阀控液压振动系统的静态计算

阀控液压振动系统用常规液压回路设计将产生较大误差,不能预知系统的结果;用动态仿真计算机辅助设计,需要有一定的数学和专业知识,且离不开计算机。本文提出的静态设计是从负载和时间变量的关系推导出系统压力、流量、振幅的静态公式,能够简单、方便地进行系统的开发设计,以获得满足要求的液压振动系统。     

汽车减振器性能检测系统的研究

减振器是汽车的一个重要零部件，其性能的优、劣直接关系到轿车的平衡性和舒适性，为了自动、快速地检验减振器的性能，我们自行研制开发了汽车减振器性能检测系统。试验台通过在恒温工况下检测流过减振器活塞油液的流量和压力之间的关系，通过计算机分析处理来检测减振器的性能。本文首先介绍了检测系统的总体结构及工作原理，然后详细介绍了试验台控制系统；系统采用上位计算机和PLC组成的两级控制系统，有较高的可靠性及控制精度。本系统现在上海汇众公司投入使用．各项性能指标良好。     

液压系统的清洗

清洗液压系统，使杂质减少到最低标准，是确保液压系统能正常工作的重要措施。本文综述了液压系统的冲洗方法，冲洗流速，液压元件和系统的清洗及清洁度等。并着重介绍了液压元件和系统的清洗方法，步骤及其有关问题。     

大型液压系统的维护

大型液压系统，如天津钢管厂的H1液压系统，油箱30m3，管道容积8m3，5台恒压变量柱塞泵最大供油2500L／min、压力13MPa，1台低压泵供油1350L／min、压力3．5MPa，171个液压执行回路控制264个液压缸及马达，软管500余根，上万个法兰及接头。为了满足自动化连续生产，要求液压执行元件的动作速度快而且必须保证整个液压系统不出故障，这就对大型液压系统的维护提出了严格的要求而且增加了困难。一、油箱及其泵站对于大泵源油箱来说，必须设置液位报警系统并经常检查，否则靠人及时发现去停液压泵站主泵不实际。这是由于液压系统大，泵站往…     

大型汽车起重机负载和闭式液压系统的功率匹配

根据大型汽车起重机典型工况的功率循环图，确定负载与液压系统匹配关系，绘制效率循环图并根据实际作业情况进行加权处理；对闭式液压系统与负载的关系进行分析；探讨优化功率匹配的方法，为高效节能闭式液压系统的设计提供理论依据。     

YZC18型振动压路机液压系统的设计与分析

针对YZC18型振动压路机采用的全液压传动进行了较为全面的分析研究.论述了YZC18型振动压路机全液压系统的方案选择、行走液压系统和振动液压系统工作原理及不同点.对于当前全液压系统在工程机械中的应用进行了尝试和探索,对于同类型产品的设计具有一定的指导作用.     

铝型材挤压机锁紧液压系统

详细分析了铝型材挤压机锁紧部分液压系统工作原理,阐述了锁紧力与锁紧泵压力,主系统压力之间的关系,并通过实例阐明紧泵压力对密封效果的作用。     

重大工程及装备中大型液压系统的基本配置及技术特征

文章以国内外典型重大工程及装备中的液压设备，介绍了液压系统的基本配置及技术特征，同时还指出了液压系统的控制目标的综合化要求。     

对未来飞机液压系统的展望

利用液压传动这种方式来作功,是从１７９５年英国制成第１台水压机开始的,至今已有２００多年的历史了,但是液压传动技术被各国重视并把它应用于航空工业,还是近６０年的事。第二次世界大战以后,随着液压元件的迅速发展及其性能的日趋完善,液压传动开始在飞机上得了广泛应用。特别是出现了高精度及快速响应的伺服阀和伺服控制系统后,经典的液压系统从元件设计计算到系统的分析仿真,可以说走上了成熟阶段。目前飞机液压系统除了系统的压力和温度参数还在继续提高外,主要还有电子信息技术在飞机液压系统上的发展,这就是机电一体化和…     

元件的选型与系统的可靠性

该文主要通过对1550No.3SACL连续退火涂层机组出口导板台穿带台摆动设备和1550No.3SACL-RTL重卷切边机组入口转向辊导板伸缩设备的系统运行中故障的分析,阐述了液压元件的选型与液压系统可靠性之间的关系。     

