A Parallel Indexing Cam Mechanism with Internal Placed Followers

A new type of parallel indexing cam mechanism is discovered.The composition of the cam profile is proposed and the formulas of the mechanism parameters are established by synthesis of its configuration and size.The equations for working pro- file and pressure angle of the cam are derived based on the inverse model and the derivative of pitch curve of cams.An example is given and demonstrates that it is available to design the new mechanism using the derived expressions.

Transmission Index Research of Parallel Manipulators Based on Matrix Orthogonal Degree

Performance index mance evaluation, and is the is the standard of perfor- foundation of both perfor- mance analysis and optimal design for the parallel manipulator. Seeking the suitable kinematic indices is always an important and challenging issue for the parallel manipulator. So far, there are extensive studies in this field, but few existing indices can meet all the requirements, such as simple, intuitive, and universal. To solve this problem, the matrix orthogonal degree is adopted, and generalized transmission indices that can evaluate motion/force trans- missibility of fully parallel manipulators are proposed. Transmission performance analysis of typical branches, end effectors, and parallel manipulators is given to illus- trate proposed indices and analysis methodology. Simula- tion and analysis results reveal that proposed transmission indices possess significant advantages, such as normalized finite （ranging from 0 to l）, dimensionally homogeneous, frame-free, intuitive and easy to calculate. Besides, pro- posed indices well indicate the good transmission region and relativity to the singularity with better resolution than the traditional local conditioning index, and provide a novel tool for kinematic analysis and optimal design of fully parallel manipulators.

FM-index分块并行算法及其实现

查询海量数据有压缩和索引两种方法来提高速度,该文结合这两种方法提出了压缩查询的方法。FM-index是一种自索引的全文查询算法,存在内存占用过大的问题,对于复杂的查询效率也不理想。该文提出分块FM-index算法,在分块的基础上采用MPI对算法进行并行化,解决了内存占用过多的问题,达到了较好的并行效率。

Pressure Angle in Parallel Mechanisms: From Planar to Spatial

This paper presents the evolution process of pressure angles from planar parallel mechanisms to spatial parallel mechanisms. Manipulability and condition number, which are frequently used in the optimum design of parallel mechanisms, are introduced from serial robots at first. Then, both theoretical analysis and practical experiences demonstrate that these concepts seem imperfect when they are used in parallel mechanisms. For this reason, this paper introduces the pressure angles in planar 4-bar mechanisms to spatial parallel mechanisms, which include redundant parallel mechanisms. Two kinds of pressure angles extracted from the determinant of direct and indirect Jacobian matrices are investigated. Moreover, two comprehensive and visible global performance indices are defined, showing the advantages in evaluating the workspace, singularity and motion/force transmission capabilities. With a 2-DOF planar and a 3-DOF spatial parallel mechanism as examples, the application of the performance indices is investigated and compared with the condition number at last. The proposed concept can be extended to other spatial parallel mechanisms.

Comparative Analysis of Characteristics of the Coupled and Decoupled Parallel Mechanisms

The existence of coupling makes the parallel mechanism possess some special advantages over the serial mechanism, while it is just the coupling that brings about the parallel mechanism some limitations, such as complex workspace, high nonlinear relationship between input and output, difficulties in static and dynamic analysis, and the development of control system, which restricts its application fields. The decoupled parallel mechanism is currently one of the research focuses of the mechanism fields, while the study on the different characteristics between the deeoupled and coupled parallel mechanisms has not been reported. Therefore, this paper performs the systematic comparative analysis of the 3-RPUR and the 3-CPR parallel mechanisms. The features of the two mechanisms are described and their movement forms are analyzed with screw theory. The inverse and forward displacement solutions are solved and the Jacobian matrices are obtained. According to the Jacobian matrices and by using the theory of physical model of the solution space, the workspace, dexterity, velocity, payload capability, and stiffness of the mechanisms are analyzed with plotting the indices atlases. The research results prove that the effects of the coupling on the parallel mechanism are double-side, and then the adoption of the decoupled parallel mechanism should be determined by the requirements of the concrete application situation. The contents of this paper should be useful for the type synthesis and practical application of the parallel mechanism.

Optimal design of the link lengths for a planar parallel manipulator

This paper addresses geometry design of a new kind of 2-DOF parallel manipulator actuated horizontally by linear actua- tors. The first step of the optimum design involves developing a non-dimensional structure of the planar 2-DOF parallel manipulator. The global conditioning index, global velocity index, global stiffness index and global payload index of the 2-DOF parallel manipu- lators are investigated, and the geometrical parameters without dimension are determined with respect to the specification on per- formances. Finally, based on the optimum non-dimensional result, the optimum dimensional parameters are achieved which is suit- able for the desired workspace. The optimum methodology of this paper is convenient and can be extended to other parallel mecha-

Feature Selection Method by Applying Parallel Collaborative Evolutionary Genetic Algorithm

Feature selection is one of the important topics in text classification. However, most of existing feature selection methods are serial and inefficient to be applied to massive text data sets. In this case, a feature selection method based on parallel collaborative evolutionary genetic algorithm is presented. The presented method uses genetic algorithm to select feature subsets and takes advantage of parallel collaborative evolution to enhance time efficiency, so it can quickly acquire the feature subsets which are more representative. The experimental results show that, for accuracy ratio and recall ratio, the presented method is better than information gain, x2 statistics, and mutual information methods; the consumed time of the presented method with only one CPU is inferior to that of these three methods, but the presented method is supe rior after using the parallel strategy.

