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  • 1.
    Arjomandi Rad, Mohammad
    et al.
    Department of Industrial and Materials Science, Chalmers University of Technology, Göteborg, Sweden.
    Cenanovic, Mirza
    Department of Product Development, Production and Design, Jönköping University, Sweden.
    Salomonsson, Kent
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Image regression-based digital qualification for simulation-driven design processes, case study on curtain airbag2023Inngår i: Journal of engineering design (Print), ISSN 0954-4828, E-ISSN 1466-1837, Vol. 34, nr 1, s. 1-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Today digital qualification tools are part of many design processes that make them dependent on long and expensive simulations, leading to limited ability in exploring design alternatives. Conventional surrogate modelling techniques depend on the parametric models and come short in addressing radical design changes. Existing data-driven models lack the ability in dealing with the geometrical complexities. Thus, to address the resulting long development lead time problem in the product development processes and to enable parameter-independent surrogate modelling, this paper proposes a method to use images as input for design evaluation. Using a case study on the curtain airbag design process, a database consisting of 60,000 configurations has been created and labelled using a method based on dynamic relaxation instead of finite element methods. The database is made available online for research benchmark purposes. A convolutional neural network with multiple layers is employed to map the input images to the simulation output. It was concluded that the showcased data-driven method could reduce digital testing and qualification time significantly and contribute to real-time analysis in product development. Designers can utilise images of geometrical information to build real-time prediction models with acceptable accuracy in the early conceptual phases for design space exploration purposes.

    Fulltekst (pdf)
    fulltext
  • 2.
    Athanasopoulos, George
    et al.
    Monash University, VIC 3145, Australia.
    Hyndman, Rob J.
    Monash University, VIC 3800, Australia.
    Kourentzes, Nikolaos
    Högskolan i Skövde, Institutionen för informationsteknologi. Högskolan i Skövde, Forskningsmiljön Informationsteknologi.
    Panagiotelis, Anastasios
    The University of Sydney, NSW 2006, Australia.
    Forecast reconciliation: A review2024Inngår i: International Journal of Forecasting, ISSN 0169-2070, E-ISSN 1872-8200, Vol. 40, nr 2, s. 430-456Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Collections of time series formed via aggregation are prevalent in many fields. These are commonly referred to as hierarchical time series and may be constructed cross-sectionally across different variables, temporally by aggregating a single series at different frequencies, or even generalised beyond aggregation as time series that respect linear constraints. When forecasting such time series, a desirable condition is for forecasts to be coherent: to respect the constraints. The past decades have seen substantial growth in this field with the development of reconciliation methods that ensure coherent forecasts and improve forecast accuracy. This paper serves as a comprehensive review of forecast reconciliation and an entry point for researchers and practitioners dealing with hierarchical time series. The scope of the article includes perspectives on forecast reconciliation from machine learning, Bayesian statistics and probabilistic forecasting, as well as applications in economics, energy, tourism, retail demand and demography. 

    Fulltekst (pdf)
    fulltext
  • 3.
    Billing, Erik
    et al.
    Umeå universitet, Institutionen för datavetenskap.
    Servin, Martin
    Institutionen för fysik, Umeå universitet.
    Composer: A prototype multilingual model composition tool2013Inngår i: MODPROD2013: 7th MODPROD Workshop on Model-Based Product Development / [ed] Peter Fritzson, Umeå: Umeå universitet , 2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Facing the task to design, simulate or optimize a complex system itis common to find models and data for the system expressed in differentformats, implemented in different simulation software tools. When a newmodel is developed, a target platform is chosen and existing componentsimplemented with different tools have to be converted. This results inunnecessary work duplication and lead times. The Modelica languageinitiative [2] partially solves this by allowing developers to move modelsbetween different tools following the Modelica standard. Another possi-bility is to exchange models using the Functional Mockup Interface (FMI)standard that allows computer models to be used as components in othersimulations, possibly implemented using other programming languages[1]. With the Modelica and FMI standards entering development, there isneed for an easy-to-use tool that supports design, editing and simulationof such multilingual systems, as well as for retracting system informationfor formulating and solving optimization problems.A prototype solution for a graphical block diagram tool for design, edit-ing, simulation and optimization of multilingual systems has been createdand evaluated for a specific system. The tool is named Composer [3].The block diagram representation should be generic, independent ofmodel implementations, have a standardized format and yet support effi-cient handling of complex data. It is natural to look for solutions amongmodern web technologies, specifically HTML5. The format for represent-ing two dimensional vector graphics in HTML5 is Scalable Vector Graphics(SVG). We combine the SVG format with the FMI standard. In a firststage, we take the XML-based model description of FMI as a form for de-scribing the interface for each component, in a language independent way.Simulation parameters can also be expressed on this form, and integratedas metadata into the SVG image. 