A CO2 tracer-gas method for local air leakage detection and characterization

A method for local measurement of air leakage rate is presented that can be used to accurately and quickly assess leakage rates across a surface, such as around a valve or hatch in a pressurized gas tank or a window in a building. The method uses a small local enclosure with constant volume placed about a region on the structure under investigation (e.g., a window), which is depressurized and injected with a small concentration of carbon dioxide as a tracer gas. The time variation of the pressure and carbon dioxide concentration inside the enclosure are monitored and used to quantify the leakage flow rate as a function of pressure difference. This method uses a small enclosure with internal mixing so that a quasi-steady-state condition is quickly achieved. Because of the small size of the enclosure, advanced data processing techniques are necessary to reduce uncertainty in determination of the rate of change of the carbon dioxide concentration that arises from sensor variability. Results of a laboratory demonstration of the proposed leakage detection and characterization device are reported for the problem of leakage through a circular hole in a plate with prescribed pressure differences. Experimental results from the laboratory tests are found to be in excellent agreement with results of a numerical simulation of leakage flow through a hole, as well as predictions from a number of empirical equations for this problem found in the literature.     

计算机辅助设计凸轮及其数控加工

介绍了如何利用计算机对于形状复杂和高精度的凸轮进行辅助设计,以及将设计结果直接在数控机床上加工的方法,分析了图解法设计的局限性和计算机辅助设计的优越性,指出了利用计算机辅助解析法设计是实现数控加工的基础,也是未来机械设计的发展方向。     

CMM Probing Accessibility in a Single Slot

This study presents a novel mathematical method for resolving the accessibility of a through slot when using coordinate measuring machines. The proposed method considers the actual shape of a probe consisting of a motor column, a stylus, and a probe tip. Also derived herein is a mathematical method to derive the feasible probe orientation of the measurement point in the bottom of a slot using a geometrical relationship between the probe and the slot.     

智能气体识别仪的研究

智能气体识别仪用以识别气体种类,它具有学习识别多种气体的功能。本文介绍了仪器的工作原理、特点及仪器的硬件和软件构成。     

Automated fixture configuration using projective geometry approach

The geometric and topological specification of a workpiece boundary is usually represented in a specific data format in a CAD database. To retrieve a set of workpiece data, to analyse its shape in addition to the machining requirements, and to determine the proper fixture configuration accordingly, are not trivial tasks when a part has a complicated shape. The real challenge is to recognise and synthesise the shape of a workpiece from its data representation. Consequently, the decision for fixturing can be made when the shape of a workpiece and the relationship of the shape and the fixturing configuration can be derived by a systematic methodology. In this paper, a projective spatial occupancy enumeration (PSOE) approach is applied as a representational and manipulating scheme for developing algorithms in automatic fixture configuration. The workpiece is projected onto the working plane of the fixture baseplate. A 2D projection is defined as a matrix of cells which can represent a workpiece with an arbitrary shape. Using a discrete search based upon the matrix of cells, the fixture types and their locations are generated according to a set of heuristic algorithms. This work is a generalisation and extension of previous works for prismatic parts. The same methodology is equally applicable in general robot grasping.     

An inverse shock response spectrum

The shock response spectrum (SRS) is a tool commonly used by application engineers that characterizes the severity of a transient acceleration. Due to the definition of the SRS, neither an analytical nor a unique inverse exists for an arbitrary function. An SRS presented without any temporal information makes creating a corresponding acceleration time history for an experimental or numerical study prohibitively difficult without a rigorous method to determine an inverse of the SRS (a corresponding time history). The present work develops a method to calculate an inverse of an arbitrary SRS using three sets of well characterized basis functions: an impulse function, a sine function/damped sine function, and a modified Morlet wavelet. These three basis functions are specifically chosen for the properties of their transformations: the impulse introduces a constant increase to the SRS above a given frequency, the sine wave introduces a narrow peak at a given frequency, and the Morlet wavelet introduces a plateau with an adjustable width and relative height. Using the definition of the SRS, the transformations of the basis functions are calculated and these expressions are used to derive a methodology for calculating an inverse SRS. The effectiveness of the method is demonstrated by several examples. The quality of an inverse SRS is evaluated by comparing the SRS of the inverse to the target SRS. This method is developed in order to provide a quick estimate of a corresponding time history; in applications where a higher fidelity representation of the SRS is needed than can be provided by the method developed, a genetic algorithm is used to optimize the coefficients of the basis functions. Given a sufficient number of basis functions for the optimization, the resulting SRS can almost exactly match a randomly generated target SRS that is nonzero over the frequency range considered. For applications in which the permissable basis functions are limited (such as for an experimental test apparatus), an extension of the genetic algorithm method is discussed.     

