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.     

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.     

An approach for generating a tasks schedule model in web-based virtual manufacturing system of screw threads

In this paper, several web-based interfaces for user interaction and a task-oriented decision approach are proposed to build a tasks schedule model and then display the manufacturing process in a virtual environment, which is created by a geometric virtual-reality-based visualization technology for screw threads generation. The proposed tasks schedule model consists of four types of objects: virtual component, state manager, transfer operator, and flow controller. The virtual component has a geometric model with kinematics and their attributes. To control the geometric model, a component controller which models the logical aspects of a component is used. The component controller should be able to implement component-level orders by operating the geometric model. For the fidelity of the tasks schedule model, a transfer operator has a set of component-level command imitating the physical mechanism of a transfer. As a result, more accurate simulation results can be expected. The flow controller makes decisions on friable transfers based on decision parameters, which are maintained by the state manager. To have better structure and easier implementation, a virtual manufacturing platform can be modeled in a hierarchical and modular manner as an integrated system consisting of a product design suite, a web interface module, and a visualization module. Meanwhile, it provides a solution of learning of manufacturing sequences, cost effective, platform independent, and sharing visualized information over the internet for virtual manufacturing. Finally, the tasks schedule model has been implemented with an example in screw threads generation.     

连续热镀锌生产线的简化与数学建模

为研究气刀处的带钢大幅抖动原因,试对带钢连续热镀锌系统进行动力学建模。整个镀锌生产线是一个复杂的大系统,动力学建模时必须对其进行适当简化,以得到一个仅包含热张紧辊、退火段带钢、沉没辊、出锌锅上行段带钢、塔顶辊、下行段带钢、转向辊和八个弹簧支承的比较简单的混杂系统力学模型。先将简化后的混杂系统分成多个子模型,用带钢张力和附加惯性载荷代替边界条件,然后基于牛顿第二定律对这些子模型进行建模,以期得到整个系统的控制方程。此项研究可为混杂系统建模提供一种新参考。     

校园文化与大学发展

校园文化看不见、摸不着，却支撑着大学的脊梁，它潜移默化影响和造就一所大学的文化品格。它不仅对大学发展起着重要作用，也是大学发展的重要内容，是大学建设的题中应有之义。为此，需要建设民主和谐，具有学术自由、人文精神和创新精神的校园文化，并将它提高到学校战略发展的高度来看，以校园文化整合学校发展战略。     

Fiber optic pressure sensor based on a single-mode fiber F–P cavity

In this paper, we propose and experimentally demonstrate a pressure sensor based on birefringent single-mode fiber F–P cavity using optical heterodyne. The proof of concept device consists of a light source, a polarizer controller, a modulator, a RF generator, a single-mode fiber Fabry–Perot cavity, a strain inspector, an erbium doped fiber amplifier, a filter, a polarizer, an optical spectrum analyzer, and a digital communication analyzer. The dynamic range of the proposed sensor is explored. The results demonstrate the new concept of fiber pressure sensors and the technical feasibility for pressure measurements.     

The interaction between two wearing surfaces I: Copper sliding on Cu-Be and Cu-Be sliding on Cu-Be

The work reported in this paper is an investigation of the interaction of the two components of a wear system with reference to the physical properties of both components. Copper sliding on Cu-Be and Cu-Be sliding on Cu-Be were studied using a ball-on-disc machine, Auger spectroscopy and microhardness measurements. The two systems are found to be qualitatively similar classic examples of severe wear. The wear of a Cu-Be disc sliding under a copper ball is, however, greater than the wear of a Cu-Be disc sliding under a Cu-Be ball. This is attributed to work hardening of the copper ball resulting from an interaction between the two wearing surfaces. Microhardness measurements show that the surface of a Cu-Be ball and a Cu-Be disc are not work hardened during a wear experiment. The surface of a copper ball is work hardened, however, and becomes significantly harder than the wear scar on a Cu-Be ball. As a result the Cu-Be disc wears at a faster rate when sliding under a copper ball than it does when sliding under a Cu-Be ball.     

