A new algorithm for tracing nests of interconnected contours

Boundary contour, a meaningful external representation of area of interest, is widely used in many manufacturing applications (e.g., part machining, rapid prototyping, cutting and packing of irregular shape patterns, and geometrical reconstruction), and appearing on an image, in many cases, are nests of interconnected contours that their information is typically required prior to subsequent manufacturing operations being performed. Presented in this paper is a new contour tracing algorithm for extracting nests of interconnected contours. The algorithm is capable of recognizing junctions between contours sharing common edges and of recommending, among alternatives, a path to proceed to obtain all interconnected contours. Morphological operations have been applied instead of component labeling to achieve the locations of nested contours on an image. The input to the algorithm is a binary image of 1-pixel-wide closed contours, and the outputs are ordered sequences of boundary pixels representing all closed contours. The algorithm has been implemented on LabVIEW, experimented with several contour patterns, and demonstrated its application in manufacturing.     

A fast triangulation algorithm for 3D reconstruction from planar contours

Aiming at the reconstruction of medical images, a fast triangulation algorithm from planar contours (FTA) is proposed in this paper. In FTA, the judgment of the similarity of counters is carried out at first. Then a traditional global optimisation method is applied to triangulating dissimilar counters. A simple local optimisation method is also applied on areas enveloped by line sections of similar counters. Through theoretical analysis and experience, the visual effect of FTA becomes approximately similar to traditional global optimisation methods and its calculating speed is much improved simultaneously. FTA was also applied to a stereo tactical radiation therapy planning system for a gamma knife (SRTPS) developed by the authors.     

结合梯度信息的主动轮廓模型图像分割算法

传统的C-V模型对于含有多灰度级目标的图像难以实现准确分割,并且分割速度非常缓慢.为了解决这些问题,提出了在C-V模型中引入梯度信息的图像分割算法.该算法在C-V模型的偏微分方程中加入了依赖于梯度信息的弱目标区域控制项和加速因子.弱目标区域控制项可以使弱目标被快速,稳定地锁定,加速因子的引入可以显著地提高C-V模型的分割速度.实验结果表明:该算法能够有效分割出弱目标和提高图像分割速度.     

基于模糊PID的自主寻迹小车控制

小车寻迹过程中由于路况不同,其数学模型的参数会不断地发生变化,这使得以往的传统PID全局参数的整定极为困难。因此提出了一种基于模糊PID的控制策略。通过模糊控制整定PID的3个参数的变化量,从而根据路况的不同,实现PID三个参数的实时调节。同时应用仿真软件对系统的数学模型分别进行了传统PID和模糊PID的仿真。最后,在以飞思卡尔车模为基础的试验平台上进行模拟试验,验证了仿真结果和理论的准确性,以及模糊PID相比于传统PID的优越性。     

Improvement and realization of linear travel-time interpolation ray tracing algorithm

The linear travel-time interpolation ray tracing algorithm has a drawback: rays can’t go round the low velocity area if the launching point, the receiving point and the low velocity area distribute on the same column (row). Aiming at the drawback, an improved algorithm is proposed on the basis of researching reconstruction theories. The given algorithm adopts a cross-scanning strategy to carry out forward processing and uses discrete points as the secondary sources to simplify backward processing. The numerical simulation experiments show that the rays can go round the low velocity areas located in the same column (row) of the launching points and the receiving points. Rays scan over the global region only once.     

A novel algorithm for quick and continuous tracing the change of radon concentration in environment

Several measurements of the radon concentration are performed by RAD7 in the University of South China. We find that 30-40 min is needed for RAD7 for tracing the concentration of the standard radon chamber. There are two reasons. The first is that the sufficient time of air cycle is needed for the radon concentration in internal cell of RAD7 equal to that of the environment; and the second is that the sufficient decay time is needed for the (218)Po concentration in internal cell of RAD7 equal to that of the radon. We used a zeroth order approximation to describe the evolution of the environment radon concentration, and obtained a novel algorithm for quick and continuous tracing the change of radon concentration. The corrected radon concentration obtained through this method is in good agreement with the reference value. This method can be applied to develop and improve the instruments for tracing the change of radon concentration quickly.     

