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  • 1.
    Adamson, Göran
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Holm, Magnus
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Moore, Philip
    Academy of Innovation & Research, Falmouth University, Cornwall, United kingdom.
    Wang, Lihui
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. KTH Royal Institute of Technology, Stockholm, Sweden.
    A Cloud Service Control Approach for Distributed and Adaptive Equipment Control in Cloud Environments2016In: Research and Innovation in Manufacturing: Key Enabling Technologies for the Factories of the Future - Proceedings of the 48th CIRP Conference on Manufacturing Systems / [ed] Roberto Teti, Elsevier, 2016, Vol. 41, p. 644-649Conference paper (Refereed)
    Abstract [en]

    A developing trend within the manufacturing shop-floor domain is the move of manufacturing activities into cloud environments, as scalable, on-demand and pay-per-usage cloud services. This will radically change traditional manufacturing, as borderless, distributed and collaborative manufacturing missions between volatile, best suited groups of partners will impose a multitude of advantages. The evolving Cloud Manufacturing (CM) paradigm will enable this new manufacturing concept, and on-going research has described many of its anticipated core virtues and enabling technologies. However, a major key enabling technology within CM which has not yet been fully addressed is the dynamic and distributed planning, control and execution of scattered and cooperating shop-floor equipment, completing joint manufacturing tasks.

    In this paper, the technological perspective for a cloud service-based control approach is described, and how it could be implemented. Existing manufacturing resources, such as soft, hard and capability resources, can be packaged as cloud services, and combined to create different levels of equipment or manufacturing control, ranging from low-level control of single machines or devices (e.g. Robot Control-as-a-Service), up to the execution of high level multi-process manufacturing tasks (e.g. Manufacturing-as-a-Service). A multi-layer control approach, featuring adaptive decision-making for both global and local environmental conditions, is proposed. This is realized through the use of a network of intelligent and distributable decision modules such as event-driven Function Blocks, enabling run-time manufacturing activities to be performed according to actual manufacturing conditions. The control system’s integration to the CM cloud service management functionality is also described.

  • 2.
    Adamson, Göran
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Wang, Lihui
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Royal Institute of Technology, Stockholm, Sweden.
    Holm, Magnus
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Moore, Philip
    Falmouth University, Cornwall, UK.
    Adaptive Robot Control as a Service in Cloud Manufacturing2015In: ASME 2015 International Manufacturing Science and Engineering Conference: Volume 2: Materials; Biomanufacturing; Properties, Applications and Systems; Sustainable Manufacturing, ASME Press, 2015, Vol. 2, p. Paper No. MSEC2015-9479-Conference paper (Refereed)
    Abstract [en]

    The interest for implementing the concept of Manufacturing-as-a-Service is increasing as concepts for letting the manufacturing shop-floor domain take advantage of the cloud appears. Combining technologies such as Internet of Things, Cloud Computing, Semantic Web, virtualisation and service-oriented technologies with advanced manufacturing models, information and communication technologies, Cloud Manufacturing (CM) is emerging as a new manufacturing paradigm. The ideas of on-demand, scalable and pay-for-usage resource-sharing in this concept will move manufacturing towards distributed and collaborative missions in volatile partnerships. This will require a control approach for distributed planning and execution of cooperating manufacturing activities. Without control based on both global and local environmental conditions, the advantages of CM will not be fulfilled.

    By utilising smart and distributable decision modules such as event-driven FBs, run-time manufacturing operations in a distributed environment may be adjusted to prevailing manufacturing conditions. Packaged in a cloud service for manufacturing equipment control, it will satisfy the control needs in CM. By combining different resource types, such as hard, soft and capability resources, the cloud service Robot Control-as-a-Service can be realised.

    This paper describes the functional perspective and enabling technologies for a control approach for robotic assembly tasks in CM, and describes a scenario for its implementation.

  • 3.
    Adamson, Göran
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Wang, Lihui
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Royal Institute of Technology, Stockholm, Sweden.
    Holm, Magnus
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Moore, Philip
    Falmouth University, Cornwall, United Kingdom.
    Feature-Based Adaptive Manufacturing Equipment Control for Cloud Environments2016In: Proceedings of the ASME 11th International Manufacturing Science and Engineering Conference, 2016, vol 2, American Society of Mechanical Engineers (ASME) , 2016, article id UNSP V002T04A019Conference paper (Refereed)
    Abstract [en]

    The ideas of on-demand, scalable and pay-for-usage resource-sharing in Cloud Manufacturing are steadily attracting more interest. For implementing the concept of Manufacturing as-a-Service in a cloud environment, description models and implementation language for resources and their capabilities are required. A standardized approach for systemived virtualization, servisilisation, retrieval, selection and composition into higher levels of functionality is necessary. For the collaborative sharing and use of networked manufacturing resources there is also a need for a control approach for distributed manufacturing equipment. In this paper, the technological perspective for an adaptive cloud service-based control approach is described, and a supporting information model for its implementation. The control is realized through the use of a network of intelligent and distributable Function Block decision modules, enabling run-time manufacturing activities to be performed according to actual manufacturing conditions. The control system's integration to the cloud service management functionality is described, as well as a feature-level capability model and the use of ontologies and the Semantic Web.

  • 4.
    Adawi, Rahim
    University of Skövde, School of Engineering Science.
    Preventing fatal effects of overworking: Product design solution2018Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    “Overworking to death” is a phenomenon that has been noticeable in developing countries. The cause of death is mainly through ischemic strokes. While the victims’ occupations differed, they all shared a common characteristic, being positioned in a sedentary work, ranging from IT workers to doctors. This project’s aim was to develop a product that prevented or decreased the strokes that derived from sedentary overwork. This was mainly tackled by preventing one of the three causes of developing blood props, slowed blood flow. In order to gather rich data of the phenomenon, a qualitative study was conducted in China, during two months. By doing an extensive structured sampling, information rich data could be gathered during a short period of time. Data were derived from observations, questionnaires and an interview, which then was interpreted to customer needs and the final product specification. The final product became a trouser with an in built dynamic compression mechanic, that can compress the veins mostly during sitting activities, in order to prevent blood stasis. The compression mechanic works like the Chinese finger trap; compressing the calves while sitting and stretching the legs forward. It is made only out of polysaccharides fibres; cotton and corn.

  • 5.
    Ahmed, Adell
    University of Skövde, School of Engineering Science.
    Analys och simulering av produktionsflödet på ett tillverkningsföretag: Simulering kombinerat med Lean-principer2018Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Production concurrence within manufacturing companies is continuously increasing due to production requirements and demand of mass produced customized goods. In order to meet customers’ requirements nowadays, companies need to increase customize production without suffering a loss of quality. In pursuance of an increased production on the main shop floor of the industrial partner involved in this project, the company investigates the idea of investing in an automated pressing machine to centralize the process outside different assembly lines. With the help of automation, simulation, and Lean, the potential of the company to reduce lead times to satisfy the customer needs can be increased.

    The aim of this final year project is to investigate the potential of a stator pressing machine to manage the supply of product parts to four assembly lines. One of the requirements is that the yearly volume of the new system could be increased by 50%.

    The methodology used in this study is based on Lean, simulation, and optimization. In order to have an overview of the problem, a situation analysis was made on the current production flow. Therefore, a data collection process was performed through observations, continuous communication with matter experts, and historical data. This data was used to analyze the system and feed the simulation model of the proposed new system. Different Lean tools were also used for the analysis and improvement of the system.

