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| 3. |
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| 4. |
- Abbasi, Saeed, 1973-
(författare)
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Towards elimination of airborne particles from rail traffic
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the investigation of wear particles from rail transport started in the late 1910s, the high mass concentrations of these particles have prompted concern among researchers interested in air quality. However, effective action has yet to be taken because relevant knowledge is still missing. This thesis provides knowledge of airborne wear particles originating from rail transport. Some aspects of their characteristic parameters, such as size, mass concentration, number concentration, and morphology, were investigated in the field and in laboratory tests. We also discuss means to mitigate non-exhaust emissions, as well as the advantages and disadvantages of various test set-ups in the seven appended journal papers:Paper A reviews recent studies of exhaust and non-exhaust emissions from rail vehicles. The results, measurements, adverse health effects, and proposed or applied solutions presented in this literature are summarized in this paper.Paper B summarizes the results of field tests we conducted. The effects of curve negotiation and braking under different real conditions were investigated in a field test in which on-board measurements were made. The elemental composition and morphology of the particles emitted and their potential sources were also investigated.Paper C describes how a pin-on-disc machine can be used to reproduce real operating conditions during mechanical train braking in a controlled laboratory setting. The results were validated by comparing the field test results with the results of laboratory studies.Paper D presents comprehensive results of laboratory studies of airborne particles from different braking materials. A new index is introduced in this paper, which can be used as a quantitative metric for assessing airborne wear particle emission rates.Paper E describes the effects of using various friction modifiers and lubricants on the characteristics of airborne particles from wheel–rail contact under lubricated and unlubricated conditions.Paper F reports work to simulate thermoelastic instability in the cast-iron braking material. We simulated the fluctuation of the flash temperature by considering the temperature dependency of the material properties and the transformation of the contact state due to thermomechanical phenomena and wear.Paper G reviews new full- and sub-scale measurements of non-exhaust emissions from ground transport. The advantages and disadvantages of on-board measurements, pin-on-disc tests, dynamometer tests, and test rig studies are discussed in this paper.
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| 5. |
- Adamsson, Niklas, 1977-
(författare)
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Interdisciplinary integration in complex product development : managerial implications of embedding software in manufactured goods
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Incorporating electronics and software systems into manufactured goods is becoming very common in manufacturing companies. New technical functions, increased flexibility, and compensation for mechanical design weaknesses are some key drivers of this technological change in our everyday products. The automotive industry exemplifies this trend, since approximately 80–90% of new functions in cars are based on electronics and software, and it is expected that at least a third of the total cost of a car will eventually be accounted for by electronics and software. However, one of the main downsides of this technological trend is the increasing number of quality issues related to these new technologies, something usually claimed to be a result of the increased product development complexity. Previous research into product development management has mainly concentrated on either physical products or software systems, but not concurrently on both. Additionally, much of the research has concentrated on issues of integrating marketing, R&D, and manufacturing in these companies, and has treated the engineering disciplines in R&D as a homogenous group. Motivated by this change in technology content and the lack of research into complex product development and especially into integration between engineering disciplines, the present work investigates how to increase operational performance in multidisciplinary engineering organizations. This work has especially focused on interdisciplinary integration and the feasibility of various so-called integration mechanisms, such as building common physical facilities, job rotation programs, the implementation and use of information and communications technology, and computer-aided engineering tools. Both qualitative and quantitative research has been performed, involving 11 different companies and over 300 respondents. Supported by the present findings, it is demonstrated that interdisciplinary integration is a crucial factor to consider, and it is concluded that certain integration mechanisms stand out as more important than others. Organizational structure, work procedures and methods, training, social systems, and computer-aided engineering were the five types of mechanisms that displayed the greatest potential for improvement. It is further concluded that the ability to successfully match the body of practices to current products is essential, since there is a high risk of current practices becoming out-dated with respect to the technology content. Furthermore, inadequate identification of or managerial ability to establish the currently most important interfaces complicate the choice of trade-offs between various technologies that are found to be essential to cope with the inherent dynamic complexity. The organizational powerbase is often re-positioned in the studied organizations, and the loss of decisive power can result in a demoralizing ignorance of newly established disciplines and their design practices. Additionally, rigid structures and counterproductive traditions can reduce the potential gains accruing from new boundary-spanning innovations, so organizational responsibilities and mandates must be declared unambiguously, in many cases differently from how they have been in the past. Based on these conclusions, it is suggested that managers in organizations like those studied must be able to do the following: cultivate software knowledge in all parts and levels of the product development organization; reassess their recruitment strategies; organize for interdisciplinary collaboration; articulate and communicate the technology fusion strategy to all disciplines; and realize and disseminate the fact that product launches do not only concern manufacturability.
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| 6. |
- Adamsson, Niklas, 1977-
(författare)
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Mechatronics engineering : New requirements on cross-functional integration
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Several industrial sectors experience an increased reliance on mechatronic systems as electronics and software are being embedded into the traditional mechanical systems of these industries. Important challenges within mechatronics engineering comes from management of multi-disciplinary development project teams and the highly complex scope of problems, which in turn require extensive coordination and integration, both in terms of technical and organisational matters. The concept of cross-functional integration in product development research has in previous research mainly addressed integration of the functions marketing, R&D, and manufacturing, and whereas the present thesis is delimited to include only the R&D organization and the functions and engineering disciplines within such an organization. The purpose with thesis has been to investigate mechatronics engineering in order to understand and explain how co-operation, integration, and knowledge sharing between engineering disciplines can be supported. This research has been realized by empirical studies in mechatronic development settings in engineering companies, but also by taking part in industrial and academic research projects that develop and study computer-aided mechatronics engineering. Findings presented in this thesis show that mechatronics is a matter of integration at three organizational levels where the most substantial needs are found to be at the team-level and the individual level. Furthermore, it is identified that to be able to succeed in mechatronics engineering, managers and engineers must look beyond disciplinary needs. Subsequently, both teamwork and competence management become key issues for management of mechatronics engineering. Finally, computer-supported and model-based development of mechatronics show great potential for successful integration of engineering disciplines, even though such technological aids are still rather immature and needs further research and development. A tentative analysis model of organizational integration for mechatronics engineering is also presented and discussed in this thesis. Based on the presented findings, it is concluded that companies incorporating electronics and software in their mechanical products must effectively manage software and electronics development of these embedded systems. Despite the focus on cross-functional integration in engineering companies, this thesis shows examples of inadequate integration of software and electronics engineering with mechanical integration in organisations dominated by the latter. Future research studies are needed to investigate the relation between factors influencing the need for organizational integration and potential integration mechanisms. To further understand mechatronics engineering it is important to look deeper into research issues such as changed conditions for the engineering profession implied by multidisciplinary settings, social systems supporting integration of disciplines, changed work conditions due to implementation of technological aids for model-based system development, relationship between product and organizational complexity, organizational designs supporting integration of engineering disciplines, and cross-disciplinary training of highly specialized engineers.