    The prototype, using SVG in conjunction with FMI, is implementedin JavaScript and allow creation and modification of block diagrams directly in the web browser. Generated SVG images are sent to the serverwhere they are translated to program code, allowing the simulation ofthe dynamical system to be executed using selected implementations. Analternative mode is to generate optimization problem from the systemdefinition and model parameters. The simulation/optimization result is 

    returned to the web browser where it is plotted or processed using otherstandard libraries.The fiber production process at SCA Packaging Obbola [4] is used asan example system and modeled using Composer. The system consists oftwo fiber production lines that produce fiber going to a storage tank [5].The paper machine is taking fiber from the tank as needed for production.A lot of power is required during fiber production and the purpose of themodel was to investigate weather electricity costs could be reduced byrescheduling fiber production over the day, in accordance with the electricity spot price. Components are implemented for dynamical simulationusing OpenModelica and for discrete event using Python. The Python implementation supports constraint propagation between components andoptimization over specified variables. Each component is interfaced as aFunctional Mock-up Unit (FMU), allowing components to be connectedand properties specified in language independent way. From the SVGcontaining the high-level system information, both Modelica and Pythoncode is generated and executed on the web server, potentially hosted ina high performance data center. More implementations could be addedwithout modifying the SVG system description.We have shown that it is possible to separate system descriptions onthe block diagram level from implementations and interface between thetwo levels using FMI. In a continuation of this project, we aim to integratethe FMI standard also for co-simulation, such that components implemented in different languages could be used together. One open questionis to what extent FMUs of the same component, but implemented withdifferent tools, will have the same model description. For the SVG-basedsystem description to be useful, the FMI model description must remainthe same, or at least contain a large overlap, for a single component implemented in different languages. This will be further investigated in futurework.

  • 4.
    Brownlee, Alexander E. I.
    et al.
    University of Stirling, United Kingdom.
    Swan, Jerry
    University of York, United Kingdom.
    Senington, Richard
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Kocsis, Zoltan A.
    The University of Manchester, United Kingdom.
    Conflict-free routing of multi-stop warehouse trucks2020Inngår i: Optimization Letters, ISSN 1862-4472, E-ISSN 1862-4480, Vol. 14, nr 6, s. 1459-1470Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The recent interest in greater vehicular autonomy for factory and warehouse automation has stimulated research in conflict-free routing: a challenging network routing problem in which vehicles may not pass each other. Motivated by a real-world case study, we consider one such application: truck movements in a tightly constrained warehouse. We propose an extension of an existing conflict-free routing algorithm to consider multiple stopping points per route. A high level metaheuristic is applied to determine the route construction and assignment of vehicles to routes. 