    The company presented ideas on how they wanted the production flow to look like, which were then further developed and used as a basis for the improvement suggestions. One requirement was that the solution had to be Lean inspired.

    The aim of the study was achieved by creating a simulation model to test how the system would behave in different configurations. A first scenario designed as a Pull flow system where the products were only produced according to demand. The second scenario was a Push based system without considering just-in-time production. The first scenario was presented as suggestion for final solution.

    The result from the simulation scenarios showed a clear difference between the two systems. The Pull flow was more suitable due to a drastic decrease in both number of products as work- in-progress and lead time. The final solution, using a Kanban method, and a suggestion for the production layout of the future production flow is presented in the report.

  • 6.
    Andersson, Daniel
    et al.
    University of Skövde, School of Engineering Science. andersson.daniel89@gmail.com.
    Andersson, David
    University of Skövde, School of Engineering Science. davdii_@live.com.
    Produktionseffektivisering med hjälp av flödessimulering och förbättringsarbete2018Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    AB Furhoffs Rostfria is a company with its base in Skövde. They are specialists in the manufacturing of stainless-steel parts, such as plumbing products, floor wells and sinks. In addition to manufacturing their own products, the company also has a subcontract to manufacture other companies’ products.

    The department where this bachelor thesis will be conducted has a subcontract to manufacturing radar cones and treats only the production of the most frequent manufactured radar cones. The department consists of seven manufacturing steps and three additional steps for one of the details.

    The purpose of the bachelor thesis is to create a simulation model that shows how potential improvement proposals would meet the expected increase of the order intake of the radar cones by streamlining the current production flow. In order to achieve this, a simulation model has been created in which the improvement proposals have been implemented. The improvement proposals that have been tested are based on the data that has been collected through production engineering methods.

    The frame of references describes the theory that constitutes the foundation for the chosen methods. In addition, areas within discrete event simulation, lean production and improvement work have been studied from other works in the literature review. These areas can in some way relate to the work and conclusions of this project.

    The empirical study was conducted by using observations according to genchi genbutsu, conversations and interviews with operators, spaghetti diagrams of the operators and the product flow as well as time studies according to the continuous method. These methods have formed the basis for both the creation of the simulation model, where the current situation is reflected, and for the development of the future state simulation model. The future state simulation model shows the implementation of the improvement proposals that increases efficiency and production volume throughout the system.

    The empirical study resulted in a visual overview of the production flow, standard times, the identification of waste as well as improvement proposals. When all the improvement proposals were implemented, the hourly production was increased by 26.6% and the lead time was reduced by 21.1%. With these improvements, the company can increase their production and profit significantly.

  • 7.
    Andersson, Martin
    University of Skövde, School of Technology and Society.
    Industrial scheduling with evolutionary algorithms using a hybrid representation2011Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Scheduling problems have been studied extensively in the literature but because they are so hard to solve, especially real-world problems, it is still interesting to find ways of solving them more efficiently. This thesis aims to efficiently solve a real-world scheduling problem by using a hybrid representation together with an optimisation algorithm. The aim of the hybrid representation is to allow the optimisation to focus on the parts of the scheduling problem where it can make the most improvement. The new approach used in this thesis to accomplish this goal, is the combination of simulation-based optimisation using genetic algorithms and dispatching rules. By using this approach, it is possible to investigate the effect of putting specified job sequences in certain machines and using dispatching rules in the other. The hypothesis is that the optimisation can use dispatching rules on non-bottleneck machines that have little impact on the overall performance of the line and some specified job sequences on bottleneck machines that are hard to be scheduled efficiently with dispatching rules. This would allow the optimisation to focus on the bottleneck machines and that would produce a more efficient search. The results from the case study shows it is a viable approach exceeding or equalling existing techniques. The hypothesis that the optimisation can focus its efforts is supported by a bottleneck analysis which corresponds with the experimental results from optimisations.

  • 8.
    Andersson, Rasmus
    et al.
    University of Skövde, School of Engineering Science.
    Hellgren, Martin
    University of Skövde, School of Engineering Science.
    ÖKAD PRODUKTIVITET GENOM STÄLLTIDSREDUCERING: En fallstudie2014Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Kongsberg Automotive (KA) is a company operating in the highly competitive automotive industry. At one of its plants located in Mullsjö, assembling of gear transmission systems is taking place. KA sees a need to increase capacity in the section by increasing productivity. A large potential for improvement are identified during the changeover between different product variants in the assembly section. The setup time reduction is expected to increase the productivity in the assembly section, which also contributes to increased flexibility in order to competitively meet customer’s flexible needs. In order to determine the starting position at the improvement work, a situation analysis and suggestions for improvement to reduce setup time can be worked out. Implementation of improvement suggestions can then be adopted. In order to document the current situation and to demonstrate improvements in the setup time reduction a simulation model was establishes. The simulation model will demonstrate an example of when to use production simulation tool.

    To implement the setup time reduction SMED (Single -Minute Exchange of Die) is used, originally developed to reduce the setup time for the press machines. The method aims at reducing setup time to under 10 minutes, the "single- minute'. Through video documentation, participant observation, and further data collection methods the present situation could be determined. This created a good picture of the operations carried out and the time consumption it corresponded to. To verify the data of the current situation timing of work elements according to snapback method was conducted. The simulation model is constructed after Banks twelve-step method with the data gathered during the project. The model is then verified against the situation analysis. When improvement proposals were formulated the values were added ​​into the model, which corresponded to the calculated time improvement proposals. The improvement proposals for the setup time are partly produced by the project, but also through a workshop with staff at KA and focusing on the five previously identified problem areas. The improvement proposals were evaluated on the workshop through a pick chart.

    Five elaborate improvements that require little effort but gives a great effect was presented to KA. To verify theoretical calculations, a pilot with four of the five improvements temporarily implemented. The results showed a reduction of setup time from 38 minutes to 3.7 minutes, which corresponds to an improvement of 90.3%.  The analysis also shows that the improvement creates a reduction in the production rate in normal assembly. In total, the improvements in this project increase OEE value in assembly section with 4.2%. Even so, one of the stated objectives of the project will not be achieved since the setup time activities are too small part of the available time in the assembly section.

  • 9.
    Andersson, Rinat
    et al.
    University of Skövde, School of Engineering Science.
    Johansson, Martin
    University of Skövde, School of Engineering Science.
    Underlag för beslut av investering i ny utrustning2016Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 10.
    Andreasson, Rebecca
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre. Department of Information Technology, Visual Information and Interaction, Uppsala University, Uppsala, Sweden.
    Lindblom, Jessica
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Thorvald, Peter
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Tool use and collaborative work of dock assembly in practice2017In: Production & Manufacturing Research, ISSN 2169-3277, Vol. 5, no 1, p. 164-190Article in journal (Refereed)
    Abstract [en]

    In order to deepen the understanding of the intrinsic interactions andinterplay between humans, tools, and environment from a systemsperspective, research in the wild (RITW) approaches have gainedtraction during recent decades as they provide a higher ecologicalvalidity of findings. This paper presents a RITW study, investigatinghow assembly, in this case dock assembly of forwarders, was donein practice. As our theoretical foundation, we used the framework ofdistributed cognition, which is one of the main pillars of RITW. Thefindings are presented in narrative form, describing and highlightingthat the workers achieve an efficient production outcome by beingintegral parts of the whole production process and doing so throughcoordination of activities benefitting the shared goal of the distributedsocio-technical system.