数控线切割机床图像矢量化的线跟踪算法改进研究

图像矢量化是指将图片或工程图纸用数字化设备输入计算机中，经过矢量化处理形成CAD文件的过程。在数控线切割机床自动编程系统中引入图像矢量化技术，能提高编程系统的智能化水平。本文列举了4种具有代表性的矢量化算法，并根据数控线切割机床加工零件图像的特点，提出了一种改进的线跟踪图像矢量化算法，实现加工零件图像的矢量化。     

A distributed interconnected control for computer-integrated manufacturing

An innovative control system architecture is considered which preserves the parallelism of the manufacturing operation with the goal of improving productivity through maximal use of resources with varying product mixes. To combine flexibility with efficiency, the expert integrated management (XIM) architecture technology is developed which governs a multiprocess environment with distributed intelligent interfaces and which controls the communication and synchronization tasks for each manufacturing situation. The performance of this distributed interconnected control system is demonstrated with the special purpose expert simulator (XIM-SIFIP), which combines the previously developed simulational facilities (XS-SIFIP, for flexible manufacturing sections and XT-SIFIP, for tool-supplying service) by means of a new information processing device that enables parallel control of the multiagent framework.     

Decentralized robust control for interconnected nonlinear systems

Decentralized robust control of strongly interconnected uncertain systems is addressed in this paper. The uncertainties we consider here may include parameter uncertainty and input disturbance that may be nonlinear and (possibly fast) time-varying. We show specially how both internal and external uncertainties are taken into considerations. This work covers a broad class of large-scale systems since the current consideration renders all previous settings as special cases. Stability analysis with the proposed controllers is provided.     

Point-projection imaging of macromolecular contours

A point-projection microscope is described which uses an electric field of several volts per nanometre to generate ions from a layer of benzene condensed in high vacuum on to the apex of a cryogenically cooled field-emitter tip. Clusters of ferritin (a spherical protein molecule) embedded in the layer, have been imaged by exposing their contours during controlled field-desorption. Image contrast is high. A magnification of 2 times 10⁵ has been achieved at a spatial resolution estimated to be better than 3 nm. Three-dimensional reconstructions of cluster morphology from a series of molecular contours are in qualitative agreement with transmission-electron micrographs of the ferritin covered emitter apex. Reproducibility of the cluster contours, and TEM images of the apex before and after imaging suggest that the imaging procedure is nondestructive.     

An interactive programming system for milling contours and pockets

The programming system discussed here is similar to APT in the definitions it uses. It can automatically generate CNC blocks for the machining of contours and pockets, bounded by linear and circular segments. The system uses simple trigonometry to analyse lines, circles and their intersections. This paper explains a number of algorithms for geometric definitions, elimination of redundant surfaces (thereby optimising the tool path), tool-path generation, etc. A new approach proposed in the present work, based on the construction of a triangle, has simplified the geometry for the case of a circle tangential to two other circles. A number of geometric construction methods and the selection of the milling process (climb versus conventional) for tool-path generation are explained. The system has been modified to machine tapered contour surfaces with a required draft angle.     

Decentralized state estimation for a large-scale spatially interconnected system

A decentralized state estimator is derived for the spatially interconnected systems composed of many subsystems with arbitrary connection relations. An optimization problem on the basis of linear matrix inequality (LMI) is constructed for the computations of improved subsystem parameter matrices. Several computationally effective approaches are derived which efficiently utilize the block-diagonal characteristic of system parameter matrices and the sparseness of subsystem connection matrix. Moreover, this decentralized state estimator is proved to converge to a stable system and obtain a bounded covariance matrix of estimation errors under certain conditions. Numerical simulations show that the obtained decentralized state estimator is attractive in the synthesis of a large-scale networked system.     

柔性结构拓扑优化设计发展概况

论述了柔性结构的特点、拓扑优化设计的基本原理与方法、国内外研究发展现状 ,以及在工程设计中的应用等问题。最后 ,列出了柔性结构拓扑优化设计的发展方向、需要解决的问题 ,以及可能解决的方案等。     

基于拓扑特征的并联机构拓扑变换

引入拓扑学理论,定义了并联机构的拓扑空间,分析了并联机构的拓扑特征;研究了并联机构的拓扑变换方法,给出了6-PSS并联机构的4种拓扑结构的几何模型,为并联机构构型的研究提供了理论基础和创新方法。     

A composite control design for suppressing mutual interference of interconnected systems

Journal of Mechanical Science and Technology - This paper presents a new disturbance decoupling and rejection method for a multi-connected system, and introduces the composite controller based on...     

