五自由度纳米级定位工作台的设计研究

提出一种新型的五自由度精密定位平台的工作原理及其设计方法。工作台采用柔性导向机构实现平移及转动功能，采用压电陶瓷作为驱动元件，外置纳米级电容传感器作为位移量测量反馈元件，采用数字PID控制方法，可以实现纳米级精度的定位。给出了多种形式柔性导向机构刚度计算公式及设计实例。

Design and control of an ultraprecision stage used in grating tiling

In petawatt laser system, the gratings used to compose pulse compressor are very large in size which can be only acquired currently by arraying small aperture gratings to form a large one instead, an approach referred to as grating tiling. Theory and experiments have demonstrated that the coherent addition of multiple small gratings to form a larger grating is viable, the key technology of which is to control the relative position and orientation of each grating with high precision. According to the main factors that affect the performance of the grating tiling, a 5-DOF ultraprecision stage is developed for the grating tiling experiment. The mechanism is formed by serial structures. The motion of the mechanism is guided by flexure hinges and driven by piezoelectric actuators and the movement resolution of which can achieve nanometer level. To keep the stability of the mechanism, capacitive position sensors with nanometer accuracy are fixed on it to provide feedback signals with which to realize closed-loop control, thus the positioning precision of the mechanism is within several nanometers range through voltage control and digital PID algorithm. Results of experiments indicate that the performance of the mechanism can meet the requirement of precision for grating tiling.}

基于有限状态机的空间对接仿真平台控制系统设计

给出了一种基于分层式有限状态机的五自由度空间对接仿真平台控制系统设计方法,对状态机进行了扩展定义.增加了一个定义于状态上的变量属性集合,使其有利于系统的代码实现.结合控制系统采用的10 ms定时中断机制,将状态机层次划分到了可以分析每个10 ms硬件中断程序所需实现的控制功能状态及其转移、继承关系的程度,可以更清晰地设计出中断程序所需要的构成结构.系统的实际应用结果证明了上述方法的有效性.

一种五自由度机电测控系统的设计与实现

文章提出了一种基于五自由度机电系统的测控系统设计方法,并从机械系统构成、测控系统结构及软硬件设计方面论述了系统实现技术。针对系统特定的功能要求,文章详细介绍了位姿组合测量和各位姿自由度控制的测控方法,并应用模块化设计和数据流分析方法进行软硬件设计。通过实验进行系统特性分析,得到运行参数指标。实验证明这种设计方法和实现技术合理可行。

基于Windows平台的开放式并联机床数控系统

以5坐标并联机床为依托,面向不同构型并联机床,采用“PMAC+IPC”双CPU为硬件平台、VisualC++6.0为软件平台,开发了基于Windows操作平台的开放式并联机床数控系统。本文介绍了本数控系统的硬件结构、软件构成,并对数控软件开发的关键技术进行了阐述。

并联机床平面约束机构误差分析与建模

针对五轴数控机床平面约束机构进行了误差分析 ,指出了并联机床平面约束机构误差主要影响因素为机构的制造误差和安装误差·前者与由其引起的约束机构顶边中点沿x方向的位移成非线性关系 ,而后者则成线性关系·提出了一种依据测量数据反演非线性误差模型的建模方法 ,给出了五轴并联机床约束机构实测信息与模型输出间的多项式误差模型·比较仿真结果与测量结果可知 ,基于上述方法建立的误差模型精确 ,进而利用该模型对机床进行实时精度补偿 ,可使机床x方向定位精度大为提高

Nd65Al10Fe25-xCox (x=0,5,10) bulk metallic glasses with wide supercooled liquid regions

Bulk metallic glasses of Nd65Al10Fe25-xCox (x=0,5,10) have been prepared in the form of 3 mm diam rods. Results of differential scanning calrimetry, dynamic mechanical thermal analysis (DMTA), and x-ray diffraction are presented for these alloys. It is shown that the glass transition and crystallization have been observed by DMTA. The reduced glass transition temperature of these glasses, defined as the ratio between the glass transition temperature T-g and the melting temperature T-l is in the range from 0.55 to 0.62. All these glasses have a large supercooled liquid region (SLR), ranging from 80 to 130 K. The high value of reduced glass transition temperature and wide SLR agree with their good glass formation ability.

