数控加工刀具变形误差补偿技术研究

在数控铣削加工的研究中,刀具变形引起的加工误差对工件的加工精度影响较大.研究了一种考虑切屑厚度影响的切削力模型,建立了由切削力引起的刀具变形加工误差的分析模型.为了提高加工精度,提出了一种线性迭代误差补偿算法,方法主要对由切削力引起的刀具变形产生的切削误差进行循环迭代补偿.通过应用数控加工中心,方案进行了验证,对补偿后...     

基于并行双模态模糊-PI补偿的多电机SMC控制

针对现有模糊-PI同步补偿器设计复杂且同步精度低等不足，提出将并行双模态模糊-PI控制算法应用到偏差耦合结构的新同步补偿策略。为了进一步提高电机间的同步与跟踪性能，采用了新型变指数趋近律的滑模控制器，在提高跟踪指令性能的同时，也提高了同步性能。仿真实验表明，与传统模糊-PI同步补偿器相比，双模模糊-PI补偿器在提高同步精度的同时也降低了设计难度，并且与改进的跟踪控制器相结合后系统的同步精度与跟踪性能都有了很大提高，验证了控制策略的有效性与可行性。     

Control of Underactuated Skid Steering Mobile Platforms Based on Extended Factitious Force Concept

In the paper new control method of skid steering mobile platforms has been presented. Such platforms are robotic objects with deficit of control inputs in dynamic model, i.e. they are dynamically under-actuated. To compensate lack of controls, it has been assumed that there are additional factitious inputs to dynamics (so-called factitious forces), which preserve possibility to control dynamical model of skid steering mobile platform, expressed in auxiliary velocities. Factitious inputs do not exist in reality therefore it was assumed that they are equal to zero equivalently. Signals calculated from implicit functions defining factitious forces make possible to approximate slipping effects and they can be taken into account by construction of control law.     

基于蚁群算法的并联机器人误差补偿方法

提出一种利用蚊群算法补偿Stewart并联机器人位姿误差的方法.基于闭环矢量法建立Stewart并联机器人位姿误差模趔,通过6个驱动杆的长度误差和铰链误差得到并联机器人的位姿误差.在位姿误差模型的基础上,利用基于网格划分策略的连续蚁群算法,通过信息素更新指导蚂蚁反复搜索,对驱动杆杆长误差进行寻优,最终补偿Stewart...     

Online Analysis of Functional MRI Datasets on Parallel Platforms

We describe a new capability for analyzing and visualizing brain activity while a subject is performing a cognitive or perceptual task in a magnetic resonance scanner. This online capability integrates geographically distributed hardware (scanner, parallel computer, visualization platform) via commodity networking. We describe how we parallelized the existing analysis software and present results for the three main classes of parallel platforms. Finally we discuss some of the new possibilities this online capability presents for scientific studies and clinical intervention.     

基于电磁补偿天平的微纳力值标准装置的性能研究

采用基于电磁补偿原理的精密天平,研制了一种微纳力值标准装置。通过高等级的标准砝码对天平进行校准,实现标准装置力值的SI溯源,在500 nN~500μN范围的力值测量标准不确定度小于0.7%。该装置用于对原子力显微镜（AFM）微悬臂弹性常数和微小力值传感器的力值提供准确的溯源。采用多自由度位置调整系统调整被测微悬臂或传感器的位置及俯仰角度,提高了定位准确度。对几种不同弹性常数的AFM微悬臂进行测量,测量结果的标准偏差小于1.6%,满足高准确度微小力值测量的要求。     

CC$:一种面向分布式众核平台的并行编程语言

CC$是一种并行编程语言,目的是解决分布式众核并行计算机的编程困难。CC$的编程模型以Multi BSP 模型为基础,将分布式众核并行计算机的硬件架构抽象为3层。数据按照存储的层次和共享范围分为5类,以便在不 同层次上提供共享。LL$还提出一类虚拟指令来解决不同层次之间的数据交换,实现数据访问的逻辑化描述。并行 程序按照3层Multi BSP超步嵌套执行。CC$具有统一的编程风格、内建的多层会共地址空间、数据访问请求的表达 式描述和数据传输编译优化4大特点。测试表明,CC$程序的运行效率高,易学易用,大幅地缩短了开发周期。     

