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  • 101.
    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.

  • 102.
    Bi, Z.M.
    et al.
    Indiana University - Purdue University of Fort Wayne.
    Wang, Lihui
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Visualisation and Verification of Communication Protocols for Networked Distributed Systems.2010In: Enterprise Networks and Logistics for Agile Manufacturing / [ed] Wang, L. & Koh, S.C.L., Springer London, 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.

  • 103.
    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.

  • 104.
    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.

  • 105.
    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.

  • 106.
    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.

  • 107.
    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.

  • 108.
    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.

  • 109.
    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.

  • 110.
    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.

  • 111.
    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.

  • 112.
    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)
  • 113.
    Björkenstam, Staffan
    et al.
    Geometry and Motion Planning group, Fraunhofer-Chalmers Center, Göteborg, Sweden.
    Nyström, Johan
    Geometry and Motion Planning group, Fraunhofer-Chalmers Center, Göteborg, Sweden.
    Carlson, Johan S.
    Geometry and Motion Planning group, Fraunhofer-Chalmers Center, Göteborg, Sweden.
    Roller, Michael
    Department of Mathematical Methods in Dynamics and Durability, Fraunhofer Institute for Industrial Mathematics, Kaiserslautern, Germany.
    Linn, Joachim
    Department of Mathematical Methods in Dynamics and Durability, Fraunhofer Institute for Industrial Mathematics, Kaiserslautern, Germany.
    Hanson, Lars
    Scania AB, Södertälje, Sweden.
    Högberg, Dan
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Leyendecker, Sigrid
    Chair of Applied Dynamics, University of Erlangen-Nuremberg, Germany.
    A framework for motion planning of digital humans using discrete mechanics and optimal control2017In: Proceedings of the 5th International Digital Human Modeling Symposium / [ed] Sascha Wischniewski & Thomas Alexander, Federal Institute for Occupational Safety and Health , 2017, p. 64-71Conference paper (Refereed)
    Abstract [en]

    In this paper we present a framework for digital human modelling using discrete mechanics and optimal control. Discrete mechanics is particularly well suited for modelling the dynamics of constrained mechanical systems, which is almost always the case when considering complex human models interacting with the environment. We demonstrate that, by using recently developed recursive dynamics algorithms, we are able to efficiently use discrete mechanics in direct optimal control methods to plan for complex motions. Besides a proper mechanical model, an appropriate objective function is paramount to achieve realistic motions as a solution to an optimal control problem. Hence, several different objective functions, such as for example minimum time or minimum applied torque over the joints, are compared, and the resulting motions are analyzed and evaluated. To further improve the model, we include basic muscular models for the muscles of the shoulder, arm and wrist, and examine how this affects the motions.

  • 114.
    Bohlin, R.
    et al.
    Fraunhofer-Chalmers Research Centre for Industrial Mathematics, Gothenburg, Sweden.
    Delfs, N.
    Fraunhofer-Chalmers Research Centre for Industrial Mathematics, Gothenburg, Sweden.
    Hanson, Lars
    Department of Product and Production Development, Chalmers University of Technology, Gothenburg, Sweden.
    Högberg, Dan
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Carlson, J. S.
    Fraunhofer-Chalmers Research Centre for Industrial Mathematics, Gothenburg, Sweden.
    Automatic creation of virtual manikin motions maximizing comfort in manual assembly processes2012In: Technologies and Systems for Assembly Quality, Productivity and Customization: Proceedings of the 4th CIRP Conference on Assembly Technologies and Systems / [ed] S. Jack Hu, Conference on Assembly Technologies & Systems (CIRP), 2012, p. 209-212Conference paper (Refereed)
    Abstract [en]

    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 tight coupling to powerful algorithms for collision-free path planning. The focus in this paper is a unified solution that automatically creates assembly motions for manikins taking kinematic constraints, balance, contact forces, collision avoidance and comfort into account. The manikin used in this work has 162 degrees of freedom - six exterior fictitious joints determine the position of the lower lumbar and the remaining ones are interior joints. The inverse kinematic problem leads to an underdetermined system allowing us to pick a solution that maximizes a scalar valued comfort function. The comfort function offers a generic way to give preference to certain poses while avoiding others, typically by considering joint limits, forces and moments on joints, and magnitude of contact forces. In order to avoid collisions, poses close to collision are penalized. The method is implemented and demonstrated on two challenging assembly operations taken from the automotive industry.