  • 11.
    Antonsson, Arvid
    et al.
    University of Skövde, School of Engineering Science.
    Hermansson, Gustaf
    University of Skövde, School of Engineering Science.
    System analysis, improvement and visualisation of a manufacturing workflow, using discrete-event simulation: A combination of discrete-event simulation and lean manufacturing2019Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This project has been initiated in cooperation with a Swedish manufacturing company. Due to increased demand and competition, the company wants to streamline its production process, increase the degree of automation and visualize specific workflows. By creating a frame of reference and a literature review, a theoretical basis for methods and concepts which has been utilized throughout the project has been obtained. With the help of the identified methods and methodologies, a current state analysis was performed. Using traditional Lean tools such as Genchi genbutsu, Ishikawa diagram and a 5-why analysis, in combination with time studies and interviews, the current state of the studied system was successfully mapped and analysed. With the help of the current state analysis, which served as a conceptual model, a simulation model of the current state was created in order to handle the large variety and the complexity of the system. The simulation model was validated and verified in order to ensure that it was “good enough” for the purpose of this project in the depiction of the real world system. During the experimental design, several improvement suggestions were created by utilizing methods such as brainstorming, Ishikawa diagram and a 5-why analysis. In a Kaizen event, onsite personnel had the opportunity to decide which suggestions that was fit for experimentation using simulation. With the result of the Kaizen event, experiments were performed in order to evaluate the proposed improvement suggestion. As a result, several new insights regarding improvements could be obtained, which provided several suggestions for an improved future state. Including a proposed automated cell. The analysis of the results did not entirely satisfy the aim of the project since certain factors could not be analysed, therefore the authors recommend that further studies are needed if proposed improvement suggestions are to be implemented.

  • 12.
    Aslam, Tehseen
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Karlsson, Ingemar
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Integrating System Dynamics and Multi-Objective Optimization for Manufacturing Supply Chain Analysis2012In: Proceedings of the 5th Swedish Production symposium (SPS'12), 2012, p. 433-441Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to address the dilemma of Supply Chain Management (SCM) within a truly Pareto-based multi-objective context. This is done by introducing an integration of System Dynamics and Multi-Objective Optimization. Specifically, the paper contrasts local optimization with global optimization for SCM in which optimal trade-off solutions in the entity level, i.e. optimizing the supply chain from the perspectives of individual (local) entities. e.g., supplier, factory, distributor and retailer, are collected and compared to those obtained from an overall supply chain level (global) optimization. An extended version of the well-known pedagogical SCM problem, the Beer Game, originally developed at MIT since the 1960s, has been used as the illustrative example. As will be discussed in the paper, the integrated multi-objective optimization and system dynamics model has been shown to be very useful for revealing that how the parameters in the Beer Game affect the optimality of the three common SCM objectives, namely, the minimization of inventory, backlog, and the bullwhip effect.

  • 13.
    Azamfirei, Victor
    University of Skövde, School of Engineering Science. 1994.
    A visualization approach for improved interpretation and evaluation of assembly line balancing solutions2018Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Future manufacturing will be characterized by the complementarity between humans and automation (human-robot collaboration). This requires new methods and tools for the design and operation of optimized manufacturing workplaces in terms of ergonomics, safety, efficiency, complexity management and work satisfaction. There have been some efforts in the recent years to propose a tool for determining optimal human-automation levels for load balancing.

    Although the topic is quite new, it shares some similarities with some of the existing research in the area of robotic assembly line balancing. Therefore, it is crucial to review the existing literature and find the most similar models and methods to facilitate the development of new optimization models and algorithms.

    One of the two contributions that this thesis gives to the research world in the RALBP context is a literature review that involves high quality articles from 1993 to beginning 2018. This literature review includes visual and comprehensive tables—and a label system— where previous research patterns and trends are highlighted.

    Visualization of data and results obtained by assembly line optimization tools is a very important topic that has rarely been studied. Data visualization would provide a: 1. better comprehension of patterns, trends and qualitative data 2. more constructive information absorption 3. better visualization of relationships and patterns between operations, and 4. better contribution to data manipulation and interaction.

    The second contribution to research found in this thesis is the use of a human modelling (DHM) tool (called IPS), which is proposed as an assessment to the ergonomic risk that a robotic assembly line may involve. This kind of studies are necessary in order to reduce one of the most frequent reasons of work absence in our today society i.e. musculoskeletal disorders (MSDs). MSDs are often the result of poor work environments and they lead to reduced productivity and quality losses at companies. In view of the above, IPS was used in order to resolve the load handling problem between human and robot, depending on their skills and availability, while fulfilling essential ISO standards i.e. 15066 and 10218:1 and :2. The literature review made it possible to select highly useful documents in developing assumptions for the experiment and contributed to consider real features detected in the industry.

    Results show that even though IPS is not capable of calculating an entire robotic assembly with human-robot collaboration, it is able to simulate a workstation constituted of one robot and one human. Finite and assembly motions for both human and robot are expected to be implemented in future versions of the software.

    Finally, the main advantages of using DHM tools in assessing ergonomic risks in RALB can be extracted from the results of this thesis. This advantages include 1. ergonomic evaluation for assembly motions 2. ergonomic evaluation for a full working day (available in future version) and 3. essential ISO standard testing (available in future version). 

  • 14.
    Barrera Diaz, Carlos Alberto
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Oscarsson, Jan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Lidberg, Simon
    Volvo Car Corporation, Skövde, Sweden.
    Sellgren, Tommy
    Volvo Car Corporation, Skövde, Sweden.
    A Study of Discrete Event Simulation Project Data and Provenance Information Management in an Automotive Manufacturing Plant2017In: Proceedings of the 2017 Winter Simulation Conference / [ed] W. K. V. Chan, A. D’Ambrogio, G. Zacharewicz, N. Mustafee, G. Wainer, E. Page, IEEE, 2017, , p. 12p. 4012-4023Conference paper (Refereed)
    Abstract [en]

    Discrete Event Simulation (DES) project data management is a complex and important engineering activity which impacts on an organization’s efficiency. This efficiency could be decreased by the lack of provenance information or the unreliability of existing information regarding previous simulation projects, all of which complicates the reusability of the existing data. This study presents an analysis of the management of simulation projects and their provenance data, according to the different types of scenarios usually found at a manufacturing plant. A survey based on simulation projects at an automotive manufacturing plant was conducted, in order to categorize the information regarding the studied projects, map the available provenance data and standardize its management. This study also introduces an approach that demonstrates how a structured framework based on the specific data involved in the different types of scenarios could allow an improvement of the management of DES projects.

  • 15.
    Bergman, Christian
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Bäckstrand, Gunnar
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Swerea IVF AB, Gothernburg, Sweden.
    Moestam, Lena
    Volvo Group Trucks Operations, Gothenburg, Sweden.
    A Library Based Tool to Assist the Generative Activity in Workstation Design2014In: Advances in Ergonomics in Design, Usability & Special Populations: Part II / [ed] Francisco Rebelo and Marcelo Soares, AHFE Conference , 2014, p. 206-214Conference paper (Refereed)
  • 16.
    Bergström, Bjarne
    et al.
    University of Skövde, School of Technology and Society.
    Sellgren, Tommy
    University of Skövde, School of Technology and Society.
    Flödessimulering och simuleringsbaserad optimering för bristidentifiering och förbättring av bearbetningslinje: Genom data-analys, modellering och flermålsoptimering2013Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
  • 17.
    Bergström, Martina
    et al.
    University of Skövde, School of Technology and Society.
    Larsson, Ida
    University of Skövde, School of Technology and Society.
    Kommunikation i kundorderprocessen: En fallstudie på OFFECCT2007Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis emphasizes the importance of efficient communication on an internal and external level as well as how an organisation should use communication in order to improve its business. Logistics is considered to be a tool for controlling different flows and it can be used to fulfil the needs and wishes of a customer. This thesis has been carried out at the furniture company OFFECCT that cooperates with internationally known designers to develop furniture for a private and public environment. A previous mapping of the orderfulfilment process at this company proved that the communication is not satisfactory. It is very important for OFFECCT as a rather small company to pull off an efficient communication on an internal and external level in order to survive on the market. Some of the reasons for focusing on communication are an increased return on investment and an improved customer service.

