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• 151.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Laser welding machine specification research2019Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

This paper presents the technical specification of a laser welding machine, which main purpose is the weld of thin aluminium sheets. With the application of laser machines in automotive, aerospace, and other industries, it has become of crucial importance for a company working in those fields to keep updated with the technological progress. In this thesis, a deep research in laser machines and its applications has been done. The primary objective of this thesis is to gather knowledge about laser machines to help our client to find the machines they need. Among the several types of machines, the difference in the choice relied on which main type of industrial laser should be used: carbon dioxide (CO2) or neodymium-doped yttrium aluminium garnet (Nd: YAG). The second objective of this thesis is to find the best way to demand those machines to the procurers: to give detailed specifications to the procurers, or to give them just guidelines on what the machine must have and should have. The key results obtained from the research were that laser source to use is the Nd: YAG and that the most appropriate shielding gas is Argon. Therefore, in conclusion, the specifications stated in the table will help our client to acquire the laser machine they demand; as well as spending the money efficiently.

• 152.
University of Skövde, School of Engineering Science.
Development of Components for a Heat Recycling Shower System2016Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis

Given the unstable state of the environment, there is an undeniable need for the development of sustainable technologies. This need affects all areas of everyday life, even the shower. Modern shower systems result in energy waste in the form of heat, which can be minimized through the implementation of a heat exchanger.

In cooperation with Consat SES this project developed a system to implement a heat exchanger using an in-shower water transportation pipe. A fitting non-electrical pump and motor were also chosen.

To develop these elements a general design methodology of defining the problem, identifying the solution space, developing concepts, testing concepts and proposing a design, was used with adaptations for the component at hand. By following this strategy for each component and then reviewing the system as a whole, a new shower system was developed with a trapezoidal water transport pipe, a wing pump, and a turgo turbine.

• 153.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Design of a Double Cantilever Beam Test Specimen and Fixture for Kink Band Formation in Unidirectional Fibre Reinforced Composites.2015Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis

Composite materials are widely used in demanding applications in aerospace and other industries. In order to understand the complex behaviour of the composite materials and their components, standardised test methods are used. One example is the double cantilever beam (DCB) test in which the test specimen is loaded in an opening, i.e., tensile mode. Failures in composite materials loaded compression are different from those in tension, for example, kink band or buckling-like failures can occur.

In this project, several DCBs are designed and a new fixture which allows for compression testing of a DCB is developed for an existing Instron testing machine. The fixture overcomes a known problem of tensile peak causing the failure of the adhesive at the inner surfaces of the DBC by applying additional compressive loads along the outer surfaces of the DBC. The compressive forces can induce the desired kink band formation so that researchers can better study the failure mode.

The conceptual development of the new DCBs and the new fixture are presented. Several prototypes of the specimens and the fixture are modelled using the three-dimensional (3D) computer-aided design software Creo Parametric 2.0.  One of the fixtures is selected to further study. The different DCB specimens are studied in order to obtain information about the kink band using 3D finite element analysis with the software programme Abaqus CAE. The selected fixture is analysed to determine if there are any areas of concern. Finally, the behaviour of the compression stress along the DCB using two pairs of forces is studied.

Unfortunately, it is determined that the tensile peak experienced by the adhesive cannot be eliminated by the application of two pairs of compressive loads, one at the free end and the other in the vicinity of the tensile peak. Several suggestions are made for future work which might serve to reduce the tensile peak; e.g., the movable force couple is applied as a surface load instead of a point load. For this, the fixture will have to be modified with a new geometry, although the DCB could be the same. This will allow further work to focus on the combined behaviour of the tensile peak and the fixture.

• 154.
University of Skövde, School of Engineering Science.
Adaptive AR-system: Adapting manufacturing instructions to worker needs2015Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis

This thesis looks at Augmented Reality (AR) and Expert Systems (ES) and how concepts from these techniques can be used to make instructions simpler for workers in the manufacturing industry. The experiment performed is based on a case study of “Block 9-11” at Volvo GTO in Skövde. A comparative study between the developed AR-system and the currently used instruction format has been made. For practical reasons the tasks and instructions were modified from the original. The results showed a similar time usage for the two systems but with a large amount of steps missed in the control group as well as a lower subjective usability-score from the testers, showing an advantage for the AR-system. In future work the plan is to further develop the adaptability-aspect, an aspect that didn’t give clear results in this study.

• 155.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Designing Augmented Reality Interfaces for Human-Robot Collaboration in Engine Assembly: Research Proposal2016Report (Other academic)

Customers are becoming more and more individualistic, products are getting more variation and the global market drives for shorter lifecycles for products. The industry is introducing more robots but even though they become more flexible there is still a need for human workers. Fenceless robots and new standards in robotics have made it possible for humans and robots to directly collaborate, allowing them to complement each other with their respective strengths. But how can humans keep up with the increased need for learning new products while collaborating with robots?Studies in using Augmented Reality (AR) show that it might help workers to perform complex operations more efficiently.AR can spatially orient information and thereby present it in context to reality. But AR in actual industrial assembly is still in its infancy, there is a lack of general AR implementations as most AR is done for specific cases and there is still little knowledge about how to generally design AR-based interfaces efficiently.This project aims to explore how AR is most efficiently used in industrial engine assembly. It focuses on cases with Human-Robot Collaboration since the current trend is clear that this will be very common in the future. The goal is to find basic design guidelines for how to best present information to workers; when to present it, what to present and how to present it.Industry representatives will help in creating an evaluation-framework that is relevant for real situations. The guidelines will be iteratively evaluated with this evaluation-framework and designed through the methodology of design science. The goal of this research project is to contribute with a framework for how to evaluate AR-based operator instructions and design guidelines that creates generally more efficient instructions for operators.

• 156.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Terminator technology - this is how it can help the manufacturing industry: The University of Skövde conducting research regarding AR as a form of support for operators2015In: The Vehicle Component, ISSN 1652-862X, no 4, p. 35-36Article in journal (Other (popular science, discussion, etc.))
• 157.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Augmented Reality Smart Glasses for Industrial Assembly Operators: A Meta-Analysis and Categorization2019In: Advances in Manufacturing Technology XXXIII: Proceedings of the 17th International Conference on Manufacturing Research, incorporating the 34th National Conference on Manufacturing Research, 10–12 September 2019, Queen’s University, Belfast, UK / [ed] Yan Jin, Mark Price, Amsterdam: IOS Press, 2019, Vol. 9, p. 173-179Conference paper (Refereed)

Augmented reality smart glasses (ARSG) are an emerging technology that has the potential to revolutionize how operators interact with information in cyber-physical systems. However, augmented reality is currently not widespread in industrial assembly. The aim of this paper is to investigate and map ARSG in manufacturing from the perspectives of the operator, of manufacturing engineering, and of its technological maturity. This mapping provides an overview of topics relevant to enabling the implementation of ARSG in a manufacturing system, thus facilitating future exploration of the three perspectives. This investigation was done using a meta-analysis of literature reviews of applications of augmented reality in industrial manufacturing. The meta-analysis categorized previously identified topics within augmented reality in industrial manufacturing and mapped those to the scope of the three perspectives.