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| 7. |
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| 8. |
- Aftab, Ahmad, 1979-
(författare)
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Model-based design of haptic devices
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efficient engineering design and development of high precision and reliable surgical simulators, like haptic devices for surgical training benefits from model-based and simulation driven design. The complexity of the design space, multi-domains, multicriteria requirements and multi-physics character of the behavior of such a product ask for a model based systematic approach for creating and validating compact and computationally efficient simulation models to be used for the design process.The research presented in this thesis describes a model-based design approach towards the design of haptic devices for simulation of surgical procedures, in case of hard tissues such as bone or teeth milling. The proposed approach is applied to a new haptic device based on TAU configuration.The main contributions of this thesis are: Development and verification of kinematic and dynamic models of the TAU haptic device. Multi-objective optimization (MOO) approach for optimum design of the TAU haptic device by optimizing kinematic performance indices, like workspace volume, kinematic isotropy and torque requirement of actuators. A methodology for creating an analytical and compact model of the quasi-static stiffness of haptic devices, which considers the stiffness of; actuation system;flexible links and passive joints.
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| 9. |
- Aghaali, Habib, 1981-
(författare)
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On-Engine Turbocharger Performance Considering Heat Transfer
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heat transfer plays an important role in affecting an on-engine turbocharger performance. However, it is normally not taken into account for turbocharged engine simulations. Generally, an engine simulation based on one-dimensional gas dynamics uses turbocharger performance maps which are measured without quantifying and qualifying the heat transfer, regardless of the fact that they are measured on the hot-flow or cold-flow gas-stand. Since heat transfer situations vary for on-engine turbochargers, the maps have to be shifted and corrected in the 1-D engine simulation, which mass and efficiency multipliers usually do for both the turbine and the compressor. The multipliers change the maps and are often different for every load point. Particularly, the efficiency multiplier is different for every heat transfer situation on the turbocharger. The heat transfer leads to a deviation from turbocharger performance maps, and increased complexity of the turbocharged engine simulation. Turbochargers operate under different heat transfer situations while they are installed on the engines. The main objectives of this thesis are: heat transfer modeling of a turbocharger to quantify and qualify heat transfer mechanisms, improving turbocharged engine simulation by including heat transfer in the turbocharger, assessing the use of two different turbocharger performance maps concerning the heat transfer situation (cold-measured and hot-measured turbocharger performance maps) in the simulation of a measured turbocharged engine, prediction of turbocharger walls’ temperatures and their effects on the turbocharger performance on different heat transfer situations. Experimental investigation has been performed on a water-oil-cooled turbocharger, which was installed on a 2-liter GDI engine for different load points of the engine and different heat transfer situations on the turbocharger by using insulators, an extra cooling fan, radiation shields and water-cooling settings. In addition, several thermocouples have been used on accessible surfaces of the turbocharger to calculate external heat transfers. Based on the heat transfer analysis of the turbocharger, the internal heat transfer from the bearing housing to the compressor significantly affects the compressor. However, the internal heat transfer from the turbine to the bearing housing and the external heat transfer of the turbine housing mainly influence the turbine. The external heat transfers of the compressor housing and the bearing housing, and the frictional power do not play an important role in the heat transfer analysis of the turbocharger. The effect of the extra cooling fan on the energy balance of the turbocharger is significant. However, the effect of the water is more significant on the external heat transfer of the bearing housing and the internal heat transfer from the bearing housing to the compressor. It seems the radiation shield between the turbine and the compressor has no significant effect on the energy balance of the turbocharger. The present study shows that the heat transfer in the turbocharger is very crucial to take into account in the engine simulations. This improves simulation predictability in terms of getting the compressor efficiency multiplier equal to one and turbine efficiency multiplier closer to one, and achieving turbine outlet temperature close to the measurement. Moreover, the compressor outlet temperature becomes equal to the measurement without correcting the map. The heat transfer situation during the measurement of the turbocharger performance influences the amount of simulated heat flow to the compressor. The heat transfer situation may be defined by the turbine inlet temperature, oil heat flux and water heat flux. However, the heat transfer situation on the turbine makes a difference on the required turbine efficiency multiplier, rather than the amount of turbine heat flow. It seems the turbine heat flow is a stronger function of available energy into the turbine. Of great interest is the fact that different heat situations on the turbocharger do not considerably influence the pressure ratio of the compressor. The turbine and compressor efficiencies are the most important parameters that are affected by that. The component temperatures of the turbocharger influence the working fluid temperatures. Additionally, the turbocharger wall temperatures are predictable from the experiment. This prediction enables increased precision in engine simulations for future works in transient operations.
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| 10. |
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| 11. |
- Agrell, Fredrik, 1971-
(författare)
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Control of HCCI by aid of Variable Valve Timings with Specialization in Usage of a Non-Linear Quasi-Static Compensation
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis is about controlling the combustion timing of the combustion concept Homogeneous Charge Compression Ignition, HCCI, by means of variable valve timings. The HCCI research usually is regarded to have started in Japan during the later part of the 1970´s. The world of HCCI has since grown and HCCI is of today researched worldwide. Of particular interest from a Swedish point of view is that Lund Institute of Technology has emerged as one of the world leading HCCI laboratories. The idea with HCCI is to combine the Otto and Diesel engine. As in an Otto engine the charge is premixed but as in a Diesel engine the operation is unthrottled and the compression heat causes the ignition. The combustion that follows the ignition takes place homogeneously and overall lean. The result is ultra low NOx and particulate emissions combined with high total efficiency. A difficulty with the HCCI-concept is that it only works in a narrow area and that there is no direct way to control the Start Of Combustion, SOC. Out of this follows that timing/phasing of the combustion is one of the main difficulties with HCCI combustion concepts. This is particularly emphasized during transient operation and calls for feedback control of the combustion timing. This work investigates one method, the variable valve timing, to achieve feedback control of the combustion phasing. From the work it can be concluded that the variable valve timing can control the combustion phasing during engine transients. In order to improve the performance a non-linear compensation from ignition delay to valve timings has been suggested, incorporated in a control structure and tested in engine test. The engine test has been performed in a single cylinder engine based on a Scania truck engine. The speed range from 500 to 1750 rpm and the load range 1.26 and 10.5 bar of netIMEP has been covered with fair transient performance.