    Fulltekst (pdf)
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  • 5.
    Chokhachian, Ata
    et al.
    The Technical University of Munich, Germany.
    Hooshyar Yousefi, Bahram
    The Vienna University of Technology, Austria.
    Toward Object-Oriented Knowledge-Based Parametric Design Thinking2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The parameter, as a variable of differentiation, defines the limits and boundaries of a system and the conditions for its operation. It is through parameters that we are able to produce certain logical relationships between different parts in design procedure. Fundamental to this, however, is the assumption that the object or phenomenawe are modeling is in fact quantifiable. Advances in computational processing have promoted our capacity, and thus faith in the ability, to systematically classify and itemize the world around us. The Parametricism Manifesto concerns itself solely with appearance and arejection of the term Parametricism in certain levels could be clearly visible within the contemporary discourse of Object-oriented and knowledge-based approach that reflects the cognitive attitude of the designer/architect regarding the object-oriented reasoning and analogy. Moreover, instead of having parametric manifestation alternate terms such as digitally intelligent design , algorithmic design, object oriented design , Context-oriented design , Parametric thinking , and even postparametric design have arisen and could be used to describe this vastly differentiated field. What these design theories do share, however, is a predilection and belief in the tool. Nowadays the project fields are information-rich contexts and the tool sets for design are able to interpret, analyze, synthesize and realize these data into the design procedure. This research mainly aims to uncover potentialities of the existing enablers and assistive technologies in context-oriented design in order to have more content-embedded architectural conceptualization solutions.

  • 6.
    Dansarie, Marcus
    Högskolan i Skövde, Institutionen för informationsteknologi. Högskolan i Skövde, Forskningsmiljön Informationsteknologi. Swedish Defence University, Stockholm, Sweden.
    sboxgates: A program for finding low gate count implementations of S-boxes2021Inngår i: Journal of Open Source Software, E-ISSN 2475-9066, Vol. 6, nr 62, s. 1-3, artikkel-id 2946Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    S-boxes are often the only nonlinear components in modern block ciphers. They are commonly selected to comply with very specific criteria in order to make a cipher secure against, for example, linear and differential attacks. An M x N S-box can be thought of as a lookup table that relates an M-bit input value to an N-bit output value, or as a set of N boolean functions of M variables (Schneier, 1996).

    Although cipher specifications generally describe S-boxes using their lookup tables, they can also be described as boolean functions or logic gate circuits. sboxgates, which is presented here, finds equivalent logic gate circuits for S-boxes, given their lookup table specification. Generated circuits are output in a human-readable XML format. The software can convert the output files into C or CUDA (a parallel computing platform for Nvidia GPUs) source code. The generated circuits can also be converted to the DOT graph description language for visualization with Graphviz (Ellson et al., 2002).

    Fulltekst (pdf)
    fulltext
  • 7.
    Deb, Kalyanmoy
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle. Högskolan i Skövde, Forskningscentrum för Virtuella system. Indian Institute of Technology, Kanpur, Uttar Pradesh, India / Aalto University School of Economics , Finland.
    Datta, Rituparna
    ndian Institute of Technology, Kanpur, Uttar Pradesh, India.
    A bi-objective constrained optimization algorithm using a hybrid evolutionary and penalty function approach2013Inngår i: Engineering optimization (Print), ISSN 0305-215X, E-ISSN 1029-0273, Vol. 45, nr 5, s. 503-527Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Constrained optimization is a computationally difficult task, particularly if the constraint functions are nonlinear and non-convex. As a generic classical approach, the penalty function approach is a popular methodology which degrades the objective function value by adding a penalty proportional to the constraint violation. However, the penalty function approach has been criticized for its sensitivity to the associated penalty parameters. Since its inception, evolutionary algorithms have been modified in various ways to solve constrained optimization problems. Of them, the recent use of a bi-objective evolutionary algorithm in which the minimization of the constraint violation is included as an additional objective has received significant attention. In this article, a combination of a bi-objective evolutionary approach with the classical penalty function methodology is proposed, in a manner complementary to each other. The evolutionary approach provides an appropriate estimate of the penalty parameter, while the solution of an unconstrained penalized function by a classical method induces a convergence property to the overall hybrid algorithm. The working of the procedure on a number of standard numerical test problems and an engineering design problem is demonstrated. In most cases, the proposed hybrid methodology is observed to take one or more orders of magnitude fewer function evaluations to find the constrained minimum solution accurately than some of the best reported existing methodologies.