• 158.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Volvo Car Corporation, Skövde, Sweden. KTH Royal Institute of Technology, Kungliga Tekniska högskolan, Stockholm.
Assessing Instructions in Augmented Reality for Human-Robot Collaborative Assembly by Using Demonstrators2017In: Manufacturing Systems 4.0 - Proceedings of the 50th CIRP Conference on Manufacturing Systems / [ed] Mitchell M. Tseng, Hung-Yin Tsai, Yue Wang, Elsevier, 2017, Vol. 63, p. 89-94Conference paper (Refereed)

Robots are becoming more adaptive and aware of their surroundings. This has opened up the research area of tight human-robot collaboration,where humans and robots work directly interconnected rather than in separate cells. The manufacturing industry is in constant need ofdeveloping new products. This means that operators are in constant need of learning new ways of manufacturing. If instructions to operatorsand interaction between operators and robots can be virtualized this has the potential of being more modifiable and available to the operators.Augmented Reality has previously shown to be effective in giving operators instructions in assembly, but there are still knowledge gapsregarding evaluation and general design guidelines. This paper has two aims. Firstly it aims to assess if demonstrators can be used to simulatehuman-robot collaboration. Secondly it aims to assess if Augmented Reality-based interfaces can be used to guide test-persons through apreviously unknown assembly procedure. The long-term goal of the demonstrator is to function as a test-module for how to efficiently instructoperators collaborating with a robot. Pilot-tests have shown that Augmented Reality instructions can give enough information for untrainedworkers to perform simple assembly-tasks where parts of the steps are done with direct collaboration with a robot. Misunderstandings of theinstructions from the test-persons led to multiple errors during assembly so future research is needed in how to efficiently design instructions.

• 159.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. KTH Royal Institue of Technology, Stockholm, Sweden.
Operators perspective on augmented reality as a support tool in engine assembly2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 72, p. 45-50Article in journal (Refereed)

Augmented Reality (AR) has shown its potential in supporting operators in manufacturing. AR-glasses as a platform both in industrial use are emerging markets, thereby making portable and hands-free AR more and more feasible. An important aspect of integrating AR as a support tool for operators is their acceptance of the technology. This paper presents the results of interviewing operators regarding their view on AR technology in their field and observing them working in automotive engine assembly and how they interact with current instructions. The observations and follow-up questions identified three main aspects of the information that the operators looked at: validating screw torque, their current assembly time, and if something went wrong. The interviews showed that a large amount of the operators were positive towards using AR in assembly. This has given an insight in both the current information interaction the operators do and their view on the potential in using AR. Based on these insights we suggest a mock-up design of an AR-interface for engine assembly to serve as a base for future prototype designs.

• 160.
University of Skövde, School of Engineering Science. tomasdanielsson@hotmail.com.
Förslag på flexibel och balanserad monteringslinje: Manuellt monteringsflöde för säsongsberoende efterfrågan2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

Volvo GTO Powertrain is facing the introduction of three new product types of products which shall replace existing product types. In the current situation are the products, which shall be replace by new product types, assembled in three separate flows. The introduction of the new product types includes that two product types are being assembled in the same assembly flow. The purpose of this report is to make suggestions on assembly flows that have the flexibility to produces two of the new product types in the same assembly flow with associated trial area. The assembly flow shall also accomplish the customer’s demand depending on season with 23 - 40 products per shift, with a difference of ± 2,5 %. To adjust the quantity that shall be produced depending on season shall be done by adjusting the quantity of fitters in the assembly flow and the quantity of operators in the trial area.

To create an understanding of the existing assembly flows has an analysis of the present situation, of the assembly flows which shall be combined into one assembly flow, been completed. The data collection in the analysis of the present situation has been completed through interviews with production engineers staff, also by studying the AviX analysis concerning the existing assembly flows. The analysis of the present situation has been founded to create an understanding of how the assembly works today.

Furthermore, Volvo has developed a proposal on how the future assembly flow shall look like. Volvo’s proposal has been founded to create an understanding of the future assembly flow with associated trial area.

To achieve the purpose of this work has two simulation models been created to test the system under different scenarios to manage the varying demand. One of the simulation models is using Volvo’s proposal on the future system and the other model has adjusted cycle times in the trial area through experiments, the work pace in the assembly flow has been rebalanced and the OEE in the trial run has been increased.

The results from the experiments are that the simulation model with adjusted cycle times, rebalanced and increased OEE is capable of coping with the varying demand on 23 – 40 products per shift. However, relatively large adjustments were required from Volvo’s proposal to achieve the desired demand. A table of staffing was created to determine how many fitters and operators were required depending on the quantity of demanded products.

• 161.
University of Skövde, School of Engineering Science.
Lot-sizing and scheduling optimization using genetic algorithm2019Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis

Simultaneous lot-sizing and scheduling problem is the problem to decide what products to be produced on which machine and in which order, as well as the quantity of each product. Problems of this type are hard to solve. Therefore, they were studied for years, and a considerable number of papers is published to solve different lotsizing and scheduling problems, specifically real-case problems. This work proposes a Real-Coded Genetic Algorithm (RCGA) with a new chromosome representation to solve a non-identical parallel machine capacitated lot-sizing and scheduling problem with sequence dependent setup times and costs, machine cost and backlogging. Such a problem can be found in real world production line at furniture manufacturer in Sweden. Backlogging is an important concept in this problem, and it is often ignored in the literature. This study implements three different types of crossover; one of them has been chosen based on numerical experiments. Four mutation operators have been combined together to allow the genetic algorithm to scan the search area and maintain genetic diversity. Other steps like initializing of the population and a reinitializing process have been designed carefully to achieve the best performance and to prevent the algorithm from trapped into the local optimum. The proposed algorithm is implemented and coded in MATLAB and tested for a set of standard medium to large-size problems taken from the literature. A variety of problems were solved to measure the impact of different characteristics of problems such as the number of periods, machines, and products on the quality of the solution provided by the proposed RCGA. To evaluate the performance of the proposed algorithm, the average deviation from the lower bound and runtime for the proposed RCGA are compared with three other algorithms from the literature. The results show that, in addition to its high computational speed, the proposed RCGA outperforms the other algorithms for non-identical parallel machine problems, while it is outperformed by the other algorithms for problems with the more identical parallel machine. The results show that the different characteristics of problem instances, like increasing setup cost, and size of the problem influence the quality of the solutions provided by the proposed RCGA negatively.

