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  • 201.
    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.
    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.

  • 202.
    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, The Virtual Systems Research Centre. University of Skövde, School of Engineering Science.
    Pehrsson, Leif
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Volvo Car Corporation, Gothenburg, Sweden.
    Antonsson, Tobias
    Volvo Car Corporation, Gothenburg, Sweden.
    Simulation-based multi-objective bottleneck improvement: Towards an automated toolset for industry2015In: Proceedings of the 2015 Winter Simulation Conference / [ed] L. Yilmaz, W. K. V. Chan, I. Moon, T. M. K. Roeder, C. Macal, and M. D. Rossetti, Press Piscataway, NJ: IEEE Press, 2015, p. 2183-2194Conference paper (Refereed)
    Abstract [en]

    Manufacturing companies of today are under pressure to run their production most efficiently in order to sustain their competitiveness. Manufacturing systems usually have bottlenecks that impede their performance, and finding the causes of these constraints, or even identifying their locations, is not a straightforward task. SCORE (Simulation-based COnstraint REmoval) is a promising method for detecting and ranking bottlenecks of production systems, that utilizes simulation-based multi-objective optimization (SMO). However, formulating a real-world, large-scale industrial bottleneck analysis problem into a SMO problem using the SCORE-method manually include tedious and error-prone tasks that may prohibit manufacturing companies to benefit from it. This paper presents how the greater part of the manual tasks can be automated by introducing a new, generic way of defining improvements of production systems and illustrates how the simplified application of SCORE can assist manufacturing companies in identifying their production constraints.

  • 203.
    Bernedixen, Jacob
    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.
    Optimal Buffer Allocation for Semi-synchronized Automotive Assembly Lines using Simulation-based Multi-objective Optimization2011In: Proceedings of the 9th Industrial Simulation Conference, Eurosis , 2011, p. 129-135Conference paper (Refereed)
    Abstract [en]

    A practical question in industry in designing or re-designing a production system is: how small can intermediated buffers be to ensure the desired production rate? This topic is usually called optimal buffer allocation as the goal is to allocate the minimum buffer capacities to optimize the performance of the line. This paper presents a case study of using simulation-based evolutionary multi-objective optimization to determine the optimal buffer capacities and positions in the reconfiguration of a real-world truck axle assembly line in an automobile manufacturer. The case study has not only revealed the applicability of the methodology in seeking optimal configurations in a truly multi-objective context, it also illustrates how additional important knowledge was gained by analyzing the optimization results in the objective space.

  • 204.
    Bertilsson, Erik
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Gustafsson, E.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Hanson, L.
    Chalmers University of Technology.
    Högberg, Dan
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Swedish engineering anthropometric web resource2011In: Proceedings of the 43rd Annual Nordic Ergonomics Society Conference / [ed] Juha Lindfors Merja Savolainen, Seppo Väyrynen, University of Oulu , 2011, p. 442-446Conference paper (Refereed)
    Abstract [en]

    Anthropometry, the study of human measurements, is central in the design of products and workplaces. This paper describes how Swedish anthropometric data is made available through a web page (www.antropometri.se) intended to be used by designers and engineers when developing new products and workplaces. With the anthropometric web resource it is possible to get mean and standard deviation values, and to calculate percentile values, for a number of anthropometric measurements. Further functionality on the web page enables simultaneous consideration of several anthropometric measurements. The web page also contains guidelines for how to use anthropometric data depending on the design task at hand.

  • 205.
    Bertilsson, Erik
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Hanson, L.
    Chalmers University of Technology.
    Högberg, Dan
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Rhén, Ida-Märta
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Creation of the IMMA manikin with consideration of anthropometric diversity2011In: Proceedings of the 21st International Conference on Production Research (ICPR), Fraunhofer Verlag , 2011Conference paper (Refereed)
    Abstract [en]

    Digital human modelling (DHM) systems are used to simulate production processes and analyse the human-machine interaction, particularly at early development stages. Consideration of anthropometric variation is central in DHM simulations due to the necessity of ensuring intended accommodation levels. This paper describes the process of how digital human models are created and defined within the IMMA software. The process begins with the definition of a number of key measurements, which acts as the basis for the definition of several boundary manikins using a confidence ellipsoid methodology. These manikins represents the appropriate confidence region and hence the anthropometric diversity. Key measurements are then entered into regression equations to define the complete set of measurements for each manikin. These measurements are based on the appropriate ISO-standard. Finally, measurements are used to define the size and alignment of each segment in the biomechanical model of the manikin. The manikins are then used to automatically simulate and analyse human-machine interaction.

  • 206.
    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
    Department of Product and Production Development, Chalmers University of Technology, Göteborg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Digital Human Model Module and Work Process for Considering Anthropometric Diversity2010In: Proceedings of the 3rd Applied Human Factors and Ergonomics (AHFE) International Conference / [ed] Gavriel Salvendy, Waldemar Karwowski, Louisville: AHFE International , 2010Conference paper (Refereed)
    Abstract [en]

    In digital human modelling (DHM), ergonomics evaluations are typically done with few human models. However, humans vary a lot in sizes and shapes. Therefore, few manikins can rarely ensure accommodation of an entire target population. Different approaches exist on how to consider anthropometric diversity. This paper reviews current  DHM  tools  and  clarify  problems  and  opportunities  when  working  with anthropometric diversity. The aim is to suggest  functionality  for a state of the art DHM  module  and  work  process  for  considering  anthropometric  diversity.  The study is done by an analysis of some of the current DHM systems and by interviews of  personnel  at  car  companies  about  their  way  of  working  with  anthropometric diversity. The study confirmed that critical production simulations are often done in early development stages with only one or a few human models. The reason for this is claimed to be time consuming processes, both at the creation of the human model but  mainly  when  correctly  positioning  the  model  in  the  CAD  environment.  The development  of  a  new  method  and  work  process  for  considering  anthropometric diversity is suggested. Necessary features for such a module are that it shall be easy to use and not require expert knowledge about the consideration of anthropometric diversity. It shall also be configurable and transparent, in a sense that it should be possible  to  work  with  own  anthropometric  data  and  ergonomics  evaluation standards. The module has to be flexible and have different entrances depending on the type of anthropometric problem being analyzed. An improved work method is expected to lead to faster and more correct analyses.

  • 207.
    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.

