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1.
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. 相似文献
2.
Hongbo Lan Yucheng Ding Jun Hong Bingheng Lu 《The International Journal of Advanced Manufacturing Technology》2008,37(3-4):341-353
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. 相似文献
3.
4.
An approach for generating a tasks schedule model in web-based virtual manufacturing system of screw threads 总被引:1,自引:1,他引:0
Janus S. Liang 《The International Journal of Advanced Manufacturing Technology》2010,46(5-8):737-755
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. 相似文献
5.
Th. Laloyaux A. A. Lucas J.-P. Vigneron Ph. Lambin H. Morawitz 《Journal of microscopy》1988,152(1):53-63
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. 相似文献
6.
7.
Jae Eun Kim 《Journal of Mechanical Science and Technology》2017,31(3):1073-1078
In the Rayleigh-Ritz approach to the mathematical model of a cantilevered beam with a tip mass, the proper selection of basis functions is critical in representing the original system by an equivalent mass-spring system. Although the fundamental bending mode shape of a beam varies for a different tip mass magnitude, the numerical values of 33/140 and 3 have been conventionally employed as those of the normalized dimensionless equivalent mass and spring constants, respectively, which correspondingly yield errors in its calculated natural frequencies. This work firstly proposes a method to evaluate more accurate values of the equivalent mass and spring for a wide range of the tip mass-to-beam mass ratio by direct use of a fundamental mode, and then proposes a new basis function as a linear combination of two polynomials, which represent static deflection shapes of a beam under a tip force and a uniformly distributed force, respectively, yielding natural frequencies fairly close to those by the continuous beam equation. 相似文献
8.
V. V. Dremov I. Y. Jum’h H. A. Maharramov P. H. Müller 《Instruments and Experimental Techniques》2013,56(5):584-588
A method for manufacturing a probe for a combined scanning tunneling and atomic-force microscope on the basis of a quartz tuning fork with a metal tip, which is equipped with an independent conductor, is described. When the probe is manufactured, the billet for a tip has the form of a rather small (in order not to change the frequency and quality factor of the quartz tuning fork) metal cone, which is glued to the end of the beam of the quartz resonator-tuning fork together with a carbon fiber as a conductor. A spark is used to form a melted ball at the vertex of the cone. The thickness of the cone near the ball is reduced to a diameter of <0.5 μm by the electrochemical technique, and the ball is then mechanically detached. The main advantage of this method is that it allows manufacturing a high-quality-factor force detector with a single super sharp and clean tip, which is made of platinum (or platinum alloys) and tungsten, with a yield of ≥80%. 相似文献
9.
10.
M.D. Sexton 《Wear》1983,85(3):375-390
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. 相似文献
11.
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. 相似文献
12.
N. S. Qu H. J. Ji Y. B. Zeng 《The International Journal of Advanced Manufacturing Technology》2014,72(5-8):677-683
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. 相似文献
13.
Dr Amy J. C. Trappey C. Richard Liu 《The International Journal of Advanced Manufacturing Technology》1993,8(5):297-304
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. 相似文献
14.
15.
A method for vibration isolation of a vertical axis automatic washing machine with a hydraulic balancer 总被引:2,自引:0,他引:2
Hai-Wei Chen Wei-Xi Ji Qiu-Ju Zhang Yi Cao Sheng-Yao Fan 《Journal of Mechanical Science and Technology》2012,26(2):335-343
This paper discusses a method for vibration isolation of a vertical axis automatic washing machine with a hydraulic balancer.
First, a way to isolate vibration through a small amplitude of the suspension rod’s axial force is proposed, and a base circle
of a cone along which the lower joint of a suspension rod moves is discussed. Based on the circle, a geometric constraint
involving the slant angle of the suspension rod, the deflection angle of the washing/spinning assembly, the suspension radius
of the tub and the eccentricity of the system at the steady state is derived. Considering that the trace along which the suspension
rod moves is also affected by the dynamics of the system, a governing equation satisfying the equilibrium conditions of the
centrifugal forces and torques is obtained. Combing the geometric constraint and governing equation together achieves a general
governing equation for vibration isolation of the system. Finally, the general governing equation is proven by simulations,
and the relations between the optimal installing height and several parameters are discussed. 相似文献
16.