Comparative Study Of The Influence Of Natural Convection On Directional Solidification Of Al-3.5 Wt% Ni And Al-7 Wt% Si Alloys

We present numerical simulations of thermosolutal convection for directional solidification of Al-3.5 wt% Ni and Al-7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al-7 wt% Si, but not in Al-3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

标量脉动“能量”传递函数与—5/3次方律

本文在Heisenberg关于速度脉动能量传递函数假设的基础上,提出标量脉动“能量”传递函数的相应形式.讨论了具有常值横向平均速度梯度与标量梯度的均匀湍流流场中关于大波数情形的标量脉动“能”谱性质。

以1-苯基-3-甲基-4-苯甲酰基代吡唑酮[5]萃取稀土和钍铀钛锆及其在分析化学中的某些应用

本文研究了以PMBP-苯萃取稀土和钍、铀、钛、锆的萃取行为。测定了La、Ce、Pr、Nd、Sm、Gd、Dy、Yb、Y、U(Ⅵ)、Ti、Th和Zr的pH_(1/2)值,计算了它们的萃取平衡常数。并介绍了近十年来作者将此萃取剂应用于铀、钍、稀土、鋰、钢铁合金及岩石中痕量稀土、钍和钙的分离和测定方面的工作。实践证明,PMOP合成简便、价格低廉、萃取能力较强,是比TTA更为优越的萃取剂。

Digitized Processing Track Generation of a Computer Integrated Multi-Functional 5-Axis Laser Processing System

Based on the computer integrated and flexible laser processing system, an intelligent measuring sub-system was developed. A novel model has been built up to compensate the deviations of the main frame-structure, and a new 3-D laser tracker system is applied to adjust the accuracy of the system. To analyze the characteristic of all kind surfaces of automobile outer penal moulds and dies, classification of types of the surface、brim and ridge(or vale) area to be measured and processed has been established, resulting in one of the main processing functions of the laser processing system. According to different type of surfaces, a 2-D adaptive measuring method based on B?zier curve was developed; furthermore a 3-D adaptive measuring method based on Spline curve was also developed. According to the laser materials processing characteristics and data characteristics, necessary methods have been developed to generate processing tracks, they are explained in details. Measuring experiments and laser processing experiments were carried out to testify the above mentioned methods, which have been applied in the computer integrated and flexible laser processing system developed by the Institute of Mechanics, CAS.

SJ-5号卫星空间流体实验系统——开展遥科学实践

本文详细介绍了SJ-5号科学卫星微重力流体实验的用户系统的体系与配置及其对空间科学实验的支持。该系统在SJ-5号空间流体8天的实验过程中,取得约12000幅流场图象和30余小时全程多路温控温测数据,实现了两层流体在两个液池内的不同物理模型的实验,并通过姿控模式的改变实现在两种微重力水平下的对比实验。这是我国科学家首次以实验图象为判据的天地可交互方式完成的空间微重力流体科学实验研究。

Prevalence Of Shear Banding In Compression Of Zr41Ti14Cu12.5Ni10Be22.5 Pillars As Small As 150 Nm In Diameter

Recently, the size dependence of mechanical behaviors, particularly the yield strength and plastic deformation mode, of bulk metallic glasses (BMG) has created a great deal of interest. Contradicting conclusions have been drawn by different research groups, based on various experiments on different BMG systems. Based on in situ compression transmission electron microscopy (TEM) experiments on Zr41Ti14Cu12.5Ni10Be22.5 (Vit 1) nanopillars, this paper provides strong evidence that shear banding still prevails at specimen length scales as small as 150 nm in diameter. This is supported by in situ and ex situ images of shear bands, and by the carefully recorded displacement bursts under load control its well as load drops under displacement control. Finite element modeling of the stress state within the pillar shows that the unavoidable geometry constraints accompanying such experiments impart a strong effect on the experimental results, including non-uniform stress distributions and high level hydrostatic pressures. The seemingly improved compressive ductility is believed to be due to such geometry constraints. Observations underscore the notion that the mechanical behavior of metallic glasses, including strength and plastic deformation mode, is size independent at least in Vit 1. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.