A robust decentralized load frequency controller for interconnected power systems

A novel design of a robust decentralized load frequency control (LFC) algorithm is proposed for an inter-connected three-area power system, for the purpose of regulating area control error (ACE) in the presence of system uncertainties and external disturbances. The design is based on the concept of active disturbance rejection control (ADRC). Estimating and mitigating the total effect of various uncertainties in real time, ADRC is particularly effective against a wide range of parameter variations, model uncertainties, and large disturbances. Furthermore, with only two tuning parameters, the controller provides a simple and easy-to-use solution to complex engineering problems in practice. Here, an ADRC-based LFC solution is developed for systems with turbines of various types, such as non-reheat, reheat, and hydraulic. The simulation results verified the effectiveness of the ADRC, in comparison with an existing PI-type controller tuned via genetic algorithm linear matrix inequalities (GALMIs). The comparison results show the superiority of the proposed solution. Moreover, the stability and robustness of the closed-loop system is studied using frequency-domain analysis.     

面向大规模个性化定制的互联工厂的数字化技术应用研究

大规模个性化定制的互联工厂是以用户互联为核心,整合用户个性化需求,并深度参与企业全流程、零距离互联生态资源,快速、低成本且高效地提供智能产品、服务和增值体验的智能制造模式。基于对大规模个性化定制的互联工厂的数字化技术应用研究,提出互联工厂的数字化技术总体实施架构,同时结合互联工厂中的实际业务需求场景,介绍数字化技术在大规模个性化定制的互联工厂中的应用实践和关键作用。通过互联工厂的数字化体系建设,实现互联工厂全流程业务智能管控、智慧运营和智能决策,最终实现降本提效,更好地服务企业管理,提升企业核心竞争力。     

A new approach for lofted B-spline surface interpolation to serial contours

This paper addresses the problem of B-spline surface interpolation to serial contours, where the number of points varies from contour to contour. A traditional approach to the problem creates a set of B-spline curves via B-spline curve interpolation to each contour, makes them compatible via degree elevation and knot insertion and performs B-spline surface lofting to get a B-spline surface that interpolates them. The approach tends to result in an astonishing number of control points in the lofted B-spline surface. This situation arises mainly from the inevitable process of progressively merging different knot vectors to make the B-spline curves compatible. This paper presents a new approach for fixing this problem. The approach includes a novel process of obtaining a set of compatible B-spline curves from the given contours. The process is based on universal parameterisation [1, 2], allowing the knots to be selected freely but leading to a more stable linear system for B-spline curve interpolation. Since the number of control points in each compatible B-spline curve is equal to the highest number of contour points, the proposed approach can realise efficient data reduction and provide a compact representation of a lofted B-spline surface while keeping the desired surface shape. Some experimental results demonstrate its usefulness and quality.     

稳态热传导下的连续体结构拓扑优化

在稳态热传导连续体拓扑优化中,提出单元总热能、节点温度、区域内节点温度平方和三类不同性能指标,推导三类指标的伴随法敏度分析公式。基于独立连续映射法建立以三类指标为约束的体积最小化模型,应用过滤技术克服拓扑优化的数值不稳定性问题,实现了稳态热传导下的连续体拓扑优化设计。通过数值算例对优化结果进行讨论,其结果验证了方法和模型的可行性和有效性。     

A simple model for estimation of dimensionless isovel contours in open channels

A simple model is proposed for predicting the dimensionless isovel contours in straight ducts and open channels. It is assumed that each element of the boundary influences the velocity at an arbitrary point in the cross section. Then, the total effect of the boundary can be obtained using integration along the wetted perimeter. In this paper, power and logarithmic laws are used, while any velocity profile can be applied in the model. The model is applied to calculate the normalized isovel contours in rectangular channels. Then they are used, in combination with a single-point velocity measurement at a cross section of the uniform flow, to estimate the discharge. The kinetic energy and momentum correction factors, and the ratio of maximum to mean velocity, are also calculated from isovel patterns. Calibration and validation of the model are carried out by comparing the results obtained with measurements of the velocity in the main flow direction along the centerline of a rectangular flume as well as in the transverse direction. Each point of measurement can be used to estimate the discharge. Then, the estimated discharge is compared with the actual measured one. Depending on the position of the measurement, the deviation of the calculated and measured discharges will be altered. Model predictions are well correlated with experimental data for rectangular open channels.