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  • 1.
    Al Hayani, Musab
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Offline Programming of Robots in Car Seat Production2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Company Purtech in Dals-Ed manufactures molded polyurethane (PUR). Examples of products that include polyurethane are car seats. Robots are used to fill the molds with PUR and to apply the release agent (wax) in the empty molds.

    Turning from online programming into a graphical offline programming of release agent spraying robots is going to simplify the process by:

    1. Applying less of release agent to avoid polluting environment, to produce an easier removal of moulds, for the sake of homogeneous moulds and for economical saving in the cost of release agent
    2. Adaption of spraying paths to variation in production speed.
    3. Programming of complex spraying trajectories to deal with sharp geometrical subsurface
    4. Decreasing onsite programming time (when program a new workpiece or modify an old one); so that robots would be free for production.

    While turning into offline programming brought the challenges of:

    1. Impact of variation in the production speed
    2. Lack of 3D models of workcell’s equipments
    3. Robot joint configuration when paths and robtargets are in move.
    4. Physical Joint limits, Singularities & Reach limits
    5. Collisions within the cell space.

    At the end, the following objectives are successfully met:

    1. Adaption of spraying programs to variation in production speed by developing and embedding a method in those programs.
    2. Graphical offline generation of spraying trajectories and optimization of those trajectories to the Purtech condition of spraying allowed time for each carrier.
    3. Simulation of release agent spraying process; and producing of a well structured RAPID program that reflect the simulated process.

              

  • 2.
    Amoson, Jonas
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lundqvist, Thomas
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    A light-weigh non-hierarchical file system navigation extension2012In: Proceedings of the 7th International Workshop on Plan 9 / [ed] Eric Jul, Dublin, Ireland, 2012, p. 11-13Conference paper (Other academic)
    Abstract [en]

    Drawbacks in organising and finding files in hierarchies have led researchers to explorenon-hierarchical and search-based filesystems, where file identity and belonging is pred-icated by tagging files to categories. We have implemented a chdir() shell extension en-abling navigation to a directory using a search expression. Our extension is light-weightand avoids modifying the file system to guarantee backwards compatibility for applicationsrelying on normal hierarchical file namespaces.

  • 3.
    Augustsson, Svante
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Human and Robot Interaction basedon safety zones in a shared work environment2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The work explores the possibility to increase the automation along a production line by introducing robots without reducing the safety of the operator. The introduction of a robot to a workstation often demands a redesign of the workstation and traditionally the introduction of physical safety solutions that can limit the access to the work area and object on the production line. This work aims to find a general solution that can be used not only in the construction industry, but also in other types of industries to allow for an increased Human and Robot Interaction (HRI) without physical safety solution. A concept solution of a dynamic and flexible robot cell is presented to allow for HRI based on safety zones in a shared work environment. The concepts are based on one robot and the usage of a 3D camera system allowing for the design of virtual safety zones, used to control the HRI. When an operator approaches the robots work area and triggers a safety zone the robot stops its work and moves away from the operator. Based on the safety requirements and triggered zones the robot will continue to work in a new area or wait until the operator leaves the work area and then continue with the interrupted work task. This will allow the operator and the robot to work together, where the operator location controls the robots workspace. Testing and validation of the presented concept showed that the wanted functionality could be obtained. It also showed limitations to the equipment and the system used during tests and raised additional aspects of the safety for HRI. Of the detected limitations the most crucial when looking at up-time for the production line, is the camera system need of a relatively dust free environment, good and constant lighting. For the safety of the system the limitation lies in the size and placing of the safety zones in combination with the disturbance from  surrounding equipment. The presented concept has proven to work, and can be applied not only for the construction industry but for all industries with manufacturing alongside production lines with large components.

  • 4.
    Augustsson, Svante
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    How to Transfer Information Between Collaborating Human Operators and Industrial Robots in an Assembly2014In: Proceedings the NordiCHI 2014: The 8th Nordic Conference on Human-Computer Interaction: Fun, Fast, Foundational, ACM Publications, 2014, p. 286-294Conference paper (Refereed)
    Abstract [en]

    Flexible human-robot industrial coproduction will be important in many small and middle-sized companies in the future. One of the major challenges in a flexible robot cell is how to transfer information between the human and the robot with help of existing and safety approved equipment. In this paper a case study will be presented where the first half focus on data transfer to the robot communicating the human's position and movements forcing the robot to respond to the triggers. The second half focuses on how to visualize information about the settings and assembly order to the human. The outcome was successful and flexible, efficient coproduction could be achieved but also a number of new challenges were found.

  • 5.
    Bennehag, David
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Wulcan, Alexander
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Claesson, ommy
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Förstudie till ett stadstäckande och öppet WiFi i Trollhättan2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Förstudien behandlar den tekniska delen av ett teoretiskt stadstäckande öppet WiFi i Trollhättan, Sverige. Trollhättans kommun beställde en förstudie från Högskolan Väst som skulle agera beslutsunderlag till hur de skulle ta ärendet vidare. Studien är begränsad till den tekniska biten, där bland annat val av utrustning, trådlösa tekniker och riskanalys av nätverket ingår. Arbetet varit väldigt teoretiskt inriktat med en metod som till största del består utav att samla information och kunskaper från vetenskapliga rapporter, teknikorienterade hemsidor och andra relaterade arbeten.De trådlösa standarder som jämfördes teoretiskt i förstudien var 802.11g och 802.11n. 802.11n valdes som den standarden som bäst passade just detta nätverk, främst för dess positiva egenskaper när det gäller täckning, hastighet och bakåtkompatibilitet. 802.11n seräven ut att garantera en säker framtid när det gäller implementering i mobila enheter. Föreslaget på utrustning består av två olika accesspunkter, antingen 2602e eller 3602e beroende på den slutgiltiga budgeten. Dessa produkter är från Cisco och klarade olikastresstester med bra resultat samtidigt som de stödde den föreslagna standarden 802.11n. WLAN controllern (Ciscos 5500-serie) som valdes ut stödjer det krav på antal accesspunkter som bestämts, samtidigt som den lämpar sig bra för eventuella framtidakrav. Routern till detta nätverk är en Cisco 891-router. Anledningen till att denna router valdes var för att den har 4 portar som kan ge ström över Ethernet till accesspunkterna. Säkerhetsanalysen gjordes med hjälp utav CORAS-metoden där det diskuteras vilka riskernätverket kan ställas inför och vad dessa risker kan få för konsekvenser. Försök till att hitta lösningar som var direkt applicerbara på det stadstäckande öppna nätverket gjordes även.Förstudien avslutas med en kostnadsberäkning av nätverket, baserad på andras tidigare arbeten och deras kostnader, speciellt från Jönköping, Helsingborg och Mountain View.

