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Li, Weilin; Luo, Min; Zhu, Lin; Monti, Antonello; Ponci, Ferdinanda
doi: 10.1177/0037549712472939pmid: N/A
Multi-agent system (MAS) protection is under investigation as a potential method for distributed control in modern electrical power systems. The coordination of the MAS is based on local measurements available to each agent’s site as well as on the information exchanged between agents over the communication network. Hence, the communication network should be considered to be a main factor in determining overall system performance.Numerical simulation is a fundamental tool of the design process. Existing electric power simulation tools can satisfactorily model traditional power systems where power and communication are considered to be decoupled and MAS are not present. Similarly, the simulation tools for communication systems have been developed independently from the application, particularly power system scenarios, so they are decoupled from the actual use of the information. If the loop between communication and power is closed and the coupling is strong, as in MAS-controlled power systems, such a simulation environment may yield unrealistic results.Aiming at filling this gap, this paper proposes a co-simulation solution for power systems, communication networks, and MAS, based on the extended capability of the co-simulation platform called VPNET. VPNET consists of three parts: Virtual Test Bed for time domain simulation of power systems, OPNET for the simulation of communication networks, and the Co-simulation Coordinator for data exchange and time synchronization between the other two simulators. The Co-simulation Coordinator has been exploited for MAS integration, as the rules of each agent are defined in the modules provided by the Co-simulation Coordinator.The proposed extended co-simulation platform is tested in the analysis of the performance of the MAS-based protection schemes of a medium-voltage DC shipboard power system. Numerical simulations have been performed for communication testing and protection testing. In the communication test, the network parameters (bandwidth and transmission time) are analyzed to evaluate the performance of the communication network under various conditions; in particular, links failure. The MAS-based protection system was then tested under various operating conditions of the communication network (latency and links failure). From the simulation results it can be seen that the designed MAS protection can handle these conditions successfully. Particularly in the link failure conditions, this co-simulation platform could simulate the re-routing process of the communication network and lead to correct protection performance, which is impossible with individual simulators alone. These simulation results show the utility of VPNET in exploring the design trade-offs between protection strategies and communication in the design phase.
Ge, Yuanzheng; Liu, Liang; Qiu, Xiaogang; Song, Hongbin; Wang, Yong; Huang, Kedi
doi: 10.1177/0037549713477682pmid: N/A
Agent-based modeling and simulation play an important role in sociological analysis for complex phenomena. The social communication behaviors can be reproduced by interactive agents, who can behave like human beings. In this paper, we propose a simulation framework of multilayer social networks to model high-resolution interaction between agents. The agent model contains three components: social networks, a demographic-based population and a schedule-based behavior. A common description of multilayer heterogeneous networks is presented. To evaluate the performance of the proposed framework, we reproduce the transmission of influenza H1N1 in an artificial classroom, and compare the simulation results with a real outbreak of influenza H1N1 at one university in Langfang, 2009. The simulation results show high correlation between social networks and the transmission of influenza, and demonstrate that individual-based social network models can well reproduce and analyze complex interacting behavior. Furthermore, experiments under controlled conditions are carried out to analyze the sensitivity of alternative parameters. The framework is able to model high-resolution, social communications from multiple aspects.
doi: 10.1177/0037549713481012pmid: N/A
In clustered sensor networks, because CHs (cluster heads) collect data from sensors and transmit the aggregated data to the sink, it is very important to elect the CHs in a secure manner. In order to protect CH elections from attackers, unpredictability, non-manipulability, and agreement property should be guaranteed in CH elections. However, existing schemes for secure CH election cannot prevent intelligent attackers from violating the properties via cooperation. In this paper, we propose a scheme that securely elects CHs by detecting intelligent attackers and excluding them. For every CH election round, each CH candidate provides reputation values to other CH candidates according to their behavior and extracts real reputation values. Then, each node evaluates the real reputation values of members in its cluster and excludes some disreputable nodes from CH candidates. The scheme greatly enhances the non-manipulability and agreement property of CH election results compared to other rival schemes. Furthermore, the scheme presents higher non-manipulability and higher agreement property than other schemes, even in an environment where message losses can occur.