  • 8.
    Endrias, Dawit H.
    et al.
    TS Tech Canada Inc..
    Feng, Hsi-Yung
    The University of British Columbia.
    Ma, Ji
    The University of British Columbia.
    Wang, Lihui
    Högskolan i Skövde, Institutionen för teknik och samhälle. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Taher, M. Abu
    The University of Western Ontario.
    A combinatorial optimization approach for evaluating minimum-zone spatial straightness errors2012Inngår i: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 45, nr 5, s. 1170-1179Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a new and robust approach for the accurate evaluation of minimumzone spatial straightness error from a set of coordinate measurement data points. The algorithm iteratively searches for the specific data points that define the minimum bound of the spatial straightness zone using combinatorial optimization. It is based on the fact that the minimum circumscribed cylinder of a point set, which is equivalent to the minimum spatial straightness zone of the measurement data, will pass through three, four, or five of the data points that constitute the convex hull vertices of the entire data set. Computed results have shown that although the presented approach may lead to increased computational time, it is robust and able to construct the exact minimum circumscribed cylinder for a given point set. The minimum-zone spatial straightness error can thus be evaluated with the best possible accuracy. The advantage of the presented algorithm is demonstrated via comparison with published computed results of existing algorithms.

  • 9.
    Eskandari, Hamidreza
    et al.
    Advanced Simulation Lab, Department of Industrial Engineering, Tarbiat Moalem University, Tehran, Iran.
    Mahmoodi, Ehsan
    Advanced Simulation Lab, Department of Industrial Engineering, Tarbiat Moalem University, Tehran, Iran.
    Fallah, Hamed
    Advanced Simulation Lab, Department of Industrial Engineering, Tarbiat Moalem University, Tehran, Iran.
    Geiger, Christopher D.
    Department of Industrial Engineering and Management Systems, University of Central Florida, Orlando, FL, USA.
    Performance analysis of comercial simulation-based optimization packages: OptQuest and Witness Optimizer2011Inngår i: Proceedings of the 2011 Winter Simulation Conference (WSC) / [ed] S. Jain; R. R. Creasey; J. Himmelspach; K. P. White; M. Fu, IEEE, 2011, s. 2358-2368Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective of this study is to evaluate and compare two commercial simulation-based optimization packages, OptQuest and Witness Optimizer, to determine their relative performance based on the quality of obtained solutions in a reasonable computational effort. Two well-known benchmark problems, the pull manufacturing system and the inventory system, are used to evaluate and compare the performance of OptQuest and Witness Optimizer. Significant validation efforts are made to ensure that simulation models developed in Arena and Witness are identical. The experimental results indicate that both optimization packages have good performance on the given problems. Both packages found near-global optimal (or satisfactory) solutions in an acceptable computation time.

  • 10.
    Gundeboina, Saidulu
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Finite Element Analysis of a Washing Machine Cylinder2010Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis a finite element model of a household washing machine cylinder is built and analysed in ABAQUS 6.9-2. The aim is to help Asko appliances in conducting similar analysis for future manufacturing of high capacity cylinders by reducing experimentation. The analysis is mainly concerned with an evenly distributed load at a constant angular velocity. The load is applied with the help of lead plates instead of clothes. The cylinder is loaded with three thin (2 mm) lead plates weighing 2 kg each. The plates with dimensional 370x240x2 mm are mounted with one strip of double sided foam tape inside the cylinder. To estimate the behavior of the cylinder the strains are measured when the cylinder is rotating at 1620 and 2200 revolution per minute (rpm). To validate the model the numerical analyses are compared with experimental results. The results clearly show that the numerical strain values fit with experimental strain values.

    Fulltekst (pdf)
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  • 11.
    Hansbo, Peter
    et al.
    Department of Mechanical Engineering, Jönköping University, Sweden.
    Rashid, Asim
    Department of Mechanical Engineering, Jönköping University, Sweden.
    Salomonsson, Kent
    Department of Mechanical Engineering, Jönköping University, Sweden.
    Least-squares stabilized augmented Lagrangian multiplier method for elastic contact2016Inngår i: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925, Vol. 116, s. 32-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a stabilized augmented Lagrange multiplier method for the finite element solution of small deformation elastic contact problems. We limit ourselves to friction-free contact with a rigid obstacle, but the formulation is readily extendable to more complex situations. © 2016 Elsevier B.V.