  • 6.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Reconfigurable and Flexible Industrial Robot Systems2014In: Advances in Robotics & Automation, ISSN 2168-9695, Vol. 3, p. 117-Article, review/survey (Other academic)
    Abstract [en]

    This paper presents a concept for reconfigurable and flexible robot systems. To reach a technology readiness level where solutions and results can be implemented in industry, the focus in this work is on systems with limited number of robots, and work scenarios which are reasonable complex but hard to automate using standard solutions.Four distinct areas have been identified as important within the concept and further studies: (i) human machine interaction, (ii) safety including collaboration, (iii) programming and deployment, and (iv) planning and scheduling. Feasibility studies have been made which addressed issues (ii) and (iii), in scenarios with collaboration between robot and human, or between two robots. For the chosen work scenario, manufacturing of structures in wood for family houses, challenges related to programming and safety was identified and possible solutions outlined.The concept and the studies indicate that feasible solutions can be found and designed given a reasonable consistent work processes and products. In this study, the processes are similar, nailing and screwing but different sizes may apply, the material is similar but variations may apply, and the construction is different of each product, but include the same type of operations at different locations. Our study confirm that human collaboration improves the ability to implement and use robots as it make it possible to move some operations to the human which otherwise would add to the complexity of the system. Furthermore, programming can also I general be simplified although methods for automatic programming has been tried out. But in some cases, the solution space is limited and the ability to move certain operations to a human simplifies the programming task. However, further work needs to be done in this area specifically related to safety issues for safe collaboration.

  • 7.
    Bolmsjö, Gunnar
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Collaborative Robots to Support Flexible Operation in a Manufacturing System2012In: Flexible Automation and Intelligent Manufacturing, FAIM 2012 / [ed] Hasse Nylund, Satu Kantti, Ville Toivonen, Seppo Torvinen, Tampere University, Finland, 2012, p. 531-538Conference paper (Refereed)
    Abstract [en]

    Collaborative robotic systems where human(s) and robot(s) cooperate in performing a common task is an attractive solution to introduce automation combined with high flexibility for tasks that have a high complexity and characterized by low volume or down to one-off. By introducing collaboration in robotics systems, the operator can complement with cognitive capacity and skill in order to gain in flexibility and agility in the task operation. This paper describes on-going work related to work on collaboration between operator and robot. User scenarios are outlined together with methods, software components and hardware to support collaboration, where some of these are under development. As the standards related to collaborative robotic systems are soon to be completed, it is expected that this type of semi-automatic systems will be important for flexible and agile automation of production which otherwise cannot be automated.

  • 8.
    Carlsson, Henric
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Production Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Production Engineering.
    General Time Synchronisation Method for PLC Programs Aiming at Virtual Verification and Development2008In: 17th IFAC World: Congress Proceedings of the 17th World Congress. The International Federation of Automatic Control. Soel, July 6-11, 2008, p. 4440-4445Conference paper (Other academic)
    Abstract [en]

    The latest state-of-the-art Computer Aided Production Engineering (CAPE) simulation technology offers OPC integration for PLC verification. A critical drawback with this technology has been identified and described within this paper. A new time synchronisation method and a simulation architecture are therefore presented and proposed. The time synchronisation method together with the architecture can be used when verifying and developing real-time dependent control logic for industrial control system, e.g. PLC with CAPE tools. The method described in this paper is general and should work on any PLCs that are compatible with the IEC 61131-3 standard. A test case was also carried out, showing that by disregarding time synchronisation it is impossible to verify real-time dependent PLC functions together with CAPE tools in a reliable way. However, the test case also shows that by applying the proposed time synchronisation method together with the described simulation architecture a successful industrial verification method is achieved

  • 9.
    Carlsson, Henrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Reliable Virtual Commissioning2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Virtual commissioning is a technique for programming, optimising and verifying industrial automated production, such as robot controllers and programmable logic controllers (PLC), off-line in a simulated environment. Compared with traditional robot off-line programming and simulation, the scope is wider and can include an entire production cell.

    Robot simulation is a well-established technique and widely used in industry today, much thanks to the RRS interface that enables simulated robot control systems to be integrated in the simulation software. A more general interface for industrial control system integration is OPC that has been an industrial de facto standard for connection between industrial control systems and regular PCs. State-of-the-art production simulation tools often include the possibility to connect an industrial control system via OPC. However, OPC suffers a major drawback when it comes to production simulation, there is no mechanism that synchronises the industrial control system with the simulation and this could lead to unreliable results from the simulation.

    Another obstacle for virtual commissioning is the amount of time that needs to be spent during the simulation model building phase, since virtual commissioning includes more signals. This does not only take more time, but it is also an error prone process that might lead to unreliable results.

    In this thesis problems related to the OPC interface and the modelling process are discussed, and suggestions how these issues can be solved are presented so reliable virtual commissioning can be achieved.