    The orderfulfilment process includes several activities, starting off with a need and is finished by the distribution of products and after sales service. The activities create a flow with different kinds of information that are to be sent in between the persons in charge of each activity. The kind of information can vary depending on where in the flow it is located. In order to communicate this information, a process to transmit the message is required so that an interpretation of the sent message is possible. By using different sorts of communication channels, a company can send certain information in a specific way to enhance the scattering of information. Communication and information can be either formal or informal depending on whether it is work related or not. Furthermore, communication should be carried out internal within the company and external with interested parties to obtain a solid organisation that changes with its surroundings. How well a company communicates information can be determined by a few factors such as actual distances and organisational structures.

    Observations and interviews at OFFECCT revealed a few problems within the communication aspects that cause an inferior customer service and difficulties to carry out the orderfulfilment process efficiently. An analysis of the empirical information resulted in a few ideas for improvements and a general process that can be used to improve communication, which are presented further in the thesis.

  • 18.
    Bernedixen, Jacob
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Automated Bottleneck Analysis of Production Systems: Increasing the applicability of simulation-based multi-objective optimization for bottleneck analysis within industry2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Manufacturing companies constantly need to explore new management strategies and new methods to increase the efficiency of their production systems and retain their competitiveness. It is of paramount importance to develop new bottleneck analysis methods that can identify the factors that impede the overall performance of their productionsystems so that the optimal improvement actions can be performed. Many of the bottleneck-related research methods developed in the last two decades are aimed mainly at detecting bottlenecks. Due to their sole reliance on historical data and lackof any predictive capability, they are less useful for evaluating the effect of bottleneck improvements.

    There is an urgent need for an efficient and accurate method of pinpointing bottlenecks, identifying the correct improvement actions and the order in which these should be carried out, and evaluating their effects on the overall system performance. SCORE (simulation-based constraint removal) is a novel method that uses simulation based multi-objective optimization to analyze bottlenecks. By innovatively formulating bottleneck analysis as a multi-objective optimization problem and using simulation to evaluate the effects of various combinations of improvements, all attainable, maximum throughput levels of the production system can be sought through a single optimization run. Additionally, post-optimality frequency analysis of the Pareto-optimal solutions can generate a rank order of the attributes of the resources required to achieve the target throughput levels. However, in its original compilation, SCORE has a very high computational cost, especially when the simulation model is complex with a large number of decision variables. Some tedious manual setup of the simulation based optimization is also needed, which restricts its applicability within industry, despite its huge potential. Furthermore, the accuracy of SCORE in terms of convergence in optimization theory and correctness of identifying the optimal improvement actions has not been evaluated scientifically.

    Building on previous SCORE research, the aim of this work is to develop an effective method of automated, accurate bottleneck identification and improvement analysis that can be applied in industry.

    The contributions of this thesis work include:

    (1) implementation of a versatile representation in terms of multiple-choice set variables and a corresponding constraint repair strategy into evolutionary multi-objective optimization algorithms;

    (2) introduction of a novel technique that combines variable screening enabled initializationof population and variable-wise genetic operators to support a more efficient search process;

    (3) development of an automated setup for SCORE to avoid the tedious manual creation of optimization variables and objectives;

    (4) the use of ranking distance metrics to quantify and visualize the convergence and accuracy of the bottleneck ranking generated by SCORE.

    All these contributions have been demonstrated and evaluated through extensive experiments on scalable benchmark simulation models as well as several large-scale simulation models for real-world improvement projects in the automotive industry.

    The promising results have proved that, when augmented with the techniques proposed in this thesis, the SCORE method can offer real benefits to manufacturing companies by optimizing their production systems.

  • 19.
    Bernedixen, Jacob
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Multiple Choice Sets and Manhattan Distance Based Equality Constraint Handling for Production Systems OptimizationIn: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765XArticle in journal (Refereed)
    Abstract [en]

    Many simulation-based optimization packages provide powerful algorithms to solve industrialproblems. But most of them fail to oer their users the techniques they needto eectively handle multiple-choice problems involving a large set of decision variableswith mixed types (continuous, discrete and combinatorial) and problems that are highlyconstrained (e.g., with many equality constraints). Yet such issues are found in manyreal-world production system design and improvement problems. Thus, this paper introducesa method to eectively embed multiple choice sets and Manhattan-distancebasedconstraint handling into multi-objective optimization algorithms like NSGA-II andNSGA-III. This paper illustrates and evaluates how these two techniques have been appliedtogether to solve optimal workload, buer and workforce allocation problems. Anexample follows, showing their application to a complex production system improvementproblem at an automotive manufacturer.

  • 20.
    Bernedixen, Jacob
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Practical Production Systems Optimization Using Multiple-Choice Sets and Manhattan Distance based Constraints Handling2014In: Industrial Simulation Conference, Skövde, June 11-13, 2014, 2014, p. 97-103Conference paper (Refereed)
    Abstract [en]

    Many simulation-based optimization packages provide powerful algorithms to solve large-scale system problems. But most of them fall short to offer their users the techniques to effectively handle decision variables that are of multiple-choice type, as well as equality constraints, which can be found in many real-world industrial system design and improvement problems. Hence, this paper introduces how multiple choice sets and Manhattan-distance-based constraint handling can be effectively embedded into a meta-heuristic algorithm for simulation-based optimization. How these two techniques have been applied together to make the improvement of a complex production system, provided by an automotive manufacturer, possible will also be presented.

  • 21.
    Bernedixen, Jacob
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Bandaru, Sunith
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    On the convergence of stochastic simulation-based multi-objective optimization for bottleneck identificationIn: International Journal of Production Research, ISSN 0020-7543, E-ISSN 1366-588XArticle in journal (Refereed)
    Abstract [en]

    By innovatively formulating a bottleneck identication problem into a bi-objective optimization,simulation-based multi-objective optimization (SMO) can be eectively used as a new method for gen-eral production systems improvement. In a single optimization run, all attainable, maximum throughputlevels of the system can be sought through various optimal combinations of improvement changes ofthe resources. Additionally, the post-optimality frequency analysis on the Pareto-optimal solutions cangenerate a rank order of the attributes of the resources required to achieve the target throughput levels.Observing that existing research mainly put emphasis on measuring the convergence of the optimizationin the objective space, leaving no information on when the solutions in the decision space have convergedand stabilized, this paper represents the rst eort in increasing the knowledge about the convergence ofSMO for the rank ordering in the context of bottleneck analysis. By customizing the Spearman's footruledistance and Kendall's tau, this paper presents how these metrics can be used eectively to provide thedesired visual aid in determining the convergence of bottleneck ranking, hence can assist the user todetermine correctly the terminating condition of the optimization process. It illustrates and evaluatesthe convergence of the SMO for bottleneck analysis on a set of scalable benchmark models as well as twoindustrial simulation models. The results have shed promising direction of applying these new metrics tocomplex, real-world applications.