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| 12. |
- Ahari, Parviz, 1947-
(författare)
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A living systems approach to product design and development
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Product development is a complex activity that involvespeople with different expertise, financial resources,materials, and machines. Organizations that carry out theseprocesses and their products are in fact living and artificialsystems. The concept of system is therefore very important fordealing with complexity of products, and their developmentprocesses. However, the concept of system is not consideredcarefully and scientifically in this context, therefore itsexplanations in design and development literature havelimitations and do not provide sufficient help for those whoare involved in the complex processes of product design anddevelopment.In this research an attempt is made to show the relevance ofsystems concepts for product development. The purpose of thisresearch is therefore to provide knowledge, and betteralternative points of view that helps to manage complexities ofproducts and product development processes, to improveunderstanding of them, to avoid problems related toconventional thinking, and to complement conventionalmethods.To provide this knowledge the weaknesses of the conventionalmethods of product development and the strengths ofunconventional systemic methods have been shown. Systemsthinking as an unconventional method has been introduced anddiscussed. These presentations include the need for a newscientific method, the meaning of system, its origin, kinds ofsystems, why, and how systems sciences are applied. Further theneed for and importance of a better theory in product designand development is shown. Living systems theory (LST) isintroduced, and explained. LST’s applications in differentdisciplines are presented. The research includes also adiscussion of the meaning of products, their places in livingsystems and what triggers their design and development.The importance of creativity, innovation, and lifelonglearning are emphasized and discussed. It has been shown howliving systems theory and other systems sciences can contributeto them. The relevance of how we see the world is discussed andit has been shown how we can and should improve our way ofseeing the world. It has also been shown that information andknowledge are not sufficient. We should also become wiser, andthis requires consideration of the long-term consequences ofour actions and it involves values and judgment.The results of this research are both descriptive andprescriptive. They provide several contributions, for example,a systemic cube (table) of artifacts (analogous withMendeleyev’s table of elements) as a model for managingcomplexity and for generating creative ideas; and a new conceptof usability engineering, which has been applied in industry indifferent projects. Further a more complete LST based model,which can be used for products and product developmentprocesses (for living and artificial systems), has beenprovided. The research uncovers also neglected aspects of LSTin product design and development and shows how they can beconsidered, these are for example the concepts of alpha- beta-,and gamma-coded information. It has also been shown how we canacquire a more complete understanding of product developmentactivities and how we can improve these processes. Thesecontributions have both academic and industrial relevance andpresent a step in the right direction–improving thequality of life.Keywords:Product design and development, living systemstheory, needs, managing complexity, modeling, systems thinking,problem solving, creativity, lifelong learning.
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| 13. |
- Ahmad, Aftab, 1979-
(författare)
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Effective development of haptic devices using a model-based and simulation-driven design approach
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Virtual reality (VR)-based surgical simulators using haptic devices can increase the effectiveness of surgical training for surgeons when performing surgical procedures in hard tissues such as bones or teeth milling. The realism of virtual surgery through a surgical simulator depends largely on the precision and reliability of the haptic device, which reflects the interaction with the virtual model. The quality of perceptiveness (sensation, force/torque) depends on the design of the haptic device, which presents a complex design space due to its multi-criteria and conflicting character of functional and performance requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, high transparency, and cost constraints.This thesis proposes a design methodology to improve the realism of force/torque feedback from the VR-based surgical simulator while fulfilling end-user requirements.The main contributions of this thesis are:1. The development of a model-based and simulation-driven design methodology, where one starts from an abstract, top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized.2. A methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device, which considers the stiffness of actuation systems, flexible links and passive joints.3. A robust design optimization approach to find the optimal numerical values for a set of design parameters to maximize the kinematic, dynamic and kinetostatic performances of a 6-degrees of freedom (DOF) haptic device, while minimizing its sensitivity to variations in manufacturing tolerances and cost, and also satisfying the allowed variations in the performance indices.4. A cost-effective approach for force/torque feedback control using force/torque estimated through a recursive least squares estimation.5. A model-based control strategy to increase transparency and fidelity of force/torque feedback from the device by compensating for the natural dynamics of the device, friction in joints, gravity of platform, and elastic deformations.
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| 14. |
- Andersson, Martin
(författare)
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An experimental investigation of spur gear efficiency and temperature : A comparison between ground and superfinished surfaces
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on reliability when testing gear efficiency and on how gear mesh efficiency can be increased without detrimental effects on the gears. Test equipment commonly used in gear research was analysed to identify important parameters for gear efficiency testing. The effect of the bearing model's load-dependent losses on gear mesh efficiency was also investigated. Two different surface finishes of gears, ground and superfinished, were investigated to determine how two different load levels during running-in affect gear mesh efficiency and changes in surface roughness. Efficiency and gear temperature were also measured for ground and superfinished gears with dip lubrication, as well as two different forms of spray lubrication (before and after gear mesh contact).Tests on a gear test rig, showed that different assemblies of the same test setup can yield different measurements of torque loss. The applied bearing model had a significant effect on the estimated gear mesh efficiency. The mesh efficiency of ground gears is affected by the running-in procedure, with a higher running-in load resulting in a higher mesh efficiency than a lower load. This effect was not seen for superfinished gears, which show the same gear mesh efficiency for both running-in loads. Gearbox efficiency increased with spray lubrication rather than dip lubrication. The gear mesh efficiency increased, and thus gear temperatures were reduced, when superfinished gears were used rather than ground gears. A lower gear temperature was measured when gears were spray lubricated at the mesh inlet rather than the mesh outlet.
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| 15. |
- Annosi, Maria Carmela
(författare)
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Regulation and Self-Regulation of Team Learning and Innovation Activities
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Self-regulated learning and innovation activities within teams are those processes with which team members collectively activate and sustain cognition, affects and behaviors which are systematically oriented towards the achievement of their team’s goals. Although research on self-managing teams exists, there remains considerable confusion on many issues including what self-regulation is and how regulation of self-regulated learning and innovation activities is carried out. A primary contribution of this dissertation is to introduce a theoretical framework for analysing and applying regulative actions in organizational environment. The aim of this dissertation is to advance the understanding on how regulation of self- managing team learning and innovation activities can happen starting from an analysis of the self-regulative learning processes of individuals within teams and of their own determinants. This dissertation has three objectives: 1) to present internal team mechanisms involved in the self-regulation of teams’ learning activities, their interactive dynamics and their corresponding major organisational determinants; 2) to rely on this novel understanding to detect relevant regulative actions which are able to indirectly influence teams’ self-regulatory learning and innovative behaviour; 3) to offer empirical evidence of how specific regulative actions affect team learning and innovation performance. We discover that there are four major constructs associated with the regulation of teams’ learning and innovation activities: feedback loops and goals equally combining learning and performance items, networks of influence made up of managers and stakeholders interacting with teams through systematic routines, training programmes for team members, dialectical perspective on learning and innovation to force in the managerial layers.