  • 10.
    Christiansson, Anna-Karin
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, B.
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden .
    Toivonen, H.
    Åbo Akademi University, Department of Chemical Engineering, Åbo, Finland.
    Mixed continuous/discrete-time output feedback H∞ control: A unified approach1999In: European Control Conference, ECC 1999 - Conference Proceedings, 1999, p. 4077-4082Conference paper (Refereed)
    Abstract [en]

    A Riccati equation (RE) based solution to the H∞ optimal control problem for mixed continuous/discrete-time systems is presented. The results unify a number of recently penetrated H∞ control problems. In the infinite-horizon case a periodic behaviour is assumed, and it is shown how the related continuous RE with jumps can be replaced by an equivalent discrete periodic RE. A related algebraic RE, which involves the system behaviour during one period, then can be formulated and solved by standard methods. Typical applications are control of continuous-time or discrete-time periodic systems, as well as multirate and sampled-data control, including mixed continuous and sampled-data measurements. © 1999 EUCA.

  • 11.
    Christiansson, Anna-Karin
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Low order sampled-data H∞ control2003In: Decision and Control, 2003. Proceedings. 42nd IEEE Conference on, 2003, Vol. 3, p. 2308-2313 Vol.3Conference paper (Refereed)
    Abstract [en]

    A method for obtaining low order sampled-data H∞ controllers is presented. The method is mainly based on a parametric static feedback controller for a plant that is augmented with the controller dynamics. The design of a full-order controller is a convex problem, while the optimisation problem for lower order controllers is non convex. The proposed method starts with design of a full-order sampled-data controller using Riccati equations. Then this controller is reduced by an ordinary model reduction technique, and the reduced controller is used as an initial value for an iterative procedure using linear matrix inequalities (LMIs) in the search for an optimal controller. The matrix inequalities are in fact linear in either the Lyapunov matrix or the static controller matrix, why the solution to the non convex problem fundamentally is given by a bilinear matrix inequality (BMI). The order of the controller is reduced until the closed loop performance degrades too much. Simulations are shown for the control of a time delayed SISO-plant where the controller order can be reduced from 8th to 3rd order. Results are also shown from control of a MIMO-model of a jet engine where the reduction is successful from 15th to 4th order. It is argued that the non convexity is handled efficiently since the procedure uses a model reduction of the full-order controller as initial value.

  • 12.
    Christiansson, Anna-Karin
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers University of Technology, Control Engineering Lab, SE-41 2 96 Goteborg, Sweden .
    Toivonen, H.
    Åbo Akademi University, Department of Chemical Engineering, FIN-20500 Abo, Finland .
    Continuous-, discrete- and sampled-data- H∞ˆž control - a unified framework2000In: IEEE Proceedings: Conference on Decision and Control (CDC), ISSN 0191-2216, Vol. 2, p. 1936-1941Article in journal (Refereed)
    Abstract [en]

    We present a unified and general framework for H∞-control in both continuous time, discrete time and combinations of these. The general result is a hybrid continuous-/discrete-time H∞ˆž-controller. Using a compact hybrid notation, the work shows a close relationship between the continuous-and discrete-time solutions. In fact, the pure continuous and discrete time equations may be obtained as two similar interpretations of the general result. There are no assumptions made on certain system matrices being zero or normalised, e.g. D11 = 0. The method is Riccati equation (RE) based, and it is shown how the continuous REs can be "lifted" into discrete ones reflecting the system behaviour during the period. Typical applications are control of continuous-time or discrete-time periodic systems, as well as multirate and sampled-data control, including mixed continuous and sampled-data measurements.

  • 13.
    Christiansson, Anna-Karin
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Toivonen, H.T.
    Åbo Akademi University, Department of Chemical Engineering, Åbo, Finland..
    Sampled-data H∞ˆž-control for time-varying hybrid systems2001In: Dynamics of continuous, discrete and impulsive systems, ISSN 1201-3390, E-ISSN 1918-2538, Dynamics of Continuous, Discrete and Impulsive Systems Series B: Applications and Algorithms, ISSN 1492-8760, Vol. 8, no 4b, p. 427-444Article in journal (Refereed)
    Abstract [en]

    This paper presents sampled-data H∞ˆž-control of linear mixed continuous-time and discrete-time systems, including a mix of continuous-time and discrete-time performance signals and disturbances. However, neither continuous-time control signals nor continuous-time measurements are included. The sampling may well be multirate, i.e. different signals may be sampled by different rates, as long as a periodic pattern is repeated over the period, consisting of a number of sampling steps. In fact, the results are applicable even to arbitrary linear time-varying systems. The sampled-data system is discretised such that the continuous-time performance is reflected in the discretised or "lifted" system. This lifted system is combined with discrete-time updates at the sampling instants to achieve the sampled-data controller. The "hold-states" case is presented as a special application, when there is also a hold circuit at the controller output. The continuous-time Riccati equations with discrete-time updates then can be replaced by one discrete-time static feedback and filter Riccati equation respectively, which also reflect the intersample behaviour. Furthermore, convergence results between the discretised Riccati solutions and the corresponding continuous-time solutions are shown, when the sampling interval decreases towards zero. Simulations are shown when the results are applied to the control of a MIMO jet-engine model.

  • 14.
    Danielsson, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science.
    An Adaptable Process Planning Tool: A Tool for Information, Communication, and Interaction in a Robot Cell2011In: ADAPTIVE 2011: the Third International Conference on Adaptive and Self-Adaptive Systems and Applications / [ed] Fox, Jorge & Rausch, Andreas, International Academy, Research and Industry Association (IARIA), 2011, p. 15-19Conference paper (Refereed)
    Abstract [en]

    This study presents work in progress on how to develop a process-planning tool to handle interaction between human operators and robots within a robot cell. First, we introduce how to include human activities in the process flow; then, we turn to our ideas for communication and feedback systems inside a robot cell. A small example of how to design interactive and re-programmable screens is presented.