  • 22.
    Bernedixen, Jacob
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Bandaru, Sunith
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Variables Screening Enabled Multi-Objective Optimization for Bottleneck Analysis of Production SystemsManuscript (preprint) (Other academic)
    Abstract [en]

    Bottleneck analysis can be defined as the process that includes both bottleneck identification and improvement. In the literature most of the proposed bottleneck-related methods address mainly bottleneck detection. By innovatively formulating a bottleneck analysis into a bi-objective optimization method, recent research has shown that all attainable, maximized TH of a production system, through various combinations of improvement changes of the resources, can be sought in a single optimization run. Nevertheless, when applied to simulation-based evaluation, such a bi-objective optimization is computationally expensive especially when the simulation model is complex and/or with a large amount of decision variables representing the improvement actions. The aim of this paper is therefore to introduce a novel variables screening enabled bi-objective optimization that is customized for bottleneck analysis of production systems. By using the Sequential Bifurcation screening technique which is particularly suitable for large-scale simulation models, fewer simulation runs are required to find the most influenacing factors in a simulation model. With the knowledge of these input variables, the bi-objective optimization used in the bottleneck analysis can customize the genetic operators on these variables individually according to their rank of main effects with the target to speed up the entire optimization process. The screening-enabled algorithm is then applied to a set of experiments designed to evaluate how well it performs when the number of variables increases is a scalable, benchmark model, as well as two real-world industrial-scale simulation models found in the automotive industry. The results have illustrated the promising direction of incorporating the knowledge of influencing variables and variable-wise genetic operators into a multi-objective optimization algorithm for bottleneck analysis.

  • 23.
    Bertilsson, Erik
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Högberg, Dan
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    Chalmers University of Technology.
    Using experimental design to define boundary manikins2012In: Work: A Journal of Prevention, Assessment and Rehabilitation, ISSN 1051-9815, Vol. 41, p. 4598-4605Article in journal (Refereed)
    Abstract [en]

    When evaluating human-machine interaction it is central to consider anthropometric diversity to ensure intended accommodation levels. A well-known method is the use of boundary cases where manikins with extreme but likely measurement combinations are derived by mathematical treatment of anthropometric data. The supposition by that method is that the use of these manikins will facilitate accommodation of the expected part of the total, less extreme, population. In literature sources there are differences in how many and in what way these manikins should be defined. A similar field to the boundary case method is the use of experimental design in where relationships between affecting factors of a process is studied by a systematic approach. This paper examines the possibilities to adopt methodology used in experimental design to define a group of manikins. Different experimental designs were adopted to be used together with a confidence region and its axes. The result from the study shows that it is possible to adapt the methodology of experimental design when creating groups of manikins. The size of these groups of manikins depends heavily on the number of key measurements but also on the type of chosen experimental design.

  • 24.
    Bi, Z. M.
    et al.
    Department of Engineering, Indiana University Purdue University Fort Wayne, Fort Wayne, IN, USA.
    Wang, Lihui
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Optimization of machining processes from the perspective of energy consumption: A case study2012In: Journal of manufacturing systems, ISSN 0278-6125, E-ISSN 1878-6642, Vol. 31, no 4, p. 420-428Article in journal (Refereed)
    Abstract [en]

    One of the primary objectives of sustainable manufacturing is to minimize energy consumption in its manufacturing processes. A strategy of energy saving is to adapt new materials or new processes; but its implementation requires radical changes of the manufacturing system and usually a heavy initial investment. The other strategy is to optimize existing manufacturing processes from the perspective of energy saving. However, an explicit relational model between machining parameters and energy cost is required; while most of the works in this field treat the manufacturing processes as black or gray boxes. In this paper, analytical energy modeling for the explicit relations of machining parameters and energy consumption is investigated, and the modeling method is based on the kinematic and dynamic behaviors of chosen machine tools. The developed model is applied to optimize the  machine setup for energy saving. A new parallel kinematic machine Exechon is used to demonstrate the procedure of energy modeling. The simulation results indicate that the optimization can result in 67% energy saving for the specific drilling operation of the given machine tool. This approach can be extended and applied to other machines to establish their energy models for sustainable manufacturing.

  • 25.
    Blomé, Mikael
    et al.
    Lunds Universitet.
    Dukic, Tania
    Chalmers.
    Hanson, Lars
    Lunds Universitet.
    Högberg, Dan
    University of Skövde, School of Engineering Science.
    Web-Based Protocol for Human Simulation Process and Documentation2003Conference paper (Other academic)
  • 26.
    Bremert, Michael
    et al.
    University of Skövde, School of Technology and Society.
    Persson, Stefan
    University of Skövde, School of Technology and Society.
    Flermålsoptimering och analys av produktionslinje samt identifiering av förbättringsmål2012Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To meet the demands from their customers Volvo Powertrain has set a new production goal for cylinder heads for 13-liter diesels engines. The production lines are built as a flow line of grouped CNC machines, served by a gantry for loading and unloading. The new production goal for one of the production lines, segment 2, is 33 cylinder heads per hour. Volvo Powertrain has also found through the production monitoring-system, Duga, that the waiting time for the loading equipment is a significant amount of the available production time.

    The aim of this project is hence twofold: (1) to verify that the calculations of the waiting time made in Duga are correct; (2) to investigate and propose improvements for the production line in order to achieve the original targeted production goal. This has been done by using simulation and simulation-based optimization technology and for this purpose a generic simulation module of a gantry was made. This project will not answer questions regarding economic consequences, staffing and quality losses in the production line.

    A simulation model has been built in the first phase of the project for a machining cell in Segment 2, which contains one gantry for the loading and unloading operations of four different CNC machining centers connected in series. The simulation model shows that the waiting time of the loading equipment in real time is not as big as what is calculated in Duga. This discrepancy is due to a misleading definition of the waiting time made in Duga.

    The generic gantry module has been used to build a simulation model of Segment 2. Three different optimization runs has been made with an optimization client from the University of Skövde. One of the optimization runs found a solution that matches Volvo Powertrains production goal. From this optimization run one preferred and realistic solution was chosen. The solution includes new levels in buffers along the production line, line balancing and improved availability to the different machines and gantries. The preferred and realistic solution increases the production rate by 10%.

     

  • 27.
    Brolin, Anna
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science.
    An investigation of cognitive aspects affecting human performance in manual assembly2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Modern manufacturing systems seem to be shifting from mass production to mass customisation, which means that systems must be able to manage changes in customer demands and requirements, new technology as well as environmental demands. This in turn leads to an increase in product variants that need to be assembled. To handle this issue, well designed and presented information is vital for assembly workers to perform effective and accurate assembly tasks. In this thesis the main focus has been to find factors that affect human performance in manual assembly. A literature review was made on the subject of manufacturing and usability as well as basic cognitive abilities used to utilise information, such as memory. This investigation identified applicable factors for assessing human cognitive performance within the research field of manufacturing. The thesis further investigates how some of these factors are handled in manual assembly, using case studies as well as observational studies. The results show that how material and information are presented to the assembler needs to be considered in order to have a positive effect on the assembly operation. In addition, a full factorial experimental study was conducted to investigate different ways of presenting material and information at the workstation while using mixed assembly mode with product variants. The material presentation factor involved the use of a material rack compared to using an unstructured kit as well as a structured kit and the information presentation factor involved using a text and number instruction compared to a photograph instruction. The results showed that using a kit is favourable compared to the traditional material rack, especially when using a structured kit combined with photographic instruction. Furthermore, the use of unstructured kits can lead to better productivity and reduced perceived workload, compared to a material rack. Although they are perhaps not as good as using a structured kit, they most likely bring a lower cost, such as man-hour consumption and space requirements. However, the number of components in an unstructured kit needs to be considered in order to keep it on a manageable level. As a conclusion, several scenarios were developed in order to understand how different assembly settings can be used in order to improve human performance at the assembly workstation.

