| 15031. |
- Lindroth, Peter, 1979
(författare)
-
Product Configuration from a Mathematical Optimization Perspective
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The optimal truck configuration for a certain customer is very specific and depends on for what transport mission and in which operating environment the truck is to be used. In addition, the customers normally specify other feature requirements ranging from visual appearance to advanced driver support systems. For this reason, the truck configurations that are made available for the customers are highly specialized. To achieve this in a cost efficient way, the manufacturer must be able to produce these configurations with a limited set of technical solutions. This is done by the use of a common architecture, in which technology is shared such that the same parts are used in different combinations, leading to a relatively small number of parts but a large number of possible configurations. This thesis presents an approach to the configuration problem by analyzing it from a mathematical optimization perspective. By assuming that a truck can be described by a number of quality measures, which different customers may appreciate differently, the problem of deciding on a good product offer can naturally be formulated within a multi-objective optimization framework. The areas within product development in which mathematical optimization can be applied are many and most often fundamentally different. In this thesis several subproblems of the whole product development problem are formulated in mathematical terms, and in the appended papers, the resulting mathematical models are considered in generalized forms. As established in the different papers, not just one optimization discipline is relevant in the product development context. The disciplines considered include multi-objective optimization, clustering, robust optimization, continuous global optimization, and nonlinear integer programming with an extension to a special type of non-sortable discrete variables. For a large number of objectives-typical in many real-world applications-multi-objective optimization becomes cumbersome; the first appended paper provides a method for problem reduction such that the representation of the Pareto optimal set is kept as accurate as possible. The second paper considers a simplification of the configuration problem of finding appropriate sets of technical solutions that are to be combined into configurations, by assuming that the decision variables are continuous and box-constrained. Clearly, real-world problems often involve uncertainties in models and/or data. In the third appended paper, a new measure of robustness of solutions to multi-objective optimization problem is developed. The preferences of the decision maker are estimated by an utility function on which the robustness measure is based. In the fourth appended paper, optimization with respect to a type of non-sortable discrete variables is addressed. Theoretical and methodological investigations are performed, and by a reformulation of the problems as nonlinear integer programming problems mathematical optimization techniques are shown to be applicable. In the last appended paper, we explore a new principle for continuous global optimization of computationally expensive functions by, for each new function evaluation, minimizing the resulting worst-case optimality gap. The main contribution of this thesis is the interpretation and formulation of a product development problem, including subproblems, in a mathematical optimization framework. The thesis has been written in close cooperation with Volvo 3P.
|
|
| 15032. |
- Lindroth, Peter, 1979
(författare)
-
Product Configuration with respect to Multiple Criteria - a Mathematical Programming Approach
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The trend in the market for trucks is that highly specialized configurations are made available for the customers and that only a few completely identical configurations are manufactured. One reason for this development is that the optimal truck configuration for a certain customer is very specific and depending on, e.g., the environment in which the truck is to be used and for what transport mission. To achieve reasonable cost levels the manufacturer must be able to produce a limited set of configurations in a cost-effective way by using the same parts in different combinations, leading to a relatively small number of parts but a large number of possible configurations. This thesis presents an approach to the configuration problem by modeling it from a multi-objective optimization perspective. By assuming that a product is described by a number of quality measures which different customers appreciate differently, the interesting configurations consist of the configurations that lie in the Pareto optimal subset of the decision space. For a large number of objectives, multi-objective optimization becomes cumbersome; therefore a first appended paper provides a method for problem reduction such that the representation of the Pareto optimal set is kept as good as possible. A second paper considers a simplification of the configuration problem by assuming that the decision variables are continuous and box constrained. A problem, in which the objective is to find an optimal representation of the Pareto optimal set, while the number of chosen values of the decision variables is limited, is formulated and solved for a number of test instances. The thesis has been written in close cooperation with the product development department of Volvo 3P.