  • 115.
    Bohlin, Robert
    et al.
    Fraunhofer-Chalmers Research Centre for Industrial Mathematics.
    Delfs, Niclas
    Fraunhofer-Chalmers Research Centre for Industrial Mathematics.
    Hanson, Lars
    Chalmers University of Technology.
    Högberg, Dan
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Carlson, J. S.
    Fraunhofer-Chalmers Research Centre for Industrial Mathematics.
    Unified solution of manikin physics and positioning - Exterior root by introduction of extra parameters2011In: Proceedings of DHM, First International Symposium on Digital Human Modeling, Université Claude Bernard Lyon , 2011Conference paper (Refereed)
    Abstract [en]

    Simulating manual assembly operations considering ergonomic load and clearance demands requires detailed modeling of human body kinematics and motions, as well as a tight coupling to powerful algorithms for collision-free path planning. The focus in this paper is kinematics including balance and contact forces, and ergonomically preferable motions in free space. A typical manikin has more than 100 degrees of freedom. 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 consider ergonomics aspects and maximizing comfort when choosing one solution.The most common approach to handle both forward and inverse kinematics is building a hierarchy of joints and links where one root must be defined. A popular place to define the root is in a body part, e.g. in a foot. This leads to a two-step procedure; (i) one level determining when to re-root when moving the root part, (ii) then the Penrose pseudoinverse is used to match the end-effectors' constraints.In this paper we propose using a fixed exterior root by introducing six additional parameters positioning the lower lumbar - three rotations and three translations. This makes it possible to reposition the manikin without a series of re-rooting operations. Another important aspect is to keep the manikin, affected by internal and external forces and moments, in balance. However, by utilizing the exterior root and its added degrees of freedom it is possible to solve the balance, positioning, contact force and comfort problems simultaneously in a unified way. A manikin was implemented, and two test cases demonstrate the applicability of the presented method.

  • 116.
    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.

  • 117.
    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, Vol. 824, 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.

  • 118.
    Brolin, Anna
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Bäckstrand, Gunnar
    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.
    Case, Keith
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Use of kitting to ease assemblers' cognitive workload2011In: Proceedings of the 43rd Annual Nordic Ergonomics Society Conference, University of Oulu , 2011, p. 77-82Conference paper (Refereed)
    Abstract [en]

    The higher level of product variation in the automotive industry leads to an increasing workload for the assembler that has to search, fetch and assemble all the variants. This puts high demands on the information that is given to the assembler to fulfil the assembly task. This paper describes the impact of information overload and sources, and their influence on the assembler. Through observations conducted in the Swedish automotive industry, the study has shown that the assembly personnel perceive the kit as structured information and that structured kits are able to present distinct information at a certain place to the assembler, which in turn reduces the searching, resulting in decreased cognitive workload.

  • 119.
    Brolin, Anna
    et al.
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Bäckstrand, Gunnar
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Thorvald, Peter
    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.
    Case, Keith
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Kitting as an information source in manual assembly2012In: Advances in Ergonomics in Manufacturing / [ed] Stefan Trzcieliński & Waldemar Karwowski, CRC Press, 2012, p. 346-353Chapter in book (Refereed)
    Abstract [en]

    In manual assembly, a strategy to meet the goal of efficient production is the increased use of kitting as a material supply principle. Even though kitting is already implemented in industry, there are still uncertainties regarding the effects of introducing kits, particularly from a human factors perspective.

    This paper presents initial steps in the development of a method to be used for the evaluation of kitting. This from an information source point of view and for studying effects related to productivity and quality. The methodology is projected to act as a foundation for how to carry out a subsequent comprehensive case study. The purpose of the case study is to explore how kitting affects the cognitive workload compared to the ordinary material rack combined with part numbers used in the current manufacturing industry. This is done by measuring productivity; time spent on assembling a product, and quality; number of assembly errors. One step in the methodology development process, which is described in this paper, was to conduct a pilot study, primarily to test the methodology related to the selection of measurement parameters, as well as for getting experiences from running the methodology with real test subjects.

  • 120.
    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.

  • 121.
    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.

  • 122.
    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. 

  • 123.
    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.

