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Precedence graph-oriented approach to optimise single-product flow-line configurations of reconfigurable manufacturing system

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INTERNATIONAL JOURNAL OF COMPUTER INTEGRATED MANUFACTURING 2009年第10期22卷 923-940页

作者： Dou, J. P. Dai, X. Meng, Z. [a]Key Laboratory of Measurement and Control of Complex Systems of Engineering (School of Automation Southeast University) Ministry of Education China

To facilitate the configuration selection of reconfigurable manufacturing systems, it needs to generate K (predefined number) best configurations as candidates for a given demand period. This paper presents a systematic approach for the problem of generating single-product flow-line (SPFL) configurations. The problem is to determine the SPFL configuration's parameters including number of workstations, number of paralleling machines and machine type as well as assigned operations for each workstation. Given an operation precedence graph (PG) and machine options for each operation, the objective is to minimise the capital costs of SPFL configurations subject to space limitation, investment limitation, and capacity constraint as well as precedence constraints among operations. For linear PG with one feasible operation sequence (FOS), a constrained K-shortest paths (CKSP) formulation is developed and a CKSP algorithm is introduced to generate K-best configurations including the optimal and near-optimal ones. For simple PG (a small number of FOSs), the K-best configurations are found by repeatedly solving the CKSP problem associated with every FOS. For general PG (numerous FOSs), a GA based approach is proposed to identify K-best configurations through searching within the optimal configurations associated with all FOSs. Case studies illustrate the effectiveness and efficiency of our approach.

关键词： reconfigurable manufacturing system configuration generation flow-line precedence graph constrained K-shortest paths genetic algorithm

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Design and optimization of database for vehicle monitoring systems

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 43-47页

作者： Yang, Yanlan Ye, Hua Fei, Shumin School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

According to the functions of database required by the vehicle monitoring system, three entities, including the vehicle, the vehicle terminal and the user, and their relationships are created and described by an entity-relationship (E-R) diagram for the database concept design. The database logical model is built. In order to improve the performance of the database application, three kinds of optimization are proposed in different aspects. First, to improve the low efficiency of data accessing caused by a huge table, multiple sub-tables are divided from the original huge table by a distributed storage solution, which greatly increases the storage capability of the database based on decentralized management. Secondly, zoning optimizations are made for the single tables with a large amount of data. Due to the parallel processing for data, a good performance can be obtained even when the data accessing is frequent. Finally, the query speed of a specific table is improved by making fair use of the clustered index under the guide of different application purposes. Performance of the database in an actual vehicle monitoring system is evaluated. The results show that the optimized database can timely respond the real-time requests of data accessing. It is powerful for data storage and management, which ensures the stability and reliability of the system performance.

关键词： Database systems

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HS joint statistics based adaptive color segmentation

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 266-271页

作者： Li, Jun Meng, Zhengda School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

An adaptive threshold segmentation algorithm based on HS joint statistics using HSI color model is introduced in order to improve the performance of image segmentation and the robustness of object recognition to illumination change. Statistics of H and S component value of all the pixels in the region of interest (ROI) is obtained after image segmentation in HSI color space. The changing rule of statistics is verified while an empirical scale factor is applied to reflect the difference between the influence of H value and S value on segmentation threshold. The threshold is thus adjusted online according to the proposed approach. Experimental results demonstrate the decrease trend of H and S component value with intensified light. Furthermore, it validates the robustness of the approach under the circumstance of changing illumination. Thus the accuracy of the vision-based robot grasping is significantly improved.

关键词： Image segmentation

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Feedback controller designed for hybrid network control system with adaptation to delay parameter

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 19-24页

作者： Chai, Lin Fei, Shumin Zhai, Junyong Jin, Haiyan Wang, Ruimin Li, Yanhong School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

A class of complex hybrid time-delay models for network control systems have been constructed by taking the characteristics of network into account. Based on a LMI(linear matrix inequality) method, a kind of Lyapunov-Krasovskii functional is employed, and the controller design is discussed for this type of systems. As input control is in discrete-time and the input delay constant is known, while state is in continuous-time and the state delay constant is not known exactly, so the system is constructed based on two models in both continuous-time domain and discrete-time domain. At the same time, a new type of adaptive control strategy for the unknown delay parameter is proposed in this paper, which realizes that the unknown delay parameter can always be reflected in the memory state-feedback controller. Delay-dependent sufficient conditions for the existence of the feedback controller in terms of LMIS are obtained.

关键词： Linear matrix inequalities

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Conceptual maps based navigation for mobile robots

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 144-148页

作者： Qian, Kun Ma, Xudong Dai, Xianzhong School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control for Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

A conceptual map model of environments is proposed for task planning of service robots in semantic knowledge space. Such model is characterized with a layered structure containing ontology, spatial and user knowledge. It is capable of inferring environmental knowledge and mapping semantic plans onto the instantial perception space. A scene recognition based method for conceptual map building and updating is proposed to support the environment learning capabilities of robots. Using such model, a layered topological and metric navigation strategy is proposed, in which map switching technique ensures that Monte Carlo localization and metric path planning are performed within each small-scale grid map. Experimental results in large-scale office environments validate the effectiveness and efficiency of robot localization and navigation, and a semantic navigation manner is achieved.