• 162.
Michigan State University.
University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. Universidad de Las Palmas de Gran Canaria. University of Minho, Campus de Azurém. Michigan State University.
An integrated approach to automated innovization for discovering useful design principles: Case studies from engineering2014In: Applied Soft Computing, ISSN 1568-4946, E-ISSN 1872-9681, Vol. 15, no 2, p. 42-56Article in journal (Refereed)

Computational optimization methods are most often used to find a single or multiple optimal or near-optimal solutions to the underlying optimization problem describing the problem at hand. In this paper, we elevate the use of optimization to a higher level in arriving at useful problem knowledge associated with the optimal or near-optimal solutions to a problem. In the proposed innovization process, first a set of trade-off optimal or near-optimal solutions are found using an evolutionary algorithm. Thereafter, the trade-off solutions are analyzed to decipher useful relationships among problem entities automatically so as to provide a better understanding of the problem to a designer or a practitioner. We provide an integrated algorithm for the innovization process and demonstrate the usefulness of the procedure to three real-world engineering design problems. New and innovative design principles obtained in each case should clearly motivate engineers and practitioners for its further application to more complex problems and its further development as a more efficient data analysis procedure.

• 163.
Michigan State University, East Lansing, USA.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Ford Motor Company, Dearborn, USA.
Generating Uniformly Distributed Points on a Unit Simplex for Evolutionary Many-Objective Optimization2019In: Evolutionary Multi-Criterion Optimization: 10th International Conference, EMO 2019, East Lansing, MI, USA, March 10-13, 2019, Proceedings / [ed] Kalyanmoy Deb, Erik Goodman, Carlos A. Coello Coello, Kathrin Klamroth, Kaisa Miettinen, Sanaz Mostaghim, Patrick Reed, Cham, Switzerland: Springer, 2019, Vol. 11411, p. 179-190Conference paper (Refereed)

Most of the recently proposed evolutionary many-objective optimization (EMO) algorithms start with a number of predefined reference points on a unit simplex. These algorithms use reference points to create reference directions in the original objective space and attempt to find a single representative near Pareto-optimal point around each direction. So far, most studies have used Das and Dennis’s structured approach for generating a uniformly distributed set of reference points on the unit simplex. Due to the highly structured nature of the procedure, this method does not scale well with an increasing number of objectives. In higher dimensions, most created points lie on the boundary of the unit simplex except for a few interior exceptions. Although a level-wise implementation of Das and Dennis’s approach has been suggested, EMO researchers always felt the need for a more generic approach in which any arbitrary number of uniformly distributed reference points can be created easily at the start of an EMO run. In this paper, we discuss a number of methods for generating such points and demonstrate their ability to distribute points uniformly in 3 to 15-dimensional objective spaces.

The full text will be freely available from 2020-02-03 00:00
• 164.
Department of Electrical and Computer Engineering, Michigan State University, USA.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
R-HV: A Metric for Computing Hyper-volume for Reference Point-based EMOs2015In: Swarm, Evolutionary, and Memetic Computing: 5th International Conference, SEMCCO 2014, Bhubaneswar, India, December 18-20, 2014, Revised Selected Papers / [ed] Bijaya Ketan Panigrahi, Ponnuthurai Nagaratnam Suganthan & Swagatam Das, Springer, 2015, p. 98-110Chapter in book (Refereed)

For evaluating performance of a multi-objective optimizationfor finding the entire efficient front, a number of metrics, such as hypervolume, inverse generational distance, etc. exists. However, for evaluatingan EMO algorithm for finding a subset of the efficient frontier, the existing metrics are inadequate. There does not exist many performancemetrics for evaluating a partial preferred efficient set. In this paper, wesuggest a metric which can be used for such purposes for both attainableand unattainable reference points. Results on a number of two-objectiveproblems reveal its working principle and its importance in assessingdifferent algorithms. The results are promising and encouraging for itsfurther use.

• 165.
University of Skövde, School of Engineering Science.
Design and Analysis of Material Handling System with Simulation-Based Optimization2018Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis

In today’s world, simulation and optimization are playing a vital role in reducing the time, cost and preserving resources. In manufacturing industries, there are ample amount of problems that go on with the expansion of the industry. In such cases, to tackle these problems simulation can be helpful to check whether any change in the current situation makes any effect on the current efficiency of the overall plant. In the presented case study, a solution to the problem of internal and external logistics has been designed by using simulation and optimization to improve part of a material flow of an organization. Basically, the organization whose major production is established in the south of Sweden deals with the manufacturing and assembly of equipment. Before the dispatch, all of them go to the painting section which is the expansion of the present shop floor. However, the design and analysis of the material handling system to feed the new painting line which is going to be established by the organization is the aim of this case study. While achieving this aim the literature regarding the discrete event simulation, Lean and Simulation-Based optimization related to the material handling system has been done. Furthermore, the appropriate material handling systems along with the different scenarios were suggested to reduce the cost and the lead times between the production line and the new painting line. To support this process a methodology combining simulation, optimization and lean production has been implemented under the framework of the design and creation research strategy. In the Kaizen workshop organized at a company with managers and stakeholders, the designed scenarios were presented and after some discussion one of them was chosen and the selected scenario was designed and optimized. Moreover, the Simulation-Based multi-objective optimization has been helpful for the optimization of the designed model proposed as a final solution.

• 166.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
HUR CIRKULÄR EKONOMI KAN IMPLEMENTERAS I SMÅ OCH MEDELSTORA FÖRETAGS PRODUKTUTVECKLING2015Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

Today’s trend of production and consumption has a linear type. Material is extracted, become products and then end up as landfill. This thesis has together with Industrial Development Center AB aimed to create a more sustainable industrial production within the region of Skaraborg, by forming a product development process according to circular economy. Circular economy advocates that there should be no waste and products and material should circulate throughout different cycles. Hence this thesis consist of a broad pre-study to collect and evaluate a big range of theories, processes and enterprise responsibilities. Later on a general product lifecycle was studied and a map of a process was made with circular economy and product development processes in mind. The work was tied together by a performance specification table. This document was also used as a basis for the evaluation of the final product development process with circular economy implemented. Finally, the result was also evaluated by an experienced user to get an initial assessment of the result’s usability for the target groups. The result was an environmentally adapted product development process and a folder explaining how and why circular economy is to support enterprises and the community.

• 167.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde. Department of Computer and Systems Sciences, Stockholm University, Kista, Sweden.
Post-analysis of multi-objective optimization solutions using decision trees2015In: Intelligent Data Analysis, ISSN 1088-467X, E-ISSN 1571-4128, Vol. 19, no 2, p. 259-278Article in journal (Refereed)

Evolutionary algorithms are often applied to solve multi-objective optimization problems. Such algorithms effectively generate solutions of wide spread, and have good convergence properties. However, they do not provide any characteristics of the found optimal solutions, something which may be very valuable to decision makers. By performing a post-analysis of the solution set from multi-objective optimization, relationships between the input space and the objective space can be identified. In this study, decision trees are used for this purpose. It is demonstrated that they may effectively capture important characteristics of the solution sets produced by multi-objective optimization methods. It is furthermore shown that the discovered relationships may be used for improving the search for additional solutions. Two multi-objective problems are considered in this paper; a well-studied benchmark function problem with on a beforehand known optimal Pareto front, which is used for verification purposes, and a multi-objective optimization problem of a real-world production system. The results show that useful relationships may be identified by employing decision tree analysis of the solution sets from multi-objective optimizations.

