Problem-Solving Behaviours, Organisational Forms and the Complexity of Tasks

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Unification of the a priori inconsistencies checking among assembly constraints in assembly sequence planning.

International audienceSequence planning generation is an important problem in assembly line design. A good assembly sequence can help to reduce the cost and time of the manufacturing process. This paper focuses on assembly sequence planning (ASP) known as a hard combinatorial optimization problem. Although the ASP problem has been tackled via even more sophisticated optimization techniques, these techniques are often inefficient for proposing feasible assembly sequences that satisfy the assembly planners' preferences. This paper presents an approach that makes easier to check the validity of operations in assembly process. It is based on a model of the assembly planners' preferences by means of strategic constraints. It helps to check a priori the consistency of the assembly constraints (strategic an operative constraints) given by the assembly system designers before and while running an assembly plan generation algorithm. This approach reduces the solution space significantly

Chose the right mutation rate for better evolve combinational logic circuits

Evolvable hardware (EHW) is a developing field that applies evolutionary algorithm (EA) to automatically design circuits, antennas, robot controllers etc. A lot of research has been done in this area several different EAs have been introduced to tackle numerous problems, as scalability, evolvability etc. However every time a specific EA is chosen for solving a particular task, all its components, such as population size, initialization, selection mechanism, mutation rate, and genetic operators, should be selected in order to achieve the best results. In the last three decade the selection of the right parameters for the EA’s components for solving different “testproblems” has been investigated. In this paper the behaviour of mutation rate for designing logic circuits, which has not been done before, has been deeply analyzed. The mutation rate for an EHW system modifies the number of inputs of each logic gates, the functionality (for example from AND to NOR) and the connectivity between logic gates. The behaviour of the mutation has been analyzed based on the number of generations, genotype redundancy and number of logic gates for the evolved circuits. The experimental results found provide the behaviour of the mutation rate during evolution for the design and optimization of simple logic circuits. The experimental results propose the best mutation rate to be used for designing combinational logic circuits. The research presented is particular important for those who would like to implement a dynamic mutation rate inside the evolutionary algorithm for evolving digital circuits. The researches on the mutation rate during the last 40 years are also summarized.Dr Hemantha Kodikara-Arachch

Adaptive electronic throttle control of road vehicles

Previous work at Loughborough University has clearly demonstrated the gains that can be made in overall performance feel through the manipulation of the engine demand map. In particular the studies have shown the importance of the throttle progression, and the relationship between throttle pedal progression and wide-open throttle performance. These studies concluded with a clear set of design guidelines for the initial set up of a vehicle to achieve optimal performance feel for a population of drivers. These studies also highlighted the wide variation in response from different subjects indicating that further gains in satisfaction could be achieved if the demand map were optimised for each driver. Failing to provide optimum performance feel for the driver can result in reduced satisfaction, in turn making vehicles less saleable and more difficult to drive through the increased concentration needed to drive the vehicle. This thesis attempts to solve the problem of demographic and driver preference variation, by developing an electronic throttle system that adapts to driver preference. [Continues.

Freight transport modal choice in North West England's Atlantic Gateway

Overuse of the road network has led to greater levels of congestion, elevated levels of road surface wear and tear and an increase in transport related air pollution. When taken in combination with the failure of attempts to balance modal split the road network’s continuing slide towards breaking point seems to be beyond question. However, circumstances have conspired to present one particular region of England with a tabula rasa for the development of new policies to influence the modal split of freight transportation. England’s economy is currently based around a London-centric model. The current move towards developing what has become known as a Northern Powerhouse is aimed at rebalancing the economy of the nation for the betterment of all of its citizens. The Atlantic Gateway is an integral part of these efforts. The devolution of powers and responsibilities from national government to regional authorities may provide an opportunity for positive change the likes of which has not be seen in the North of England since the beginning of the industrial revolution. Different regions are influenced by their own geographical and infrastructure constraints. Devolution ensures that decisions are made locally and are therefore more able to meet local needs. A greater understanding of what influences modal choice within the Atlantic Gateway allows local policy makers to make better informed decisions on how to accommodate the increasing levels of freight transportation on the existing local transport infrastructure. Two different multi-criteria decision making analysis tools are utilised in this study. The first model uses the Analytic Hierarchy Process (AHP) to determine the weights of a range of criteria identified as influencing modal choice. The second model combines AHP with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) to allow the modes of transport under consideration to be ranked. This AHP-TOPSIS approach was adopted to address the limited data made available by the freight transportation industry in support of this research and the inadequacy of the data which is publicly available from mainstream sources. With billions of Pounds having been spent over many years to balance modal split it was disappointing to find that today, in the North West of England, road is still, by far, the preferred mode for transporting freight. The margin by which road leads the other modes within this geographical region shows the degree to which modal shift policy has so far failed. It also shows the amount of work needed to be done if modal shift is to be delivered in the future

Simulation product fidelity: a qualitative & quantitative system engineering approach

La modélisation informatique et la simulation sont des activités de plus en plus répandues lors de la conception de systèmes complexes et critiques tels que ceux embarqués dans les avions. Une proposition pour la conception et réalisation d'abstractions compatibles avec les objectifs de simulation est présentée basés sur la théorie de l'informatique, le contrôle et le système des concepts d'ingénierie. Il adresse deux problèmes fondamentaux de fidélité dans la simulation, c'est-à-dire, pour une spécification du système et quelques propriétés d'intérêt, comment extraire des abstractions pour définir une architecture de produit de simulation et jusqu'où quel point le comportement du modèle de simulation représente la spécification du système. Une notion générale de cette fidélité de la simulation, tant architecturale et comportementale, est expliquée dans les notions du cadre expérimental et discuté dans le contexte des abstractions de modélisation et des relations d'inclusion. Une approche semi-formelle basée sur l'ontologie pour construire et définir l'architecture de produit de simulation est proposée et démontrée sur une étude d'échelle industrielle. Une approche formelle basée sur le jeu théorique et méthode formelle est proposée pour différentes classes de modèles des systèmes et des simulations avec un développement d'outils de prototype et cas des études. Les problèmes dans la recherche et implémentation de ce cadre de fidélité sont discutées particulièrement dans un contexte industriel.In using Modeling and Simulation for the system Verification & Validation activities, often the difficulty is finding and implementing consistent abstractions to model the system being simulated with respect to the simulation requirements. A proposition for the unified design and implementation of modeling abstractions consistent with the simulation objectives based on the computer science, control and system engineering concepts is presented. It addresses two fundamental problems of fidelity in simulation, namely, for a given system specification and some properties of interest, how to extract modeling abstractions to define a simulation product architecture and how far does the behaviour of the simulation model represents the system specification. A general notion of this simulation fidelity, both architectural and behavioural, in system verification and validation is explained in the established notions of the experimental frame and discussed in the context of modeling abstractions and inclusion relations. A semi-formal ontology based domain model approach to build and define the simulation product architecture is proposed with a real industrial scale study. A formal approach based on game theoretic quantitative system refinement notions is proposed for different class of system and simulation models with a prototype tool development and case studies. Challenges in research and implementation of this formal and semi-formal fidelity framework especially in an industrial context are discussed