Kim, Seokhyun; Lee, Jaeheung; Park, Yongsu; Cho, Yookun
doi: 10.1177/0037549713485499pmid: N/A
Distributed trigger counting (DTC) is a problem related to the detection of w triggers with n nodes in large-scale distributed systems that have general characteristics of complex adaptive systems. The triggers come from an external source, and no a priori information about the triggers is given. DTC algorithms can be used for distributed monitoring and global snapshots. When designing an efficient DTC algorithm, the following goals should be considered: minimizing the overall message complexity and distributing the loads for detecting triggers among nodes. In this paper, we propose a randomized algorithm called TreeFill, which satisfies the message complexity of O(nlog(w/n)) with high probability. The maximum number of received messages to detect w triggers in each node is O(log(w/n)) with high probability. These results satisfy the lower bounds of DTC problems. We prove the upper bounds of TreeFill. The performance of TreeFill is also evaluated by means of an agent-based simulation using NetLogo. The simulation results show that TreeFill uses about 54–69% of the messages used in a previous work called CoinRand. The maximum number of received messages in each node of TreeFill is also smaller than that in the previous work.
Sharif Ullah, A M M; Shamsuzzaman, M
doi: 10.1177/0037549713482174pmid: N/A
Fuzzy Monte Carlo Simulation (FMCS) uses both the probability density function (pdf) and possibility distributions (e.g., fuzzy numbers) to model the uncertainty/imprecision associated with the input parameters and, then, to simulate the uncertainty/imprecision associated with the output parameters. A probability–possibility transformation is needed to transfer the information of a fuzzy number into its equivalent pdf, while performing the simulation. This study deals with an approach of FMCS that uses a point-cloud-based probability–possibility transformation. Let x(t), t = 0,1,…, n, be a set of points that represents some random states of an uncertain/imprecise quantity. The collection of points (x(t), x(t+i)), t = 0,…, n–i, i∈ {1,2,…} is called point-cloud, providing a visual/computational representation of variability, modality, and ranges associated with the quantity. This study identifies the pdf and possibility distribution (fuzzy number) underlying a given point-cloud. Using these distributions, the relationships between the triangular fuzzy number and unimodal pdf (normal/uniform distributions) are identified. Two numerical examples are described elucidating the effectiveness of the proposed transformation. The first example deals with the issue of monitoring a FMCS process. The other example deals with the issue of making a decision by using FMCS.
doi: 10.1177/0037549713482733pmid: N/A
In this paper, a general Stewart Platform Simulation tool (STEWSIM) is developed for robot designers and researchers. The STEWSIM uses an efficient connection matrix algorithm that has been developed for kinematic design of all possible types of general Stewart platforms (GSPs), such as 3×3, 3×4, 3×5 … 6×5 and 6×6 with an arbitrary number of legs varying between three and six. This new interactive simulation software based on the MATLAB Graphical User Interface (GUI) provides a suite of analyses, such as inverse and forward kinematics, Jacobian matrix, dexterity, workspace, singularity analysis and trajectory planning, using different kinds of roll-pitch-yaw or Euler angle sets. The STEWSIM also provides the visualization of the GSPs, graphical representation of the workspace, and graphic animation of trajectories specified by inverse kinematics in three-dimensional space. Furthermore, it provides an environment to compare the kinematic performances of the designed GSPs with arbitrary configuration. As a kinematic design, analysis and simulation software, the STEWSIM provides researchers with the ability to change the parameters interactively for designing their manipulators with optimum specifications, such as leg lengths and attachment points. The usage of this simulation tool may result in new types of feasible robotic manipulators that can be used for practical applications in industry.
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