• 168.
University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Department of Computer and Systems Sciences, Stockholm University, Stockholm, Sweden.
Integration of data mining and multi-objective optimisation for decision support in production system development2014In: International journal of computer integrated manufacturing (Print), ISSN 0951-192X, E-ISSN 1362-3052, Vol. 27, no 9, p. 824-839Article in journal (Refereed)

Multi-objective optimisation (MOO) is a powerful approach for generating a set of optimal trade-off (Pareto) design alternatives that the decision-maker can evaluate and then choose the most-suitable configuration, based on some high-level strategic information. Nevertheless, in practice, choosing among a large number of solutions on the Pareto front is often a daunting task, if proper analysis and visualisation techniques are not applied. Recent research advancements have shown the advantages of using data mining techniques to automate the post-optimality analysis of Pareto-optimal solutions for engineering design problems. Nonetheless, it is argued that the existing approaches are inadequate for generating high-quality results, when the set of the Pareto solutions is relatively small and the solutions close to the Pareto front have almost the same attributes as the Pareto-optimal solutions, of which both are commonly found in many real-world system problems. The aim of this paper is therefore to propose a distance-based data mining approach for the solution sets generated from simulation-based optimisation, in order to address these issues. Such an integrated data mining and MOO procedure is illustrated with the results of an industrial cost optimisation case study. Particular emphasis is paid to showing how the proposed procedure can be used to assist decision-makers in analysing and visualising the attributes of the design alternatives in different regions of the objective space, so that informed decisions can be made in production systems development.

• 169.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Konceptuell utveckling av interiören hos en framtida fullt autonom bil2016Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

The goal with this thesis project has been to collect information for a technical consulting company in order to increase their knowledge about autonomous systems and vehicular communication. The status of how various operators work with active safety systems and how the systems are implemented in current and future vehicles has been investigated through extensive literature studies, interviews and market research. The autonomous systems can collect information from the surrounding through sensors and contribute to better traffic efficiency, increased safety, lighter cars and a better environment. Through vehicle communication, the vehicle can communicate with each other in order to guarantee a safe ride. In 2030 the inner city constitutes of autonomous, electrified public transport to transport people on demand, meanwhile private cars are prohibited. Potential needs for the human in a fully, autonomous car has been identified and various product development methods has been applied in order to develop two conceptual solutions for a future car interior. The solutions show the interaction between human and system since entertainment and comfort becomes important in a fully, autonomous car. Each solution is state-owned and holds four passengers. In the solutions, the seats are placed in regard to facilitate communication between the passengers. The passengers can be entertained or informed individually or collectively by text, sound and images.

• 170.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Function Block Algorithms for Adaptive Robotic Control2014Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis

• 171.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Emulering av en produktioncell med Visionguidning: Virtuell idrifttagning2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

Using a virtual twin of a production cell, makes it possible for programming and different functional testing of panels to be performed in early stages of development. A virtual twin contributes to a simpler debugging and to identify problems and minimize cost in commissioning of the production cell. The aim for the project is to investigate how well an emulated cell will perform compared to the real production cell in a factory acceptance test. Another objective is to investigate how you can use real CAD models in the emulation and what type of criteria the models should meet. The project had a lot of challenges and one of them was the difficulty to emulate the safety systems. This was solved by bypassing the safety in the PLC program. One important thing about emulation is communication between the different software used in the system. In this project, it proved successful to distribute the software on three computers to ease the workload of the programs used in the emulation. To use the emulated model instead of the real system is still in the research phase but in this project a lot of useful applications could be identified that could change commissioning in the future.

• 172.
University of Skövde, School of Engineering Science.
Sensitivity analysis of optimization: Examining sensitivity of bottleneck optimization to input data models2016Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis

The aim of this thesis is to examine optimization sensitivity in SCORE to the accuracy of particular input data models used in a simulation model of a production line. The purpose is to evaluate if it is sufficient to model input data using sample mean and default distributions instead of fitted distributions. An existing production line has been modeled for the simulation study. SCORE is based on maximizing any key performance measure of the production line while simultaneously minimizing the number of improvements necessary to achieve maximum performance. The sensitivity to the input models should become apparent the more changes required. The experiments concluded that the optimization struggles to obtain convergence when fitted distribution models were used. Configuring the input parameters to the optimization might yield better optimization result. The final conclusion is that the optimization is sensitive to what input data models are used in the simulation model.

• 173.
University of Skövde, School of Engineering Science.
Förändring av arbetssätt med hjälp av emulering: Vid automationsprojekt mot industrin2018Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

På uppdrag av Projektengagemang AB i Skövde har detta projekt genomförts för att studera möjligheten att kvalitetssäkra automationsprojekt bättre med hjälp av emulering. I projektets sammanhang innebär det att representera hela eller delar av automationssystemet virtuellt. För att lyckas med projektet har forskning inom områden som projektledning och virtuella miljöer studerats för att undersöka vad som i dagsläget är möjligt att genomföra. Med hjälp av litteraturen utformades ett intervjuprotokoll för genomförande av en intervjustudie. Beställande och levererande företag av automationsutrustning har bidragit för att ge en realistisk bild av hur automationsprojekt genomförs, kvalitetssäkras samt vad som idag är problematiskt. Sammanställningen och analysen av intervjustudien tyder på att vikt skall läggas vid planering och nedbrytning av projekt, för att ha en tydlig plan från början. Samt att virtuella miljöer kan användas för att testa programkod tidigare i projekt, alltså i mindre kritiska lägen. Efter en granskning av Projektengagemangs förutsättningar i förhållande till intervjustudien framkom att det finns brister och förbättringspotential gällande programstruktur och kvalitetssäkring. Förslaget för att öka kvalitetssäkringen med hjälp av emulering innefattar skapandet av ett arbetskoncept där en emuleringsmodell tillsammans med en kravspecifikation används för framtagning av ett grundprogram. Samt att företagets konstruktionsgranskning utökas till att inkludera kontroll av både programmering och eventuell emuleringsmodell. I förslaget till Projektengagemang lämnas 2 olika konfigurationer som skulle kunna användas för att inkludera skapandet och användning av emuleringsmodeller i projekt. Vilket skulle öka kvalitetssäkringen markant. I dagsläget påverkas inte ledtiden markant med införandet av emulering, dock finns möjligheten på längre sikt. Ytterligare kravställningar behöver tas i beaktning innan val av mjukvaror sker, eftersom förutsättningarna för varje projekt påverkar byggnationen av en emuleringsmodell.