  • 124.
    Brolin, Erik
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Consideration of anthropometric diversity: Methods for virtual product and production development2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ergonomics and Human Factors address factors important to consider in the product and production development process. This is done through a User Centred Design process where focus is put on human-machine interactions. Digital human modelling (DHM) tools provide and facilitate rapid simulations, visualisations and analyses of the human-machine interactions in a virtual environment. Anthropometry, the study of human measurements, is central in DHM simulations due to the necessity of ensuring intended accommodation levels. Several methods have been described to consider the anthropometric diversity that exists within human populations. Still, many simulations are done with few human models, so called manikins, in industry today due to the time consuming processes when working with many manikins in current DHM tools. Hence, there is a need for better tools and methods. To increase the understanding among DHM users there is also a need to illustrate differences in results when using different approaches, and to evaluate the validity of the assumptions that methods for anthropometric diversity consideration are based upon.

    In this thesis current methods for anthropometric diversity considerations have been reviewed and the differences in evaluation results when utilizing different approaches have been analysed. New methods and functionality have been developed and implemented in DHM tools and the possibilities to include more physical characteristics and in turn consider more aspects of human diversity have been explored. Results shows that the proposed methods are advantageous compared to approaches often used in industry today and will, if used, increase the consideration of anthropometric diversity when using DHM tools for the design of products and workplaces.

  • 125.
    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.

  • 126.
    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.

  • 127.
    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.

  • 128.
    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)
  • 129.
    Brolin, Erik
    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.
    Hanson, Lars
    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 / Industrial Development, Scania CV, Södertälje, Sweden.
    Björkenstam, Staffan
    Fraunhofer-Chalmers Centre, Gothenburg, Sweden.
    Virtual test persons based on diverse anthropometric data for ergonomics simulations and analysis2017In: Proceedings of the 49th NES 2017 Conference "Joy at Work", Lund, August 20-23, 2017 / [ed] Anna-Lisa Osvalder, Mikael Blomé and Hajnalka Bodnar, Lund: Lund University, Faculty of Engineering , 2017, p. 232-239Conference paper (Refereed)
    Abstract [en]

    This paper describes a study where diverse anthropometric data is included in the process of generating data for a group of virtual test persons. Data on body size, strength and ROM were either collected on an individual level or predicted and synthesized and then used in cluster analyses to generate six unique virtual test persons. Results show that the method is able to generate detailed virtual test persons which enables more realistic and accurate simulations, as strength and ROM data is included into the motion prediction algorithms used to generate motions.

  • 130.
    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.
    Adaptive regression model for prediction of anthropometric data2017In: International Journal of Human Factors Modelling and Simulation, ISSN 1742-5549, Vol. 5, no 4, p. 285-305Article in journal (Refereed)
    Abstract [en]

    This paper presents and evaluates an adaptive linear regression model for the prediction of unknown anthropometric data based on a flexible set of known predictive data. The method is based on conditional regression and includes use of principal component analysis to reduce effects of multicollinearity between the predictive variables. Results from the study show that the proposed adaptive regression model produces more accurate predictions compared to a flat regression model based on stature and weight, and also compared to a hierarchical regression model, that uses geometric and statistical relationships between body measurements to create specific linear regression equations in a hierarchical structure. An additional evaluation shows that the accuracy of the adaptive regression model increases logarithmically with the sample size. Apart from the sample size, the accuracy of the regression model is affected by the number of, and on which measurements that are, variables in the predictive dataset.

  • 131.
    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.

  • 132.
    Brolin, Erik
    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.
    Hanson, Lars
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Industrial Development, Scania CV, Södertälje.
    Örtengren, Roland
    Chalmers University of Technology, Gothenburg.
    Development and evaluation of an anthropometric module for digital human modelling systems2019In: International Journal of Human Factors Modelling and Simulation, ISSN 1742-5549, Vol. 7, no 1, p. 47-70Article in journal (Refereed)
    Abstract [en]

    This paper presents the development of a software module and a graphical user interface which aims to support the definition of anthropometry of manikins in a digital human modelling (DHM) tool. The module is developed from user interviews and literature studies, as well as mathematical methods for anthropometric diversity consideration. The module has functionality to create both single manikins and manikin families, where it is possible to combine or analyse different population datasets simultaneously. The developed module and its interface have been evaluated via focus group interviews and usability tests by DHM tool users. Results from the studies show that the developed module and its interface has relevant functionality, fits well into industrial work processes, and is easy to use. The study also identifies possibilities to further increase usability.