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| 16. |
- Asplund, Fredrik
(författare)
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Risks Related to the Use of Software Tools when Developing Cyber-Physical Systems : A Critical Perspective on the Future of Developing Complex, Safety-Critical Systems
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing complexity and size of modern Cyber-Physical Systems (CPS) has led to a sharp decline in productivity among CPS designers. Requirements on safety aggravate this problem further, both by being difficult to ensure and due to their high importance to the public.Tools, or rather efforts to facilitate the automation of development processes, are a central ingredient in many of the proposed innovations to mitigate this problem. Even though the safety-related implications of introducing automation in development processes have not been extensively studied, it is known that automation has already had a large impact on operational systems. If tools are to play a part in mitigating the increase in safety-critical CPS complexity, then their actual impact on CPS development, and thereby the safety of the corresponding end products, must be sufficiently understood.An survey of relevant research fields, such as system safety, software engineering and tool integration, is provided to facilitate the discussion on safety-related implications of tool usage. Based on the identification of industrial safety standards as an important source of information and considering that the risks posed by separate tools have been given considerable attention in the transportation domain, several high-profile safety standards in this domain have been surveyed. According to the surveyed standards, automation should primarily be evaluated on its reliable execution of separate process steps independent of human operators. Automation that only supports the actions of operators during CPS development is viewed as relatively inconsequential.A conceptual model and a reference model have been created based on the surveyed research fields. The former defines the entities and relationships most relevant to safety-related risks associated with tool usage. The latter describes aspects of tool integration and how these relate to each other. By combining these models, a risk analysis could be performed and properties of tool chains which need to be ensured to mitigate risk identified. Ten such safety-related characteristics of tool chains are described.These safety-related characteristics provide a systematic way to narrow down what to look for with regard to tool usage and risk. The hypothesis that a large set of factors related to tool usage may introduce risk could thus be tested through an empirical study, which identified safety-related weaknesses in support environments tied both to high and low levels of automation. The conclusion is that a broader perspective, which includes more factors related to tool usage than those considered by the surveyed standards, will be needed.Three possible reasons to disregard such a broad perspective have been refuted, namely requirements on development processes enforced by the domain of CPS itself, certain characteristics of safety-critical CPS and the possibility to place trust in a proven, manual development process. After finding no strong reason to keep a narrow perspective on tool usage, arguments are put forward as to why the future evolution of support environments may actually increase the importance of such a broad perspective.Suggestions for how to update the mental models of the surveyed safety standards, and other standards like them, are put forward based on this identified need for a broader perspective.
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| 17. |
- Asplund, Fredrik
(författare)
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Safety and Tool Integration, A System-Theoretic Process Analysis
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report I detail a System-Theoretic Process Analysis (STPA) hazard analysis of the tool integration of development environments for embedded systems. Building on results from previous studies I generalize and expand on earlier findings regarding the relationship between safety and tool integration. To prepare for the analysis I customized STPA for the context of tool integration. This customization allowed me to subsequently design and analyze three versions of a tool chain originally provided by an industrial partner. A net result of 85, 98 and 73 risks was identified, in comparison to 25 integration weaknesses identified through expert knowledge. The design of the different versions of the tool chain and a comparison of the identified risks with the integration weaknesses allowed me to validate the usefulness of STPA for both identifying and correctly categorizing risks and causes in the context of tool integration. An analysis of my results also points out the fact that STPA is not a silver bullet, without enough expertise it is easy to omit important parts of process models and thus arrive at incomplete conclusions. In regard to the relationship between safety and tool integration nine properties were identified, properties that need to be supported correctly to avoid hazards in the context of tool integration. These properties require support throughout a noticeable part of a development environment to have an impact and derive much of that impact from the possibility to centralize them. They also interrelate, so that often several of them need to be handled to mitigate one type of risk. However, introducing support for them across a whole development environment is likely to be costly, or even impossible. Furthermore, introducing support for these properties will mitigate some risks, but also create other risks at higher levels of organization. These properties therefore point to the size a development environment, the number of contexts towards which the development environment can be verified and the effort required to ensure the added requirements at higher levels of organization as deciding factors on whether the effort to support them should be made (other efforts, more efficient in those particular cases, could otherwise be considered). The existence of these properties also point to the possibility of developing and pre-qualifying tools and tool chains based on the assumption that some or all of these properties will be supported by the final development environment. This could potentially lower, or at least distribute, the cost of the final qualification.
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| 18. |
- Asplund, Fredrik, 1977-
(författare)
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Tool Integration and Safety : A Foundation for Analysing the Impact of Tool Integrationon Non-functional Properties
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing complexity of embedded systems development is becoming difficult to handle with development environments based on disjoint engineering tools. Support for interactions between various engineering tools, especially through automated means, has therefore received an increased amount of attention during the last few years. The subsequent increase in the amount of tool integration is leading to an increased impact of tool integration on non-functional properties of development efforts, development environments and end products. At the same time there is a lack of methods and tools for analysing the relationship between these properties and tool integration. To establish a foundation for analysing this generic relationship, the specific relationship between tool integration and the safety of end products is analysed in this thesis.A survey was conducted to analyze the State of the Art of tool integration as related to safety. This survey specifically identified the lack of an efficient handling of tool integration by modern safety standards as an important concern. In relation to this survey, three theories were identified as of specific importance. These are the school of thought known as Systems Thinking, the Systems-Theoretic Accident Model and Processes (STAMP) causality model and the System-Theoretic Process Analysis (STPA) hazard analysis technique.Building on these theories, this thesis provides original contributions intended to (1) describe concepts and models related to tool integration and safety (the first and second contribution), (2) link tool integration to safety in a way that reduces complexity during analysis (the third contribution) and (3) propose how to interpret and make use of the implications of the presented theories and the first three contributions (the fourth and fifth contribution).• The first contribution is a new conceptual model of a development effort that emphasizes tool integration.• The second contribution is a new reference model for tool integration in highly heterogeneous environments.• The third contribution consists of nine safety-related tool chain properties, i.e. properties of tool chains that could mitigate at least part of the risks introduced by tool integration.• The fourth contribution is a proposition on how to identify safety implications due to a high level of automation of tool integration.• The fifth contribution is a proposition for a new software tool qualification process.