面向数据湖存取性能优化的数据并行处理技术研究

本文围绕数据湖应用背景下海量数据的高性能存取需求,以新型数据存储模型和分布式存储及缓存机制为目标,通过对数据湖存储结构、数据访问模式和数据处理方法进行分析,开展数据湖存取性能优化问题研究。首先,结合数据湖系统中的文件系统存储方式,设计了一种基于列式存储的数据存储结构,并通过索引优化技术提高数据访问速度。其次,针对数据湖中常用的批处理和流处理这两种访问模式,提出了一种基于数据分区和缓存机制的访问优化方案,以提高数据访问的效率和稳定性。最后,针对数据湖在大规模数据情况下更新和增量计算出现的计算时间长问题,提出了一种基于Spark并行计算和分布式文件系统(Hadoop Distributed File System,HDFS)的数据处理方案,以提高数据处理的速度和可靠性。实验结果表明,本文提出的数据湖存储性能优化技术相对于现有方法能够有效地提高数据的存储、访问和处理效率。

Reliability Comparison Between Parallel and Cold-standby Two-unit System Under Poisson Shock

This paper investigates the comparison problem of the reliability index between a parallel and a cold-standby system,both of which are consisting of two identical units.On the contrary to the general intuitive result,we proved that,under the condition that the system is shocked by a Poisson stream,the life time of the parallel system is longer than that of the cold-standby one in the sense of probability.

基于知识图谱的并行管道风险指标体系构建与分析

为准确评价并行管道的风险等级,统计了2004—2024年有关并行管道风险的国内知网文献,通过聚类、共现和突变的知识图谱分析,确定了国内有关的研究进展和演进趋势,获取了指标体系的构建方式和方法,并结合G1法和危险度确定不同类型并行管道的综合风险水平。结果表明,该领域的高频关注点集中在并行间距、环境因素、腐蚀和管道特性方面,研究对象主要为油气并行管道,且多采用赋权法进行风险评价;并行间距对并行管道风险的影响最大,其次为敷设环境;隧道段并行管道的危险度最大,其次为同桥段并行管道和埋地段并行管道。研究结果可反映并行管道的真实风险水平,提出的方法合理、有效。

国产ARM架构上的关系数据库组件优化技术研究

随着ARM架构处理器的兴起,其在数据库领域的应用前景日益广阔。文中深入探讨了如何在国产ARM架构上优化关系数据库组件,特别是在存储引擎、计算引擎及查询引擎等关键组件方面。利用国产ARM架构与主流X86架构的差异进行优化,并通过实验验证了优化的效果。实验结果显示,经过优化的数据库关键组件在国产ARM架构上提高了数据库性能,为数据库技术的国产化发展提供了有力支持。

新型3UPRR并联机构的运动学分析与多目标优化

根据基于方位特征方程的并联机构拓扑设计理论和方法,提出一种三平移3UPRR并联机构,通过矢量法建立运动学方程并计算得到位置正解和逆解。分别研究工作空间、灵巧度、全域同向系数、全域最小奇异值等性能指标。建立多维性能指标优化目标,选择具有降维和多重信息有效融合特点的主成分分析法(PCA),得到不依赖主观选择的机构评价函数,通过给定运动轨迹仿真验证支链驱动副位移连续且无明显突变跳跃。最后通过SolidWorks软件模拟零件抓取过程进行仿真验证,研究可为该类机器人的设计应用奠定理论基础。

基于运动/力传递性能的索并联机器人尺度综合研究

索并联机器人使用柔性绳替代传统并联机器人的刚性连杆,以控制末端动平台,在搬运、医疗康复等领域得到了广泛应用。为了解决索并联机器人设计过程中存在的尺度综合问题,对索并联机器人的性能评估指标进行了研究。首先,根据螺旋理论确定了索并联机器人驱动输入与运动输出的运动/力传递关系,并提出了局部运动/力传递性能指标,评估了其在指定工作空间下的全局运动/力传递性能;然后,借助空间模型法,得到了索并联机器人在参数设计空间的性能图谱,并基于参数设计空间的性能图谱,对索并联机器人进行了尺度综合,以得到优化后的尺寸参数;最后,采用了平面3自由度索并联机构的试验样机,对运动学可达工作空间进行了试验验证,试验了得到了优化尺寸参数下的运动可达工作空间。研究结果表明:利用尺度综合方法优化后的机构允许姿态角达到|θ|≤60°的工作空间,占总工作空间的95.1%,可达工作空间提高了29.4%;优化后机构姿态角达到|θ|≤80°的工作空间,占总工作空间的67.3%,可达工作空间提高了81.3%;优化后允许机构姿态角达到|θ|=80°的工作空间,占总工作空间的14.5%,可达工作空间提高了172%。因此,对运动/力传递性能尺寸参数进行优化,可避免索并联机器人工作空间内的奇异位形,满足绳索单向力传递的特性要求,可在索并联机器人设计中作为尺度综合的依据。

