关键词： BNNTs   Carbon doping   Defect   Mechanical properties  

摘要： By the employment of molecular dynamic simulations (MD), we investigated the mechanical properties of defective single-walled Boron nitride nanotubes (SWBNNTs) with zigzag and armchair chirality's. After removing different numbers of atoms from nanotubes' surface and putting samples under uniaxial tensile loading at constant strain rate Young's modulus, failure stress and failure strain were calculated and the results demonstrated that the young's modulus of armchair structures was higher than those of zigzag structure in every type of vacancy defect. However, failure strain and stress of zigzag structure were higher than armchair except in three atom vacancy defect type 2 in which one B and two N atoms were deleted from the surface. Furthermore, we considered the mechanical behavior of BNNTs with different numbers of doped carbon atoms. We found that Young's modulus did not have a constant trend via rising in the number of carbon. The armchair structure showed higher or equal moduli compared to zigzag one except in one carbon-doped BNNTs. The maximum modulus of doped structures was observed in configuration antheacene for both chirality's. Failure properties of zigzag doped BNNTs with 2, 4 and 6 carbon atoms and also 3 carbon rings doping were higher than those of armchair structure while in other doped BNNTs (2,4 and 5 carbon rings) reverse results were collected.

关键词： 二自由度并联机械手   简化刚体动力学模型   前馈控制   H_∞控制器  

摘要： 本文针对一种二自由度并联机械手高速运动状态下的动力学控制方法展开研究。通过对并联机械手简化刚体动力学模型的建模误差进行溯源分析,提出了一种基于双系数补偿分配策略的建模方法,对机械手的简化刚体动力学模型进行了优化,并基于该简化模型建立了机械手的动力学前馈控制方法。为进一步提高控制过程的鲁棒性,结合H_∞控制方法提出了一种H_∞+动力学前馈的控制方法。在建立机械手整机机电联合仿真系统的基础上,对所提出的两种控制方法进行了详细的仿真和对比。仿真结果表明,本文提出的控制方法可以减少力矩扰动对伺服电机输出带来的影响,大大减小了机械手末端的定位误差,提高了机械手的控制精度。

关键词： 传感器   动力学模型   机械臂   单片机  

摘要： 为了实现对机械臂动力学模型的校准,提出了一种基于MPU6050芯片的机械臂动力学数据采集系统,并完成系统的软硬件设计。该系统的硬件部分主要用于采集机械臂各关节的三坐标轴线加速度和角加速度数据,并将数据进行存储,同时送给上位机,软件部分采用C语言进行编程,完成传感器到存储器及存储器到上位机的数据通讯。实际应用表明,该系统能够准确的记录机械臂的实际动力学数据,多组传感器的配置方便动力学解耦分析,与其理论动力学模型进行比照,可实现动力学校准。

关键词： 柔性机械臂   动力学建模   动力学控制  

摘要： 本文将围绕柔性机械臂动力学建模与控制进行研究,注重柔性机械臂系统描述以及柔性机械臂数学模型的构建,旨在保证柔性机械臂系统的完整性,为后续研究工作奠定基础。

关键词： 机械产品   机械设施   运行效率  

摘要： 如今随着科技的不断创新与发展,使得各类机械产品的性能、精确度以及使用寿命等方面都有了十分显著的提升,这些内容也正是加强机械产品设计的主要部分。而工程机械臂是各种工程机械设施最为主要的部件之一,是充分展现工程机械动力学性能的基础,能够有效的提高工程机械的质量、运行效率以及安全,对工程机械的准确程度方面有着重要的影响,所以本文就对其进行了研究。

关键词： Quantum dynamics   Non self-adjoint Hamiltonian   Decision making  

摘要： In recent works we have used quantum tools in the analysis of the time evolution of several macroscopic systems. The main ingredient in our approach is the self-adjoint Hamiltonian H of the system S. This Hamiltonian quite often, and in particular for systems with a finite number of degrees of freedom, gives rise to reversible and oscillatory dynamics. Sometimes this is not what physical reasons suggest. We discuss here how to use non self-adjoint Hamiltonians to overcome this difficulty: the time evolution we obtain out of them show a preferable arrow of time, and it is not reversible. Several applications are constructed, in particular in connection to information dynamics. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Udwadia-Kalaba方程   约束关系   多体系统   动力学建模   双机械臂  

摘要： Udwadia-Kalaba方程为多体系统的动力学建模提供了一种新的思路。以双机械臂协同搬运物体为研究对象,针对Udwadia-Kalaba方程建模过程中存在的获取解析形式的约束关系和数值解存在误差的问题,给出了一种具有广泛意义的约束关系,并对Udwadia-Kalaba方程进行了改进。仿真结果证明了提出方法的有效性。

关键词： 技术报告会   中国工程院院士   王玉明   流体传动与控制   流体动力   动力传动   国际技术交流   行业知名专家  

摘要： 2019年10月23日-10月26日,“PTC ASIA 2019高新技术展区国际技术交流报告会”成功在上海新国际展览中心举办。本届报告会得到行业知名专家曾广商、王玉明二位中国工程院院士,国际同业组织VDMA金斯利先生和来自于中国、德国、日本、英国、美国的国际知名企业专家,国内知名院校和科研院所的大力支持。在此,我们深表荣幸并衷心感谢!报告会现场观众认真聆听、积极互动,良好的效果让我们倍感欣慰,这一切都激励着我们继续努力,为流体传动与控制技术进步添砖加瓦,为世界流体动力产业发展贡献新的力量!为了让更多的同仁了解本届技术报告会实况,我们应行业需求对专家的精彩报告进行编辑整理,陆续发表在2020年《液压气动与密封》杂志和微信平台上(公众号:chpsa-yqm),供学习分享。敬请关注!

关键词： 工业机械臂   动力学   仿真  

摘要： 针对工业机械臂进行动力学分析的常用方法是利用Lagrange方程进行动力学建模后再实行仿真计算。利用Pieper准则,将五自由度工业机械臂动力学方程展开式简化,即将腕部与手抓部的关节视为外部干扰,只针对前三关节进行动力学分析;提出一种针对简化后的模型利用开源引擎ODE完成机械臂动力学计算;在建立的机械臂三维仿真平台上利用ODE进行仿真的方法。仿真结果表明:该仿真方法不仅可实现机械臂的实时控制,还能得到机械臂动力学参数曲线图。为解决机械臂动力学仿真中效率低和实时性差的问题提供了理论依据。

关键词： mechanical performance   molecular dynamic simulations   polyimide   SiO2 composites   silica coupling agent   surface modification  

摘要： The effect of covalent bonds and the SiO2 concentration on the interface structure and the performance of polyimide/SiO2 (PI/SiO2) composites is investigated by molecular dynamic simulation. To enhance the interface interaction, the silica coupling agent is treated as a bridge to connect PI chains with SiO2 particles. The SiO2 content is controlled by adjusting the number of PI chains. The results show that the bonded interface structure not only increases the interfacial non-bond energy and the number of the hydrogen bonds, but also strengthens the tensile strength, Young's modulus, shear modulus, and the glass transition temperature of the composites. As the SiO2 concentration increases, the non-bond interaction energy between each PI chain and SiO2 particle increases and the non-bond interaction energy in the bonded composites are higher than that of the unbonded. The number of hydrogen bonds in the bonded composites is sensitive to the SiO2 concentration, but there is no obvious relationship in the unbonded composites. Young's modulus and shear modulus of PI/SiO2 composites are higher than that of the unbonded at the same doping concentration. Therefore, establishing the bonded interface structure is an effective way to improve the interface stability and the properties of composite materials.