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| 19. |
- Behere, Sagar, 1981-
(författare)
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Architecting Autonomous Automotive Systems : With an emphasis on Cooperative Driving
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing usage of electronics and software in a modern automobile enables realization of many advanced features. One such feature is autonomous driving. Autonomous driving means that a human driver’s intervention is not required to drive the automobile; rather, theautomobile is capable of driving itself. Achieving automobile autonomyrequires research in several areas, one of which is the area of automotive electrical/electronics (E/E) architectures. These architectures deal with the design of the computer hardware and software present inside various subsystems of the vehicle, with particular attention to their interaction and modularization. The aim of this thesis is to investigate how automotive E/E architectures should be designed so that 1) it ispossible to realize autonomous features and 2) a smooth transition canbe made from existing E/E architectures, which have no explicit support for autonomy, to future E/E architectures that are explicitly designed for autonomy.The thesis begins its investigation by considering the specific problem of creating autonomous behavior under cooperative driving condi-tions. Cooperative driving conditions are those where continuous wireless communication exists between a vehicle and its surroundings, which consist of the local road infrastructure as well as the other vehicles in the vicinity. In this work, we define an original reference architecture for cooperative driving. The reference architecture demonstrates how a subsystem with specific autonomy features can be plugged into an existing E/E architecture, in order to realize autonomous driving capabilities. Two salient features of the reference architecture are that it isminimally invasive and that it does not dictate specific implementation technologies. The reference architecture has been instantiated on two separate occasions and is the main contribution of this thesis. Another contribution of this thesis is a novel approach to the design of general, autonomous, embedded systems architectures. The approach introduces an artificial consciousness within the architecture, that understands the overall purpose of the system and also how the different existing subsystems should work together in order to meet that purpose.This approach can enable progressive autonomy in existing embedded systems architectures, over successive design iterations.
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| 20. |
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| 21. |
- Behere, Sagar, 1981-
(författare)
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Reference Architectures for Highly Automated Driving
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Highly automated driving systems promise increased road traffic safety, as well as positive impacts on sustainable transportation by means of increased traffic efficiency and environmental friendliness. The design and development of such systems require scientific advances in a number of areas. One area is the vehicle's electrical/electronic (E/E) architecture. The E/E architecture can be presented using a number of views, of which an important one is the functional view. The functional view describes the decomposition of the system into its main logical components, along with the hierarchical structure, the component inter-connections, and requirements. When this view captures the principal ideas and patterns that constitute the foundation of a variety of specific architectures, it may be termed as a reference architecture. Two reference architectures for highly automated driving form the principal contribution of this thesis. The first reference architecture is for cooperative driving. In a cooperative driving situation, vehicles and road infrastructure in the vicinity of a vehicle continuously exchange wireless information and this information is then used to control the motion of the vehicle. The second reference architecture is for autonomous driving, wherein the vehicle is capable of driver-less operation even without direct communication with external entities. The description of both reference architectures includes their main components and the rationale for how these components should be distributed across the architecture and its layers. These architectures have been validated via multiple real-world instantiations, and the guidelines for instantiation also form part of the architecture description. A comparison with similar architectures is also provided, in order to highlight the similarities and differences. The comparisons show that in the context of automated driving, the explicit recognition of components for semantic understanding, world modeling, and vehicle platform abstraction are unique to the proposed architecture. These components are not unusual in architectures within the Artificial Intelligence/robotics domains; the proposed architecture shows how they can be applied within the automotive domain. A secondary contribution of this thesis is a description of a lightweight, four step approach for model based systems engineering of highly automated driving systems, along with supporting model classes. The model classes cover the concept of operations, logical architecture, application software components, and the implementation platforms. The thesis also provides an overview of current implementation technologies for cognitive driving intelligence and vehicle platform control, and recommends a specific setup for development and accelerated testing of highly automated driving systems, that includes model- and hardware-in-the-loop techniques in conjunction with a publish/subscribe bus. Beyond the more "traditional" engineering concepts, the thesis also investigates the domain of machine consciousness and computational self-awareness. The exploration indicates that current engineering methods are likely to hit a complexity ceiling, breaking through which may require advances in how safety-critical systems can self-organize, construct, and evaluate internal models to reflect their perception of the world. Finally, the thesis also presents a functional architecture for the brake system of an autonomous truck. This architecture proposes a reconfiguration of the existing brake systems of the truck in a way that provides dynamic, diversified redundancy, and an increase in the system reliability and availability, while meeting safety requirements.
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| 22. |
- Bergendahl, Magnus
(författare)
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Collaboration and competition in firm-internal ideation management : Two alternatives – and a third way out
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The passive reliance on ideas to spontaneously emerge within companies is today replaced with more active and continuous ideation management that embraces employees from different functions and knowledge-domains within the company to create and develop ideas. A frequently observed feature in the active management of ideation is the reliance on collaboration and competition mechanisms. These mechanisms use the strength of enabling people to working together towards a shared interest (collaboration) and the power of enabling people to outperform each other in submitting the best idea (competition). The existing research on collaboration and competition in ideation is found inconclusive about their effects as collaboration is stated to both enhance and hamper performance, and as competition is claimed to both drive and reduce performance in ideation. This constitutes a limitation to the management of ideation as it reduces the ability to actively and purposefully guide ideation through a deliberate use of the two mechanisms.The aim of this thesis is to investigate collaboration and competition mechanisms in firm-internal ideation. A multi-methodological approach has been deployed using three different studies: a multiple case study, a survey, and an experiment. This has allowed for the phenomenon of ideation to be studied using different perspectives and for the individual results to be triangulated. The empirical data has been acquired from both industry and experiments with university students.The conducted research has revealed that the inconsistencies on the effects from the two mechanisms are possible to understand and resolve by applying a more detailed level of analysis. When competition is decomposed into components of individual- and group competition, it is found that individual competition drives idea quantity and that it hampers collaboration, whereas group competition instead is found to induce collaboration and to nurture idea quality. This indicates that competition can be used to manage levels of collaboration in ideation, thereby bridging the two mechanisms.This thesis further presents that the individual effects from each of the mechanisms are complementary to each other. This implies that the effect from each mechanism is retained when combined with the other mechanisms, and that the combined effect is equal to, or even greater than, the sum of the individual effects. This combined use is found to drive both ideation efficiency and motivation, and is offering management an interesting third alternative, out of the two mechanisms, of how firm-internal ideation can be managed in a more effective and efficient manner.An analytical framework is included, presenting the interrelationships between the mechanisms, motivation, ideation behavior and the ideation performance.