  • 15.
    Danielsson, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Haijun, Xing
    University West.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    A Simulation-Based Optimization Approach for Holonic Manufacturing Systems2012In: Flexible Automation and Intelligent Manufacturing, FAIM 2012: Helsinki, 10-13 June / [ed] Hasse Nylund, Satu Kantti, Ville Toivonen, Seppo Torvinen, Tampere University, Finland: Tampere University of Technology, 2012, p. 515-522Conference paper (Refereed)
    Abstract [en]

    Holonic Manufacturing System (HMS) is an integrated multi-agent technology that represents the developing direction in the automation field. HMS can be represented as a non-hierarchical manufacturing architecture with no or limited supervision. However, it is a challenge for a single holon in a non-hierarchical system to make globally optimal decisions. This paper presents a simulation-based optimization method for HMS by introducing a new wizard holon. A wizard holon collects the necessary information from the entire HMS and uses Discrete Event System (DES) simulation to evaluate the cost of different decisions. Since a non-hierarchical approach is used the wizard input is only treated as an advice to achieve more globally optimal decisions. The decisions are still taken by the local holon. Even for an experienced operator it might be hard to predict the outcome of a decision in a critical situation. Hence, wizard advices are valuable for all types holons, including machines, robots, and operators.

  • 16.
    Danielsson, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    He, Jun
    University West.
    Integration of humans into a multi-agent system2013In: ESM'2013 The 2013 European Simulation and Modelling Conference / [ed] Stephan Onggo and Antonin Kavicka, Ostend, Belgien: EUROSIS-ETI Publication , 2013, p. 257-259Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to describe on-going work in the integration of humans in automated manufacturing systems. The intention is to achieve a flexible manufacturing system to meet the rapid developing and changing of today’s industry. The approach is based on a control concept with multi-agents. Humans, which are considered as a valuable factor in industrial production, are proposed as flexible agent resources for the automated manufacturing system.

    A test case was performed on a manufacturing system where three different groups of humans where integrated in the system; inspection, carrier and recovery. The P-SOP agent generator was used to automatically generate IEC 61131-3 PLC control code for the system.

  • 17.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Three-dimensional friction stir welding of inconel 718 using the ESAB Rosio FSW-Robot2013In: ASM Proceedings of the International Conference: Trends in Welding Research, Chicago, IL, 2013, p. 829-833Conference paper (Refereed)
    Abstract [en]

    Robotic Friction Stir Welding (FSW) facilitates for increased welding flexibility, and allows for studies of forces in three dimensions without having the high cost of a stiff 5-axes FSW machine. Recent developments in tool materials and welding equipment motivate this study on FSW of high-strength alloys by a robot in a three dimensional workspace. New concepts of aircraft engines suggest higher temperatures to increase engine efficiency, requiring more durable materials such as the nickel-based alloy 718. The ESAB Rosio™ FSW robot, used in this study, can deliver up to 15kN downforce and 90Nm torque. This is sufficient for welding high-strength alloys of limited thickness. This study focuses on the process forces during friction stir welding of Inconel 718 with thickness up to 3mm in butt-joint configuration. A newly developed threaded Poly-Crystalline Boron Nitride (PCBN) tool with convex shoulder is used in a local argon-shielded atmosphere. Initial tests are performed in a stiff FSW machine in position controlled mode. The measured process forces in position control are later on used as parameters on the force-controlled robot. Different backing bar materials are investigated with the aim to decrease the risk of root defects. Tool steel and regular inconel backing bars are proven to be too soft for this purpose and alternatives are suggested. The optimal welding parameters are tuned to combine a good weld quality with the process forces that can be obtained by the robot. Preheating is used to further decrease the need of high process forces. Copyright © 2013 ASM International® All rights reserved.

  • 18.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Deflection model for robotic friction stir welding2014In: Industrial robot, ISSN 0143-991X, E-ISSN 1758-5791, Vol. 41, no 4, p. 365-372Article in journal (Refereed)
    Abstract [en]

    Purpose - This paper aims to present a deflection model to improve positional accuracy of industrial robots. Earlier studies have demonstrated the lack of accuracy of heavy-duty robots when exposed to high external forces. One application where the robot is pushed to its limits in terms of forces is friction stir welding (FSW). This process requires the robot to deliver forces of several kilonewtons causing deflections in the robot joints. Especially for robots with serial kinematics, these deflections will result in significant tool deviations, leading to inferior weld quality. Design/methodology/approach - This paper presents a kinematic deflection model, assuming a rigid link and flexible joint serial kinematics robot. As robotic FSW is a process which involves high external loads and a constant welding speed of usually below 50 mm/s, many of the dynamic effects are negligible. The model uses force feedback from a force sensor, embedded on the robot, and predicts the tool deviation, based on the measured external forces. The deviation is fed back to the robot controller and used for online path compensation. Findings - The model is verified by subjecting an FSW tool to an external load and moving it along a path, with and without deviation compensation. The measured tool deviation with compensation was within the allowable tolerance for FSW. Practical implications - The model can be applied to other robots with a force sensor. Originality/value - The presented deflection model is based on force feedback and can predict and compensate tool deviations online.

  • 19.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Thermoelectric method for temperature measurement in friction stir welding2013In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 18, no 7, p. 541-550Article in journal (Refereed)
    Abstract [en]

    Previous research within friction stir welding (FSW) has demonstrated that online control of welding parameters can improve the mechanical properties and is necessary for certain applications to guarantee a consistent weld quality. One approach to control the process is by adapting the heat input to maintain a stable welding temperature, within the specified operating boundaries. This requires accurate in-process temperature measurements. This paper presents a novel method to measure the temperature at the interface of the FSW tool and workpiece. The method is based on the thermoelectric effect between dissimilar materials. The measurements are compared to thermocouple measurements and to a physical model and show good correspondence to each other. Experiments demonstrate that the method can quickly detect temperature variations, due to geometrical variations of the workpiece or due to parameter changes. This allows use of the method for online control of robotic FSW.