  • 208.
    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.
    Wondmagegne, Yosief
    University of Skövde.
    Multidimensional consideration of anthropometric diversity2011In: Proceedings of DHM, First International Symposium on Digital Human Modeling, Université Claude Bernard Lyon , 2011, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Boundary manikins, the concept of creating statistically extreme cases to accommodate a big part of the less extreme population has been known for decades. Despite this, many ergonomics simulations are done with few human models. This fact can be explained by the time consuming processes when working with many manikins in current digital human modelling (DHM) tools, but may also be a result of difficulty to understand how these manikins are calculated and defined. This paper focuses on the method of defining boundary manikins and how that functionality can be integrated into a DHM tool. Examples of boundary case methods in the literature often use Principal Component Analysis (PCA) which makes it possible to reduce the dimensions of the problem without much loss of the variance of the analysed data. Using PCA often demands some extent of manual analysis at the critical stage of reducing dimensions. This paper will explain a similar methodology for ceating boundary manikins from any number of variables, i.e. anthropometric variables chosen as key measurements. This method of creating a group of manikins is intended to be used in an automatic simulation feature in the IMMA software being developed in the associated research project. By using the method, a confidence region in the standardized space is created from eigenvectors and scaled eigenvalues of a correlation matrix. Boundary manikins are chosen at the ends of the axes of the enclosing confidence region, and one manikin of mean values is also added to the group of manikins. In the method presented here, the number of manikins created depends directly on the number of variables, which lead to the fact that the decision making of which key measurements to consider has to be done carefully to not create an overwhelming number of manikins. In comparison with one method using PCA, the method presented in this paper creates more manikins with a bigger difference in the max and min values of the chosen key measurements. If a limited number of cases are of crucial interest, then using PCA to reduce the dimensions of the problem is a good method to use. But if it is possible to create automated simulations the limitation of the number of manikins might not be so important. This will, though, depend heavily on the speed of the automated simulations.

  • 209.
    Bertilsson, 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.
    Keyvani, Ali
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden / Innovatum AB, Trollhättan, Sweden.
    Högberg, Dan
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Hanson, Lars
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Assessment of manikin motions in IMMA2012In: Advances in Applied Human Modeling and Simulation / [ed] Vincent G. Duffy, Boca Raton: CRC Press, 2012, p. 235-244Chapter in book (Refereed)
    Abstract [en]

    When evaluating human-machine interaction in a virtual environment using Digital human modelling (DHM) it is important to ensure that the predicted motions lie within the range of behavioural diversity for different people within a population. This paper presents a study in which a comparison is made between motions predicted by the DHM tool IMMA (Intelligently Moving Manikin) and motions from real humans stored in a motion database. Results show similar motions but the predicted motions were in total statistically significantly different compared to the motions performed by real persons. The differences are most likely due to the balance function and joint constraints that the IMMA tool uses for predicting motions. Differences can also be due to other factors, aside of body size, such as age, gender or strength that affects the movement behaviour.

  • 210.
    Bertilsson, Erik
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Svensson, Erik
    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
    Department of Product and Production Development, Chalmers University of Technology, Göteborg, Sweden / Industrial Development, Scania CV, Södertälje, Sweden.
    Use of digital human modelling and consideration of anthropometric diversity in Swedish industry2010In: Proceedings of the 42nd annual Nordic Ergonomic Society Conference, 2010Conference paper (Refereed)
    Abstract [en]

    This  paper  study  and  clarify  problems,  needs  and  opportunities  when  working  with anthropometric  diversity  in  digital  human  modelling  (DHM)  systems.  A  comparison between  product  development  and  production  development  in  Swedish  automotive industry is made. Interviews with DHM users and ergonomics specialists about their way of working with anthropometric diversity confirmed that simulations are often done with only one or  a  few  human models.  The reason for  this  is  claimed  to  be  time  consuming processes, both at the creation of the human model but mainly when correctly positioning the model in the CAD environment.

  • 211.
    Bevilacqua, Fernando
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre. Federal University of Fronteira Sul, Chapecó, Brazil.
    Engström, Henrik
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Backlund, Per
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Accuracy Evaluation of Remote Photoplethysmography Estimations of Heart Rate in Gaming Sessions with Natural Behavior2018In: Advances in Computer Entertainment Technology: 14th International Conference, ACE 2017, London, UK, December 14-16, 2017, Proceedings / [ed] Adrian David Cheok, Masahiko Inami, Teresa Romão, Springer, 2018, 1, p. 508-530Conference paper (Refereed)
    Abstract [en]

    Remote photoplethysmography (rPPG) can be used to remotely estimate heart rate (HR) of users to infer their emotional state. However natural body movement and facial actions of users significantly impact such techniques, so their reliability within contexts involving natural behavior must be checked. We present an experiment focused on the accuracy evaluation of an established rPPG technique in a gaming context. The technique was applied to estimate the HR of subjects behaving naturally in gaming sessions whose games were carefully designed to be casual-themed, similar to off-the-shelf games and have a difficulty level that linearly progresses from a boring to a stressful state. Estimations presented mean error of 2.99 bpm and Pearson correlationr = 0.43, p < 0.001, however with significant variations among subjects. Our experiment is the first to measure the accuracy of an rPPG techniqueusing boredom/stress-inducing casual games with subjects behaving naturally.

  • 212.
    Bevilacqua, Fernando
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre. Federal University of Fronteira Sul, Chapecó, Brazil.
    Engström, Henrik
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Backlund, Per
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Automated analysis of facial cues from videos as a potential method for differentiating stress and boredom of players in games2018In: International Journal of Computer Games Technology, ISSN 1687-7047, E-ISSN 1687-7055, article id 8734540Article in journal (Refereed)
    Abstract [en]

    Facial analysis is a promising approach to detect emotions of players unobtrusively, however approaches are commonly evaluated in contexts not related to games, or facial cues are derived from models not designed for analysis of emotions during interactions with games. We present a method for automated analysis of facial cues from videos as a potential tool for detecting stress and boredom of players behaving naturally while playing games. Computer vision is used to automatically and unobtrusively extract 7 facial features aimed to detect the activity of a set of facial muscles. Features are mainly based on the Euclidean distance of facial landmarks and do not rely on pre-dened facial expressions, training of a model or the use of facial standards. An empirical evaluation was conducted on video recordings of an experiment involving games as emotion elicitation sources. Results show statistically signicant dierences in the values of facial features during boring and stressful periods of gameplay for 5 of the 7 features. We believe our approach is more user-tailored, convenient and better suited for contexts involving games.

  • 213.
    Bevilacqua, Fernando
    et al.
    Computer Science, Federal University of Fronteira Sul, Chapecó 89802 112, Brazil.
    Engström, Henrik
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Backlund, Per
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Game-Calibrated and User-Tailored Remote Detection of Stress and Boredom in Games2019In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 19, no 13, p. 1-43, article id 2877Article in journal (Refereed)
    Abstract [en]

    Emotion detection based on computer vision and remote extraction of user signals commonly rely on stimuli where users have a passive role with limited possibilities for interaction or emotional involvement, e.g., images and videos. Predictive models are also trained on a group level, which potentially excludes or dilutes key individualities of users. We present a non-obtrusive, multifactorial, user-tailored emotion detection method based on remotely estimated psychophysiological signals. A neural network learns the emotional profile of a user during the interaction with calibration games, a novel game-based emotion elicitation material designed to induce emotions while accounting for particularities of individuals. We evaluate our method in two experiments (n = 20 and n = 62) with mean classification accuracy of 61.6%, which is statistically significantly better than chance-level classification. Our approach and its evaluation present unique circumstances: our model is trained on one dataset (calibration games) and tested on another (evaluation game), while preserving the natural behavior of subjects and using remote acquisition of signals. Results of this study suggest our method is feasible and an initiative to move away from questionnaires and physical sensors into a non-obtrusive, remote-based solution for detecting emotions in a context involving more naturalistic user behavior and games.

