A multi-agent approach for design consistency checking

The last decade has seen an explosion of interest to advanced product development methods, such as Computer Integrated Manufacture, Extended Enterprise and Concurrent Engineering. As a result of the globalization and future distribution of design and manufacturing facilities, the cooperation amongst partners is becoming more challenging due to the fact that the design process tends to be sequential and requires communication networks for planning design activities and/or a great deal of travel to/from designers' workplaces. In a virtual environment, teams of designers work together and use the Internet/Intranet for communication. The design is a multi-disciplinary task that involves several stages. These stages include input data analysis, conceptual design, basic structural design, detail design, production design, manufacturing processes analysis, and documentation. As a result, the virtual team, normally, is very changeable in term of designers' participation. Moreover, the environment itself changes over time. This leads to a potential increase in the number of design. A methodology of Intelligent Distributed Mismatch Control (IDMC) is proposed to alleviate some of the related difficulties. This thesis looks at the Intelligent Distributed Mismatch Control, in the context of the European Aerospace Industry, and suggests a methodology for a conceptual framework based on a multi-agent architecture. This multi-agent architecture is a kernel of an Intelligent Distributed Mismatch Control System (IDMCS) that aims at ensuring that the overall design is consistent and acceptable to all participating partners. A Methodology of Intelligent Distributed Mismatch Control is introduced and successfully implemented to detect design mismatches in complex design environments. A description of the research models and methods for intelligent mismatch control, a taxonomy of design mismatches, and an investigation into potential applications, such as aerospace design, are presented. The Multi-agent framework for mismatch control is developed and described. Based on the methodology used for the IDMC application, a formal framework for a multi-agent system is developed. The Methods and Principles are trialed out using an Aerospace Distributed Design application, namely the design of an A340 wing box. The ontology of knowledge for agent-based Intelligent Distributed Mismatch Control System is introduced, as well as the distributed collaborative environment for consortium based projects

A practical assessment of network orientated load control for the intelligent network

The purpose of this thesis is to assess a new method of controlling load in Intelligent Networks (INs). This will be done through the analysis of experimentation results and comparison with existing methods of IN load control. This exercise will result in the investigation and validation of the proposed benefits being offered by this new methodology and the unveiling of its disadvantages. The methodology is known as network-orientated load control for the IN. Network-orientated load control is demonstrated using the MARINER Service Traffic Load Control System developed by the European Commission’s Advanced Communication, Technologies and Services (ACTS) Multi-Agent Architecture for Distributed Intelligent Network Load Control and Overload Protection (MARINER) Project. This system is shown to be a network-orientated load control application operating at the service level, built specifically for Intelligent Networks. Network-orientated load control is then assessed by deploying the MARINER System on a model of the IN, and running an exhaustive series of experiments. These experiments are structured to test the proposed benefits, limitations and disadvantages of networkorientated load control. The conclusions drawn from the results of these trials are then compared with existing IN load control characteristics, and used to make an assessment of network-orientated load control for the Intelligent Network

Distributed LQR control of multi-agent systems

The thesis develops optimal control methods for designing distributed cooperative control schemes in multi-agent networks. First, the model of a completely connected multi-agent network is presented, consisting of identical dynamically decoupled agents controlled by a centralized LQR (Linear Quadratic Regulator) based controller. The structure of the solution, as well as controller's spectral and robustness properties are presented. A special case of centralized control where the optimal solution for the whole network can be constructed from the solution of single agent LQR system is given. The problem is extended to distributed control where the special structure is imposed onto the information flow between agents and only local interaction is considered. A systematic method is given for computing the performance loss of various distributed control configurations relative to the performance of the optimal centralized controller. Necessary and sufficient conditions are derived for which a distributed control configuration pattern arising from the optimal centralized solution does not entail loss of performance if the initial state vector lies is a certain subspace of state-space which is identified. It is shown that these conditions are always satisfied for systems with communication/control networks corresponding to complete graphs with a single link removed. The procedure is extended for the purposes of analysing the performance loss of an arbitrary distributed configuration. Cost increase due to decentralisation is quantified by introducing three cost measures corresponding to the worst-case, best-case and average directions in which the initial state of the system lies. Finally, a cooperative scheme is presented for controlling arbitrary formations of low speed experimental UAVs (Unmanned Aerial Vehicles) based on a distributed LQR design methodology. Each UAV acts as an independent agent in the formation and its dynamics are described by a 6-DOF (six degrees-offreedom) nonlinear model. This is linearised for control design purposes around an operating point corresponding to straight flight conditions and simulated for longitudinal motion. It is shown that the proposed controller stabilises the overall formation and can control effectively the nonlinear multi-agent system. Also, it is illustrated via numerous simulations that the system provides reference tracking and that is robust to environmental disturbances such as nonuniform wind gusts acting on a formation of UAVs and to the loss of communication between two neighbouring UAVs