  • 133.
    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.

  • 134.
    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, Vol. 825, 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.

  • 135.
    Brownlee, Alexander E. I.
    et al.
    University of Stirling, United Kingdom.
    Swan, Jerry
    University of York, United Kingdom.
    Senington, Richard
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Kocsis, Zoltan A.
    The University of Manchester, United Kingdom.
    Conflict-free routing of multi-stop warehouse trucks2019In: Optimization Letters, ISSN 1862-4472, E-ISSN 1862-4480Article in journal (Refereed)
    Abstract [en]

    The recent interest in greater vehicular autonomy for factory and warehouse automation has stimulated research in conflict-free routing: a challenging network routing problem in which vehicles may not pass each other. Motivated by a real-world case study, we consider one such application: truck movements in a tightly constrained warehouse. We propose an extension of an existing conflict-free routing algorithm to consider multiple stopping points per route. A high level metaheuristic is applied to determine the route construction and assignment of vehicles to routes. 

  • 136.
    Bäckstrand, Gunnar
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Information Flow and Product Quality in Human Based Assembly2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Information is an important part of the manual assembly process. Information provides the user with the means to fulfil assembly tasks so that the right quality as well as high productivity are accomplished. This thesis addresses issues connected to information and information use in a modern manual assembly environment, and how these issues affect human operators, quality and productivity. The overall objectives of the research were to gain further knowledge on how attention affects the internal reject rate, to investigate these phenomena in industrial and laboratory environments and finally to propose a suitable evaluation method to be utilised at the design stage of an information system.

    Studies were performed with the purpose of investigating how the assembly personnel were affected by the information and how it affected quality and productivity. The studies were performed in an assembly plant and in the laboratory. Quantitative data collection included 10 days and nights of production where the information impact on quality was investigated. Connected to this study was a qualitative survey performed among 171 persons from the assembly personnel. The laboratory study took place during three days, approximately eight hours each day. It involved 30 persons, all experienced assembly workers from the reference assembly plant. The focus of this study was how information affected the personnel and thereby the productivity.

    The findings revealed that information affected the quality rates and productivity and that this can be linked to how the information is presented as well as when the information is presented. It was possible to link these findings to the outcome of a successful information search process, and to conclude that a use of an evaluation method or work process during the product lifecycle could have made it possible to avoid some of the problems connected to the information presentation. This is the basis for a proposed pragmatic evaluation method. The method was tested as a support system during the design of a prototype user interface to be used at the pilot plant.

    The major contribution of this research is the connection between attention and quality as well as the connection between attention and productivity. Knowledge regarding the importance of presenting the information at the right time must also be regarded as an important and proven contribution.

  • 137.
    Bäckstrand, Gunnar
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Intuitiv montering2012In: Teknik och tillväxt, no 2, p. 24-24Article in journal (Other (popular science, discussion, etc.))
  • 138.
    Bäckstrand, Gunnar
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre. Swerea IVF AB, Stockholm.
    Bergman, Christian
    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.
    Moestam, Lena
    Volvo Trucks GTT, Gothenburg.
    Lean and its impact on workplace design2013In: Proceedings of NES 2013, 45th Nordic Ergonomics & Human Factors Society conference, Iceland, August 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Lean analyses and following corrections of workstations are typically performed reactively, i.e. solving problems that already exist. However, there are benefits of enhanced proactivity related to the consideration of lean and human factors, as this would reduce the need for updating workstations. The approach presented here utilises a company specific, reactive lean evaluation methodology, but applied proactively, in the workstation design phase. Results gave that many assessment items in fact can be proactively addressed. This way, ergonomic and lean workstations that support quality, performance and wellbeing for a diversity of workers, can be built right the first time.