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| 23. |
- Berglund, Anders, 1974-
(författare)
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Two facets of Innovation in Engineering Education : The interplay of Student Learning and Curricula Design
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis covers two main perspectives ofinnovation; first, innovation is regarded as an outcome-related mechanism wherelearning is expressed through artefact presentations at the end of adevelopment process; second, innovation comprises a change mechanism in theprocess of student learning, influencing educators to reconsider new methods andpractices. Building on qualitative data from engineering design courses, theaim has been to explore how learning elements in engineering educationinfluence students during early-phase innovation. By implementing andpracticing learning elements, early-phase innovation could strengthen both currentand future engineering curricula, courses, and programmes.This thesis put attention to authentic experiences in which learning elementsis acted upon by students and targeted, defined, and refined by educators.Introducing learning elements need educators to manifest learning efforts moreexplicitly to match students’ capability to interpret new knowledge. Adoptinglearning elements that challenge existing paths of action are characterized by diversity, proactivity, opennessand motivation. For students to excel in the exploration of early-phaseinnovation, it is important to identify when, how and to what extent leaningelements can be reinforced. Thestrengthened understanding by students is mirrored in improved ability to takeaction and apply relevant knowledge in distinct learning situations. Theopportunity to influence student learning provides the design and redesign of curricula,courses and programmes as a prime feature to leaning elements relevant to early-phaseinnovation. To successfully pursue innovation in engineering education abalance is necessary between responsible actors integrating learning elementsand by those determined to learn.
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| 24. |
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| 25. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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Investigation of pitting resistance in ultra clean IQ-Steel vs commonly used conventional steel; 158Q vs 16MnCr5 : Back-to-back pitting tests
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- KTH Machine Design has conducted pitting tests on gears made out of two different types of steel in a standard back-to-back pitting test rig (FZG). The tested gears were produced from Ovako’s IQ-Steel in grade 158Q and compared to the behaviour of a reference steel, commonly used conventional steel in grade 16MnCr5 (reference steel, RS). The test method is a mechanical test procedure generally used to determine the pitting load capacity of gear transmission lubricants, but in this study the purpose was to compare the pitting load capacity of the two steel types. The report is based on the test procedure described in FVA – Information sheet Research Project No. 371 (Practice Relevant Pitting Test) with minor changes. Time to failure and photographs of the fatigue damages are presented in this report. One gear tooth from each steel type was analysed using SEM. The results, which are based on six tests in total (three gear pairs IQ-Steel and three RS-steel), indicate that the IQ-Steel has better surface durability than the reference steel. To better understand the mechanisms involved, further tests are suggested.
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| 26. |
- Bergseth, Ellen, 1979-
(författare)
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On tribological design in gear tooth contacts
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The correct tribological design will have a considerable effect on a gear’s service life and efficiency. The purpose of this thesis is to clarify the impact of variation in the gear tooth flank tribological system on the gear contact load capacity – to increase the understanding of how surface topography and lubricant interact.In this thesis the variation in surface topography inherent in the manufacturing method has been shown, by experimental work and computer simulations, to be an important factor for the contact condition in the early life of gears. Surface analysis revealed that the formation and composition of surface boundary layers depends strongly on the chemical composition of the lubricant, but also on pre-existing surface boundary layers. Additionally, surface boundary layers play a major role in frictional behaviour, wear and in allowing the lubricant to react properly with the surfaces.Paper A presents the current ISO 6336 calculation of surface durability. A robust design approach was used to investigate the extent to which the current standard for calculation of surface durability allows for manufacturing variations and the choice of lubricant.Paper B investigates the extent to which a logarithmical profile modification can increase gear contact pressure robustness compared to traditional lead profiles for gears.Paper C compares different gear manufacturing methods and their as-manufactured (fresh unworn) surface topographies, using measured surface topographies as input to a contact simulation program.Paper D examines surface boundary layer formation and the corresponding wear in relation to different anti-wear additives in an environmentally adapted base oil.Papers E and F make use of specimens with surface topographies imitating two gear manufacturing methods (grinding and superfinishing) to be used in a twin-disc and barrel-on-disc machine respectively. The contacts are analysed by friction measurements and simulations combined with methods for surface analysis.
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| 27. |
- Bernemyr, Hanna, 1975-
(författare)
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Volatility and number measurement of diesel engine exhaust particles
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, emission legislations for engine exhaust particles are mass based. The engines of today are low-emitting with respect to particle mass, with the emissions approaching the detection limit of the current measurement method. This calls for new and improved measurement methods. Both from the point of view of the engine developers and regarding human health effects, particle number seem to be the particle property of greatest interest to legislate upon. Recently, a proposal for a new particle number based measurement methodology has been put forward by the United Nations Economic Commission for Europe (UN ECE). The gas and particle mixture (the aerosol) of engine exhaust is not a stable system. The size and the number of the particles change over time as the temperature and pressure change. Particle number measurements call for dilution which changes the gas-phase concentrations of the condensing gases. The dilution process alters the conditions in the aerosol and thereby influences the measurements. Within the current project it was desired to better understand the outcome of particle number measurements and the complexities of particle sampling, dilution and conditioning prior to measurements. Two experimental set-ups have been developed within the project. The first system includes a rotating disc diluter followed by a volatility Tandem Differential Mobility Analyser (v-TDMA). The second set-up, called the EMIR-system, includes ejector diluters in series followed by a stand-alone Condensation Particle Counter (CPC). After the development of these experimental set-ups, the v-TDMA has been used to study the volatility and the size distributed number concentration of exhaust particles. The EMIR-system was used for total number concentration measurements including only the solid fraction of the aerosol. The experimental work has given practical experience that can be used to estimate the benefits and disadvantages of upcoming measuring methodology. For the engine developers, in order to produce engines that meet future legislation limits, it is essential to know how the measurement procedure influences the aerosol. In summary, the experimental studies have shown that the number of nucleation mode particles is strongly affected by varied dilution. No upper threshold value of the dilution has been found where the dilution effect diminishes. The volatility studies have shown that it is mainly the nucleation mode particles that are affected by heat. The v-TDMA instrument have shown to be a sensitive analytical tool which, if desired to use for further engine exhaust particle characterization, needs some development work. Experimental work with the EMIR-system, which in principle is similar to the instruments proposed for a future standard, shows that these types of measurement systems are sensitive to small changes in the detector cut-off. The major outcome of the project lies in the new detailed knowledge about particle number measurements from engines.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
- Biehl, Matthias
(författare)
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A Modeling Language for the Description and Development of Tool Chains for Embedded Systems
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of embedded systems is typically supported by a number of diverse development tools. To achieve seamless tool support throughout the embedded systems development process, tool chains are constructed as software solutions that integrate the development tools. Tool chains have grown from ad-hoc solutions to complex software systems, since they need to support distributed engineering, integration conventions, a specific set of tools and the complete product development process used in a company. In practice, the development of tool chains that fulfill these needs is difficult and time-consuming, since it is a largely unsupported, manual engineering task. In addition, tool chains are typically described using general purpose modeling languages or languages borrowed from other domains, which contributes to the accidental complexity of tool chain development. Due to the increasing sophistication and size of tool chains, there is a need for a systematic, targeted description and development approach for tool chains.This thesis contributes with a language for the systematic description of tool chains and semi-automated techniques to support their development.The Tool Integration Language (TIL) is a domain-specific modeling language (DSML) for tool chains that allows describing tool chains explicitly, systematically and at an appropriate level of abstraction. TIL concepts are from the domain of tool integration and express the essential design decisions of tool chains at an architectural level of abstraction. A TIL model serves as a basis for the development of a tailored tool chain.Semi-automated techniques for the specification, analysis and synthesis support the development of tool chains that are described as TIL models. Specification techniques support the creation and refinement of a tool chain model that is aligned to a given development process and set of tools. Domain-specific analysis techniques are used to check the alignment of the tool chain model with the supported process. Synthesis techniques support the efficient realization of the specified tool chain model as a software solution that conforms to integration conventions.Experiences from case studies are presented which apply TIL to support the creation of tool chains. The approach is evaluated, both qualitatively and quantitatively, by comparing it to traditional development methods for tool chains. The approach enables the efficient development of tailored tool chains, which have the potential to improve the productivity of embedded systems development.
