting model, based on rearrangements of five-atom subclusters,can describe the plastic strain behaviour of BMGs in a temperature range from room temperature to the supercooled liquid region. To confirm the effectiveness of the atomic concordant shifting model, a comparative investigation between the vacancy/atom model and the concordant shifting model is carried out based on the estimation of the strain rate deduced from two models. Our findings suggest that the atomic concordant shifting model rather than the vacancy/atom exchange model can well predict the large strain rate in the superplasticity of BMGs.