Robust scene recognition using a GA and real-world raw-image

This paper presents a new concept of scene recognition by a genetic algorithm (GA), using the 2-D gray-scale image of a working space, termed here as raw-image, and a model shaping the 2-D top-surface of a target object. In fact here, the problem of object recognition in the raw-image is changed into an optimization problem of a model-based evaluation function. We make use in this research of a GA, as a search and optimization method. This GA employs a model-based fitness function as its objective function to perform the search of a target in the raw-image. In this research, three object models, namely a frame model, a surface model, and a surface-strips model are investigated in order to determine which one is the best for scene recognition in a noisy environment. Also, in order to appraise the recognition performance of each model, a comparative study is performed by analyzing the answers to the following criteria questions: sensitivity, reliability, and speed. The effectiveness of the method has been verified through experiments using real-world raw-images, and the method has shown its robustness of object recognition with the surface-strips model, in spite of the noises in the scene.     

Spatial distribution and polarization dependence of the optical near-field in a silicon microfabricated probe

This paper reports on the spatial distribution and polarization behaviour of the optical near-field at the aperture of a Si micromachined probe. A sub-100 nm aperture at the apex of a SiO₂ tip on a Si cantilever was successfully fabricated by selective etching of the SiO₂ tip in a buffered-HF solution using a thin Cr film as a mask. The aperture, 10–100 nm in size, can be reproducibly fabricated by optimizing the etching time. The optical throughput of several apertures was measured. For a 100 nm aperture, a throughput of 1% was approved. The probe shows a very high optical throughput owing to the geometrical structure of the tip. The spatial distribution of the near-field light is measured and simulated using a finite difference-time domain method. The polarization behaviour of apertures with different shapes was analysed using a photon counting camera system.     

无磁热量表中的一种流量校准方法

热量表是计量热流回路所释放热量的智能仪器。它主要由流量传感器、配对温度传感器、主控MCU和液晶显示等部分组成。其中流量计量的准确程序直接决定了热量表的精度等级。论述了以TI MSP430F135作为主控MCU的热量表的工作原理，讨论了该叶轮式无磁热量表流量测量的动态校准原理，并给出软硬件设计及分析。     

A re-configurable cross-sectional imaging system for reverse engineering based on a CNC milling machine

This paper presents a novel reverse engineering digitizing system for full part geometry, which is based on a cross-sectional imaging device built in a NC milling machine. The system successively captures a picture for each planar cross-section contour of the part by end-milling and CCD imaging, and builds the geometry for both external and internal surfaces of the complex 3D part based on a set of the vectored cross-sectional contours. The system mainly consists of three components: a NC milling machine, a cross-sectional imaging device and a computer control unit. Some issues involving the principle and process flow of the system, encasing materials, cross-sectional imaging and NC code generation, etc. are described in detail. Built on an existing NC milling machine, a portable device for capturing the cross-sectional images is designed, which includes an isolated light source, a digital camera, a protective case, a rigid arm and a robust tripod. The device, connected to a computer control unit, serves as a highly flexible accessory for the NC milling machine, constructing the cross-sectional imaging system for reverse engineering. Furthermore, the error analysis and accuracy assessment of the system are also addressed. A typical case is discussed in detail to illustrate the applications of the system. Such a re-configurable digitizing system for reverse engineering offers a number of advantages, such as the functional extension of an existing NC milling machine, low costs, and rapid construction. As a result, this system provides a feasible and useful scheme for many enterprises to construct their own reverse measuring system based on existing equipment to aid in rapid product development and extend the function of existing equipment.