  • 139.
    Bäckstrand, Gunnar
    et al.
    Volvo Powertrain.
    Brolin, Anna
    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.
    Case, Keith
    Loughborough University.
    Supporting Attention in Manual Assembly and its Influence on Quality2010In: 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]

    Modern manufacturing information systems allow fast distribution of, and access to, information. One of the  main purposes with an information system within  manual assembly is to improve product quality, i.e. to ensure that assembly errors are as few as possible. Not only  must an information system contain the right information, it must  also  provide  it  at  the  right  time  and  in  the  right  place.  The  paper  highlights some of the concerns related to the design and use of information systems in manual assembly.  The  paper  describes  a  study  that  focuses  on  the  correlation  between active information seeking behaviour and assembly errors. The results are founded on  both  quantitative  and  qualitative  methods.  The  study  indicates  that  by  using simplified information carriers, with certain characteristics, the assembly personnel more easily could interpret the information, could to a higher degree be prompted (triggered) about product variants and could also be able to prepare physically and mentally   for   approaching   products   arriving   along   the   assembly   line.   These conditions  had  positive  influence  on  quality,  i.e.  gave  a  reduction  of  assembly errors.

  • 140.
    Bäckstrand, Gunnar
    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.
    Variants = Customer value?2010In: Standards News Magazine, no 2, p. 17-19Article in journal (Other (popular science, discussion, etc.))
  • 141.
    Bäckstrand, Gunnar
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre. Swerea IVF.
    Thorvald, Peter
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Nylén, Ulf
    University of Skövde, External Relations and Communication Office.
    Flexibel montering möter industrins utmaningar2013In: Teknik och tillväxt, no 3, p. 5-Article in journal (Other (popular science, discussion, etc.))
  • 142.
    Carlberger, Thomas
    et al.
    SAAB Automobile AB, Trollhättan, Sweden.
    Biel, Anders
    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.
    Influence of temperature and strain rate on cohesive properties of a structural epoxy adhesive2009In: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 155, no 2, p. 155-166Article in journal (Refereed)
    Abstract [en]

    Effects of temperature and strain rate on the cohesive relation for an engineering epoxy adhesive are studied experimentally. Two parameters of the cohesive laws are given special attention: the fracture energy and the peak stress. Temperature experiments are performed in peel mode using the double cantilever beam specimen. The temperature varies from −40 to + 80°C. The temperature experiments show monotonically decreasing peak stress with increasing temperature from about 50 MPa at −40°C to about 10 MPa at + 80°C. The fracture energy is shown to be relatively insensitive to the variation in temperature. Strain rate experiments are performed in peel mode using the double cantilever beam specimen and in shear mode, using the end notch flexure specimen. The strain rates vary; for peel loading from about 10−4 to 10 s−1 and for shear loading from 10−3 to 1 s−1. In the peel mode, the fracture energy increases slightly with increasing strain rate; in shear mode, the fracture energy decreases. The peak stresses in the peel and shear mode both increase with increasing strain rate. In peel mode, only minor effects of plasticity are expected while in shear mode, the adhesive experiences large dissipation through plasticity. Rate dependent plasticity, may explain the differences in influence of strain rate on fracture energy between the peel mode and the shear mode.

  • 143.
    Carlberger, Thomas
    et al.
    SAAB Automobile AB.
    Stigh, Ulf
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Dynamic testing and simulation of hybrid joined bi-material beam2010In: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 48, no 8, p. 609-619Article in journal (Refereed)
    Abstract [en]

    A specimen is developed for real-like low velocity impact testing of bi-material joint configurations. Six different joint configurations are analysed. Two engineering adhesives are evaluated with and without discrete mechanical fasteners, i.e. adhesive and hybrid joints. Experiments and simulations are performed. The simulations are performed using adhesive cohesive finite elements. Simulations show good agreement with experiments in impact energy and overall deformation mode. The histories of applied load vs. load-point deflection show reasonably good correlation. The results show that the impact energy consumption depends on the joint integrity. A threshold value for the fracture energy of the adhesive seems to exist. Beneath this value, adhesive and discrete fastener work together increasing the impact energy capacity. Above this value the discrete fastener has a negative effect, and may be regarded as a stress concentration.