• 174.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
High cycle fatigue crack growth in Mode I of adhesive layers: modelling, simulation and experiments2014In: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 190, no 1-2, p. 125-146Article in journal (Refereed)

• 175.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Samarbetet mellan människa och automation i det avhjälpande underhållet: behovsanalys och krav på framtida utveckling av automationsutrustning2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

The project has explored the interaction between humans and automation within the remedial maintenance on two manufacturing companies. The purpose of the project is to contribute to the interaction between humans and automation and by that make it successful in the future. The study has investigated how the present interaction is designed, where there is a need for interaction, how the interaction can be designed in the future together with the requirements that will need to be achieved to get there. In this study there is also a focus on sustainable development and how the interaction affects it. The result of the project is produced by performing two attendance observations, one at each company and four semi-structured interviews at each company. Today a lot of communication is done by phone to get the attention of personnel and summon them to the machine that has stopped. The troubleshooting of the machine is done in a panel or with a computer if deeper troubleshooting is needed. The computer needs to be connected to the machine. Today there are some technics that are present but these are not used due to the fact that they are perceived tedious to use. These technics are communication radio, mouse and keyboard. The result of the study indicates that there is a need for more information in all the phases of a remedial maintenance work. It also shows that the technics needs to be more mobile compared to how it is today. The authors recommends that handheld devices are used in the future and that softwares such as voice recognition, Virtual Reality and Augmented Reality are used within the handheld devices. Smartwatches are also interesting in an attention point of view where alarm messages can be shown. There is a belief that with more information and more mobility the maintenance will be more effective in the future and that the time for remedial maintenance will reduce. The authors strongly recommend that all technics that will be implemented need to first be tested in a realistic environment and by the people that should use it.

• 176.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Deformationsanalys av klämvillkor av en vevaxel2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

Crankshaft deformation is studied in connection with clamping conditions in a whirl milling machine before a cutting process. The purpose of the project is to increase knowledge about the deformation behaviour of the crankshaft and its important functional surfaces by performing analyses using the finite element method (FEM). Volvo Cars in Skövde, Sweden is currently managing unwanted crankshaft deformation occurrence by using time consuming physical testing methods. Therefore, the company wish to use virtual analyses instead of physical tests. This work also leads to a determination if FEM is an applicable tool in order to maintain narrow tolerances of the crankshaft. Using virtual analyses instead of physical tests would be time saving and would also have a positive impact on the environment.

The computer software Abaqus is used to implement the deformation analyses that are also evaluated against physical measurements done with a tensile testing machine (Instron) and thereby be able to ensure the reliability of the used FE model. FE analyses are mainly performed to evaluate the deformation of the crankshaft associated with clamping. Two different crankshaft types are being analysed. A FE model is created for each crankshaft along with applied boundary and load conditions according to performed mechanical analysis of the crankshaft.

Obtained results show that the thrust bearing sides of the crank pins on the crankshaft deform in the range of $10^{-2}$ mm when the crankshaft is compressed during clamping with 0.2 mm. This deformation is considered to entail a risk for a processing error to occur. At the same time the analyses show which surfaces are most/least deformed. Evaluation according to the tensile testing indicates that the direction of the crankshaft deformation corresponds to the analysis but slight deviation of the deformation magnitude is present. The deviations can be explained by variations of the E-module within the crankshaft while the defined E-module in Abaqus has a constant value. Furthermore, there is a possibility that sources of error from the tensile tests can have an influence on the obtained results from the physical measurements.

Conducted analyses indicates that FEM is applicable for crankshaft deformation analyses and recommendations of a suitable FE model are provided. A potential solution of the deformation problem is considered to be the calculation of optimal clamping force.

• 177.
University of Skövde, School of Engineering Science.
Implementering av ekodesignmetoder i Nobias befintliga designprocess2017Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis

The bachelor project has been carried out at the University of Skövde in collaboration with Nobia AB. The purpose of the project was to implement eco-design methods into the company’s existing design process and to accomplish a case study of a cabinet door. The purpose of the case study was to verify the proposed eco-design process and suggest a material for a cabinet door.

Sustainable development, eco-design and lifecycle were studied during the literature study. Interviews were carried out to study the design process at Nobia and to identify the different activities in every phase of the process. The phases were Idea Generation, Concept Development, Product Development and Industrialization. Several eco-design methods were studied to assess their potential to be implemented into Nobia’s existing design process, for example Status Analysis and various Checklists. The expected characteristics of the eco-design process were compiled into a requirement specification.

The methods which were implemented into Nobia’s existing design process resulted in an Eco-design process which consisted of Ekostrategihjul, Philips five fast, Jämförelsematris, Eco-design portfolio, Environmental Failure Mode and Effect Analysis and Scorecard. The case study was initiated by compiling a requirement specification. The most promising materials were Medium Density Fibreboard, bamboo and fir. Through analysis of various materials fir was considered as the best material because of low levels of pollution during transportation, good access to the raw material and it is also locally manufactured.

The results show that the use of eco-design within product development entails many advantages, such as, a pleasant place of work, motivated staff, and a more sustainable design process. A sustainable design process will contribute to the development of sustainable products, which entails a better environment.

• 178.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Vision-Based Perception for Localization of Autonomous Agricultural Robots2017Doctoral thesis, comprehensive summary (Other academic)

In this thesis Stefan investigates how cameras can be used for localization of an agricultural mobile robot. He focuses on relative measurement that can be used to determine where a weeding tool is operating relative a weed detection sensor. It incorporates downward-facing perspective cameras, forward-facing perspective cameras and omnidirectional cameras. Stefan shows how the camera’s ego-motion can be estimated to obtain not only the position in 3D but also the orientation. He also shows how line structures in the field can be used to navigate a robot along the rows.

• 179.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
School of Information Science, Computer and Electrical Engineering, Halmstad University, Halmstad, Sweden.
Analysis of two visual odometry systems for use in an agricultural field environment2018In: Biosystems Engineering, ISSN 1537-5110, E-ISSN 1537-5129, Vol. 166, p. 116-125Article in journal (Refereed)

This paper analyses two visual odometry systems for use in an agricultural field environment. The impact of various design parameters and camera setups are evaluated in a simulation environment. Four real field experiments were conducted using a mobile robot operating in an agricultural field. The robot was controlled to travel in a regular back-and-forth pattern with headland turns. The experimental runs were 1.8–3.1 km long and consisted of 32–63,000 frames. The results indicate that a camera angle of 75° gives the best results with the least error. An increased camera resolution only improves the result slightly. The algorithm must be able to reduce error accumulation by adapting the frame rate to minimise error. The results also illustrate the difficulties of estimating roll and pitch using a downward-facing camera. The best results for full 6-DOF position estimation were obtained on a 1.8-km run using 6680 frames captured from the forward-facing cameras. The translation error (x,y,z) is 3.76% and the rotational error (i.e., roll, pitch, and yaw) is 0.0482 deg m−1. The main contributions of this paper are an analysis of design option impacts on visual odometry results and a comparison of two state-of-the-art visual odometry algorithms, applied to agricultural field data.

The full text will be freely available from 2020-03-01 00:01
• 180.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Reductions in Energy Consumption through Process Optimisation and Variable Production2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

Energy efficiency is becoming an important objective for modern manufacturing industry. The aim of this work is to improve energy efficiency of an automated system. Since a majority of production processes are limited by an external bottleneck, the hypothesis of this work is that reducing the processing rate of the restricted processes can lead to saving in energy and resources. A methodology based on optimisation at process, cell and line levels is developed and evaluated over different scenarios.The developed methodology is then applied to a simulated production cell to study its efficacy quantitatively. In this particular case, the proposed approach yields a decrease in energy consumption of 49% at maximum production capacity. This decrease can be greater if there is an external factor such as low demand or another stage in the production line.