  • 28.
    Brolin, Anna
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Brolin, Erik
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Second cycle education program in virtual ergonomics and design2018In: Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018): Volume VII: Ergonomics in Design / [ed] Sebastiano Bagnara, Riccardo Tartaglia, Sara Albolino, Thomas Alexander, Yushi Fujita, Cham: Springer, 2018, p. 1058-1065Conference paper (Refereed)
    Abstract [en]

    Current product and production development tends to become more complex where principal design decisions are made in very early development phases when product data only exist in virtual formats. To support this virtual product realisation process there exist a number of tools and technologies. Considering ergonomics and human factors in an increasingly complex process with often complex tools requires competent people able to handle multidisciplinary development challenges in a proactive manner. To answer the need for educational programs to cover these issues the School of Engineering Science at University of Skövde has developed a new master (second cycle) program Virtual Ergonomics and Design. The aim with the program is to give students and future product and production developers, necessary knowledge and skills to effectively use virtual tools for analysis, development, and verification of ergonomics and integrate ergonomics and user aspects into the product realisation process. This is achieved through a number of courses that partly forms a core within the subject Virtual product realisation but also provides in-depth knowledge in ergonomics. Students will in a possible future role as design or production engineers have a great influence on ergonomics in manufacturing departments but also better perception of ergonomics, higher motivation and knowledge of support tools and methods for ergonomics integration.

  • 29.
    Brolin, Anna
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, UK.
    Case, Keith
    Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, UK.
    Thorvald, Peter
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Cognitive Aspects Affecting Human Performance in Manual Assembly2016In: Advances in Manufacturing Technology XXX / [ed] Yee Mey Goh, Keith Case, IOS Press, 2016, p. 231-236Conference paper (Refereed)
    Abstract [en]

    This paper concerns the handling of information in assembly work environments. Several studies involving both literature reviews, case studies andobservations were conducted to find factors that affect human performance in manual assembly. The main experiment with 36 subjects used a mixed method design with a quantitative study, including time and errors as dependant measures,a qualitative study, including workload ratings, and a questionnaire. The experiment involved the assembly of a pedal car and the components werepresented using structured kits, unstructured kits and material racks. Assembly information was presented as text & component numbers or photographs, and situations with and without component variation were considered. Among theresults it was found that assembly times and workload ratings were lower when using a kit, whereas using a material rack resulted in perceived decreased workflow and increased stress and frustration. Assembly times and workload ratings were lower when using photographs, whereas using text and numbers increased mental workload.

  • 30.
    Brolin, Anna
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Case, Keith
    Loughborough University, United Kingdom.
    Thorvald, Peter
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Interaction Effects Affecting Human Performance in Manual Assembly2018In: 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, Netherlands: IOS Press, 2018, p. 265-270Conference paper (Refereed)
    Abstract [en]

    This paper presents an experimental study aimed at investigating interaction effects affecting personnel in manual assembly. The main experiment with 36 subjects used a mixed method design which included a quantitative study, including time and errors as dependent measures, and a qualitative study, including workload ratings and a questionnaire. The overall task in the experiment was to assemble components on a pedal car. The main factors involved were assembly information (text & component numbers or photographs), material presentation (using structured kits, unstructured kits and material racks) and component variation (situations with and without component variation). It was found that performance, measured in assembly time, was best when combining photographs with no component variants and when using an unstructured kit.

  • 31.
    Brolin, Anna
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Department of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, United Kingdom.
    Thorvald, Peter
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Case, Keith
    Department of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, United Kingdom.
    Experimental study of cognitive aspects affecting human performance in manual assembly2017In: Production & Manufacturing Research, ISSN 2169-3277, Vol. 5, no 1, p. 141-163Article in journal (Refereed)
    Abstract [en]

    This study investigate different ways of presenting material and information at workstations while using mixed assembly mode with product variants. The experimental set up annotated an assembly line involving 36 subjects. The material presentation factor involved the use of a material rack compared to using an unstructured kit as well as a structured kit. The information presentation factor involved using a text and number instruction compared to a photograph instruction, and situations with and without component variation were considered. Results show that assembly times and workload ratings were lower when using a kit, whereas using a material rack resulted in perceived decreased workflow and increased stress and frustration. Moreover, assembly times and workload ratings were lower when using photographs, whereas using text and numbers increased mental workload. The results could be useful when planning work places and production systems in order to obtain a better workflow and an increased human performance. 

  • 32.
    Brolin, Erik
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Chalmers University of Technology.
    Anthropometric diversity and consideration of human capabilities: Methods for virtual product and production development2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Contemporary product and production development is typically carried out with the support of computer tools where the design of products and workstations are originated and evaluated within virtual environments. Ergonomics addresses factors important to consider in the product and production development process to ensure a good fit between humans and the items being designed. Digital human modelling (DHM) tools enable simulations and analyses of ergonomics in virtual environments. Anthropometry is central when using DHM tools for product and production development to ensure that the design fits the intended proportion of the targeted population from a physical perspective. Several methods have been prescribed to consider the anthropometric diversity that exists within human populations. Still many DHM based simulations in product and production development processes are done with approaches that are poor in representing anthropometric diversity. Hence, there is a need for better tools and methods that would support DHM tool users to more effectively and efficiently consider anthropometric diversity in the design process.

    In this thesis current methods for anthropometric diversity considerations have been reviewed and new methods and functionality have been developed and implemented in a DHM tool. Mathematical models have been developed to consider three specific parts important to the consideration of anthropometric diversity: generation of suitable test cases, prediction of missing anthropometric data and implementation of more diverse anthropometric variables such as strength and flexibility. Results show that the proposed methods are accurate and advantageous compared to approaches often used in industry today. The mathematical models for generation of suitable test cases and prediction of missing anthropometric data have been implemented in an anthropometric software module. The module has undergone usability testing with industry DHM tools users. The developed anthropometric module is shown to answer to relevant needs of DHM tool users and fit into the work processes related to DHM simulations and ergonomics analyses utilised in industry today.

  • 33.
    Brolin, Erik
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Hanson, Lars
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Digital human arm models with variation in size, strength and range of motion2014In: / [ed] Masaaki Mochimaru and Makiko Kouchi, 2014Conference paper (Refereed)
    Abstract [en]

    Digital human modelling (DHM) systems can be used to simulate production processes and analyse the human-machine interaction, particularly at early design stages. The human-machine interaction is affected and limited by factors or characteristics belonging to the human user and the machine or product but also the surrounding environment. DHM systems consider in most cases only physical user capabilities and with focus on consideration of body size related anthropometric diversity. However, the human-machine interaction is not only affected by the size and proportions of a user but for example also the user´s muscle strength and range of motion (ROM). This paper describes a study where diversity in strength and ROM, together with diversity in body size, is implemented in the process of creating data for a group of human arm models. A literature study was done to investigate the diversity of strength and ROM and the correlation between such measurements and body size data. The results from the literature study showed that there is little correlation between body size, strength and ROM. The study also showed that there are few published studies where body size, strength and ROM have been tested at the same time. From the literature study, generic correlation coefficients between body size, strength and ROM were synthesized. Using these correlation coefficients and Principal Component Analysis, data for a group of 14 female arm models with varying body size, strength and ROM were calculated. The results show that it is possible to introduce additional variables such as strength and ROM, but also that data of the correlation between body size and other types of anthropometric measurements are scarce. New measurement studies are important to decrease the uncertainties when predicting correlation coefficients between body size, strength and ROM variables.