  • 214.
    Bi, Z. M.
    et al.
    Department of Engineering, Indiana University Purdue University Fort Wayne, Fort Wayne, IN, United States.
    Wang, Lihui
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    A Study on Optimal Machine Setups Using an Energy Modeling Approach2012In: Proceedings of NAMRI/SME, Society of Manufacturing Engineers, North American Manufacturing Research Institution of SME , 2012, p. 571-579Conference paper (Refereed)
    Abstract [en]

    In this paper, energy models are developed based on the kinematic and dynamic behaviors of chosen machine tools. One significant benefit of the developed energy models is their inherited relationship to the design variables involved in the manufacturing processes. Therefore, they can be readily applied to optimize process parameters to reduce energy consumption. A new parallel kinematic machine Exechon is used as a case study to demonstrate the procedures of energy model development with direct relation to appropriate process parameters. The derived energy model is then used for simulation of drilling operations on aircraft components to demonstrate its feasibility. Simulation results indicate that the developed energy model has led to an optimized machine setup which only consumes less than one-third of the energy of an average machine setup over the workspace. This approach can be extended and applied to other machines to establish their energy models for green manufacturing.

  • 215.
    Bi, Z. M.
    et al.
    Department of Engineering, Indiana University Purdue University Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805, United States.
    Wang, Lihui
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Advances in 3D data acquisition and processing for industrial applications2010In: Robotics and Computer-Integrated Manufacturing, ISSN 0736-5845, E-ISSN 1879-2537, Vol. 26, no 5, p. 403-413Article, review/survey (Refereed)
    Abstract [en]

    A critical task of vision-based manufacturing applications is to generate a virtual representation of a physical object from a dataset of point clouds. Its success relies on reliable algorithms and tools. Many effective technologies have been developed to solve various problems involved in data acquisition and processing. Some articles are available on evaluating and reviewing these technologies and underlying methodologies. However, for most practitioners who lack a strong background on mathematics and computer science, it is hard to understand theoretical fundamentals of the methodologies. In this paper, we intend to survey and evaluate recent advances in data acquisition and progressing,and provide an overview from a manufacturing perspective. Some potential manufacturing applications have been introduced, the technical gaps between the practical requirements and existing technologies discussed, and research opportunities identified.

  • 216.
    Bi, Z. M.
    et al.
    Queen's University Belfast, UK.
    Wang, Lihui
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Design of a Cobot with Three Omni-Wheels2009In: Proceedings of the 19th International Conference on Flexible Automation and Intelligent Manufacturing / [ed] Farhad Nabhani, Catherine Frost, Sara Zarei, Munir Ahmad, William. G. Sullivan, Gemini International Ltd , 2009, p. 360-367Conference paper (Refereed)
    Abstract [en]

    Collaborative robots (Cobots) have been proposed to guide and assist human operators to move heavy objects in a given trajectory. Most of the existing cobots us steering wheels; typical drawbacks of using steering wheels include (i) the difficulty to follow a trajectory with a curvature larger than that of the base platform, (ii) the difficulty to mount encoders on steering wheels due to self-spinning of the wheels, and (iii) the difficulty to quarantine dynamic control performance since it is purely kinematic control. In this paper, a new cobot with the omni-wheels has been proposed, and its design model has been developed, and a simulation has been conducted to validate this control performance.

  • 217.
    Bi, Z. M.
    et al.
    Indiana University Purdue University Fort Wayne.
    Wang, Lihui
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Energy Modeling of Machine Tools for Optimization of Machine Setups2012In: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, Vol. 9, no 3, p. 607-613Article in journal (Refereed)
    Abstract [en]

    In this paper, a new energy model is developed based on the kinematic and dynamic behaviors of a chosen machine tool. One significant benefit of the developed energy model is their inherited relationship to the design variables involved in the manufacturing processes. Without radical changes of the machine tool’s structure, the proposed model can be readily applied to optimize process parameters to reduce energy consumption. A new parallel kinematic machine Exechon is used as a case study to demonstrate the modeling procedure. The derived energy model is then used for simulation of drilling operations on aircraft components to verify its feasibility. Simulation results indicate that the developed energy model has led to an optimized machine setup which only consumes less than one-third of the energy of an average machine setup over the workspace. This approach can be extended and applied to other machines to establish their energy models for green and sustainable manufacturing.

  • 218.
    Bi, Z. M.
    et al.
    Indiana University Purdue University Fort Wayne.
    Wang, Lihui
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Feasibility Study on a Collaborative Robot with Omni-wheels2010In: Proceedings of the 12th Mechatronics Forum Biennial International Conference / [ed] Thomas Kennel, Zürich: IWF Institute of Machine Tools and Manufacturing , 2010, p. 114-120Conference paper (Refereed)
    Abstract [en]

    Robotics has brought radical changes to maximise the productivity of modern manufacturing. However, a full  automation  is  not  always  advantageous;  sometimes  robots  and  human  being  must  work  together  in  a shared  environment  to  meet  specific  requirements.  A  robot  used  in  a  collaborative  environment  is  a collaborative robot. In this paper, a collaborative robot to assist human being’s locomotion is considered: omni-wheels  are  used  to  increase  the  flexibility  and  mobility  of  the  robot  and  they  are  controlled dynamically  to  confine  the  robot  in  a  prescribed  trajectory.  The  new  control  algorithms  are  developed  to meet the following challenges (a) unpredictable driving force from a human operator; (b) the rotation of an omni-wheel along two axes but with one independent motion; and (c) the strongly-coupled kinematics and dynamics of the mobile robot.

  • 219.
    Bi, Z. M.
    et al.
    Indiana University-Purdue University Fort Wayne, USA.
    Wang, Lihui
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Optimal design of reconfigurable parallel machining systems2009In: Robotics and Computer-Integrated Manufacturing, ISSN 0736-5845, E-ISSN 1879-2537, Vol. 25, no 6, p. 951-961Article in journal (Refereed)
    Abstract [en]

    A reconfigurable machining system is usually a modularized system, and its configuration design concerns the selections of modules and the determination of geometric dimensions in some specific modules. All of its design perspectives from kinematics, dynamics, and control have to be taken into considerations simultaneously, and a multidisciplinary design optimization (MDO) tool is required to support the configuration design process. This paper presents a new MDO tool for reconfigurable machining systems, and it includes the following works: (i) the literatures on the computer-aided design of reconfigurable parallel machining systems have been reviewed with a conclusion that the multidisciplinary design optimization is essential, but no comprehensive design tool is available to reconfigurable parallel machining systems; (ii) a class of reconfigurable systems called reconfigurable tripod-based machining system has been introduced, its reconfiguration problem is identified, and the corresponding design criteria have been discussed; (iii) design analysis in all of the disciplines including kinematics, dynamics, and control have been taken into considerations, and design models have been developed to evaluate various design candidates; in particular, the innovative solutions to direct kinematics, stiffness analysis for the design configurations of tripod-based machines with a passive leg, and concise dynamic modelling have been provided; and (iv) A design optimization approach is proposed to determine the best solution from all possible configurations. Based on the works presented in this paper, a computer-aided design and control tool have been implemented to support the system reconfiguration design and control processes. Some issues relevant to the practical implementation have also been discussed.