• 181.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Analys av lagerhaveri2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis

The short lifespan of a bearing is analyzed in a carousel wheel at Skara Sommarland. The aim of this report is to find the cause of failure for the bearing. The machine that is to be analyzed is mounted on the ground between the rails. Unpredictable breakdowns for the machine causes high expenses, as maintenance has to be carried out and the carousel has to be shut down, which makes it unable to generate revenue from customers. A number of bearings was analyzed using a microscope. The purpose of this analysis was to identify, categorize and compare the microscope pictures with SKF’s reference pictures. Results from the analysis show that the unsuitable loads have very little effect on bearing failure. Results from the microscope analysis shows clear images of damage in the bearing. Traces of scratches and indentations on the inside indicates that dust and particles have contaminated the bearing. The pictures also show rust on the inside of the bearing. To avoid or minimize the problem of short bearing life, some improvements are suggested. One suggestion is to make some sort of cover to lower or prevent moisture and water from entering the bearing. Two concepts for the cover were developed for suggestions on how these bearing covers might look like. The concepts were mainly developed to keep water out of the bearing. To ensure that contaminations are the biggest cause of bearing failure, more microscope analyses of the bearings should be performed in the future.

• 182.
Chalmers University of Technology, Gothenburg, Sweden.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre. Insert Coin, Gothenburg, Sweden. Tecnologico de Monterrey, Mexico. Profactor, Studgart, Austria.
Conceptualizing Embodied Automation to Increase Transfer of Tacit knowledge in the Learning Factory2018In: "Theory, Research and Innovation in Applications": 9th International Conference on Intelligent Systems 2018 (IS’18) / [ed] Ricardo Jardim-Gonçalves, João Pedro Mendonça, Vladimir Jotsov, Maria Marques, João Martins, Robert Bierwolf, IEEE, 2018, p. 358-364, article id 8710482Conference paper (Refereed)

This paper will discuss how cooperative agent-based systems, deployed with social skills and embodied automation features, can be used to interact with the operators in order to facilitate sharing of tacit knowledge and its later conversion into explicit knowledge. The proposal is to combine social software robots (softbots) with industrial collaborative robots (co-bots) to create a digital apprentice for experienced operators in human- robot collaboration workstations. This is to address the problem within industry that experienced operators have difficulties in explaining how they perform their tasks and later, how to turn this procedural knowledge (knowhow) into instructions to be shared among other operators. By using social softbots and co-bots, as cooperative agents with embodied automation features, we think we can facilitate the ‘externalization’ of procedural knowledge in human-robot interaction(s). This enabled by the capabilities of social cooperative agents with embodied automation features of continuously learning by looking over the shoulder of the operators, and documenting and collaborating with them in a non-intrusive way as they perform their daily tasks.

• 183.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Porto, Portugal / INESC TEC, Porto, Portugal. Jönköping University, Jönköping, Sweden / Uppsala University, Sweden. University of Hormozgan, Bandar Abbas, Iran.
Assembly line balancing problem: a comparative evaluation of heuristics and a computational assessment of objectives2018In: Journal of Modelling in Management, ISSN 1746-5664, E-ISSN 1746-5672, Vol. 13, no 2, p. 455-474Article in journal (Refereed)

Purpose – The purpose of this study is to firstly investigate the efficiency of the most commonly used performance measures for minimizing the Number of Workstations (NWs) in approaches addressing Simple Assembly Line Balancing Problem (SALBP) for both straight and U-shaped line. Secondly, this study aims to provide a comparative evaluation of 20 constructive heuristics to find solutions to the SALBP-1.

Design/methodology/approach – 200 problems are solved by 20 different constructive heuristics for both straight and U-shaped assembly line. Moreover, several comparisons have been made to evaluate the performance of constructive heuristics.

Findings – Minimizing the Smoothness Index (SI) is not necessarily equivalent to minimizing the NWs, therefore, it should not be used as the fitness function in approaches addressing the SALBP-1. Line efficiency (LE) and the idle time (IT) are indeed reliable performance measures for minimizing the NWs. The most promising heuristics for straight and U-shaped line configurations for SALBP-1 are also ranked and introduced.

Practical implications – Results are expected to help scholars and industrial practitioners to better design effective solution methods for having a most balance assembly line. This study will further help with choosing the most proper heuristic with regard to the problem specifications and line configuration.

Originality/value – There is limited research assessing the efficiency of the common objectives for SALBP-1. This study is among the first to prove that minimizing the workload smoothness is not equivalent to minimizing the NWs in SALBP-1 studies. This work is also one of the first attempts for evaluating the constructive heuristics for both straight and U-shaped line configurations.

• 184.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Department of Industrial Engineering, Minab Higher Education Center, University of Hormozgan, Bandar Abbas, Iran / Modern Technology Development and Implementation Research Center, University of Hormozgan, Bandar Abbas, Iran. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
An Interpretive Structural Modeling of Teamwork Training in Higher Education2019In: Education Sciences, E-ISSN 2227-7102, Vol. 9, no 1, p. 1-20Article in journal (Refereed)

In the past decade, the importance of teamwork training in higher education and employers’ enthusiasm for recruiting team players have been widely discussed in the literature. Yet, the process through which effective teamwork training is developed in a higher education setting has not yet been properly discussed. The present study aims to map the precedence relationships among the key determinants of teamwork training effectiveness and explain the process through which an effective teamwork training program can be developed. The study first conducted an extensive review of the literature to highlight the key determinants of effective teamwork training. Next, the study benefitted from an interpretive structural modeling technique and captured the opinions of a group of teamwork training experts to further map the interrelationships among the potential determinants that were identified. By listing the key determinants of effective teamwork training, mapping their interrelationships, and identifying their driving and dependence power, the present study is expected to help practitioners and academicians through providing a detailed understanding of the process through which an effective teamwork training program can be developed in a higher education context.

• 185.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Department of Industrial & Systems Engineering, Tarbiat Modares University, Tehran, Iran. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Assembly Line Balancing Type-E with Technological Requirement: A Mathematical Model2018In: Advances in Manufacturing Technology XXXII: Proceedings of the 16th International Conference on Manufacturing Research, incorporating the 33rd National Conference on Manufacturing Research, September 11–13, 2018, University of Skövde, Sweden / [ed] Peter Thorvald, Keith Case, Amsterdam: IOS Press, 2018, p. 183-188Conference paper (Refereed)

This study is motivated by a real-world assembly line in an automotive manufacturing company and it addresses the simple assembly line balancing problem type-E (SALBPE). The SALBPE aims to maximize the balance efficiency (BE) through determining the best combinations of cycle time and station number. To cope with the problem, a mixed integer nonlinear programming (MINLP) model is proposed. The MINLP model differs from the existing ALBPE models as it includes the technological requirements of assembly tasks and optimizes the variation of workload beside the BE. The validity of the proposed model is tested by solving the real-world case study and a set of benchmark problems.