Design of Remote Control Nuclear Radiation Detector

For the issue of nuclear radiation detection,this paper designs a remote control nuclear radiation detector which can trace a pre-determined route,avoid obstacles effectively,and can be controlled remotely by users wirelessly or through voice command.It can effectively replace manual probing due to convenience,flexibility and safety.The system mainly consists of a nuclear detection module,a voice control module,a route tracing module,an obstacle avoidance module,a data transmission module,storage and a display module,and a D.C.machine.An MSP430 microcontroller is used as a control chip to control the motor and the system uses infrared technology and ultrasonic sensors to achieve intelligent tracing and obstacle avoidance.Moreover,it applies a voice module and data transmission module to remotely controlling the device.The radiation data is shown on an LCD screen.     

Lateral resolution of the scanning tunnelling microscope

A theoretical study of the current distribution in a model which extracts the prominent characteristics of a tip-surface geometry in a scanning tunnelling microscope is presented. The sample is a Sommerfeld metal with a planar surface while the tip, also made of a Sommerfeld metal with a planar surface, presents a hemispherical protrusion. Schrödinger's equation is solved by using a form of the finite element method suitable to treat the three-dimensional tunnelling problem. We have derived the current distribution for several values of the protrusion radius and for various gaps between the electrodes. From these results, we investigate the ideal resolution of the scanning tunnelling microscope for realistic values of these geometrical parameters. Though applied to a rather simple model, at this stage, our method appears to be a suitable scheme for further, more refined computations, accounting for the detailed atomic structure of the electrodes.     

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.     

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。     

Automatic bias-reduction controller for a scanning tunneling microscope

In order to protect the sample and the tip against current transients in a scanning tunneling microscope, which in most cases damages the scanned surface and the tip, when using a bias higher than 1V, we have designed a simple and low-cost circuit that limits the tunneling current. During the evolution of the current transient, when the current exceeds a pre-determined value, a fast feedback control mechanism immediately reduces the bias and prevents the current transient from developing. In addition, we designed a fast pre-amplifier that works with this controller. We have shown that this mechanism provides a better scanning image compared to a system without such a mechanism.     

电控单体泵燃油喷射系统耦合仿真

以某一典型的电控单体泵供油单元、可压缩高压油管以及机械式一级弹簧喷油器组成的燃油喷射系统为原型,建立了电控单体泵燃油喷射系统和喷油正时控制策略的耦合仿真模型,为多学科领域复杂系统建模仿真提供了解决方案和系统工程设计的完整平台.     

Massless links with external forces and bushing effect for multibody dynamic analysis

When the contribution of lightweight components to the total energy of a system is small, the inertia effects are sometimes ignored by replacing them to massless links. For example, a revolute-spherical massless link generates two kinematic constraint equations between adjacent bodies and allows four relative degrees of freedom. In this paper, to implement a massless link systematically in a computer program using the velocity transformation technique, the velocity transformation matrix of massless links is derived and numerically implemented. The velocity transformation matrix for a revolute-spherical massless link and a revolute-universal massless link are appeared as a 6X4 matrix and a 6X3 matrix, respectively. A massless link model in a suspension composite joint transmitting external forces is also developed and the numerical efficiency of the proposed model is compared to a conventional multibody model. For a massless link transmitting external forces, forces acting on links are resolved and transmitted to the attached points with a quasi-static assumption. Numerical examples are presented to verify the formulation.     

Stable microwave coaxial cavity plasma system at atmospheric pressure

We present a systematic study of the development of a novel atmospheric microwave plasma system for material processing in the pressure range up to 760 torr and the microwave input power up to 6 kW. Atmospheric microwave plasma was reliably produced and sustained by using a cylindrical resonator with the TM(011) cavity mode. The applicator and the microwave cavity, which is a cylindrical resonator, are carefully designed and optimized with the time dependent finite element Maxwell equation solver. The azimuthal apertures are placed at the maximum magnetic field positions between the cavity and the applicator to maximize the coupling efficiency into the microwave plasma at a resonant frequency of 2.45 GHz. The system consists of a magnetron power supply, a circulator, a directional coupler, a three-stub tuner, a dummy load, a coaxial cavity, and a central cavity. Design and construction of the resonant structures and diagnostics of atmospheric plasma using optical experiments are discussed in various ranges of pressure and microwave input power for different types of gases.     