  • 220.
    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.

  • 221.
    Bi, Z. M.
    et al.
    Indiana University - Purdue University of Fort Wayne, USA.
    Wang, Lihui
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Visualisation and Verification of Communication Protocols for Networked Distributed Systems2010In: Enterprise Networks and Logistics for Agile Manufacturing / [ed] Lihui Wang, S. C. Lenny Koh, London: Springer, 2010, p. 333-357Chapter in book (Other academic)
    Abstract [en]

    The successful design and application of a large and complex manufacturing system relies not only  on  the  maturity  of  its  fundamental  design,  but  also  on  the  technologies  for  seamless integration  and  coordination  of  system  components,  since  a  large  manufacturing  or  logistic system  often  adopts  a  decentralised  control  architecture  to  manage  its  complexity.  System components  are  usually  distributed;  their  behaviours  are  enacted  locally  and  autonomously. The control objective at the system-level is achieved by the executions of the sub-objectives at the component level, subjected to the condition that the controls of the sub-systems have to be coordinated via effective communication. In developing algorithms for communication and coordination  of  a  networked  distributed  system,  algorithm  verification  is  complicated  and trivial,  due  to  the  invisible  information  system.  In  this  chapter,  we  propose  to  use  the conventional   simulation   tool,   Deneb/QUEST,   for   modelling   and   visualisation   of   the coordinating  behaviours.  Its  vivid  graphical  environment  can  be  a  great  assistance  in accelerating  software  debugging  and  verification  and  in  reducing  the  time  for  software development. General architecture of a networked distribute system is introduced, the system components  are  analysed,  and  the  correspondences  between  these  components  and  QUEST elements  are  established.  A  case  study  for  the  verification  of  ring  extrema  determination (RED) algorithm is used as an example to illustrate the general procedure and the feasibility of the proposed approach.

  • 222.
    Bi, Z.M.
    et al.
    Indiana University Purdue University Fort Wayne.
    Wang, Lihui
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Dynamic control model of a cobot with three omni-wheels2010In: Robotics and Computer-Integrated Manufacturing, ISSN 0736-5845, E-ISSN 1879-2537, Vol. 26, no 6, p. 558-563Article in journal (Refereed)
    Abstract [en]

    In this paper, a new collaborative robot with omni-wheels has been proposed and its dynamic control has been developed and validated. Collaborative robots (Cobots) have been introduced to guide and assist human operators to move heavy objects in a given trajectory. Most of the existing cobots use steering wheels; typical drawbacks of using steering wheels include the difficulties to (i) follow a trajectory with a curvature larger than that of the base platform, (ii) mount encoders on steering wheels due to self-spinning of the wheels, and (iii) quarantine dynamic control performance since it is purely kinematic  control.  The  new  collaborative  robot  is  proposed  to  overcome  the  above-mentioned shortcomings. The methodologies for its dynamic control are focused and the simulation has been conducted to validate the control performance of the system.

  • 223.
    Biel, Anders
    University of Skövde, School of Technology and Society.
    Cohesive laws for adhesives at repeated loading: an experimental methodManuscript (Other academic)
  • 224.
    Biel, Anders
    University of Skövde, School of Technology and Society.
    Constitutive behaviour and fracture toughness of an adhesive layer2005Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    This report presents the fracture energy and the complete stress – elongation relation for a structural adhesive loaded in modus I. The experiments are performed on the Double Cantilever Beam (DCB) specimen and the method to analyse the experiments is based on the J-integral approach which means that the energy release rate, i.e. J, is measured continuously during an experiment. Since J is given by the area under the stress – elongation relation for the adhesive layer, both the fracture energy and the stress – elongation relation can be measured in the experiments. The geometry of the specimens is varied in order to examine if the evaluated stress – elongation relation is a unique constitutive relation for the adhesive layer. No dependence on the specimen geometry has been detected provided that the adherends only deform elastically. If the adherends are allowed to deform plastically the fracture energy increases and the stress – elongation relation from the elastically deforming tests cannot be used to simulate the structural behaviour. This is interpreted as an effect of a substantially shorter damage zone with the plastically deforming adherends. An evaluation of effects of the loading rate is also performed. This shows that the fracture energy increases with the loading rate. A number of standardized methods are available to evaluate the fracture properties of adhesives from experiments on the DCB-specimen. Furthermore, alternative methods have recently been suggested by Tamuzs et al. (2003). In an effort to examine the accuracy of the alternative methods, FE-simulations are performed and evaluated according to the alternative methods. The simulations are based on the stress – elongation relation evaluated from the present experiments. Large differences between the correct and the evaluated fracture energies are found for most of the methods. Two of the methods show good accuracy and appear particularly promising. Stress whitening is used to evaluate the length of the damage zone. This length compares reasonably well with the length evaluated from FE-simulations of the experiments.

  • 225.
    Biel, Anders
    University of Skövde, School of Technology and Society.
    Mechanical behaviour of adhesive layers: experimental methods, cohesive laws, and fracture mechanics2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Adhesive joining is today viewed as one of the key technologies to achieve decreased emissions in the automobile industry. To decrease weight, optimal material selection often results in different materials for different parts. This leads to the necessity to join mixed material. Here, the use of adhesives is the most promising joining technology. For a rational design process, good models for strength analysis of adhesively joined structures are essential. With cohesive modelling, fracture of the adhesive layer is modelled with a stress-deformation law. This law - often denoted a cohesive law - gives the traction exerted on the adherends due to the deformation of the adhesive layer. This thesis is concerned with experimental methods to measure cohesive properties of engineering adhesives and standardized methods to measure the fracture energy of adhesives. A new method to measure cohesive laws is developed. With this method, the cohesive law of an epoxy adhesive is measured in shear. In peel loading, with elastically deforming adherends, the cohesive law is shown to be independent of the geometry of the specimen. If the adherends deform plastically the fracture energy increases. Experiments are performed in order to determine the temperature dependence of the cohesive layer for an epoxy adhesive. It is shown that the peak stress is strongly dependent on the temperature while the fracture energy shows only small temperature dependence. Experiments are also performed to study the influence of strain rate in peel and shear loading. The experiments show that the peak stress increases with an increasing strain rate and that the fracture energy increase in peel loading and decreases in shear with increasing strain rate. A new method to experimentally determine the relation between damage and plasticity in the adhesive during the fracture process is developed. For the present adhesive, it is shown that only minor plasticity occurs during the fracture process in peel loading. For peel, several commonly used methods to evaluate the fracture energy using the double cantilever beam specimen are critically studied. For some methods the error in evaluated fracture energy is larger than 40 %. It is shown that the evaluated fracture energy is more dependent on the choice of method than on the cohesive properties of the adhesive layer.