基于PC总线模板的并联式温度补偿器件优选

并联式温度补偿具有近似性，特别是当传感器和温度补偿器件特性分散性都较大时。利用标准总线模板研制了一专用系统，该系统能对传感器和温度补偿器件进行优化组合，最大限度的改善补偿效果。     

基于推后补偿的时钟同步算法研究

时钟同步精度是网络时间同步的重要指标。目前网络节点的增多及涉及行业领域的扩大,给时钟同步精度提出了更高的要求,因此需要研究新的时钟同步算法提高时钟同步精度。本文以网络时钟同步的单向比较法为研究对象,针对其在时钟同步精度上的不足,提出了一种新的时钟同步算法,并给出了此算法在PPS信号同步中的应用,实验结果表明所提出的时钟同步算法提高了PPS信号的传递精度。该算法简单明了,易于工程实现。     

SIMD-BF模型上的并行FWHT算法研究

蝶形网络是并行计算中的一种重要的网络拓扑结构.并行计算模型是并行算法设计和分析的基础.文章以并行FFT算法的基本思想为基础,根据快速Walsh-Hadamard变换的两种蝶式计算流图,提出SIMD-BF模型上的两种并行FWHT算法.算法分析的结果表明:离散Walsh-Hadamard变换算法的复杂度为O(n2);快速W...     

Unactuated Force Control of 5-DOF Parallel Robot Based on Fuzzy PI

International Journal of Control, Automation and Systems - This paper investigates the fuzzy position/force hybrid control for a class of 5-degree-of-freedom (DOF) redundantly actuated parallel...     

A New Cable-Based Parallel Robot with Three Degrees of Freedom

In this paper, a new cable-based parallel robot is introduced. In this robot, the cables are used to not only actuate the end-effector but apply the necessary kinematic constrains to provide three pure translational degrees of freedom. In order to maintain tension in the cables, a collapsible element called “spine” is used between the end-effector and the robot’s base. The kinematic analysis of this robot is similar to that of a rigid link parallel manipulator as long as the cables are in tension. The rigidity of this robot which corresponds to having all cables in tension is studied thoroughly and it is proved that a single spine with a finite force is sufficient to guarantee rigidity for any external load at any position of the workspace.     

基于运动学正解的三转动并联机构迭代补偿控制

首先建立三转动并联机构的运动学方程,研究该并联机构的运动学反解和运动学正解,然后建立该机 构的动力学方程并分析其动力学特性．基于该机构研制了能复现自行武器行进时的车体姿态变化过程的动态模拟器 试验台．该试验台利用运动学反解算法进行闭环控制,并采用基于运动学正解的开环迭代补偿控制算法修正姿态驱 动信号,使试验台的响应逐渐逼近期望的姿态指令．测试表明该系统时域波形复现精度优于95%,验证了迭代补偿 控制的有效性．     

基于结构网格的大规模并行计算研究

通过求解RANS方程和Menter's k-Omega SST两方程湍流模型,以及采用多重网格加速收敛技术、基于多块结构网格的通用数据传输方法和区域分解负载平衡技术,实现CFD软件的并行计算。在国家超算长沙中心的"天河"系统上完成了软件的移植、测试,并实现翼身组合体外形的2048处理器核数、网格规模上亿单元的大规模并行计算,并行效率达到48%,较大幅度地缩短了计算周期,提高了工作效率。通过对DLR-F6的模拟,在气动力系数精确求解、超大规模网格模拟的快速收敛和网格收敛性研究等方面取得了初步结果,为下一步大规模工程实际应用打下了坚实基础。     