  • 144.
    Carlberger, Thomas
    et al.
    SAAB Automobile AB.
    Stigh, Ulf
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Influence of Layer Thickness on Cohesive Properties of an Epoxy-Based Adhesive: An Experimental Study2010In: The journal of adhesion, ISSN 0021-8464, E-ISSN 1563-518X, Vol. 86, no 8, p. 814-833Article in journal (Refereed)
    Abstract [en]

    Cohesive laws are determined for different layer thicknesses of an engineering adhesive. The shape of the cohesive law depends on the adhesive layer thickness. Of  the  two  parameters  of  the  cohesive  law—the  fracture  energy  and  thestrength—the fracture energy is more sensitive to thickness variation than the strength. The fracture energy in peel mode (Mode I) increases monotonically as the thickness is increased from 0.1 to about 1.0 mm. At an adhesive thickness of 1.5 mm, the fracture energy is slightly lower than for a 1.0 mm adhesive thickness, indicating a maximum between 1.0 and 1.5 mm. In shear mode (Mode II), the thickness dependence is not as strong, but an increasing trend in fracture energy with increasing adhesive thickness is evident. A slight decrease in strength with increasing adhesive thickness is found in both loading modes.

  • 145.
    Carlberger, Thomas
    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.
    Vilka hållfasthetsegenskaper har limfogen?: Simulering på Högskolan i Skövde ger svaren2014In: Fordonskomponenten, ISSN 2000-7299, no 3, p. 46-47Article, review/survey (Other (popular science, discussion, etc.))
    Abstract [sv]

    Att beräkna limfogars hållfasthet är inte helt enkelt, vilket beror på spänningskoncentrationens inflytande vid limfogens kanter.

    Materialmekanik vid Högskolan i Skövde har specialiserat sig på hållfasthetssimulering av limfogar genom kohesiv modellering.

  • 146.
    Case, Keith
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre. Mechanical and Manufacturing Engineering, Loughborough University, UK.
    Marshall, Russell
    Department of Design and Technology, Loughborough University, UK.
    Högberg, Dan
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Summerskill, Steve
    Department of Design and Technology, Loughborough University, UK.
    Gyi, Diane
    Department of Human Sciences, Loughborough University, UK.
    Sims, Ruth
    Department of Design and Technology, Loughborough University, UK.
    HADRIAN: Fitting Trials by Digital Human Modelling2009In: Digital Human Modeling: Second International Conference, ICDHM 2009 Held as Part of HCI International 2009 San Diego, CA, USA, July 19-24, 2009 Proceedings / [ed] Vincent G. Duffy, Springer Berlin/Heidelberg, 2009, p. 673-680Conference paper (Refereed)
    Abstract [en]

    Anthropometric data are often described in terms of percentiles and too often digital human models are synthesised from such data using a single percentile value for all body dimensions. The poor correlation between body dimensions means that products may be evaluated against models of humans that do not exist. Alternative digital approaches try to minimise this difficulty using pre-defined families of manikins to represent human diversity, whereas in the real world carefully selected real people take part in 'fitting trials'. HADRIAN is a digital human modeling system which uses discrete data sets for individuals rather than statistical populations. A task description language is used to execute the evaluative capabilities of the underlying SAMMIE human modelling system as though a 'real' fitting trial was being conducted. The approach is described with a focus on the elderly and disabled and their potential exclusion from public transport systems.

  • 147.
    Chiet, Cheong Wen
    et al.
    Universiti Tunku Abdul Rahman, Malaysia.
    Ching, Ng Tan
    Universiti Tunku Abdul Rahman, Malaysia.
    Huat, Saw Lip
    Universiti Tunku Abdul Rahman, Malaysia.
    Fathi, Masood
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Tzuu, Tan Jaw
    Universiti Tunku Abdul Rahman, Malaysia.
    The Integration of Lean and Green Manufacturing for Malaysian Manufacturers: A Literature Review to Explore the Synergies between Lean and Green Model2019In: International Conference on Sustainable Energy and Green Technology 2018 / [ed] Chong Wen Tong, Wang Chin-Tsan, Bernard Saw Lip Huat, Institute of Physics Publishing (IOPP), 2019, Vol. 268, article id 012066Conference paper (Refereed)
    Abstract [en]

    In general, profitability and efficiency have been the main interest for organization. However, the increasing concerns for the environment from government, regulators, customers and other stakeholders has forced companies to seek for alternatives to achieve green objectives. The difficulties faced by organizations are lack of awareness and guideline in implementing green practices in their daily operation. Under constrained resources, employers are reluctant to spend money on something unclear. During the last decade, lean manufacturing seems to be visible trend in most of the manufacturing industries in Malaysia. As lean tends to emphasize on waste reduction, it provides similarity between lean and green. Therefore, it is a better atmosphere to deploy green practices and tools under existing lean manufacturing. The purpose of this paper is to present a review on the synergies between green and lean and identifying the determinants that affecting both lean and green manufacturing for Malaysian manufacturers. The determinant obtained are financial benefit, incentive, legislation, stakeholder, management commitment, technology, environmental awareness and brand image or competitiveness. Besides, the authors identified and suggested future research directions on developing an integrated lean-green model for daily operation. This study aims to assist researchers to identify the opportunities and challenges on lean-green model and this review is useful for manufacturers and government in developing manufacturing policies and guideline.