  • 20.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Temperature control of robotic friction stir welding using the thermoelectric effect2014In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 70, no 1-4, p. 375-383Article in journal (Refereed)
    Abstract [en]

    Friction stir welding (FSW) of non-linear joints receives an increasing interest from several industrial sectors like automotive, urban transport and aerospace. A force-controlled robot is particularly suitable for welding complex geometries in lightweight alloys. However, complex geometries including three-dimensional joints, non-constant thicknesses and heat sinks such as clamps cause varying heat dissipation in the welded product. This will lead to changes in the process temperature and hence an unstable FSW process with varying mechanical properties. Furthermore, overheating can lead to a meltdown, causing the tool to sink down into the workpiece. This paper describes a temperature controller that modifies the spindle speed to maintain a constant welding temperature. A newly developed temperature measurement method is used which is able to measure the average tool temperature without the need for thermocouples inside the tool. The method is used to control both the plunging and welding operation. The developments presented here are applied to a robotic FSW system and can be directly implemented in a production setting.

  • 21.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Process and Product Development.
    Oqueka, Jens
    University West, Department of Engineering Science.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Investigation of path compensation methods for robotic friction stir welding2012In: Industrial robot, ISSN 0143-991X, E-ISSN 1758-5791, Vol. 39, no 6, p. 601-608Article in journal (Refereed)
    Abstract [en]

    Purpose – Friction stir welding (FSW) is a novel method for joining materials without using consumables and without melting the materials. The purpose of this paper is to present the state of the art in robotic FSW and outline important steps for its implementation in industry and specifically the automotive industry.

    Design/methodology/approach – This study focuses on the robot deflections during FSW, by relating process forces to the deviations from the programmed robot path and to the strength of the obtained joint. A robot adapted for the FSW process has been used in the experimental study. Two sensor-based methods are implemented to determine path deviations during test runs and the resulting welds were examined with respect to tensile strength and path deviation.

    Findings – It can be concluded that deflections must be compensated for in high strengths alloys. Several strategies can be applied including online sensing or compensation of the deflection in the robot program. The welding process was proven to be insensitive for small deviations and the presented path compensation methods are sufficient to obtain a strong and defect-free welding joint.

    Originality/value – This paper demonstrates the effect of FSW process forces on the robot, which is not found in literature. This is expected to contribute to the use of robots for FSW. The experiments were performed in a demonstrator facility which clearly showed the possibility of applying robotic FSW as a flexible industrial manufacturing process.

  • 22.
    de Blanche, Andreas
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Namaki, Nima
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Mankefors-Christiernin, Stefan
    University West, Department of Economics and IT, Division of Computer Engineering.
    Multicore Clusters for CFD Simulations: Comparative Study of Three CFD-Softwares2012In: PROCEEDINGS OFTHE 2012 INTERNATIONAL CONFERENCE ONPARALLEL AND DISTRIBUTED PROCESSING TECHNIQUES ANDAPPLICATIONS, PART II / [ed] Hamid R. Arabnia, Hiroshi Ishii, Minoru Ito Kazuki Joe, Hiroaki Nishikawa, CSREA Press, 2012, p. 855-852Conference paper (Refereed)
    Abstract [en]

    Multicore processors have come to stay, fulfill Moore’s law and might very well revolutionize the computer industry. However, we are now in a transitional period before the new programming models, numerical algorithms and general computer architecture have been developed and the software has been rewritten. This paper focuses on the effects multicore based systems have on industrial computational fluid dynamics (CFD) simulations. The most significant finding was that five of the models ran faster when only one process was executed on each multicore node instead of two. In these cases the execution time was increased by between 6.5% and 64% with a median increase of 10% when utilizing both cores.

  • 23.
    Denys, Kristof
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Circular motion for robotized metal deposition: verification and implementation2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Metal deposition is an additive layered manufacturing process that deposits molten metal droplets on a substrate and by repeating this process layer by layer, a complex shaped 3D geometry can be manufactured.

    In this thesis, the metal deposition process is performed by a robot with a wire feeder tool and a laser as energy source to melt the metal wire. The robot programming for robotized metal deposition process can be completely automated by computer aided robotics software. University West is currently developing an add-in application in a computer aided robotics software, Process Simulate, that is capable of programming the robotized metal deposition process.

    The first goal of this thesis was to verify the up to now developed software and the process from CAD drawing down to robot code. Another goal was to find and implement an algorithm that will reduce the number of locations on a circular arc to three locations.

    The algorithm to minimize the locations must be capable of changing all the different curvature paths to linear and circular arc motions which are easy to translate to robot code. The user should be able to decide the fitting precision of the approximated motion path to the original path.

    A real robot cell setup is modelled in Process Simulate. This lets Process Simulate generate the correct robot code for that specific cell.  Since each robot cell has its own unique setup, a custom script will be developed that changes the universal robot code, that Process Simulate generates, to the custom robot code required in this specific robot cell.

    The software is improved and tested from CAD drawing down to robot code but still needs to be debugged more and needs implementation of some non-existing features.