  • 12.
    Hansbo, Peter
    et al.
    Department of Mechanical Engineering, Jönköping University, Sweden.
    Salomonsson, Kent
    Department of Mechanical Engineering, Jönköping University, Sweden.
    A discontinuous Galerkin method for cohesive zone modelling2015Inngår i: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925, Vol. 102-103, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose a discontinuous finite element method for small strain elasticity allowing for cohesive zone modeling. The method yields a seamless transition between the discontinuous Galerkin method and classical cohesive zone modeling. Some relevant numerical examples are presented. © 2015 Elsevier B.V.

  • 13.
    Lowe, Robert
    University of Hertfordshire.
    The Evolution of Affective Displays and Related Strategies2007Doktoravhandling, monografi (Annet vitenskapelig)
  • 14.
    Lowe, Robert
    et al.
    Adaptive Systems Research Group, School of Computer Science, University of Hertfordshire.
    Cañamero, Lola
    Adaptive Systems Research Group, School of Computer Science, University of Hertfordshire.
    Nehaniv, Chrystopher L.
    Adaptive Systems Research Group, School of Computer Science, University of Hertfordshire.
    Polani, Daniel
    Adaptive Systems Research Group, School of Computer Science, University of Hertfordshire.
    The Evolution of Affect-Related Displays, Recognition and Related Strategies2004Inngår i: Artificial Life IX: Proceedings of the Ninth International Conference on the Simulation and Synthesis of Living Systems / [ed] Jordan Pollack, Mark Bedau, Phil Husbands, Takashi Ikegami, & Richard A. Watson, MIT Press, 2004, s. 176-181Konferansepaper (Fagfellevurdert)
  • 15.
    Lowe, Robert
    et al.
    Adaptive Systems Research Group, Faculty of Engineering and Information Sciences, University of Hertfordshire.
    Cañamero, Lola
    Adaptive Systems Research Group, Faculty of Engineering and Information Sciences, University of Hertfordshire.
    Nehaniv, Chrystopher
    Adaptive Systems Research Group, Faculty of Engineering and Information Sciences, University of Hertfordshire.
    Polani, Daniel
    Adaptive Systems Research Group, Faculty of Engineering and Information Sciences, University of Hertfordshire.
    Strategies in the Evolution of Affect Related Displays and Recognition2004Inngår i: The Logic of Artificial Life: Abstracting And Synthesizing The Principles Of Living Systems: Proceedings of the 6th German Workshop on Artificial Life, April 14-16, 2004, Bamberg, Germany, IOS Press, 2004, s. 89-95Konferansepaper (Fagfellevurdert)
  • 16.
    Lowe, Robert
    et al.
    Adaptive Systems Research Group, Faculty of Engineering and Information Sciences, University of Hertfordshire, United Kingdom.
    Polani, Daniel
    Adaptive Systems Research Group, Faculty of Engineering and Information Sciences, University of Hertfordshire, United Kingdom.
    Preventing bluff agent invasions in honest societies2003Inngår i: Advances in Artificial Life: 7th European Conference, ECAL 2003, Dortmund, Germany, September 14-17, 2003. Proceedings / [ed] Wolfgang Banzhaf, Jens Ziegler, Thomas Christaller, Peter Dittrich, Jan T. Kim, Berlin, Heidelberg: Springer, 2003, s. 118-127Konferansepaper (Fagfellevurdert)
  • 17.
    Mohammad, Arjomandi Rad
    et al.
    Department of Product Development, School of Engineering, Jönköping University, Sweden.
    Salomonsson, Kent
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Cenanovic, Mirza
    Department of Product Development, School of Engineering, Jönköping University, Sweden.
    Balague, Henrik
    Autoliv AB, Vårgårda, Sweden.
    Raudberget, Dag
    Department of Product Development, School of Engineering, Jönköping University, Sweden.
    Stolt, Roland
    Department of Product Development, School of Engineering, Jönköping University, Sweden.
    Correlation-based feature extraction from computer-aided design, case study on curtain airbags design2022Inngår i: Computers in industry (Print), ISSN 0166-3615, E-ISSN 1872-6194, Vol. 138, artikkel-id 103634Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many high-level technical products are associated with changing requirements, drastic design changes, lack of design information, and uncertainties in input variables which makes their design process iterative and simulation-driven. Regression models have been proven to be useful tools during design, altering the resource-intensive finite element simulation models. However, building regression models from computer-aided design (CAD) parameters is associated with challenges such as dealing with too many parameters and their low or coupled impact on studied outputs which ultimately requires a large training dataset. As a solution, extraction of hidden features from CAD is presented on the application of volume simulation of curtain airbags concerning geometric changes in design loops. After creating a prototype that covers all aspects of a real curtain airbag, its CAD parameters have been analyzed to find out the correlation between design parameters and volume as output. Next, using the design of the experiment latin hypercube sampling method, 100 design samples are generated and the corresponding volume for each design sample was assessed. It was shown that selected CAD parameters are not highly correlated with the volume which consequently lowers the accuracy of prediction models. Various geometric entities, such as the medial axis, are used to extract several hidden features (referred to as sleeping parameters). The correlation of the new features and their performance and precision through two regression analyses are studied. The result shows that choosing sleeping parameters as input reduces dimensionality and the need to use advanced regression algorithms, allowing designers to have more accurate predictions (in this case approximately 95%) with a reasonable number of samples. Furthermore, it was concluded that using sleeping parameters in regressionbased tools creates real-time prediction ability in the early development stage of the design process which could contribute to lower development lead time by eliminating design iterations. 