  • 148.
    Claesson, Frida
    et al.
    University of Skövde, School of Technology and Society.
    Hilletofth, Per
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    In-transit distribution as a strategy in a global distribution system2011In: International Journal of Shipping and Transport Logistics, ISSN 1756-6517, E-ISSN 1756-6525, Vol. 3, no 2, p. 198-209Article in journal (Refereed)
    Abstract [en]

    Distribution has become a key factor in today’s logistics system due to companies’ desires to achieve considerable economies of scale in production, achieved by focused factories, as well as customers’ demands for shorter lead-times and customer adapted products. The purpose of this research is to investigate if the in-transit distribution strategy may offer companies a competitive advantage and may be used as a complement to the centralised distribution strategy and/or the decentralised distribution strategy. This study shows that the in-transit distribution strategy can give major competitive advantages by offering rather short lead-times for customers without having to store products locally in warehouses. This, in turn, gives lower warehousing costs, lower tied-up capital, a less interrupted manufacturing, and steady and continuous production volumes. In order to be successful with this strategy, it takes good planning, working closely with customers, good market knowledge, and an enterprise resource planning (ERP) system that is able to support the strategy sufficiently. Among these factors, low variation in demand as well as manufacturing output is required, and furthermore distribution lead time needs to be predictable.

  • 149.
    Claesson, Frida
    et al.
    University of Skövde, School of Technology and Society.
    Hilletofth, Per
    University of Skövde, The Virtual Systems Research Centre. University of Skövde, School of Technology and Society.
    Hilmola, Olli-Pekka
    Lappeenranta University of Technology.
    Supply Chain Planning in Automotive Sector: Swedish Case Study2011In: Conradi Research Review, ISSN 1459-0980, Vol. 6, no 2, p. 33-54Article in journal (Refereed)
    Abstract [en]

    This research aims to enhance the current level of knowledge from supply chain planning (SCP) by analyzing the importance of collaboration, information exchange and a supporting information system in its successful execution. These are examined through a case study from international manufacturing company, which operates in automotive industry with its global manufacturing network. Research reveals that collaboration is a complex and important issue of SCP, and occurs simultaneously in vertical and horizontal dimensions. It is important to select strategic partners and to develop a structured work processes and routines. The main objective of collaboration is to determine common goals and objectives and to facilitate the exchange of information; these together drive the performance of a supply chain higher. A sufficient information system supporting the SCP is vital to facilitate collaboration, and information exchange between the different supply chain participants. However, currently in the case company quite many phases of SCP are completed without appropriate and integrated information systems and the process itself contains several manual phases.

  • 150.
    Conder, Marston
    et al.
    University of Auckland, New Zealand.
    Stokes, Klara
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. National University of Ireland Maynooth, Co. Kildare, Ireland.
    New methods for finding minimum genus embeddings of graphs on orientable and non-orientable surfaces2019In: Ars Mathematica Contemporanea, ISSN 1855-3966, Vol. 17, no 1, p. 1-35Article in journal (Refereed)
    Abstract [en]

    The question of how to find the smallest genus of all embeddings of a given finite connected graph on an orientable (or non-orientable) surface has a long and interesting history. In this paper we introduce four new approaches to help answer this question, in both the orientable and non-orientable cases. One approach involves taking orbits of subgroups of the automorphism group on cycles of particular lengths in the graph as candidates for subsets of the faces of an embedding. Another uses properties of an auxiliary graph defined in terms of compatibility of these cycles. We also present two methods that make use of integer linear programming, to help determine bounds for the minimum genus, and to find minimum genus embeddings. This work was motivated by the problem of finding the minimum genus of the Hoffman-Singleton graph, and succeeded not only in solving that problem but also in answering several other open questions.

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