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| 32. |
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| 33. |
- Biehl, Matthias
(författare)
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Supporting model evolution in model-driven development of automotive embedded system
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Innovative functions in cars, such as active safety systems and advanced driver assistance systems, are realized as embedded systems. The development of such automotive embedded systems is challenging in several respects: the product typically has several crosscutting system properties, experts of diverse disciplines need to cooperate and appropriate processes and tools are required to improve the effciency and the complexity management of development. Model-driven development captures the architecture of the embedded system in the form of models with well-defined metamodels. Model-driven development provides a partial solution to some of the challenges of embedded systems development, but it also introduces new challenges. Models do not remain static, but they change over time and evolve. Evolution can change models in two ways: (1) by making design decisions and adding, deleting or changing model elements, or (2) by reusing models in different tools. We propose support for both aspects of model evolution. (1) When models are changed, the design decisions and the justification for the change are usually neither captured nor documented in a systematic way. As a result, important information about the model is lost, making the model more difficult to understand, which hampers model evolution and maintenance. To support model evolution, design decisions need to be captured explicitly using an appropriate representation. This representation reduces the overhead of capturing design decisions, keeps the model and the design decision documentation consistent and links the design decision documentation to the model. As a result, the captured design decisions provide a record of the model evolution and the rationale of the evolution. (2) Several models and views are used to describe an embedded system in different life cycle stages and from the viewpoints of the involved disciplines. To create the various models, a number of specialized development tools are used. These tools are usually disconnected, so the models cannot be transferred between different tools. Thus, models may become inconsistent, which hampers understandability of the models and increases the cost of development. We present a model-based tool integration approach that uses a common metamodel in combination with model transformation technology to build bridges between different development tools. We apply this approach in a case study and integrate several tools for automotive embedded systems development: A systems engineering tool, a safety engineering tool and a simulation tool. As a part of future work, we plan to extend the tool integration approach to exchange not only models but also the attached documentation of design decisions. As a result, the design decision documentation is linked consistently to corresponding model elements of the various tool-specific models, supporting model evolution across several development tools
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| 34. |
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| 35. |
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| 36. |
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Börjesson, Fredrik, 1965-
(författare)
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Approaches to Modularity in Product Architecture
- 2012
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modular product architecture is characterized by the existence of standardized interfaces between the physical building blocks. A module is a collection of technical solutions that perform a function, with interfaces selected for company-specific strategic reasons. Approaches to modularity are the structured methods by which modular product architectures are derived. The approaches include Modular Function Deployment (MFD), Design Structure Matrix (DSM), Function Structure Heuristics and many other, including hybrids. The thesis includes a survey of relevant theory and a discussion of four challenges in product architecture research, detailed in the appended papers. One common experience from project work is structured methods such as DSM or MFD often do not yield fully conclusive results. This is usually because the algorithms used to generate modules do not have enough relevant data. Thus, we ask whether it is possible to introduce new data to make the output more conclusive. A case study is used to answer this question. The analysis indicates that with additional properties to capture product geometry, and flow of matter, energy, or information, the output is more conclusive. If product development projects even have an architecture definition phase, very little time is spent actually selecting the most suitable tool. Several academic models are available, but they use incompatible criteria, and do not capture experience-based or subjective criteria we may wish to include. The research question is whether we can define selection criteria objectively using academic models and experience-based criteria. The author gathers criteria from three academic models, adds experience criteria, performs a pairwise comparison of all available criteria and applies a hierarchical cluster analysis, with subsequent interpretation. The resulting evaluation model is tested on five approaches to modularity. Several conclusions are discussed. One is that of the five approaches studied, MFD and DSM have the most complementary sets of strengths and weaknesses, and that hybrids between these two fundamental approaches would be particularly interesting. The majority of all product development tries to improve existing products. A common criticism against all structured approaches to modularity is they work best for existing products. Is this perhaps a misconception? We ask whether MFD and DSM can be used on novel product types at an early phase of product development. MFD and DSM are applied to the hybrid drive train of a Forwarder. The output of the selected approaches is compared and reconciled, indicating that conclusions about a suitable modular architecture can be derived, even when many technical solutions are unknown. Among several conclusions, one is the electronic inverter must support several operating modes that depend on high-level properties of the drive train itself (such as whether regeneration is used). A modular structure for the electronic inverter is proposed. Module generation in MFD is usually done with Hierarchical Cluster Analysis (HCA), where the results are presented in the form of a Dendrogram. Statistical software can generate a Dendrogram in a matter of seconds. For DSM, the situation is different. Most available algorithms require a fair amount of processing time. One popular algorithm, the Idicula-Gutierrez-Thebeau Algorithm (IGTA), requires a total time of a few hours for a problem of medium complexity (about 60 components). The research question is whether IGTA can be improved to execute faster, while maintaining or improving quality of output. Two algorithmic changes together reduce execution time required by a factor of seven to eight in the trials, and improve quality of output by about 15 percent.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
- Chen, DeJiu
(författare)
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Architecture for Mechatronics Software Systems : A Survey of Related Concepts
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- One promising approach to managing complexity and ensuring qualities of software systems is through software architecture, denoting the science and art of software structuring. In this report, some important concepts, theories, and methods of software architecture from software engineering will be studied. Since these technologies are developed with generic software applications in mind, there is generally a lack of support for many important aspects of embedded computer control, such as timing and constrained resources. This has limited the potential benefits of exploiting architecture-based reasoning in the development of embedded control software. Future research should focus on integrating embedded computer control specific semantics and implementation constraints with these general technologies.