  • 34.
    Brolin, Erik
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society. Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Hanson, Lars
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Högberg, Dan
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Örtengren, Roland
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Conditional Regression Model for Prediction of Anthropometric Variables2013In: 2013 Digital human modeling symposium / [ed] Matt Reed, 2013Conference paper (Refereed)
    Abstract [en]

    In digital human modelling (DHM) systems consideration of anthropometry is central. Important functionality in DHM tools is the regression model, i.e. the possibility to predict a complete set of measurements based on a number of defined independent anthropometric variables. The accuracy of a regression model is measured by how well the model predicts dependent variables based on independent variables, i.e. known key anthropometric measurements. In literature, existing regression models often use stature and/or body weight as independent variables in so-called flat regressions models which can produce estimations with large errors when there are low correlations between the independent and dependent variables. This paper suggests a conditional regression model that utilise all known measurements as independent variables when predicting each unknown dependent variable. The conditional regression model is compared to a flat regression model, using stature and weight as independent variables, and a hierarchical regression model that uses geometric and statistical relationships between body measurements to create specific linear regression equations in a hierarchical structure. The accuracy of the models is assessed by evaluating the coefficient of determination, R2 and the root-mean-square deviation (RMSD). The results from the study show that using a conditional regression model that makes use of all known variables to predict the values of unknown measurements is advantageous compared to the flat and hierarchical regression models. Both the conditional linear regression model and the hierarchical regression model have the advantage that when more measurements are included the models will give a better prediction of the unknown measurements compared to the flat regression model based on stature and weight. A conditional linear regression model has the additional advantage that any measurement can be used as independent variable. This gives the possibility to only include measurements that have a direct connection to the design dimensions being sought. Utilising the conditional regression model would create digital manikins with enhanced accuracy that would produce more realistic and accurate simulations and evaluations when using DHM tools for the design of products and workplaces.

  • 35.
    Brolin, Erik
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Högberg, Dan
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Hanson, Lars
    Industrial Development, Scania CV, Södertalje, Sweden / Chalmers University of Technology, Gothenburg, Sweden.
    Description of boundary case methodology for anthropometric diversity consideration2012In: International Journal of Human Factors Modelling and Simulation, ISSN 1742-5549, Vol. 3, no 2, p. 204-223Article in journal (Refereed)
    Abstract [en]

    This paper describes and evaluates the boundary case methodology for the simultaneous consideration of variance for a number of selected anthropometric variables. The methodology includes the calculation of key dimension values for extreme but likely anthropometric measurement combinations. This data can be applied when utilising digital human modelling (DHM) tools for proactive design work and entered as input data when representative manikins are defined. The mathematical procedure is clearly described and exemplified to demonstrate how to use the methodology in design work. The outcome of the method is illustrated and compared using several different cases where the number of measurements is varied and where principal component analysis (PCA) is used to reduce the number of dimensions in one case. The paper demonstrates that the proposed boundary case method is advantageous compared to approaches based on the use of univariate percentile data in design.

  • 36.
    Brolin, Erik
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Design of a Digital Human Modelling Module for Consideration of Anthropometric Diversity2014In: Advances in Applied Digital Human Modeling / [ed] Vincent Duffy, AHFE Conference , 2014, p. 114-120Conference paper (Refereed)
  • 37.
    Brolin, Erik
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Chalmers University of Technology, Gothenburg, Sweden.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Chalmers University of Technology, Gothenburg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Örtengren, Roland
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Adaptive regression model for synthesizing anthropometric population data2017In: International Journal of Industrial Ergonomics, ISSN 0169-8141, E-ISSN 1872-8219, Vol. 59, p. 46-53Article in journal (Refereed)
    Abstract [en]

    This paper presents the development of an adaptive linear regression model for synthesizing of missing anthropometric population data based on a flexible set of known predictive data. The method is based on a conditional regression model and includes use of principal component analysis, to reduce effects of multicollinearity between selected predictive measurements, and incorporation of a stochastic component, using the partial correlation coefficients between predicted measurements. In addition, skewness of the distributions of the dependent variables is considered when incorporating the stochastic components. Results from the study show that the proposed regression models for synthesizing population data give valid results with small errors of the compared percentile values. However, higher accuracy was not achieved when the number of measurements used as independent variables was increased compared to using only stature and weight as independent variables. This indicates problems with multicollinearity that principal component regression were not able to overcome. Descriptive statistics such as mean and standard deviation values together with correlation coefficients is sufficient to perform the conditional regression procedure. However, to incorporate a stochastic component when using principal component regression requires raw data on an individual level.

    Relevance to industry

    When developing products, workplaces or systems, it is of great importance to consider the anthropometric diversity of the intended users. The proposed regression model offers a procedure that gives valid results, maintains the correlation between the measurements that are predicted and is adaptable regarding which, and number of, predictive measurements that are selected.

  • 38.
    Brolin, Erik
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Industrial Development, Scania, Scania CV, Södertälje, Sweden / Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Örtengren, Roland
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Generation and evaluation of distributed cases by clustering of diverse anthropometric data2016In: International Journal of Human Factors Modelling and Simulation, ISSN 1742-5557, Vol. 5, no 3, p. 210-229Article in journal (Refereed)
    Abstract [en]

    This paper describes a study where diversity in body size, strength and joint range of motion, together with diversity in other capability measurements, is included in the process of generating data for a group of test cases using cluster analysis. Descriptive statistics and correlation data was acquired for 15 variables for different age groups and both sexes. Based on this data, a population of 10,000 individuals was synthesised using correlated random numbers. The synthesised data was used in cluster analyses where three different clustering algorithms were applied and evaluated; hierarchical clustering, k-means clustering and Gaussian mixture distribution clustering. Results from the study show that the three clustering algorithms produce groups of test cases with different characteristics, where the hierarchical and k-means algorithm give the most diverse results and where the Gaussian mixture distribution gives results that are in between the first two.

  • 39.
    Brolin, Erik
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Mahdavian, Nafise
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Hanson, Lars
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Industrial Development, Scania CV, Södertälje.
    Johansson, Joakim
    Bombardier Transportation Sweden AB, Västerås.
    Possibilities and challenges for proactive manufacturing ergonomics2019In: Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018): Volume VIII: Ergonomics and Human Factors in Manufacturing, Agriculture, Building and Construction, Sustainable Development and Mining / [ed] Sebastiano Bagnara, Riccardo Tartaglia, Sara Albolino, Thomas Alexander, Yushi Fujita, Cham: Springer, 2019, p. 11-20Conference paper (Refereed)
    Abstract [en]

    This paper identifies and describes product development activities where ergonomics issues could be considered and illustrates how that could be done through a number of different approaches. The study is divided into two parts where an interview study is done to identify where in a product development process consideration of ergonomics issues are or could be done. The second part of the study includes an observation, motion capture and simulation study of current manufacturing operations to evaluate and compare three different assessment approaches; observational based ergonomics evaluation, usages of motion capture data and DHM simulation and evaluation. The results shows the importance of consideration of ergonomics in early development phases and that the ergonomics assessment process is integrated in the overall product and production development process.