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. 相似文献
17.
《Nuclear Instruments and Methods in Physics Research》1984,211(3):534-537
Following the thallium formate solution and the thallium formate-malonate (Clerici) solution, we have tested several lead compound solutions and a tetrabromoethane heavy liquid as a Cherenkov radiator material for a total absorption counter (calorimeter). We report here the results of optical transmission measurements of a binary solution of lead acetate and lead propionate and of a tetrabromoethane heavy liquid. We present also a result of trials of mixing organic scintillators in these heavy liquids to increase the light output. At present, we have neither obtained an adequate scintillator for lead compound solutions, nor for a tetrabromoethane heavy liquid. However, we obtained a promising indication of getting scintillations from a mixture of thallium formate-malonate (Clerici) solution, water and a liquid scintillator added with a surfactant and a naphthalene in a colloidal state. We need to examine the data more carefully and quantitatively before making a definite affirmative conclusion. 相似文献
18.
在各种长度和直径的圆柱体或空心圆柱体的外圆柱面上沿横截面圆周方向钻削,有较高的位置精度要求且呈多层均匀分布或多层非均匀分布或螺旋均匀分布或螺旋非均匀分布的孔和螺纹孔的方法进行了研究,重点介绍了长度与外径比&gt;5的圆柱体或空心圆柱体。研究发现,目前常见的固定式钻模、回转分度式钻模、移动式钻模、翻转式钻模和盖板式钻模都不是最佳选择,因为它们的钻模板均为长方体,与圆柱面不能完全配合,导致夹紧元件和定位元件的结构复杂,形式单一且制造周期长,成本高,夹紧钻模的方式单一。套式钻模的钻模板为空心圆柱体,空心圆柱体的独特之处是使套式钻模可与圆柱面完美配合,夹紧元件和定位元件的结构简单,形式灵活且制造周期短,成本低,夹紧钻模的方式灵活,从而使其成为在各种长度和直径的圆柱体或空心圆柱体的外圆柱面上钻削各种排列组合方式的孔和螺纹孔的最佳选择。 相似文献
19.
Seungwoo Lee Seungwoo Han Husang Lee 《Journal of Mechanical Science and Technology》2007,21(8):1244-1252
Reliability refers to the ability of a part, device or system to conduct an intended function in a given condition for a certain
period of time. A mechanical system or structure such as a machine tool exercises the capacity of the entire system with regard
to the various constituent parts that are connected to each other; as such, the reliability of the parts constituting the
system determines the reliability of the entire system. A tool post is a device designed to efficiently provide the tools
necessary for the processing of a turning machine: the parts used in a hard turning machine which requires higher stiffness
must provide greater reliability. For the purposes of this study, the reliability of a tool post, which has the highest failure
rate of a turning machine system, was assessed. In order to conduct a reliability assessment of a given tool post, reliability
prediction using a failure rate database, weak point analysis, the manufacture of a reliability tester and the calculation
of reliability testing and quantitative reliability criteria were also carried out. By so doing, the failure rate, the MTBF
(Mean time between failures) and other factors could be calculated. Furthermore, the results can also be applied to other
parts of the turning machine or to a reliability assessment of a subsystem by using the suggested assessment method. 相似文献
20.
A chromel-constantan coaxial surface junction thermocouple has been designed, fabricated, calibrated, and tested to measure the temperature-time history on the surface of a body in a hypersonic freestream of Mach 8 in a shock tunnel. The coaxial thermocouple with a diameter of 3.25 mm was flush mounted in the surface of a hemisphere of 25 mm diameter. The hypersonic freestream was of a very low temperature and density, and had a flow time of about a millisecond. Preliminary test results indicate that the thermocouple is quite sensitive to low temperature-rarefied freestreams, and also has a response time of a few microseconds (≈5?μs) to meet the requirements of short duration transient measurements. The sensor developed is accurate, robust, reproducible, and is highly inexpensive. 相似文献