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| 45. |
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| 46. |
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| 47. |
- Chen, Dejiu, 1969-
(författare)
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Systems Modeling and Modularity Assessment for Embedded Computer Control Applications
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractThe development of embedded computer control systems(ECS) requires a synergetic integration of heterogeneoustechnologies and multiple engineering disciplines. Withincreasing amount of functionalities and expectations for highproduct qualities, short time-to-market, and low cost, thesuccess of complexity control and built-in flexibility turn outto be one of the major competitive edges for many ECS products.For this reason, modeling and modularity assessment constitutetwo critical subjects of ECS engineering.In the development ofECS, model-based design is currently being exploited in most ofthe sub-systems engineering activities. However, the lack ofsupport for formalization and systematization associated withthe overall systems modeling leads to problems incomprehension, cross-domain communication, and integration oftechnologies and engineering activities. In particular, designchanges and exploitation of "components" are often risky due tothe inability to characterize components' properties and theirsystem-wide contexts. Furthermore, the lack of engineeringtheories for modularity assessment in the context of ECS makesit difficult to identify parameters of concern and to performearly system optimization. This thesis aims to provide a more complete basis for theengineering of ECS in the areas of systems modeling andmodularization. It provides solution domain models for embeddedcomputer control systems and the software subsystems. Thesemeta-models describe the key system aspects, design levels,components, component properties and relationships with ECSspecific semantics. By constituting the common basis forabstracting and relating different concerns, these models willalso help to provide better support for obtaining holisticsystem views and for incorporating useful technologies fromother engineering and research communities such as to improvethe process and to perform system optimization. Further, amodeling framework is derived, aiming to provide a perspectiveon the modeling aspect of ECS development and to codifyimportant modeling concepts and patterns. In order to extendthe scope of engineering analysis to cover flexibility relatedattributes and multi-attribute tradeoffs, this thesis alsoprovides a metrics system for quantifying componentdependencies that are inherent in the functional solutions.Such dependencies are considered as the key factors affectingcomplexity control, concurrent engineering, and flexibility.The metrics system targets early system-level design and takesinto account several domain specific features such asreplication and timing accuracy. Keywords:Domain-Specific Architectures, Model-basedSystem Design, Software Modularization and Components, QualityMetrics.
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| 48. |
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| 49. |
- Cronhjort, Andreas
(författare)
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Droplet Velocities in a Liquid Spray
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A method to look into a dense liquid spray has beenevaluated. The spray was mechanically sliced to remove theobscuring parts of it, thus gaining optical access to theinternal regions and thereby allowing for visualization ofpreviously unavailable parts of the spray. The width of themechanical slit was 100 µm, which was significantlysmaller than earlier experiments performed by otherresearchers. The approach was applied to a diesel fuel spray,and velocities were measured by means of image analysis appliedto double-exposed images of droplets in the spray.To perform the evaluation a test rig wasdeveloped, whereliquid sprays could be optically studied under controlledconditions. In the test rig diesel fuel was injected into apressurized vessel with optical access, which was achievedusing two glass windows, one for the light from the flash, andthe other for the camera. The necessary optics and the camerawere fitted on a rail, to allow for easy adjustment of thefocus. Personal computers controlled the injection sequence andthe image acquisition. The injector used was a prototype withan internal hydraulic pressure booster, which deliversapproximately 100 MPa peak injection pressure. The nozzle usedwas a specially manufactured one with an axial orifice, inorder to fit into the available vessel. The diameter of thenozzle orifice was 110 µm, and the orifice length was 700µm. The temperature in the vessel was 300 K and the gaspressure 3 MPa. The gas in the vessel was air, and consequentlythe gas density was about 35 kg/m3.Enlarging optics in conjunction with a solid-state camerawas used to acquire the images. The magnification of the opticswas about ten times, the useful resolution 10 µm, and thedepth of field approximately 100 µm. The double-exposureswere achieved in two different ways, in the beginning by meansof a spark discharge flash unit able to deliver multiplesparks, with a flash duration of approximately 300 ns, butlater with the shutter of the camera in combination with axenon discharge flash lamp, to achieve shorter exposure times.The spray was lighted up from behind by the flashlight, andconsequently the droplets were visible as dark regions againsta bright background.It was considered convenient to work with an imagevelocimetry software for which the source code was accessible,and for that reason primarily in-house developed codes wereused. Three different velocimetry approaches were evaluated,namely cepstrum, cepstrum with the low frequency pedestalremoved from the intermediate spectrum, and finallyauto-correlation. It was concluded that the most powerfulalgorithm was the cepstrum with pedestal removal. However, thismethod showed significant sensitivity to variations in inputdata, and was therefore rejected. Auto-correlation wasconsidered the most rugged algorithm, and as the images were tobe processed in an automated manner, it was decided thatauto-correlation was to be used.In order to make the final algorithm able to discard imagesfrom which it failed to get correct velocity data, a number offilters and thresholds were used. The filter parameters and thethreshold levels were adjusted manually to treat a smallreference group of images correctly before they were applied tothe real data.Keywords:Liquid spray, diesel spray, dropletvelocities, droplet sizes, spray visualization, sliced spray,particle image velocimetry, spectrum, cepstrum,cross-correlation, auto-correlation.
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| 50. |
- Dahlén, Lars, 1969-
(författare)
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On applied CFD and model development in combustion systems development for DI diesel engines
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soot mediated oil thickening, normally referred to asoilsoot, is a well known problem that can cause increased wearon lubricated moving or rubbing components in diesel engines.The ambition of this thesis is to understand the mechanisms ofcombustion and soot formation that pave the way for thisproblem and use this knowledge in the development of apredictive model for soot contamination of the oil. Anadditional task, however, is the use of Computational FluidDynamics (CFD) as the platform for development of the oilsootmodel.A preliminary hypothesis for soot contamination of the oilis formulated from a combination of theoretical reasoning andprevious experimental evaluations. This states that the oilsootgrowth rate is the result of particle deposition in the oilfilm on the cylinder liner, followed by scraping ofcontaminated oil to the crank case by the piston rings. Acontrolling factor here is assumed to be thermophoresis, whichhas been identified in the past as the dominating particletransport mechanism within the viscous sublayer at combustionchamber surfaces and hence governs the rate of particledeposition in the oil film on the liner.A thermophoretic particle deposition model is suggested forthe calculation of soot deposition on the liner from local sootdistribution as predicted by the standard CFD code. The modelis evaluated through parameter studies comprising the influenceof injection timing, liner temperature, topland height,injected fuel quantity, equivalence ratio, boost pressure andspeed, and the agreement between simulations and measurementsis generally good. It is concluded that the peak in-cylindersoot concentration is more important to oilsoot growth than theexhaust soot level. Moreover, changes in in-cylinder sootdistribution has strong effect on soot mediated oil thickening.Consequently, an important practical guideline to reduce sootmediated oil thickening is to end injection“ontime”, i.e. before the spray guided diffusion flame isdirected into the squish region rather than into the pistonbowl.
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