关键词： 多体动力学   逆动力学模型   参数优化  

摘要： 针对移动串联机械手不能很好的满足高速、大负载、准确作业等性能要求,提出轮式悬架移动并联机械手这一新的构型.基于逆多体动力学相关理论,考虑建模方法的通用性与完备性,在笛卡尔坐标系下构建了系统逆动力学模型,并以此为基础,综合考虑系统驱动电机能耗为优化指标,进行移动并联机械手构型优化.最后提出二维搜索优化算法并进行数值仿真进行验证,得到一组最优机械手几何参数.

关键词： 地铁   电气火灾   系统动力学   安全投入   仿真  

摘要： 在揭示地铁电气火灾机械方面影响因子的基础之上,运用系统动力学理论与分析方法,构建地铁电气火灾机械方面影响因子仿真模型,对各影响因子进行动态预测。通过对比分析不同因子的安全投入增长率对机械方面安全水平的影响大小,论证安全投入与系统安全水平的相互关系,总结出最为有效地投资方案。结果为地铁安全管理工作提供一定的理论指导,有助于提高地铁安全管理决策的科学性和预见性。

关键词： 空间算子   广义―α算法   树型   广义动力学   高效率  

摘要： 研究树型柔性航天器动力学高效率建模和高精度广义―α的数值求解算法。利用拓扑结构和连接矩阵的方法描述树型机械多体系统,采用图论的方法将树型系统分解为多条链式系统;对系统中铰的驱动情况分别定义为主动铰和被动铰,通过铰链的类型以及判断是刚性体或者柔性体,基于空间算子代数理论建立树型系统的动力学模型;采用广义―α算法求解加速度约束的动力学微分—代数方程组。最后通过软件编制仿真验证本研究内容的正确性和高效性。

关键词： 驾驶机器人   车辆   联合仿真   动力学模型   虚拟样机  

摘要： 为提高驾驶机器人的设计效率,对机器人的机械腿进行了动力学分析与建模,并建立了机器人驾驶车辆的联合仿真模型。机械腿动力学模型由机械结构和伺服电机两部分组成,其仿真模型由ADAMS和MATLAB/Simulink软件共同建立,在此基础上引入Car Sim软件建立车辆模型,并以Simulink为平台建立了基于闭环速度控制的"驾驶机器人-车辆"联合仿真模型。仿真结果表明,驾驶机器人机械腿的动力学模型具有良好的动态响应特性,且所搭建的联合仿真模型能够完成基本的车速跟踪仿真实验,为下一步改进驾驶机器人的机械结构及控制策略提供了虚拟样机模型。

关键词： 农业劳动力转移   农业机械化发展   浙江省   农业发展   城镇化进程   农产品价格   非农产业   生产成本  

摘要： 随着国内工业化、城镇化进程的加快和非农产业的快速发展，大量农业劳动力转移或流动到高收入的非农行业，使得农业劳动力短缺。与此同时，目前国内农业发展面临农产品价格“天花板”封顶、生产成本“地板”抬升等新挑战，迫切需要加快转变农业发展方式。

关键词： 无动力包装   柔性设计   尺寸微调   创新设计  

摘要： 介绍机械式无动力自动封箱机的主要机构及其工作原理和整个装置的工作过程。阐述无动力包装功能以及尺寸自动微调功能的实施方案及其在纸箱包装过程中的重要性。论证本设计的合理性,创新性及实用性。

关键词： Duffing系统   双参数   混沌   分形  

摘要： 建立了一个机械Duffing动力学系统的物理模型及其动力学方程。研究表明,在该系统中,随着系统参数的变化,系统可呈现出各种非线性动力学现象,包括不动点、周期运动以及混沌运动。通过研究系统参数的变化,可确定出系统周期运动和混沌运动相互转换的区域,即混沌边缘。研究表明,当单个系统参数变化时,可以通过分岔图确定出混沌的边缘;当两个参数变化时,系统的混沌边缘可以在平面上展现出来,并具有分形结构。

关键词： Nitrides   Films   Hardness   Mechanical properties   Strength  

摘要： The structural and mechanical properties of NbN and Nb-Si-N films have been investigated both experimentally and theoretically, in their as-deposited and annealed states. The films were deposited using magnetron sputtering at substrate bias (U-B) between 0 and -70 V. While NbN films were found to crystallize in the cubic delta-NbN structure, Nb-Si-N films with Si content of 11-13 at% consisted of a two phases nanocomposite structure where delta-NbN nanocrystals were embedded in SiNx amorphous matrix. Films deposited at U-B = 0 V were highly (001)-textured. Application of substrate bias potential led to a depletion of light atoms, and caused a grain size refinement concomitantly with the increase of (111) preferred orientations in both films. The maximum hardness was 28 GPa and 32 GPa for NbN and Nb-Si-N films, respectively. NbN and Nb-Si-N filais deposited at U-B = -70 V exhibited compressive stress of -3 and -4 GPa, respectively. After vacuum annealing, a decrease in the stress-free lattice parameter was observed for both films, and attributed to alteration of film composition. To obtain insights on interface properties and related mechanical and thermal stability of Nb-Si-N nanocomposite films, first principles molecular dynamics simulations of NbN/SiNx heterostructures with different structures (cubic and hexagonal) and atomic configurations were carried out. All the hexagonal heterostructures were found to be dynamically stable and weakly dependent on temperature. Calculation of the tensile strain-stress curves showed that the values of ideal tensile strength for the delta-NbN(111)- and epsilon-NbN(001)-based heterostructures with coherent interfaces and Si3N4-like Si2N3 interfaces were the highest with values in the range 36-65 GPa, but lower than corresponding values of bulk NbN compound. This suggests that hardness enhancement is likely due to inhibition of dislocation glide at the grain boundary rather than interfacial strengthening due to Si-N chemical bond

关键词： 液压碎石机械手   机械臂   刚柔耦合   惯性冲击  

摘要： 液压碎石机械手机械臂的柔性效应对零件的强度、液压缸的受力等都产生不可忽略的影响,因此有必要对其进行刚柔耦合分析。本文基于有限元分析软件Hyper Mesh、ANSYS和动力学分析软件ADAMS,建立了某液压碎石机械手的刚柔耦合模型,分析比较了不同制动加速度下惯性冲击对柔性化大臂的强度和液压缸受力的影响。仿真分析表明,该方法可实现对大型机械臂的刚柔耦合分析,为臂架系统的设计改进提供理论依据。

关键词： Mechanical properties   Molecular dynamics simulation   BKS potential   Short-range cutoff  

摘要： Pair-wise BKS potential for silica glass was modified by changing the short-range cutoff to improve the prediction of mechanical properties. Classical molecular dynamic (MD) simulations were carried out by using this modified potential and better prediction of mechanical properties at ambient conditions and their changes with pressure at room temperature were shown. It was further observed that there was no major change in structural properties when different short-range cutoffs were used to relax the glass. To better understand the contribution of structure to the mechanical properties, samples quenched under various cooling rated and one structure optimized in first principles calculations were used. It was seen that the improvement of structure has a less effect than improving the interaction potential in determining the mechanical properties of BKS silica glass. The strength and weakness of the BKS potential for silica glass was discussed. (C) 2016 Elsevier BM. All rights reserved.