LQR distributed cooperative control of a formation of low-speed experimental UAVs

The paper presents a cooperative scheme for controlling arbitrary formations of low speed experimental UAVs based on a distributed LQR design methodology. Each UAV acts as an independent agent in the formation and its dynamics are described by a 6-DOF (degrees of freedom) nonlinear model. This is linearized for control design purposes around an operating point corresponding to straight flight conditions and simulated only for longitudinal motion. It is shown that the proposed controller stabilizes the overall formation and can control effectively the nonlinear multi-agent system. Also, it is shown via numerous simulations that the system provides reference tracking and that is robust to environmental disturbances such as nonuniform wind gusts acting on a formation of four UAVs and to the loss of communication between two neighbouring UAVs

Multi-Agent System Based Distributed Voltage Control in Distribution Systems

Distribution System is a standout among the most complex entities of the electric power grid. Moreover, voltage quality sustainability till customer premises, with the introduction of Distributed Generation (DG), is one of the most frenzied control areas. Previously, SCADA in cohesion with Wide Area Measurement Systems (WAMS) was a dependable control strategy, yet as the ever growing and complex distribution system is advancing towards the Smart Grids, control strategies are becoming more and more distributed in spite of the centralized one. A detailed literature review of the voltage control methods ranging from the centralized one to the fully distributed agent based control is conducted. In the light of the previous researches, a distributed voltage control based on Multi-Agent System is proposed, as the agents based control strategies, are becoming well known day by day, due to its autonomous control and decision making capacity. To make the proposed algorithm fully distributed, token transversal through the network and agents communication to remove voltage violation over least correspondence and measurements of the system, are utilized. Following instant voltage control at the load nodes, a penalty function is employed to keep the voltage value curve throughout the network as close as possible to the nominal, with minimum network losses and minimum voltage damage. The authentication of the devised control algorithm is acknowledged by utilizing a Greenfield distribution Network, which is based on the realistic loading data. Agents and the controlling logic are codded in Matlab ® programming software. A sensitivity analysis is performed based on DG penetration to have the complete overview of the proposed methodology. The principle objective of the technique is to keep the voltage value within the standard limit of ±10% of the nominal, at all load nodes while instantly utilizing voltage control entities like DGs, Static VAR Compensator (SVCs) and On-Load Tap Changer (OLTC). In addition, the optimization of network losses and voltage level close to nominal is to be accomplished by the penalty function implementation

A customizable multi-agent system for distributed data mining

We present a general Multi-Agent System framework for distributed data mining based on a Peer-to-Peer model. Agent protocols are implemented through message-based asynchronous communication. The framework adopts a dynamic load balancing policy that is particularly suitable for irregular search algorithms. A modular design allows a separation of the general-purpose system protocols and software components from the specific data mining algorithm. The experimental evaluation has been carried out on a parallel frequent subgraph mining algorithm, which has shown good scalability performances

A new model for solution of complex distributed constrained problems

In this paper we describe an original computational model for solving different types of Distributed Constraint Satisfaction Problems (DCSP). The proposed model is called Controller-Agents for Constraints Solving (CACS). This model is intended to be used which is an emerged field from the integration between two paradigms of different nature: Multi-Agent Systems (MAS) and the Constraint Satisfaction Problem paradigm (CSP) where all constraints are treated in central manner as a black-box. This model allows grouping constraints to form a subset that will be treated together as a local problem inside the controller. Using this model allows also handling non-binary constraints easily and directly so that no translating of constraints into binary ones is needed. This paper presents the implementation outlines of a prototype of DCSP solver, its usage methodology and overview of the CACS application for timetabling problems

An improved multi-agent simulation methodology for modelling and evaluating wireless communication systems resource allocation algorithms

Multi-Agent Systems (MAS) constitute a well known approach in modelling dynamical real world systems. Recently, this technology has been applied to Wireless Communication Systems (WCS), where efficient resource allocation is a primary goal, for modelling the physical entities involved, like Base Stations (BS), service providers and network operators. This paper presents a novel approach in applying MAS methodology to WCS resource allocation by modelling more abstract entities involved in WCS operation, and especially the concurrent network procedures (services). Due to the concurrent nature of a WCS, MAS technology presents a suitable modelling solution. Services such as new call admission, handoff, user movement and call termination are independent to one another and may occur at the same time for many different users in the network. Thus, the required network procedures for supporting the above services act autonomously, interact with the network environment (gather information such as interference conditions), take decisions (e.g. call establishment), etc, and can be modelled as agents. Based on this novel simulation approach, the agent cooperation in terms of negotiation and agreement becomes a critical issue. To this end, two negotiation strategies are presented and evaluated in this research effort and among them the distributed negotiation and communication scheme between network agents is presented to be highly efficient in terms of network performance. The multi-agent concept adapted to the concurrent nature of large scale WCS is, also, discussed in this paper