Numerical analysis of hydrodynamic process of circular-translational-moving polishing (CTMP)

By keeping a pad moving relative to a wafer along a circular path without rotation, we developed a polishing technique called circular-translational-moving polishing (CTMP), which permits multidirectional polishing of the work piece and thus bears the advantage of isotropic polishing and a potential increase of material removal rate (MRR) on the wafer. To illuminate the mechanisms of CTMP and determine the optimum process variables in a CTMP process, a three-dimensional hydrodynamic lubrication model for CTMP with a smooth and rigid pad under a quasi-stable state is established in a polar coordinate system. The model equations are further calculated numerically by the finite difference method. The instantaneous distribution of fluid pressure is obtained, which shows that a negative pressure exists. The reason for negative pressure in CTMP and its effect on polishing is discussed. Moreover, the nominal clearance of the fluid film, roll, and pitch angles under different working conditions are obtained in terms of the applied load, moments, and polishing velocity. The obtained numerical analysis can be used as guidance for choosing operation parameters in a practical CTMP application.     

Wire electrochemical machining using reciprocated traveling wire

Wire electrochemical machining (WECM) is a cutting process in which the workpiece acts as an anode and the wire as a cathode. WECM is typically used to cut plates and exhibits a great advantage over wire electro-discharge machining, namely, the absence of a heat-affected zone around the cutting area. The enhancement of WECM accuracy is a research topic of great interest. In WECM, the homogeneity of the machined slit has a decisive influence on the machining accuracy. This is the first study in which the integration of pulse electrochemical machining (ECM) and a reciprocated traveling wire electrode was used to improve the homogeneity of this slit. The experimental results show that the combination of pulse ECM and a reciprocated traveling wire electrode could enhance the accuracy of WECM and that generally a low applied voltage, pulse duty cycle, and electrolyte concentration; an appropriate traveling wire velocity; and a high pulse frequency and feeding rate enhance the accuracy and stability of WECM. Finally, a microstructure with a slit width of 177 μm, with a standard deviation of 1.5 μm, and with an aspect ratio of 113 was fabricated on a stainless steel substrate measuring 20 mm in thickness.     

Free-form curves cutting using flexible circular saw

A flexible circular saw, which can be used in a novel machining process for high-speed carbon fiber-reinforced plastic (CFRP) plate cutting, was developed. In this process, the saw is deflected like a bowl-like shape. A cross-section of the saw body then forms a circular arc. A curved line can therefore be cut without interference by the bowl-like deflection. In addition, the radius of the cross-section of the saw body can be controlled by adjusting the deflection. This process therefore allows curves to be cut with a varied radius using a single saw. This process can carry out high-speed curved-line cutting with a feed rate of 3 m/min on a CFRP plate. However, it is difficult to cut free-form curves using a flexible circular saw. Therefore, in this research, a new technique that can cut free-form curves using a flexible circular saw was proposed. Then, a cutting test applying the technique was carried out.     

便携式微机控制风速测量仪

本文主要阐述一种便携式微机控制风速测量仪的主要功能,硬件系统结构和工作原理。这种风速测量仪以高性能的８７５１单片机为核心,由存储器和Ｉ／Ｏ接口电路等部件组成,各部件之间的信息传递采用总线结构形式,面板采用键盘操作各功能由程序控制,从而实现测量、数据记录、数据处理、综合分析等全自动化功能,是一种智能化仪表。     

没有针轮的摆线变速机

在摆线针轮减速机中,针轮是由针齿壳、针齿销、套3种精密零件组成;在摆线曲面的线形探索中,找到了摆线的法线运动规律,设计出摆线的法向导杆机构,用普通圆柱铣刀和砂轮沿法向导杆进给和切削,准确地创成加工各种摆线及其等距曲线.从而可以制造出纯滚动啮合的外齿和内齿摆线轮,使得由十几以致上百个零件组成的针轮只需一个内齿摆线轮取代,进而制造没有针轮的摆线减速机,使减速机的效率显著提高,单级的最大减速比由现在的87提高到200以上.