  • 24.
    Ericsson, Mikael
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Ryberg, Anders
    Nilsson, Jim
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers.
    Off-Line Simulation of Advanced Stereo Vision Welding Applications2010In: Machine Vision and Applications, ISSN 0932-8092, E-ISSN 1432-1769Article in journal (Refereed)
  • 25.
    Glorieux, Emile
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying. Department of Signals and Systems, Chalmers University of Technology, Gothenburg, Sweden.
    A Constructive Cooperative Coevolutionary Algorithm Applied to Press Line Optimisation2014In: Proceedings of the 24th International Conference on Flexible Automation and Intelligent Manufacturing: Capturing Competitive Advantage via Advanced Manufacturing and Enterprise Transformation / [ed] F. Frank Chen, Lancaster, PA, USA: DEStech Publications, Inc. , 2014, p. 909-916Conference paper (Refereed)
    Abstract [en]

    Simulation-based optimisation often considers computationally expensive problems. Successfully optimising such large scale and complex problems within a practical time frame is a challenging task. Optimisation techniques to fulfil this need to be developed. A technique to address this involves decomposing the considered problem into smaller subproblems. These subproblems are then optimised separately. In this paper, an efficient algorithm for simulation-based optimisation is proposed. The proposed algorithm extends the cooperative coevolutionary algorithm, which optimises subproblems separately. To optimise the subproblems, the proposed algorithm enables using a deterministic algorithm, next to stochastic genetic algorithms, getting the flexibility of using either type. It also includes a constructive heuristic that creates good initial feasible solutions to reduce the number of fitness calculations. The extension enables solving complex, computationally expensive problems efficiently. The proposed algorithm has been applied on automated sheet metal press lines from the automotive industry. This is a highly complex optimisation problem due to its non-linearity and high dimensionality. The optimisation problem is to find control parameters that maximises the line’s production rate. These control parameters determine velocities, time constants, and cam values for critical interactions between components. A simulation model is used for the fitness calculation during the optimisation. The results show that the proposed algorithm manages to solve the press line optimisation problem efficiently. This is a step forward in press line optimisation since this is to the authors’ knowledge the first time a press line has been optimised efficiently in this way.

  • 26.
    Glorieux, Emile
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Automation Systems.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Manufacturing Processes. Chalmers.
    Optimised Control of Sheet Metal Press Lines2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Determining the control parameters for sheet metal press lines is a large scale and complex optimisation problem. These control parameters determine velocities, time constants, and cam values of critical interactions between the equipment. The complexity of this problem is due to the nonlinearities and high dimensionality. Classical optimisation techniques often underperform in solving this kind of problems within a practical timeframe. Therefore, specialised techniques need to be developed for these problems. An existing approach is simulation-based optimisation, which is to use a simulation model to evaluate the trial solutions during the optimisation. In this paper, an efficient simulation-based optimisation algorithm for large scale and complex problems is proposed. The proposed algorithm extends the cooperative coevolutionary algorithm, which optimises subproblems separately. Hence, the optimisation problem must be decomposed into subproblems that can be evaluated separately. To optimise the subproblems, the proposed algorithm allows using embedded deterministic algorithms, next to stochastic genetic algorithms, getting the flexibility of using either type. It also includes a constructive heuristic that creates good initial feasible solutions to expedite the optimisation. The extension enables solving complex, computationally expensive problems efficiently. The proposed algorithm has been applied on an automated sheet metal press line from the automotive industry. The objective is to find control parameters that maximise the line’s production rate. The results show that the proposed algorithm manages to find optimal control parameters efficiently within the practical timeframe. This is a step forward in press line optimisation since to the authors’ knowledge this is the first time a press line has been optimised efficiently in this way.

  • 27.
    Hagqvist, Petter
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Instrumentation and estimation for high temperature control2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within a variety of industrially relevant high temperature production processes such as welding, heat treatment and metal deposition, the quality of the manufactured component is largely affected by how well parameters can be controlled during processing. These parameters might be, in the case of metal deposition, power input, material feed, or a parameter which is common for all of the aforementioned processes: material temperature. The ability to correctly measure, or in other ways estimate process parameters is vital in order to successfully control high temperature processes such as above 700 degrees Celsius. In this work, instrumentation and estimation solutions adapted to high temperature control are proposed and implemented with a focus on the laser metal wire deposition process. Special attention is given to temperature measurements on specimens with varying emissivity as commonly found in high temperature processes. A calibration procedure for a single-wavelength pyrometer is also presented together with a general discussion on limitations of such a system for measurands with varying emissivity. A new method for non-contact emissivity compensated temperature estimations using a spectrometer is presented. Simulations and industrially relevant experiments have been carried out validating the method. The theoretical framework for the developed method will be further investigated in the future together with additional experimental validation. In addition to temperature measurements, a method for real-time process control of laser metal wire deposition has been developed and implemented with good results. This control scheme estimates and controls the tool-to-workpiece distance based on resistance measurements. Such measurements allow for placement of instruments outside of the processing chamber and easy integration into existing equipment. Future work will be directed towards incorporation of resistance measurements into an iterative learning control scheme. Also, improvement on the resistance-distance model and further investigation into suitable signal processing methods for the resistance signal will be pursued.

  • 28.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Automatic detection of material phase transitions from spectroscopic data2013In: Proceedings of the IECON 2013: 39th Annual Conference of the IEEE Industrial Electronics Society, IEEE, 2013, p. 2384-2389Conference paper (Refereed)
    Abstract [en]

    When using a temperaturemeasurementmethod which utilizes spectral information for measuring the temperature of varying emissivity measurands, there is a need for a temperature reference at some point in time. In this work, such a reference is created from the spectral radiance data already used by the temperature measurement method. A method of using knowledge of the measurand material's phase transitions and spectral radiance data as a temperature reference is presented. Through automatical identification of phase transitions from radiance spectra employing signal processing, the temperature is known at a certain instance in time, just like required by the temperature measurement method. Three methods for automatic identification of material phase transitions from spectroscopic data are examined and evaluated. The methods are, based on derivatives, steady-state identification and cross correlation respectively. They are introduced and evaluated using experimental data collected from a solidifying copper sample. All methods proved to identify the phase transitions correctly. The addition of automatic phase transition identification supplements the existing temperature measurement method such that it becomes a stand alone, reference free method for measuring the true absolute temperature of a measurand with varying emissivity.