关键词： Navigation

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Intelligent vehicle monitoring system based on WebGIS and mobile video

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 192-197页

作者： Zhou, Hui Ye, Hua Yang, Yanlan School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

In order to solve the problems of inaccurate positioning in current vehicle monitoring systems, an intelligent vehicle monitoring system based on mobile video and WebGIS (Web geographic information system) is proposed and designed. The system is composed of front-end equipment, system platform and client. The instant image information captured by vehicle mobile video and the GPS(global positioning system) positioning location information received by the terminal are transmitted from front-end to system platform via the GPRS(general packet radio service) mobile communications platform. Also, a highly compressed digital video and audio codec technology standard named H.264/AVC is employed to compress the real-time mobile video information and the Google Maps API is called to display the current position of vehicles on the electronic map. Furthermore, the spatial analysis capabilities of GIS plus the GPS information not only make tracking feasibly, but also provide aid in decision making. It is shown that the system can not only reproduce the video data timely and accurately, but also accurately position the mobile vehicles so as to provide a better service in monitoring, control, management, analysis, decision-making and command functions, which expands the application fields and development prospects of WebGIS and mobile video monitoring technology.

关键词： Global positioning system

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Applications of Berkeley DB in home energy monitor system

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 92-97页

作者： Bao, Jing Ye, Hua Sun, Xiaojie Li, Jian School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

In order to achieve the goal of data statistic and task management under the embedded systems, together with the consideration of processing speed and the internal storage capacity, the embedded database is introduced. The features of embedded database are small in size, multi-functional, portable, highly efficient and stable. Taking the data management in the home energy monitor system as an example, a statistical method of time sharing is proposed. The embedded database Berkeley DB is transplanted, and the resource occupancy and response speed before and after using Berkeley DB are compared. Testing data show that although taking up more storage resources, the use of Berkeley DB provides more efficient data management capabilities. The application of Berkeley DB improves the system response, and provides a better human-computer interaction. Under the allowance of the hardware resources of device, this practice of using space for performance is feasible.

关键词： Information management

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Scale adaptable mean shift object tracking based on image fragments

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 131-135页

作者： Wang, Aqin Yang, Wankou Sun, Changyin School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control for Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

The classical mean shift tracking algorithm is apt to make errors or lose the target if the target is occluded for a very long time. Thus an improved mean shift tracking algorithm is proposed. This algorithm divides the target into multiple fragments and integrates spatial information by using different weights of each image fragment. The similarity coefficient between target template and candidate template consists of the Bhattacharyya coefficients of the corresponding multiple fragments. Experimental results show that the proposed method is efficient when the target is occluded for a long time. A new method named edge-histogram is used. This method is based on original scale updating mechanism and make a further judgment that whether the target is smaller or not by calculating the Bhattacharyya coefficient between the target's edge-histograms of the current frame and the previous one. Experimental results show that the proposed algorithm can deal with the scale problem very well.

关键词： Graphic methods

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Smooth path design for mobile service robots based on improved A* algorithm

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 155-161页

作者： Shan, Wei Meng, Zhengda School of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

When it comes to the issue of path planning for mobile service robots in structured indoor environments, traditional A* algorithm fails to display a good performance of real-time path tracking. Therefore, a new method is proposed to design a near-optimal smooth path. Mobile robots can thus track the path smoothly and reach the goal fast. At first, the improved A* algorithm is applied to plan a proper trajectory for the mobile robot. Then a key-point optimization process is applied to make the global path simplified to be connections among a series of key points. The most important improvement lies in the introduction of the polar polynomials curve to smooth the path according to the constraints of position, curvature and slope. However, when the arc turns become 90° or more, the optimized piecewise-polynomial-function curve is generated to replace the original one. Experimental results prove that the path generated meets the dynamic characteristics of the mobile robots as well as the geometric features. The requirements of quick real-time computation of path tracking process can be well satisfied.

关键词： Mobile robots

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A new method for compensating phase-shifting error in phase measuring profilometry

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Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) 2010年第SUPPL. 1期40卷 302-307页

作者： Zhu, Lin Da, Feipeng Gai, Shaoyan Research Institute of Automation Southeast University Nanjing 210096 China Key Laboratory of Measurement and Control of Complex Systems of Engineering of Ministry of Edu. Southeast University Nanjing 210096 China

A new phase-shifting error compensating algorithm for phase-measuring profilometry is proposed. In this error detecting algorithm, it is supposed that sinusoidal fringe is projected to the plate, thus the phase differences between adjacent pixels are equal. Three adjacent phase points are taken as the research object. Combining the principle of phase compensation measurement, each phase of the point is presented as an equation containing the phase-shifting error. According to the characteristics that the phase differences between adjacent pixels are equal, an equation to calculate the phase-shifting error is constructed. Then the phase shifting error is taken into account in the original algorithm for error compensation. Simulation results show the inhibitory effect of the error compensation by using the novel algorithm. The proposed algorithm is also used for three-dimensional reconstruction. The final result shows that the new compensation algorithm is better than the original one obviously. This error compensating algorithm can effectively improve the accuracy of three-dimensional measurement.

关键词： Error compensation

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