    Fulltekst (pdf)
    fulltext
  • 18.
    Pettersson, Kerstin
    Högskolan i Skövde, Institutionen för vård och natur.
    Växelverkan mellan intuitiva idéer och formella resonemang: En fallstudie av universitetsstudenters arbete med en analysuppgift2008Inngår i: Nordisk matematikkdidaktikk, ISSN 1104-2176, Vol. 13, nr 1, s. 29-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [sv]

    Studiens syfte är att visa hur en växelverkan mellan intuitiva idéer och formella resonemang kan gestalta sig i en problemlösningsprocess. Studien visar att universitetsstudenter redan under sitt första år av matematikstudier förmår utnyttja en sådan växelverkan. En grupp studenter har arbetat med en analysuppgift som berör begreppen funktion och derivata samt inkluderar ett induktionsbevis. Studenterna utnyttjar i den kreativa processen intuitiva idéer och formella resonemang i ett dynamiskt samspel. Växlingarna har ett flertal funktioner: att kontrollera intuitiva uppfattningar, att skaffa nya utgångspunkter för problemlösningsprocessen, att ekonomisera resonemang och att driva arbetet vidare.

  • 19.
    Smedberg, Henrik
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Knowledge discovery for interactive decision support and knowledge-driven optimization2023Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Multi-objective optimization involves the simultaneous optimization of several objective functions. In real-world problems, these objectives are often in conflict, giving rise to trade-offs in the optimal solutions from the optimization process. All these solutions are equally viable, with no single solution being better or worse than the others. Typically, decision makers have certain preferences that guide the selection of a final solution for practical implementation. While most multi-criteria decision analysis methods focus on the performance of solutions in the objective space, it is important to note that practically relevant knowledge is often found in the design space. Access to this knowledge can provide decision makers with meaningful insights into the problem and the optimization process, leading to more informed decision-making.

    This thesis develops and employs methods for knowledge discovery in the context of multi-objective optimization. By emphasizing explicit knowledge representations, this thesis investigates how extracted knowledge can be processed and presented to decision-makers in an interactive manner for insightful decision support. This thesis also explores how extracted knowledge from preferred solutions can be integrated into the algorithms or the multi-objective optimization problem itself, to improve the convergence behavior of optimization algorithms. This approach, called Knowledge-Driven Optimization (KDO), can be implemented either offline or online. Offline KDO involves incorporating knowledge obtained from previous optimization runs into future problem scenarios of a similar nature, restricting the search process to preferred regions of the objective space. A main challenge with such approaches is the storage and retrieval of relevant past knowledge, as well as modifications to the optimization problem formulation. In contrast, online KDO involves integrating knowledge discovery methods with optimization algorithms and utilizing the knowledge obtained during their runtime to enhance the search process, driving algorithms towards better convergence in preferred regions of the objective space. This approach necessitates the development of new search operators capable of incorporating and exploiting various forms of knowledge.