  • 226.
    Biel, Anders
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Alfredsson, K. Svante
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Carlberger, Thomas
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Adhesive Tapes; Cohesive Laws for a Soft Layer2014In: Procedia Materials Science, ISSN 2211-8128, Vol. 3, p. 1389-1393Article in journal (Refereed)
    Abstract [en]

    For adhesive tapes, the strain before fracture often exceeds 500%. Although the maximum stresses are quite modest the high strains to fracture result in impressive fracture energy. Due to hydrostatic stress the fracture process often starts by nucleation of microscopic cracks inside the layer. The final crack path is usually close to one of the adherends.

    Repeated experiments are performed both with DCB-specimens and butt-joints. The used adhesive tape is an acrylic foam tape with a thickness of 1.1 mm and a width of 19 mm. The geometry of the specimen is adapted to the properties of the soft layer. For the DCB-specimen this implies that the length of the specimen is about 1 m. The evaluated cohesive laws from the DCB- specimens give a fracture energy of 2 kN/m and a maximum stress about 0.5 MPa. For the butt-joints, the evaluated cohesive law corresponds well to the results from the DCB-experiments. However, the strain to fracture is slightly smaller. The stress in these specimens is distributed over a larger area and a nucleated crack rapidly crosses the load bearing area and fails the joint prematurely. For both kinds of experiments the evaluated cohesive laws show a small linear part. After this part there is an almost linear strain-hardening phase until fracture.

  • 227.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Carlberger, Thomas
    Influences of temperature on cohesive parameters for adhesives2007In: Proceedings of the 28th Risø International Symposium on Materials Science, Risö national laboratory , 2007Conference paper (Refereed)
    Abstract [en]

    Experiments are performed to evaluate the temperature dependence of the stress-elongation relation for an engineering epoxy adhesive. Seven temperatures from -40ºC to 80ºC are considered. At each temperature, about seven experiments are performed with a double cantilever beam specimen. The experiments are evaluated using an inverse solution. The results show that the peak stress decreases monotonically with temperature, from about 55 MPa at -40ºC to about 11 MPa at 80ºC. Thus, the shape of the stress-elongation relation varies with the temperature. At higher temperatures, the fracture energy decreases slightly.

  • 228.
    Biel, Anders
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Chaudhry, Mobina
    Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden.
    Gustafsson, Stefan
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Nygren, Håkan
    Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden.
    The use of MgO-paste as a biodegradeable bone cement2016In: Materials Today: Proceedings, E-ISSN 2214-7853, Vol. 3, no 2, p. 556-561Article in journal (Refereed)
    Abstract [en]

    The use of MgO-paste as bone cement was tested on titanium cylinders implanted into rat tibia. The evaluation of bone healingwas made with the retention force (pull-out) test, light microscopy and ESEM/ EDX. Preimplantation of the MgO-paste into drillperforations of rat tibia increased the retention of the titanium implant 6-fold. The error was expressed as the 95% confidenceinterval of means (n=10 bones in each group). The observed difference between 3.46+/-0.71 N/mm2 for Ti-cylinders implantedwith MgO-paste and 0.56+/-0.26 N/mm2 for Ti-cylinders implanted directly into the bone, is statistically significant (p<0.01).The increase of retention force, caused by MgO is parallel to an increased thickness of the compact bone surrounding the implantand closer contact between bone and implant.Histological examination of the implant-related bone showed that the MgO-induced bone growth is mediated by the formation ofa bone-inducing matrix. The matrix contains organic substance, most likely proteins.

  • 229.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, School of Technology and Society.
    An analysis of the evaluation of the fracture energy using the DCB-specimen2007In: Archives of Mechanics, ISSN 0373-2029, Vol. 59, no 4-5, p. 311-327Article in journal (Refereed)
    Abstract [en]

    The methods to estimate the fracture energy using DCB-specimens as advocated in common standards. For instance, ASTM D 3433 and BS 7991:2001 are based on a compliance method, i.e. on linear elastic fracture mechanics (LEFM). Since the mechanical properties of almost all adhesives are non-linear, errors are generated. In some of the standards, the non-linear behaviour is compensated for by the use of correction terms generated from the experiments. An analysis of the methods of evaluation the fracture energy from experiments is performed. This analysis is performed first by simulating an experiment using realistic data for an engineering adhesive and then, by analysing the results with different methods. In this way, the correct fracture energy is known beforehand and the error in the evaluated fracture energy can be determined. In the present work it is shown that the magnitude of this error depends on the length of the crack. The results show that some commonly  used methods generate substantial errors when a large region of non-linear deformation precedes the crack tip. It is also shown that methods based on nonlinear fracture methods do not produce this kind of error.

  • 230.
    Biel, Anders
    et al.
    Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark.
    Stigh, Ulf
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Cohesive zone modelling of nucleation, growth and coalesce of cavities2017In: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 204, no 2, p. 159-174Article in journal (Refereed)
    Abstract [en]

    The stress-deformation relation i.e. cohesive law representing the fracture process in an almost incompressible adhesive tape is measured using the double cantilever beam specimen. As in many ductile materials, the fracture process of the tape involves nucleation, growth and coalesce of cavities. This process is studied carefully by exploiting the transparency of the used materials and the inherent stability of the specimen configuration. Utilising the path independence of the J -integral, the cohesive law is measured. The law is compared to the results of butt-joint tests. The law contains two stress peaks—the first is associated with nucleation of cavities at a stress level conforming to predictions of void nucleation in rubber elasticity. The second stress peak is associated with fracture of stretched walls between fully-grown cavities. After this second peak, a macroscopic crack is formed. The tape suffers at this stage an engineering strain of about 800%. A numerical analysis with the determined cohesive law recreates the global specimen behaviour.

  • 231.
    Biel, Anders
    et al.
    Karlstad University.
    Stigh, Ulf
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Comparison of J-integral methods to experimentally determine cohesive laws in shear for adhesives2019In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 94, p. 64-75Article in journal (Refereed)
    Abstract [en]

    High-quality simulation methods demand accurate material models. In simulations an adhesive can be represented by a cohesive layer. A cohesive layer model utilizes a cohesive law to represent the homogenized mechanical behaviour of a layer with a thickness. In the current paper we use three experimental methods to measure the cohesive law in shear using the ENF-specimen; one of the methods is novel and is also useful for evaluation of experiments with the ELS-specimen. Two sets of experiments are performed, one with elastic substrates and one with plastically deforming substrates. Each experiment is evaluated using all three methods. The evaluation shows that all methods provide reasonable data; the results are similar if the substrates are elastic. With smaller specimens, the substrates deform plastically and one of the methods is identified as the most accurate.

  • 232.
    Biel, Anders
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Damage and plasticity in adhesive layer: an experimental study2010In: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 165, no 1, p. 93-103Article in journal (Refereed)
    Abstract [en]

    An experimental method is developed to identify a suitable model of in-elastic behaviour of an adhesive layer. Two prototype models are considered: an elastic-plastic model where the in-elasticity is considered due to permanent straining of the adhesive and an elastic-damage model where the in-elasticity is due to a reduction in elastic stiffness. Simulations show that the evaluated property is sensitive to the choice of model. In the experimental study of an engineering epoxy adhesive, the elastic-damage model fits the experiments. The study also reveals that plasticity and damage accumulated at the crack tip influences the evaluated fracture properties.