  • 29.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Heralic, Almir
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Production System. Chalmers.
    Resistance based iterative learning control of additive manufacturing with wire2015In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 31, p. 116-123Article in journal (Refereed)
    Abstract [en]

    This paper presents successful feed forward control of additive manufacturing of fully dense metallic components. The study is a refinement of former control solutions of the process, providing more robust and industrially acceptable measurement techniques. The system uses a solid state laser that melts metal wire, which in turn is deposited and solidified to build the desired solid feature on a substrate. The process is inherently subjected to disturbances that might hinder consecutive layers to be deposited appropriately. The control action is a modified wire feed rate depending on the surface of the deposited former layer, in this case measured as a resistance. The resistance of the wire stick-out and the weld pool has shown to give an accurate measure of the process stability, and a solution is proposed on how to measure it. By controlling the wire feed rate based on the resistance measure, the next layer surface can be made more even. A second order iterative learning control algorithm is used for determining the wire feed rate, and the solution is implemented and validated in an industrial setting for building a single bead wall in titanium alloy. A comparison is made between a controlled and an uncontrolled situation when a relevant disturbance is introduced throughout all layers. The controller proves to successfully mitigate these disturbances and maintain stable deposition while the uncontrolled deposition fails.

  • 30.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Heralic, Almir
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers.
    Resistance measurements for control of laser metal wire deposition2014In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 54, no March, p. 62-67Article in journal (Refereed)
    Abstract [en]

    A method for controlling robotized laser metal wire deposition online by electrical resistance metering is proposed. The concept of measuring the combined resistance of the wire and the weld pool is introduced and evaluated for automatic control purposes. Droplet formation, detachment of the wire from the weld pool and stubbing can be hard to avoid during processing due to the sensitive process and short reaction times needed for making on-line adjustments. The implemented system shows a possible route for automatic control of the process wherein such problems can be avoided automatically. The method proves to successfully adjust the distance between the tool and the workpiece through controlling the robot height position, thus increasing stability of the laser metal wire deposition process.

  • 31.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Kristoffersen, Hans
    Swerea IVF AB, Box 104, SE-431 22 Mölndal, Sweden.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Temperature Monitoring of Induction Hardening Using Spectral Pyrometry2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-7Conference paper (Refereed)
    Abstract [en]

    In this study, a recently developed multispectral temperature measurement method is applied for temperature monitoring of induction hardening of steel. An industry-like induction heating process is used for evaluating the method and an automatic calibration procedure is presented. Thermocouples and a conventional pyrometer are used for comparison, showing that the multispectral method gives more accurate results than the conventional pyrometer. These results confirm that the multispectral method is well suited for accurate, non-contacting temperature measurements for induction hardening processes. Enabling measurements which have previously not been possible. This enables fast selection of process parameters which can improve productivity.

  • 32.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Emissivity estimation for high temperature radiation pyrometry on Ti–6Al–4V2013In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 46, no 2, p. 871-880Article in journal (Refereed)
    Abstract [en]

    The paper demonstrates a versatile procedure suitable for industrial implementation of temperature measurement on a hot titanium alloy. The driving force has been the need for an accurate temperature measurement during additive manufacturing using laser welding technology where Ti–6Al–4V-wire is melted. The challenges consider both industrial constraints and the varying emissivity of the surface. Measurements makes use of a narrow bandwidth spot radiation pyrometer and a calibration procedure for estimation of the surface temperature through spectral emissivity estimation. The theoretical results are validated through experiments. A number of difficulties in radiation temperature measurements for metals with varying surface properties are discussed; especially the case of surface oxidation. The uncertainty in temperature reading due to the uncertainty in the emissivity estimate is established along with a model that qualitatively describes surface oxidation. The procedure is expected to be useful for several manufacturing applications where it is important to control high temperatures.

  • 33.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Process and Product Development.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers.
    Emissivity compensated spectral pyrometry for varying emissivity metallic measurands2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 2, p. 025010-Article in journal (Refereed)
    Abstract [en]

    A novel method for converting electromagnetic spectral radiance information into emperature measurements is presented. It allows for varying spectral emissivity of the metallic measurand during the course of the measurement. Such variations are due to e.g. thermal oxidation or temperature dependent emissivity. Based on the assumption that emissivity changes with time and temperature in a continuous manner, it is further assumed that an emissivity estimate at one sample instance can be derived from the estimated emissivity found at the previous samples together with updated spectral information. This leads to successive recalculations of spectral emissivity together with corresponding temperature values. The proposed algorithm has been proven to give accurate temperature estimates from a measurement based on data captured by a standard UV-Vis spectrophotometer even for an oxidizing Ti-6Al-4V specimen in a temperature range between 900K and 1400K. The method however, is not limited to these wavelength- or temperature-ranges.

  • 34.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Process and Product Development.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers.
    Emissivity compensated spectral pyrometry-algorithm and sensitivity analysis2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 2, p. 025011-Article in journal (Refereed)
    Abstract [en]

    In order to solve the problem of non-contact temperature measurements on an object with varying emissivity, a new method is herein described and evaluated. The method uses spectral radiance measurements and converts them to temperature readings. It proves to be resilient towards changes in spectral emissivity and tolerates noisy spectral measurements. It is based on an assumption of continuous changes in emissivity and uses historical values of spectral emissivity and temperature for estimating current spectral emissivity.

    The algorithm, its constituent steps and accompanying parameters are described and discussed. A thorough sensitivity analysis of the method is carried out through simulations. No rigorous instrument calibration is needed for the presented method and is therefore industrially tractable.