• 186.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
An optimization model for balancing assembly lines with stochastic task times and zoning constraints2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 32537-32550, article id 8663269Article in journal (Refereed)

This study aims to bridge the gap between theory and practice by addressing a real-world assembly line balancing problem (ALBP) where task times are stochastic and there are zoning constraints in addition to the commonly known ALBP constraints. A mixed integer programming (MIP) model is proposed for each of the straight and U-shaped assembly line configurations. The primary objective in both cases is to minimize the number of stations; minimizing the maximum of stations’ mean time and the stations’ time variance are considered secondary objectives. Four different scenarios are discussed for each model, with differences in the objective function. The models are validated by solving a real case taken from an automobile manufacturing company and some standard test problems available in the literature. The results indicate that both models are able to provide optimum solutions for problems of different sizes. The technique for order preference by similarity to ideal solution (TOPSIS) is used to create reliable comparisons of the different scenarios and valid analysis of the results. Finally, some insights regarding the selection of straight and U-shaped layouts are provided.

• 187.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Faculty of Management and Economics, Tarbiat Modares University, Tehran, Iran.
An improved genetic algorithm with variable neighborhood search to solve the assembly line balancing problem2019In: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077Article in journal (Refereed)
• Purpose – This study aims to propose an efficient optimization algorithm to solve the assembly line balancing problem (ALBP). The ALBP arises in high-volume, lean production systems when decision makers aim to design an efficient assembly line while satisfying a set of constraints.
• Design/methodology/approach – An improved genetic algorithm (IGA) is proposed in this study to deal with ALBP in order to optimize the number of stations and the workload smoothness.
• Findings – To evaluate the performance of the IGA, it is used to solve a set of well-known benchmark problems and a real-life problem faced by an automobile manufacturer. The solutions obtained are compared against two existing algorithms in the literature and the basic genetic algorithm. The comparisons show the high efficiency and effectiveness of the IGA in dealing with ALBPs.
• Originality/value – The proposed IGA benefits from a novel generation transfer mechanism that improves the diversification capability of the algorithm by allowing population transfer between different generations. In addition, an effective variable neighborhood search is employed in the IGA to enhance its local search capability.
• 188.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Hormozgan, Bandar Abbas, Iran. Tarbiat Modares University, Tehran, Iran.
An optimization model for material supply scheduling at mixed-model assembly lines2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 72, p. 6p. 1258-1263Article in journal (Refereed)

This study is motivated by a real case study and addresses the material supply problem at assembly lines. The aim of the study is to optimally schedule the delivery of raw material at assembly lines while using the minimum number of vehicles. To cope with the problem an original mixed integer linear programming model has been proposed based on the assumptions and constraints observed in the case study. The validity of the model has been examined by solving several real cases and analysing different scenarios. The results of the study show the efficiency and effectiveness of the model.

• 189.
Dept. of Electronics and Computing, Mondragon Unibertsitatea, Arrasate-Mondragón, Spain.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Dept. of Electronics and Computing, Mondragon Unibertsitatea, Arrasate-Mondragón, Spain.
Virtual commissioning of a robotic cell: An educational case study2019In: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA, Institute of Electrical and Electronics Engineers Inc. , 2019, p. 820-825Conference paper (Refereed)

The emergence of software tools for testing control programs and virtual commissioning (VC) in industrial automation projects makes it possible to shorten lead times and improve product quality, but it also brings to light the need for competent technicians in these technologies. The academic environment can support the education of future professionals by reproducing and solving industrial problems in the classroom. This article presents a use case in which students work on a project to develop and validate the control system of a robotic cell. The study compares the conventional way of working against the use of a digital twin and exposes the benefits of it.

• 190.
Mälardalen University, Eskilstuna, Sweden.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Mälardalen University, Eskilstuna, Sweden. Division of Industrial Engineering and Management, University of Uppsala, Uppsala, Sweden. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Simulation-based Optimization for Facility Layout Design in Conditions of High Uncertainty2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 72, p. 334-339Article in journal (Refereed)

Despite the increased use of Simulation based Optimization, the design of facility layout is challenged by high levels of uncertainty associatedwith new production processes. Addressing this issue, this paper aims to understand the conceptual modeling activities of Simulation-basedOptimization for facility layout design in conditions of high uncertainty. Based on three in-depth case studies, the results of this paper showhow characterization criteria of production systems can be used in conceptual modelling to reduce uncertainty. These results may be essentialto support managers and stakeholders during the introduction of new production processes in the design of facility layouts.

• 191.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Suitability of a virtual commissioning model for energy optimization of a gantry robot2019Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

Manufacturing production systems are increasingly forced to join the path of sustainability regarding their typical room for improvement in terms of clean technology and energy usage. However, implementing these eco-friendly measures on facilities is a double-edged sword since the results are not usually guaranteed and could end up being extra energy wastages. Even though nowadays it is usually made for sequence fixing and training tasks, virtual commissioning comes alternatively into action showing up to test energy optimization attempts preventing the premature execution issues that could happen.

This project has developed a VC model of a gantry crane system from a Volvo operation including energy consumption monitoring, aiming to test its suitability on energy optimization tasks. The development has been accomplished following the design and creation methodology through the use of Matlab, Codesys and Simumatik 3D and quantitative results are given specifically from different energy modeling drafts until reaching the closest result to the real system consumption. Once the true to reality model was developed, the optimization test was carried out decreasing the maximum velocity of the system behavior to see the energy consumption variation. This constitutes the ultimate test and its results are discussed coming into the conclusion that the VC model is suitable for energy optimization of the treated operation but would require reconfigurations for aggressive velocity changes.

• 192.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace Engine Systems.
Improved remaining useful life estimations for on-condition parts in aircraft engines2016Licentiate thesis, comprehensive summary (Other academic)

This thesis focuses on obtaining better estimates of remaining life for on-condition (OC) parts in aircraft engines. Aircraft engine components are commonly classified into three categories, life-limited parts (LLP), OC-parts and consumables. Engine maintenance typi-cally accounts for 10% to 20% of aircraft-related operating cost. Current methods to esti-mate remaining life for OC parts have been found insufficient and this thesis aims to devel-op a method that obtains better life estimates of OC part. Improved life estimates are es-sential to facilitate more reliable maintenance plans and lower maintenance costs. In the thesis, OC parts that need a better life estimates are identified and suitable prognosis methodologies for estimating the remaining life are presented.

Three papers are appended to the thesis. The first paper lays out the main principles of air-craft engine maintenance and identifies the potential for improving maintenance planning by improving the remaining life estimation for the OC parts. The paper concludes that re-search is needed to find better estimates so that the right amount of maintenance is per-formed at each maintenance occasion.