  • 233.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Stigh, Ulf
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Damage and plasticity of adhesive layers: an experimental study2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 10, p. 2280-2285Article in journal (Refereed)
    Abstract [en]

    Time independent inelasticity is often modelled as due to plasticity and/or damage. The difference is manifested at reversed loading; plasticity reveals itself by a remaining strain in the unloaded state while damage is revealed by a decrease in the elastic stiffness during unloading. With thin adhesive layers, the deformation is inhomogeneously distributed along the layer. Large deformations occur at the ends of the layer. In the more central parts, the layer is virtually undeformed. This makes a direct measurement of the unloading properties virtually impossible. In the present paper, novel experiments are performed in order to evaluate the inelastic properties of epoxy adhesives. The load is first increased to a level corresponding to 50, 60, 70 or 80% of the fracture energy. The load is then reversed. The first step creates a zone of inelastically deformed adhesive at the start of the layer. During a final loading phase, the properties of this zone are analysed. Major differences due to the loading direction are observed. Some comparisons with simulation models are performed.

  • 234.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, School of Technology and Society.
    Effects of constitutive parameters on the accuracy of measured fracture energy using the DCB-specimen2008In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, no 10, p. 2968-2983Article in journal (Refereed)
    Abstract [en]

    Several methods exist to estimate the fracture energy for adhesive joints using the double cantilever beam specimen and linear elastic fracture mechanics. Since the mechanical properties of all adhesives are non-linear, errors are generated. By use of an exact solution experiments are simulated. These are evaluated with eight different methods. The influence of the constitutive parameters is systematically studied. This influence is small for most methods. The error due to the choice of evaluation method is considerably larger. One of the commonly used methods gives accurate results; the error is less than 3%. However, most methods yield substantial errors.

  • 235.
    Biel, Anders
    et al.
    Department of Wind Energy, Technical University of Denmark.
    Stigh, Ulf
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Measurement of tensile properties of fibres using a DCB-specimen2015In: 20th International Conference on Composite Materials: Copenhagen, 19-24th July 2015 / [ed] Ole Thybo Thomsen, Bent F. Sørensen, Christian Berggreen, 2015Conference paper (Refereed)
    Abstract [en]

    Constitutive data are needed at extreme strains to increase the understanding of fracture processes. Ordinary tensile tests ends prematurely due to localization and large amounts of elastic energy stored in the specimens prior to fracture. A novel method is proposed to perform tensile tests using a double cantilever beam specimen. To verify the method a large specimen is developed and tested. Similar results are achieved with the present method as with more standardized methods giving confidence in the method. The specimen should be possible to minimise to provide data with small specimens.

  • 236.
    Biel, Anders
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Stigh, Ulf
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Strength and toughness in shear of constrained layers2018In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 138, p. 50-63Article in journal (Refereed)
    Abstract [en]

    Confined layers may fracture in shear. This occurs, for example in adhesive joints and composite materials. A common mechanism for shear fracture is the formation of shear hackles associated with an expansion of the layer. This makes shear toughness and strength depend on the constraint of the expansion. By constraining the expansion using external loading in experiments, the expansion is reduced but not totally inhibited. The experiments are evaluated using the path independent properties of the J-integral. It is shown that the shear toughness increases for the more constrained case. Thus, from a strength analysis perspective, ignoring the expansion leads to a conservative estimate of the fracture properties. Extrapolation of the evaluated properties to totally inhibited expansions gives the traction separation relation and the fracture toughness for a layer in simple shear.

  • 237.
    Biel, Anders
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Walander, Tomas
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Life Sciences.
    A Critical Study of an Alternative Method to Measure Cohesive Properties of Adhesive Layers2012In: Proceedings of the 19th European Conference on Fracture, Kazan Scientific Centre of the Russian Academy of Sciences , 2012Conference paper (Refereed)
    Abstract [en]

    A perfect experiment is only sensitive to the properties to be analysed. However, evaluation of experimental results is always based on assumptions. Depending on the assumptions, the derived results are more or less correct. In this paper a method based on linear elastic fracture mechanics is compared to a method based on the path independence of the J-integral and the assumptions of the existence of a cohesive zone. Contrary to the other methods, the J-integral method only rests on the assumption that the material of the specimen has a strain energy density that not explicitly depends on the position in the direction of crack propagation. That is, the conditions for J to be path independent. Evaluation of simulated experiments gives the exact value of the fracture energy. The alternative method is based on linear elastic fracture mechanics. Contrary to the conventional methods we use an expression where the crack length is eliminated in favour of the flexibility of the specimen.

    Influences of assumptions are studied both experimentally and numerically. Differences in stiffness are achieved by changing the type of adhesive and the layer thickness. Two different adhesives are studied. One is a modern crash resistant epoxy adhesive, SikaPower-498. This is a relatively stiff and tough adhesive. The other adhesive is a soft and extremely tough polyurethane based adhesive, Sikaflex-UHM. Two layer thicknesses are tested; 1.0 mm for the epoxy and 3.0 mm for the polyurethane based adhesive. The results show that the two methods give similar results for the thinner and stiffer epoxy adhesive but differences are recorded for the soft polyurethane based adhesive. This analysis gives a better understanding of the evaluation methods and their limitations and possibilities to extract cohesive laws.

  • 238.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Walander, Tomas
    University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, School of Technology and Society.
    Influence of Edge-boundaries on the Cohesive Behaviour of an Adhesive Layer2012In: ASME 2012 International Mechanical Engineering Congress and Exposition, November 9–15, 2012, Houston, Texas, USA: Volume 8: Mechanics of Solids, Structures and Fluids, ASME Press, 2012, p. 507-511Conference paper (Refereed)
    Abstract [en]

    In comparison with other adhesives e.g. epoxies, polyurethane adhesives (PUR) are soft. In automotive applications, the thickness of PUR-adhesive layers is between about 2 to 5 mm. Since these adhesives cure by moisture, the width of the joints is limited. Often, the width is only marginally larger than the thickness of the layer. In numerical FE-simulations it is now common to represent epoxy adhesive layers by cohesive elements. With this model, both stress distribution and fracture can be modelled using mesh sizes that allows for large-scale analyses. Material properties are usually the result from experiments with coupon type specimens, e.g. the double cantilever beam specimen (DCB). With PUR-adhesives this approach is problematic. The adhesive is very flexible and effects from the edge-boundaries cannot be ignored. In order to study the influence of the edge-boundaries in peel loading, experiments with the DCB-specimens are performed. Specimens with a layer thickness of 3 mm and three different widths between 10.6 mm to 40.6 mm are studied. The PUR-adhesive SikaFlex-UHM is used. All the experiments are performed at a constant loading rate. The cohesive law is measured. The experimental results show that the maximum peel stress is increasing with an increasing width of the specimen, i.e. when the influences from the edges decrease. When the width increases from 10.6 mm to 40.6 mm, the maximum evaluated peak stress increases from about 5 MPa to about 7 MPa. From visual inspections during the experiments it is conjectured that crack growth starts with voids initiating inside the adhesive. At a critical point, the voids rapidly reach the surface and crack growth starts.