  • 40.
    Carlsson, Annika
    University of Skövde, School of Engineering Science.
    Kapacitetsanalys av produktionsflöde: - Med hjälp av produktionssimulering och traditionella produktionstekniska verktyg2014Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Volvo GTO in Skövde belongs to manufacturing and supply engines for truck customers worldwide. All engines to be sent for export goes through a production flow, CBU-line. CBU-line is an assembly line that not since construction in 1996 has undergone any major layout changes of substance, although the details of the flow changed. The object of the project is that by analyzing access conditions in order to determine the flow capacity and to produce focus areas for future improvement efforts.

    The flow lacks a large amount of the production engineering data necessary to assess its capabilities. Based on this a number of methods have been used together to create a picture of the current state of flow. Methods such as time study, work-study and AviX study have been conducted to identify bottlenecks in flow. While it is clear how much work is categorized in value-added in whole flow and per station. In addition to these traditional production engineering tools, there have been a production simulation. Implemented analyzes consistently shows a common bottleneck in the production flow which becomes the focus of improvement efforts.

    Through simulation analysis, the flow technical capacity estimated to be approximately 40 % higher than the throughput that occurs in the flow today. Simulation Analysis based on one developed suggestion for improvement indicates a potential increase of 32 %. To create the conditions to achieve this requires systematic efforts to reduce the effect of interference and wastage in the flow comprising over 70 % of all activity in the flow. The work has proposed that with relatively simple means to reduce bottleneck and increase throughput through the flow.

  • 41.
    Danielsson, Thomas
    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
    Abstract [en]

    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.

  • 42.
    Delfs, Niclas
    et al.
    Fraunhofer-Chalmers Research Centre, Gothenburg, Sweden.
    Bohlin, Robert
    Fraunhofer-Chalmers Research Centre, Gothenburg, Sweden.
    Hanson, Lars
    Industrial Development, Scania CV, Södertälje, Sweden.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Carlson, Johan S.
    Fraunhofer-Chalmers Research Centre, Gothenburg, Sweden.
    Introducing Stability of Forces to the Automatic Creation of Digital Human Postures2013Conference paper (Refereed)
    Abstract [en]

    Although the degree of automation is increasing in manufacturing industries, many assembly operations are performed manually. To avoid injuries and to reach sustainable production of high quality, comfortable environments for the operators are vital. Poor station layouts, poor product designs or badly chosen assembly sequences are common sources leading to unfavorable poses and motions. To keep costs low, preventive actions should be taken early in a project, raising the need for feasibility and ergonomics studies in virtual environments long before physical prototypes are available. Today, in the automotive industries, such studies are conducted to some extent. The full potential, however, is far from reached due to limited software support in terms of capability for realistic pose prediction, motion generation and collision avoidance. As a consequence, ergonomics studies are time consuming and are mostly done for static poses, not for full assembly motions. Furthermore, these ergonomic studies, even though performed by a small group of highly specialized simulation engineers, show low reproducibility within the group.Effective simulation of manual assembly operations considering ergonomic load and clearance demands requires detailed modeling of human body kinematics and motions as well as a fast and robust inverse kinematics solver. In this paper we introduce a stability measure rewarding poses insensitive to variations in contact points and contact forces. Normally this has been neglected and only the balance of moment and forces has been taken into account. The manikin used in this work has 162 degrees of freedom and uses an exterior root. To describe operations and facilitate motion generation, the manikin is equipped with coordinate frames attached to end-effectors like hands and feet. The inverse kinematic problem is to find joint values such that the position and orientation of hands and feet matches certain target frames during an assembly motion. This inverse problem leads to an underdetermined system of equations since the number of joints exceeds the end-effectors’ constraints. Due to this redundancy there exist a set of solutions, allowing us to pick a solution that maximizes a scalar valued comfort function. Many objectives are included in the comfort function, for example in terms of joint angles, joint moments and solid objects’ distance to the manikin. The proposed stability measure complements the earlier balance criterion and is combined into the comfort function. By increasing the importance of this function the digital human model will reposition to a more stable pose. The digital human model will be tested on a set of challenging assembly operations taken from the automotive industry to show the effect of the stability measure.

  • 43.
    Dhanal, Avirat
    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
    Abstract [en]

    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.

  • 44.
    Dudas, Catarina
    et al.
    University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H.C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Boström, Henrik
    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)
    Abstract [en]

    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.

  • 45.
    Eklind, Sebastian
    et al.
    University of Skövde, School of Engineering Science.
    Larsson, Michelle
    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
    Abstract [en]

    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.

  • 46.
    Fathi, Masood
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Fontes, Dalila Benedita Machado Martins
    University of Porto, Portugal / INESC TEC, Porto, Portugal.
    Urenda Moris, Matias
    Jönköping University, Jönköping, Sweden / Uppsala University, Sweden.
    Ghobakhloo, Morteza
    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)
    Abstract [en]

    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.

  • 47.
    Fathi, Masood
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Nourmohammadi, Amir
    Department of Industrial & Systems Engineering, Tarbiat Modares University, Tehran, Iran.
    Ng, Amos H. C.
    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)
    Abstract [en]

    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.

  • 48.
    Fathi, Masood
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Nourmohammadi, Amir
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Syberfeldt, Anna
    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 2169-3536Article in journal (Refereed)
    Abstract [en]

    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.

  • 49.
    Fathi, Masood
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Syberfeldt, Anna
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Ghobakhloo, Morteza
    University of Hormozgan, Bandar Abbas, Iran.
    Eskandari, Hamidreza
    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)
    Abstract [en]

    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.

  • 50.
    Frantzén, Marcus
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    A real-time simulation-based optimisation environment for industrial scheduling2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In order to cope with the challenges in industry today, such as changes in product diversity and production volume, manufacturing companies are forced to react more flexibly and swiftly. Furthermore, in order for them to survive in an ever-changing market, they also need to be highly competitive by achieving near optimal efficiency in their operations. Production scheduling is vital to the success of manufacturing systems in industry today, because the near optimal allocation of resources is essential in remaining highly competitive.

     

    The overall aim of this study is the advancement of research in manufacturing scheduling through the exploration of more effective approaches to address complex, real-world manufacturing flow shop problems. The methodology used in the thesis is in essence a combination of systems engineering, algorithmic design and empirical experiments using real-world scenarios and data. Particularly, it proposes a new, web services-based, industrial scheduling system framework, called OPTIMISE Scheduling System (OSS), for solving real-world complex scheduling problems. OSS, as implemented on top of a generic web services-based simulation-based optimisation (SBO) platform called OPTIMISE, can support near optimal and real-time production scheduling in a distributed and parallel computing environment. Discrete-event simulation (DES) is used to represent and flexibly cope with complex scheduling problems without making unrealistic assumptions which are the major limitations of existing scheduling methods proposed in the literature.  At the same time, the research has gone beyond existing studies of simulation-based scheduling applications, because the OSS has been implemented in a real-world industrial environment at an automotive manufacturer, so that qualitative evaluations and quantitative comparisons of scheduling methods and algorithms can be made with the same framework.

     

    Furthermore, in order to be able to adapt to and handle many different types of real-world scheduling problems, a new hybrid meta-heuristic scheduling algorithm that combines priority dispatching rules and genetic encoding is proposed. This combination is demonstrated to be able to handle a wider range of problems or a current scheduling problem that may change over time, due to the flexibility requirements in the real-world.  The novel hybrid genetic representation has been demonstrated effective through the evaluation in the real-world scheduling problem using real-world data.

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