The second paper describes the aircraft and its engine from a system of system perspective. The aim of the paper is to show that no system is stronger than its weakest part and that there is a potential to increase the availability and readiness of the complete system, the aircraft engine, by introducing better life estimates for OC parts. Furthermore, a review of all engine parts, no matter if they are life-limited or on-condition, which needs to be incor-porated in a replacement model for maintenance optimization, is given. The paper con-cludes that the reliability of the complete aircraft engine would be increased if better life estimates are presented also for the OC parts.

The third paper includes an evolved analysis of the subject and the analysis moves deeper in to a subsystem/module of the engine, the low pressure turbine. The specific subsys-tem/module is further analyzed to show the potential of increased reliability for the subsys-tem/module and the complete system, the aircraft engine, if better life estimates for the OC parts are obtained. Methods on how to estimate remaining life is discussed in this paper. It is stated that life estimates can be based on visual inspections, available testing methods (e.g. non destructive testing ) or new techniques that may be need to be developed based on remaining useful life estimations. To estimate the remaining life for the OC parts well es-tablished prognostic techniques such as physic-based, data-driven, symbolic, hybrid, or context awareness approaches that combine contextual/situation information awareness will be considered.

• 193.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace.Engine Systems.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace Engine Systems.
Aircraft engines: A maintenance trade-off in a complex system2015Conference paper (Refereed)

An aircraft engine is a system of systems with several degrees of complexity. It is important to perform the correct amount of maintenance at each individual maintenance event. A mathematical replacement model is used to ensure that the correct amount of maintenance is performed. However, this paper shows that the reliability of this model could be improved if there were a better way to estimate the life length of on-condition maintained engine parts.

• 194.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Luleå University of Technology. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace.
On-Condition Parts versus life limited parts: A trade off in aircraft engines2016In: Current Trends in Reliability, Availability, Maintainability and Safety: An Industry Perspective / [ed] U. Kumar, A. Ahmadi, A. K. Verma & P. Varde, 2016, p. 253-262Conference paper (Refereed)
• 195.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace Engine Systems, Trollhättan, Sweden.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace Engine Systems, Trollhättan, Sweden.
RUL estimation and maintenance optimization for aircraft engines: A system of system approach2016In: International Journal of Systems Assurance Engineering and Management, ISSN 0975-6809, E-ISSN 0976-4348, Vol. 7, no 4, p. 450-461Article in journal (Refereed)

An aircraft engine is a system of systems with several degrees of complexity. It is important to perform the correct amount of maintenance at each individual maintenance event. A mathematical replacement model is used to ensure that the correct maintenance is performed. The reliability of the results from the mathematical replacement model will be improved if there is a better way to estimate the life length for on-condition engine parts.

• 196.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace Engine Systems, Trollhättan, Sweden. Department of Information Engineering, University of Florence, Florence, Italy. Department of Information Engineering, University of Florence, Florence, Italy.
Maintenance, prognostics and diagnostics approaches for aircraft engines2016In: 3rd IEEE International Workshop on Metrology for Aerospace, MetroAeroSpace 2016: Proceedings, IEEE, 2016, p. 403-407Conference paper (Refereed)

In avionics application one of the most important competition factors is the reliability, given that the failure occurrence may leads to a critical state for the functioning of the aircraft. Different maintenance, prognostics and diagnostics approaches are possible with the final aim to optimize both system's availability and safety. Aircraft engines represent a safety critical part of the airplane. For this reason it is a key issue to allocate the proper amount of maintenance at each individual maintenance event. In this paper a mathematical replacement model is proposed to guarantee that the correct amount of maintenance is performed.

• 197.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. GKN Aerospace Engine Systems.
More reliable aircraft engine maintenance optimization by a classification framework for on-condition parts2014In: Proceedings of the 6th Swedish Production Symposium, SPS14, Gothenburg, Sweden, Chalmers , 2014Conference paper (Refereed)
• 198.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Volvo Group Trucks Operations, Powertrain Production Skövde, Skövde, Sweden. Volvo Group Trucks Operations, Powertrain Production Skövde, Skövde, Sweden.
Dynamic maintenance priority of a real-world machining line2016In: Proceedings of the 7th Swedish Production Symposium, 2016Conference paper (Refereed)

To support the shop-floor operators, decision support systems (DSS) are becoming more and more vital to the success of manufacturing systems in industry today. In order to get a DSS able to adapt to disturbances in a production system, on-line data are needed to be able to make optimal or near-optimal decisions in real-time (soft real-time). This paper investigates one part of such a system, i.e. how different priorities of maintenance activities (planned and unplanned) affect the productivity of a production system. A discrete-event simulation model has been built for a real-world machining line in order to simulate the decisions made in subject to disturbances. This paper presents a way of prioritizing operators and machines based on multiple criteria such as competence, utilization, distance, bottleneck, and Work-In-Process. An experimental study based on the real-world production system has shown promising results and given insights of how to prioritize the operators in a good way. Another novelty introduced in this paper is the use of simulation-based optimization to generate composite dispatching rules in order to find good tradeoffs when taking a decision of which machine or operator to select.

• 199.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
Production simulation education using rapid modeling and optimization: Successful studies2015In: Proceedings of the 2015 Winter Simulation Conference / [ed] L. Yilmaz, W. K. V. Chan, I. Moon, T. M. K. Roeder, C. Macal, and M. D. Rossetti, Piscataway, NJ: IEEE Press, 2015, p. 3526-3537Conference paper (Refereed)

A common issue facing many simulation educators is that students usually spend excessive time to struggle with the programming and statistic parts of the simulation courses, and simply very little time to learn running systems analysis. If the students are coming from industry, and not the campus, then the problem becomes even worse. We observed this problem around 2005 and started to develop a new simulation software, a factory conceptual design toolset, partly aimed to address this problem. A new set of educational courses has since then been developed around the software for teaching production systems analysis, with both the campus students and managers/engineers from industry in mind. In this paper, we briefly introduce the software and share our experiences and some representative, successful studies conducted by the students in the past years.

• 200.
University of Skövde, School of Engineering Science.
University of Skövde, School of Engineering Science.
Effektivisering av konstruktörens arbete i produktutvecklingsprocessen med hjälp av 3D-modeller och detaljritningar2017Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis

This project was made for the Bachelor Degree Project in Product Design Engineering course at the University of Skövde by Cecilia Frydén and Nadia Omri in cooperation with the engineering company ÅF during the spring of 2017. ÅF’s designers spends several hours creating 3D-models and detail drawings as manufacturing information for the manufacturing phase of the product development. Some of this time is suspected to be spent unnecessary since some of the information generated by the designers might not be used during the manufacturing process. The aim of the project is to generate a solution to increase the efficiency of the designer’s workflow while generating Product Manufacturing Information (PMI) without compromising the manufacturer’s understanding of the information. Research upon the product manufacturing information generation and handling was done in order to identify its main issues. Observation and interviews were done in order to identify its users and clarify the main purpose of the manufacturing information. The result provides reduced PMI in the 3D-model and uses a 3D-PDF to communicate the PMI to the manufacturers. This was decided from evaluations with the manufacturers and designers and is believed to improve the communication between them but also to make the designer’s workflow more efficient.

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