  • 239.
    Billborg, Marcus
    University of Skövde, School of Humanities and Informatics.
    STUDIE AV LJUS SOM NARRATIV I EN LABYRINT2014Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete handlar om att undersöka en narrativ ljussättning av en labyrint och går i bakgrunden igenom hur ljussättning har fungerat genom tiderna fram till idag, samt hur forskning kring ljus i dataspel ser ut i dagsläget. Därefter följer problemformuleringen som utgår från två perspektiv, vilka är förstapersonsperspektiv samt top-downperspektiv. Frågeställningen vill undersöka en skillnad i hur en narrativ ljussättning uppfattas ur de olika perspektiven i en labyrintisk miljö. Problemformuleringen går även igenom hur utvärderingsmetoden var tänkt att fungera i relation till detta. Sedan går utvärderingskapitlet igenom resultatet av studien där en analys av tio intervjuer med respondenter som genomfört studien presenteras. Arbetet avslutas sedan med en diskussion kring hur arbetet gick tillväga och vad man kan säga om resultatet, vilket var att ljuset uppfattades som viktigt av båda perspektiven, samt en hypotes kring möjliga framtida arbeten som arbetet potentiellt kan leda till.

  • 240.
    Billing, Erik
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    A New Look at Habits using Simulation Theory2017In: Proceedings of the Digitalisation for a Sustainable Society: Embodied, Embedded, Networked, Empowered through Information, Computation & Cognition, Göteborg, Sweden, 2017Conference paper (Refereed)
    Abstract [en]

    Habits as a form of behavior re-execution without explicit deliberation is discussed in terms of implicit anticipation, to be contrasted with explicit anticipation and mental simulation. Two hypotheses, addressing how habits and mental simulation may be implemented in the brain and to what degree they represent two modes brain function, are formulated. Arguments for and against the two hypotheses are discussed shortly, specifically addressing whether habits and mental simulation represent two distinct functions, or to what degree there may be intermediate forms of habit execution involving partial deliberation. A potential role of habits in memory consolidation is also hypnotized.

  • 241.
    Billing, Erik
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Hanson, Lars
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Lamb, Maurice
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Digital Human Modelling in Action2019In: Proceedings of the 15th SweCog Conference / [ed] Linus Holm, Erik Billing, Skövde: University of Skövde , 2019, p. 25-28Conference paper (Refereed)
  • 242.
    Billing, Erik
    et al.
    Umeå universitet, Institutionen för datavetenskap.
    Hellström, Thomas
    Umeå universitet, Institutionen för datavetenskap.
    Janlert, Lars Erik
    Umeå universitet, Institutionen för datavetenskap.
    Predictive learning from demonstration2011In: Agents and Artificial Intelligence: Second International Conference, ICAART 2010, Valencia, Spain, January 22-24, 2010. Revised Selected Papers / [ed] Filipe, Joaquim; Fred, Ana; Sharp, Bernadette, Berlin: Springer Verlag , 2011, 1, p. 186-200Chapter in book (Refereed)
    Abstract [en]

    A model-free learning algorithm called Predictive Sequence Learning (PSL) is presented and evaluated in a robot Learning from Demonstration (LFD) setting. PSL is inspired by several functional models of the brain. It constructs sequences of predictable sensory-motor patterns, without relying on predefined higher-level concepts. The algorithm is demonstrated on a Khepera II robot in four different tasks. During training, PSL generates a hypothesis library from demonstrated data. The library is then used to control the robot by continually predicting the next action, based on the sequence of passed sensor and motor events. In this way, the robot reproduces the demonstrated behavior. PSL is able to successfully learn and repeat three elementary tasks, but is unable to repeat a fourth, composed behavior. The results indicate that PSL is suitable for learning problems up to a certain complexity, while higher level coordination is required for learning more complex behaviors.

  • 243.
    Billing, Erik
    et al.
    Umeå universitet, Institutionen för datavetenskap.
    Hellström, Thomas
    Umeå universitet, Institutionen för datavetenskap.
    Janlert, Lars Erik
    Umeå universitet, Institutionen för datavetenskap.
    Simultaneous control and recognition of demonstrated behavior2011Report (Other academic)
    Abstract [en]

    A method for Learning from Demonstration (LFD) is presented and evaluated on a simulated Robosoft Kompai robot. The presented algorithm, called Predictive Sequence Learning (PSL), builds fuzzy rules describing temporal relations between sensory-motor events recorded while a human operator is tele-operating the robot. The generated rule base can be used to control the robot and to predict expected sensor events in response to executed actions. The rule base can be trained under different contexts, represented as fuzzy sets. In the present work, contexts are used to represent different behaviors. Several behaviors can in this way be stored in the same rule base and partly share information. The context that best matches present circumstances can be identified using the predictive model and the robot can in this way automatically identify the most suitable behavior for precent circumstances. The performance of PSL as a method for LFD is evaluated with, and without, contextual information. The results indicate that PSL without contexts can learn and reproduce simple behaviors. The system also successfully identifies the most suitable context in almost all test cases. The robot's ability to reproduce more complex behaviors, with partly overlapping and conflicting information, significantly increases with the use of contexts. The results support a further development of PSL as a component of a dynamic hierarchical system performing control and predictions on several levels of abstraction. 

  • 244.
    Billing, Erik
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Hellström, Thomas
    Institutionen för Datavetenskap, Umeå Universitet.
    Janlert, Lars-Erik
    Institutionen för Datavetenskap, Umeå Universitet.
    Simultaneous recognition and reproduction of demonstrated behavior2015In: Biologically Inspired Cognitive Architectures, ISSN 2212-683X, Vol. 12, p. 43-53, article id BICA114Article in journal (Refereed)
    Abstract [en]

    Predictions of sensory-motor interactions with the world is often referred to as a key component in cognition. We here demonstrate that prediction of sensory-motor events, i.e., relationships between percepts and actions, is sufficient to learn navigation skills for a robot navigating in an apartment environment. In the evaluated application, the simulated Robosoft Kompai robot learns from human demonstrations. The system builds fuzzy rules describing temporal relations between sensory-motor events recorded while a human operator is tele-operating the robot. With this architecture, referred to as Predictive Sequence Learning (PSL), learned associations can be used to control the robot and to predict expected sensor events in response to executed actions. The predictive component of PSL is used in two ways: 1) to identify which behavior that best matches current context and 2) to decide when to learn, i.e., update the confidence of different sensory-motor associations. Using this approach, knowledge interference due to over-fitting of an increasingly complex world model can be avoided. The system can also automatically estimate the confidence in the currently executed behavior and decide when to switch to an alternate behavior. The performance of PSL as a method for learning from demonstration is evaluated with, and without, contextual information. The results indicate that PSL without contextual information can learn and reproduce simple behaviors, but fails when the behavioral repertoire becomes more diverse. When a contextual layer is added, PSL successfully identifies the most suitable behavior in almost all test cases. The robot's ability to reproduce more complex behaviors, with partly overlapping and conflicting information, significantly increases with the use of contextual information. The results support a further development of PSL as a component of a dynamic hierarchical system performing control and predictions on several levels of abstraction. 