    In both offline and online KDO, the veracity and accuracy of the extracted knowledge are critical factors. The thesis validates the effectiveness of the developed methods using various benchmark and engineering optimization test problems, and use-cases from the manufacturing industry. A particular focus is given to generating explicit knowledge that is both meaningful to human decision makers, and can easily be processed algorithmically. The main contributions of this thesis are methods for discovering relevant knowledge about the convergence characteristics of problems, a decision support system for interactive knowledge discovery, and algorithms for realizing both offline and online KDO by incorporating knowledge into the optimization process.

    Fulltekst (pdf)
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  • 20.
    Smedberg, Henrik
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    A Modular Knowledge-Driven Mutation Operator for Reference-Point Based Evolutionary Algorithms2022Inngår i: IEEE Congress of Evolutionary Computation, CEC - Conference Proceedings, IEEE, 2022Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Although an entire frontier of Pareto-optimal solutions exists for multi-objective optimization problems, in practice, decision makers are often only interested in a small subset of these solutions, called the region of interest. Specialized optimizers, such as reference-point based evolutionary algorithms, exist that can focus the search to only find solutions inside this region of interest. These algorithms typically only modify the selection mechanism of regular multi-objective optimizers to preferentially select solutions that conform to the reference point. However, a more effective search may be performed by additionally modifying the variation mechanism of the optimizers, namely the crossover and the mutation operators, to preferentially generate solutions conforming to the reference point. In this paper, we propose a modular mutation operator that uses a recent knowledge discovery technique to first find decision rules unique to the preferred solutions in each generation. These rules are then used to build an empirical distribution in the decision space that can be sampled to generate new mutated solutions which are more likely to be closer to the preferred solutions. The operator is modular in the sense that it can be used with any existing reference-point based evolutionary algorithm by simply replacing the mutation operator. We incorporate the proposed knowledge-driven mutation operator into three such algorithms, and through benchmark test problems up to 10 objectives, demonstrate that their performance improves significantly in the majority of cases according to two different performance indicators. 

  • 21.
    Smedberg, Henrik
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Finding Influential Variables in Multi-Objective optimization Problems2020Inngår i: 2020 IEEE Symposium Series on Computational Intelligence (SSCI), IEEE, 2020, s. 173-180Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of evolutionary algorithms for solving multi-objective optimization problems leaves the decision makers with a set of Pareto-optimal solutions to be considered in their decision making. Multi-objective optimization problems offer two spaces for a decision maker to analyze, the decision space and the objective space. In the literature, most of the focus has been on analyzing the objective space, however, in this paper, two procedures are presented for analyzing the decision space by identifying the variables that predominantly influence the structure of the objective space. Both procedures employ a recently proposed rule mining approach, which is used to find significant rules in terms of the variables. The rules are then combined and an influence score is calculated. The method is demonstrated on four problems, two scalable test problems (DTLZ2 and WFG2) with cases of three, five and seven objectives, one engineering design problem and one simulation-based optimization problem. The experiments show that the proposed approach is able to identify influential variables in most problem cases. 

  • 22.
    Smedberg, Henrik
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Ng, Amos H. C.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Knowledge-Driven Multi-Objective Optimization Using Variable ImportanceManuskript (preprint) (Annet vitenskapelig)
  • 23.
    Smedberg, Henrik
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Riveiro, Maria
    Högskolan i Skövde, Institutionen för informationsteknologi. Högskolan i Skövde, Forskningsmiljön Informationsteknologi. Jönköping University.
    Ng, Amos H. C.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningsmiljön Virtuell produkt- och produktionsutveckling.
    Mimer: A web-based tool for knowledge discovery in multi-criteria decision support2023Inngår i: IEEE Computational Intelligence Magazine, ISSN 1556-603X, E-ISSN 1556-6048Artikkel i tidsskrift (Annet vitenskapelig)
1 - 23 of 23
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