|
|
| 15033. |
|
|
| 15034. |
|
|
| 15035. |
|
|
| 15036. |
- Lindskog, Erik, 1988
(författare)
-
A Framework for Systematic use of Realistic Visualisation to Support Layout Planning of Production Systems
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The process of designing production systems comprises a sequence of steps toward the final design and realisation. Layout planning is a significant part of this process. Its outcome should be a layout which matches the existing spatial conditions of the factory building and desired performance of the production system. To support layout planning, virtual representations of layouts can be created to plan and evaluate layout alternatives. Costly problems can arise during the realisation, if the virtual representations are inaccurate or lack details of the factory building and planned production systems. 3D laser scanning can be used to create accurate and detailed virtual representations by capturing the spatial conditions of existing factory buildings. The data from a 3D laser scan can be used for realistic visualisation of the existing factory building. If this is combined with 3D CAD models of new equipment, the planned production system layout can also be visualised realistically. Realistic visualisation has been shown to enable accurate planning and evaluation of production system layouts, but it does require a systematic working method. The aim of this thesis is to outline and evaluate a framework for systematic use of realistic visualisation to support layout planning of production systems. This aim is addressed using an action research design; this incorporates five industrial studies targeting industrial projects designing production systems. The framework is outlined and evaluated based on the results of the industrial studies. The outlined framework follows a project model for production systems design. It includes several design activities which rely on realistic visualisation of the planned production system layouts. The framework can be used to support the layout planning of industrial projects designing production systems. Its outcomes include making the correct decisions, reducing costly risks and problems and reducing overall project time. Layout planning supported by realistic visualisation allows manufacturing companies to reduce uncertainty when realising planned production systems.
|
|
| 15037. |
- Lindskog, Erik, 1988
(författare)
-
Towards Realistic Visualisation of Production Systems
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Redesigning a production system is a complex process for which numerous virtual tools are available to support the planning process. These virtual tools are used to forecast and analyse the production system prior to implementing the redesign, which makes it possible to identify and prevent costly problems during the planning process. However, such problems occur anyhow due to incorrect information in the virtual representation of the production system and misunderstandings between experts responsible for different areas of the production system. These problems can be avoided by supporting the planning process with realistic and accurate information regarding the existing and redesigned production system.The aim of this thesis is to show that realistic visualisation can support the process of redesigning production systems, in order to reduce the time required for planning and implementation. Three industrial studies were carried out to evaluate how realistic visualisation can be created to support the redesign process. These industrial studies focused mainly on discussing redesign considerations in groups of experts with different areas of responsibility. Additionally, two workshops were carried out to identify what information these experts found important to include in the realistic visualisations.The results show the potential of using 3D laser scanning to create realistic visualisations of production systems with high accuracy. These visualisations can be used to present existing and redesigned production systems in a way that is easy for a wide range of people to understand. Redesigned systems can be visualised by combining 3D laser scan data with 3D CAD models to enable discussion and analysis of redesign alternatives. The support of realistic visualisation can reduce the time required for planning and implementing the redesigned production systems by enabling effective and accurate planning.
|
|
| 15038. |
|
|
| 15039. |
- Lindskog, Stefan, 1967, et al.
(författare)
-
Adding Security to QoS Architectures
- 2004
-
Ingår i: Perspectives on Multimedia: Communication, Media and Information Technology. - 0470868635 ; , s. 145-158
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In a Quality of Service (QoS) aware communication system, a user is able to choose between various service classes, each with different reliability, predictability, and efficiency degrees. However, until now security has not been recognized as a parameter in QoS architectures and no security-related service classes have been defined. This implies that users have no chance of configuring their level of security, which is remarkable. This paper contains a survey of QoS architectures as seen from a security point of view and gives some initial ideas on how QoS architectures can be extended with a security dimension.
|
|
| 15040. |
- Lindskog, Stefan
(författare)
-
Modeling and Tuning Security from a Quality of Service Perspective
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Security has traditionally been thought of as a system or network attribute that was the result of the joint endeavors of the designer, maintainer and user, among others. Even though security can never reach a level of 100%, the aim has been to provide as much security as possible, given the boundary conditions in question. With the advent of, e.g., many low-power computing and communication devices it has become desirable to trade security against other system parameters, such as performance and power consumption. Thus, in many situations, tunable or selectable security, rather than maximal security, is desirable. The overall focus of this thesis is therefore how security with a tunable level could be achieved and traded against other parameters. To this end, basic security primitives, such as the intrusion process, flaws, and impairments, are studied. This contributes to a deeper understanding of fundamental problems and paves the way for security modeling. This part of the work provides a great deal of experimental data that are also used for modeling purposes. Attempts to model and systemize security are made based on the knowledge thus achieved. The relation between security and dependability is touched upon, and the use of physical separation to achieve certain desirable security properties is pointed out. However, most of the modeling research is devoted to suggesting methods for achieving different security levels, i.e., tuning security, in particular for networked applications. Here, the widespread Quality of Service (QoS) concept turns out to be a proper means to embed this novel concept, and a taxonomy for tunable data protection services is suggested. Two data protection services are developed in order to test and verify the concept of tunable security. The evaluations are limited to networked applications and confidentiality through selective encryption schemes. The tests show good agreement between experimental and theoretical results.It is clear that future applications will require security that can be set to a desired level in order to optimize total system performance. This thesis shows that this is possible and gives some ideas as to how selectable security can be generally attainable.
|
|