颗粒复合材料代表体元并行建模算法研究

为了利用细观力学方法研究复合固体推进剂材料的力学性能,需要建立具有代表性的推进剂细观胞元模型,针对当前算法普遍存在的计算效率低下问题,依据分子动力学思想生成颗粒堆积模型的性能特性,通过分析负载均衡和消息通信,提出了并行模型的三个准则,设计了区域分解的并行策略,并利用共享存储并行和分布式存储并行两级并行手段实现了并行算法。最后在IBMBladeCenter集群平台上通过实例证明算法可以缓解负载均衡并缩减通信开销,上述试验数据验证了算法的高效性,达到了提高胞元生成效率的目的。     

并联机构力传递的分析

以Delta 并联机构为例,利用矢量力学方法和虚功原理建立静力传递数学模型．通过模型仿真分析了 机构运动件重力补偿力矩．提出了机构的力传递能力概念,探讨了工作点的力传递能力和力雅可比矩阵条件数的关 系,初步分析了给定工作空间力传递能力的分布．提出的力传递指标和所得结论可用于优化Delta 机构以及其他机 构的力传递性能．     

并联预紧式六维力传感器动态力响应分析

提出一种并联预紧式双层结构六维力传感器,介绍了该传感器的结构特点和优点.并基于多自由度系统振动力学对该六维力传感器进行动态力响应分析.首先结合该传感器的结构特点对其进行静力学分析,在此基础上建立了传感器系统的振动力学模型;然后推导出系统的运动微分方程,通过求解运动微分方程,得到了系统在动态力作用下广义坐标的响应以及各分...     

基于PVM的并行算法研究

随着数据库规模的增长，数据挖掘技术变得非常重要，而且从数据库中挖掘隐藏的规则也变得十分必要．提出了一种在数据库中发现关联规则的并行Apriori算法，并在并行虚拟机(PVM)环境下实现了该算法．该算法是通过在处理器间分割数据来实现数据的并行化的．     

Analysis and Experiments on the Force Capabilities of Centripetal-Force-Actuated Microrobotic Platforms

This paper studies the capabilities of a microrobotic platform, driven by vibrating motors, to generate and impart micromanipulation forces of desired type and magnitude. First, an analysis is carried out on the nature of the actuation forces of the motion mechanism of the platform. The results demonstrate that the oscillating nature of these forces does not allow their direct use for micromanipulations. Consequently, further analysis is conducted to identify the conditions, under which the platform's actuation forces can be exploited for micromanipulations. To this end, a dynamic model of a single-dimensional pushing operation is developed, comprising the dynamics of the platform, the manipulator and the object. It is demonstrated by simulation that the forces imparted on the manipulated object depend on the physical parameters of the platform-manipulator system. Accordingly, a set of nonlinear equations involving platform-manipulator system parameters, is formulated that describes the conditions for developing micromanipulation forces of appropriate type and magnitude. The solution of this set of equations yields a range of parameter values, which are used as guidelines in the design and construction of a manipulator that is capable of applying smooth and controllable forces to manipulated objects. Using the parameter values suggested by the developed analysis, a needle type manipulator, appropriate for force feedback applications, is designed, built, and mounted on an experimental prototype of the microrobotic platform. Using this manipulator, experiments demonstrate the force capabilities of the microrobotic platform and verified the analytical and simulation results.     

An Evaluation of Architectural Platforms for Parallel Navier-Stokes Computations

We study the computational, communication, and scalability characteristics of a computational fluid dynamics application, which solves the time-accurate flow field of a jet using the compressible Navier-Stokes equations, on a variety of parallel architectural platforms. The platforms chosen for this study are a cluster of workstations (the LACE experimental testbed at NASA Lewis), a shared-memory multiprocessor (the CRAY Y-MP), and distributed-memory multiprocessors with different topologies (the IBM SP and the CRAY T3D). We investigate the impact of various networks connecting the cluster of workstations on the performance of the application and the overheads induced by popular message-passing libraries used for parallelization. The work also highlights the importance of matching the memory bandwidth to processor speed for good single processor performance. By studying the performance of an application on a variety of architectures, we are able to point out the strengths and weaknesses of each of the example computing platforms. This revised version was published online in June 2006 with corrections to the Cover Date.