  • 245.
    Billing, Erik
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Lindblom, JessicaUniversity of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.Ziemke, TomUniversity of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Proceedings of the 2015 SWECOG conference2015Conference proceedings (editor) (Refereed)
  • 246.
    Billing, Erik
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Lowe, Robert
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre. Department of Applied IT, University of Gothenburg, Sweden.
    Sandamirskaya, Yulia
    Institute of Neuroinformatics, University of Zurich and ETH Zurich, Switzerland.
    Simultaneous Planning and Action: Neural-dynamic Sequencing of Elementary Behaviors in Robot Navigation2015In: Adaptive Behavior, ISSN 1059-7123, E-ISSN 1741-2633, Vol. 23, no 5, p. 243-264Article in journal (Refereed)
    Abstract [en]

    A technique for Simultaneous Planning and Action (SPA) based on Dynamic Field Theory (DFT) is presented. The model builds on previous workon representation of sequential behavior as attractors in dynamic neural fields. Here, we demonstrate how chains of competing attractors can be used to represent dynamic plans towards a goal state. The presentwork can be seen as an addition to a growing body of work that demonstratesthe role of DFT as a bridge between low-level reactive approachesand high-level symbol processing mechanisms. The architecture is evaluatedon a set of planning problems using a simulated e-puck robot, including analysis of the system's behavior in response to noise and temporary blockages ofthe planned route. The system makes no explicit distinction betweenplanning and execution phases, allowing continuous adaptation of the planned path. The proposed architecture exploits the DFT property of stability in relation to noise and changes in the environment. The neural dynamics are also exploited such that stay-or-switch action selection emerges where blockage of a planned path occurs: stay until the transient blockage is removed versus switch to an alternative route to the goal.

  • 247.
    Binnberg, Dennis
    et al.
    University of Skövde, School of Engineering Science.
    Johansson, Viktor
    University of Skövde, School of Engineering Science.
    Virtual Commissioning: Emulation of a production cell2016Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Volvo is continually updating and replacing their equipment and want to investigate the possibility to shorten the time it takes to implement changes and shorten the time in commissioning projects. The use of an emulation model of a production cell can shorten the commissioning time since the equipment and sequence of the cell can be thoroughly tested before implementation. Volvo also wants to investigate the possibility to validate equipment using emulation. The main objectives are to find an emulation software that suits Volvo’s needs and build an emulation model of an actual production cell at Volvo called G750. A literature review was performed in which the authors gained knowledge about virtual commissioning, simulation and emulation and the usage of these. A market survey was conducted in order to find emulation software that could handle Volvo’s complex production equipment consisting of ABB robots and Siemens PLC. A method for building emulation models of existing production equipment was found during the literature review. The software used to build the emulation model was Simumatik3D. Other software used to make the model as realistic as possible includes RobotStudio, WinCC and PLCSIM. The emulation model handles approximately 350 inputs and outputs. When the emulation model was finished experiments were conducted in order to answer research questions and to reach the main objectives. The experiments validate that the emulation model is representative of the real production cell regarding programming, fail scenarios and movement.

  • 248.
    Birgersson, David
    University of Skövde, School of Informatics.
    Skräck och avsky: Att framkalla stötande känslor i skräck2014Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [sv]

    Syftet med denna studie är att undersöka i vilken grad olika fysiska avvikelser kring en humanoids ögon/syn kan framkalla stötande känslor, de fysiska avvikelser som undersöks är: sjukdom, stympning och mutation. Studien byggde bland annat kring teorier kopplade till attraktivitet och hälsa och undersökte hur man kan använda ohälsa för att väcka stötande känslor.

    Inför studien skapades totalt åtta porträtt, en för varje fysisk avvikelse samt kön. En enkät skickades sedan ut till män och kvinnor i åldrarna 18-29 där de fick ta ställning till porträtten genom att gradera dem utifrån en 7-siffrig skala.

    Resultatet i undersökningen visade att majoriteten av respondenterna upplevde den fysiska avvikelse mutation som mest stötande, detta på grund av dess omänskliga utseende. Det fanns dock en problematik kring användningen av 3D modeller i undersökningen, framtida arbete skulle gynnas av att använda ett annat medium, exempelvis fotografi.

  • 249.
    Birtic, Martin
    University of Skövde, School of Engineering Science.
    An Open Data Model for Emulation Models of Industrial Components2018Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Emulation is a technology, historically mostly used for virtual commissioning of automated industrial systems, and operator training. Trends show that new areas for deployment are being investigated. One way to broaden the scope of emulation technology is to increase emulation detail level. The University of Skövde conduct research within emulation technology, and are developing a higher detail level emulation platform performing  on component level. For transparent and systematic development of component models on this level, an open, extensible, and flexible data model for emulation models of industrial components is wanted. This thesis is contributing to this endeavour by developing a first draft of such a data model. A demonstration is also conducted by implementing a few components into the developing emulation environment, using XML as file format. An iterative "design and creation" methodology was used to develop and implement an object oriented data model. A selected set of industrial components were used to develop and demonstrate the data model, and the final result is visually represented as a class diagram together with explanatory documentation. Using the methodology and data modelling strategy used in this thesis, systematic and transparent development of emulation models on component level is possible in an extensible and flexible manner.

  • 250.
    Birtic, Martin
    University of Skövde, School of Engineering Science.
    SUGGESTIONS TO CONSIDER WHEN ENGAGING IN THE PROCESS OF DEVELOPING A SYSTEM DYNAMICS MODEL FOR FREQUENT ATTENDERS IN HEALTHCARE2019Independent thesis Advanced level (degree of Master (One Year)), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Healthcare systems face many challenges that prevent them from reaching their full potential. Overcoming these challenges can be very difficult in part because of their complexity. Predicting all the possible effects that improvement attempts may create is difficult and high-quality decision support material is difficult to obtain. System dynamics modeling and simulation is a technology that has been applied for some time within the healthcare domain in order to assist the decision-making process. This technology has gained increased interest in the domain over the past decade. This project analyses the application of system dynamics modeling to a specific problem in the healthcare sector, namely that of frequent attenders to the emergency department. A literature review is performed to extract suggestions that could be considered when engaged in the process of developing a system dynamics model for managing frequent attenders in healthcare. It has been found that the research on frequent attenders and their management is very heterogeneous and ambiguous making it difficult to draw strong conclusions about the effectiveness of different management strategies. Model builders are forced to turn to other sources for model data. It is also found that system dynamics modeling of frequent attenders has not yet been done. This situation led to the expansion of the search scope to include related modeling research as the basis for suggestion extraction. 65 suggestions are extracted into three broad categories with the limitation of not being strictly specific to the modeling of frequent attenders, but have a more general nature. And although their value is not evaluated, it is hoped that they could contribute as inspiration to certain system dynamics model development endeavors.

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