基于ADAMS的平行分度凸轮机构的动力学仿真

以包装机组中的平行分度凸轮机构为研究对象,开发了平行分度凸轮机构CAD/CAM系统。利用其生成的精确轮廓数据,在Pro/E环境下创建了凸轮三维实体。通过Mechanism/Pro无缝接口实现了在ADAMS环境下虚拟样机的创建。对碰撞接触理论进行了研究,并对平行分度凸轮机构进行了动力学仿真,得到了很有实际应用价值的结论。

平行分度凸轮机构虚拟设计研究

系统分析了平面共轭分度凸轮曲面的形成特点 ,建立了适用于各类平行分度凸轮机构的一般数学模型与方程。在此基础上 ,探讨了平行分度凸轮实体建模方法及该类产品的虚拟设计问题 ,并以SolidEdge软件为平台 ,编制了应用程序 ,进行了大量的实例计算。提出的实体建模方法 ,可为深入研究该类共轭分度凸轮产品的虚拟设计问题奠定基础。

平行分度凸轮机构CAD系统的研发

采用面向对象的可视化开发工具Visual C++6.0和OpenGL技术,利用模块化的开发方法, 解决了平行分度凸轮机构的参数化设计、实体建模、三维图形显示与控制、运动仿真、机构分析等一系列问题。所完成的CAD系统实现了平行分度凸轮机构的快速、准确、动态设计,可缩短产品设计开发周期,降低生产试制成本。

基于R树的分布式并行空间索引机制研究

为提高分布式并行计算环境下海量空间数据管理与并行化处理的效率,基于并行空间索引机制的研究,设计一种多层并行R树空间索引结构。该索引结构以高效率的并行空间数据划分策略为基础,以经典的并行计算方法论为依据,使其结构设计在保证能够获得较好的负载平衡性能的前提下,更适合于海量空间数据的并行化处理。以空间范围查询并行处理的系统响应时间为性能评估指标,通过实验证明并行空间索引结构具有设计合理、性能高效的特点。

面向批量插入优化的并行存储引擎MTPower

针对多核处理器的特点,文章提出了一个符合MySQL接口标准的并行存储引擎MTPower.该存储引擎着重利用多核处理器的并行计算能力提升批量插入过程中的索引产生过程,主要包含存储引擎接口、并行批量线性Hash索引、并行批量B+树插入、支持并行访问的磁盘存储缓冲等部分.测试结果表明,在批量插入记录且需要创建Hash和B+树索引时,MTPower的性能比经典的单线程存储引擎MyISAM最高可以提高6.1倍和4.8倍;在系统中线程总数略大于处理器核数时,MTPower可以达到最佳性能;在处理器核的数量增加时,MTPower的性能也能随之提高.

双作用式平行分度凸轮机构

提出了双作用式平行分度凸轮机构,并按研究齿轮啮合的方法研究其凸轮廓线。该机构的主要特点是,在主动轴和从动轴上同时布置滚子和凸轮,且主动滚子中心恰好位于主动瞬心线上。按本文的方法设计特殊速比函数,可使与主动滚子啮合的从动凸轮廓线不会产生曲率干涉。该机构的优点是:因驱动力臂较大、压力角情况良好以及约束得到强化,使得机构具有良好的运动性能。

平行分度凸轮机构建模与运动仿真分析研究

针对平行分度凸轮机构设计和验证问题,提出一种平行分度凸轮建模和分度机构运动仿真分析方法。通过对平行分度凸轮机构的分度运动进行分析,利用齐次坐标变换法建立平行分度凸轮轮廓曲面数学模型,软件编程采集轮廓曲面数据点,用Creo建立机构三维模型并装配后输出到Adams,建立机构虚拟样机并进行运动学特性仿真。对仿真数据绘制的运动规律特性曲线与理论曲线进行对比分析。结果表明,角加速度曲线波动较大,机构存在的冲击和振荡,主要位于不同的滚子退出和进入啮合阶段与不同滚子工作轮廓曲线交接处;给出对应的设计改进和加工措施,即采用圆角过渡工作轮廓曲线交点、提高轮廓曲线数据点采样精度、选择合适的运动规律及样条曲线插补加工轮廓曲面能减少机构运动的冲击和振荡。