  • 35.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part II: Automatic deposition using feedback controlArticle in journal (Refereed)
  • 36.
    Johansson, Daniel
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Jibing, Gustav
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Krantz, Johan
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Prestandajämförelse mellan Amazon EC2 och privat datacenter2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Publika moln har sedan några år tillbaka blivit ett alternativ för olika företag att använda istället för lokala datacenter. Vad publika moln erbjuder är en tjänst som gör det möjligt för företag och privatpersoner att hyra datorkapacitet. Vilket gör att de inte längre behöver spendera pengar på resurser som inte används. Istället för att köpa en stor andel hårdvara och uppskatta hur stor kapacitet som man behöver kan man nu istället så smått börja utöka efter behov eller minska ifall det önskas. Därmed behöver företag inte spendera pengar på hårdvara som inte används eller har för lite datorkapacitet, vilket skulle kunna resultera i att stora batcharbeten inte blir färdiga i tid och i och med det kan företaget förlora potentiella kunder. Potentiella problem  kan dock uppstå när man i ett moln virtualiserar och försöker fördela datorkapacitet mellan flera tusen instanser. Där även skalbarhet inte ska ha några begränsningar, enligt moln-leverantörerna.

    I denna rapport har vi med hjälp av olika benchmarks analyserat prestandan hos den största publika moln-leverantören på marknaden, Amazon, och deras EC2- och S3-tjänster. Vi har genomfört prestandatester på systemminne, MPI och hårddisk I/O. Då dessa är några av de faktorer som hindrar publika moln från att ta över marknaden, enligt artikeln Above The Clouds -  A Berkely View of Cloud Computing [3].  Sedan har vi jämfört resultaten med prestandan på ett privat moln i ett datacenter. Våra resultat indikerar att prestandan på det publika molnet inte är förutsägbar och måste få en ordentlig skjuts för att stora företag ska ha en anledning till att börja använda det.

  • 37.
    Lennartson, Bengt
    et al.
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Middleton, R.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Unified, periodic & sampled data H control using the delta operator2004In: Decision and Control, 2004. CDC. 43rd IEEE Conference on, 2004, Vol. 3, p. 2364-2369Conference paper (Refereed)
    Abstract [en]

    A unified and general framework is presented for H<sub>&infin;</sub> control of mixed continuous-time and discrete-time time-varying (periodic) systems. Using the delta operator, a close relationship is shown between the continuous- and discrete-time solutions. No assumptions are made on certain system matrices being zero or normalized, which makes the approach general and easy to apply. A combined continuous/discrete-time lifting procedure is shown to be useful, especially for ill-conditioned systems. This procedure together with the delta formalism results in a numerically robust design method concerning both short and long sampling periods for systems with W-conditioned dynamics, including widely spread eigenvalues.

  • 38.
    Lennartson, Bengt
    et al.
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Middleton, R.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    McKelvey, T.
    Low order sampled data H control using the delta operator and LMIs2004In: Decision and Control, 2004. CDC. 43rd IEEE Conference on, 2004, Vol. 4, p. 4479-4484Conference paper (Refereed)
    Abstract [en]

    A procedure for H optimization of low order controllers for discrete-time and sampled-data systems is presented in this paper. Generally, low order H controllers may be achieved by solving bilinear matrix inequalities (BMIs). In this paper an iterative alternation between two LMIs gives a suboptimal solution. To avoid local minima in this search the initial controller is obtained by a frequency weighted controller reduction scheme, where the closed loop properties of a full order controller is taken into account. A minimal number of parameters in the state space realization of the controller also reduces the complexity and improves numerical robustness. The complete presentation is based on delta operator models, which shows a close relationship between the continuous- and discrete-time solutions. The sensitivity of the ordinary discrete-time shift operator LMI formulation to small sampling periods is also analyzed.

  • 39.
    Lindman, Linus
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Automatisering av serversäkerhetsvalidering2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis evaluates whether there exists a tool that the corporation Zetup can use seeing that they search for a concept to validate standardized and secured installs of various servers. The validation of these installs should be able to be automated, verified continuously during a systems lifetime and should also be able to be modified for specific conditions.

    The tool that was chosen for this evaluation was the security organization Center for Internet Security’s CIS-CAT Benchmark Assessment Tool which uses XML-files, so called benchmarks, consisting of a number of verifications which checks whether a target system is configured in conformity with security configurations that the Center for Internet Security has produced for maximal information security. A run of CIS-CAT results in a HTML-document which explicitly presents the result of each verification specified and grades the configuration of the target system. For this purpose, Zetup has chosen 22 requirements that their standard server should live up to. Most of these verifications were already configured, others had to be created.

    Initially, it was verified that the server was configured in accordance with the recommendations. Then, 10 misconfigurations were introduced to verify that the tool actually could find all misconfigurations.

    The evaluation showed that the tool is very useful. CIS-CAT was easily configured according to the organizations specific conditions and all introduced misconfigurations were found. CIS-CAT complies with the requirements Zetup has set although disadvantages also emerged. A great advantage is that with a tool such as this, you can start working proactively and discover misconfigurations before they affect a system negatively. Disadvantages worth mentioning are for example that the tool is not very helpful when it comes to error messages when misconfiguring the benchmark file. Another disadvantage is that a lot of resources are required when working with a tool like this; Benchmarks must be maintained and modified as new requirements emerge and old ones vanish. Also, someone must review the result of every run of CIS-CAT and fix each encountered misconfiguration

  • 40.
    Nia, Nima K.
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Efficient geometrical simulation and virtual commissioning performed in stamping2012In: Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies & Factory Automation (ETFA 2012), Polen: IEEE, 2012, p. 1-8Conference paper (Refereed)
    Abstract [en]

    In order to  perform efficient geometrical simulation and virtual commissioning in stamping, three fields are investigated namely: simulation building time, collision detection time and optimization time. Hence, reducing time is the main theme of this paper. To reduce simulation building time and optimization time, an efficient stamping simulation model is built and tested. Collision detection time is examined by a relative motion method based on 3D to 2D geometrical collision detection. The presented results mean that simulation and virtual commissioning can be performed at least ten times faster compared to standard approaches.

  • 41.
    Nia, Nima K.
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Toward efficient geometrical simulation and virtual commissioning in stamping2012In: p. 1-12Article in journal (Refereed)
  • 42.
    Nia, Nima Khansari
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Efficient simulation and optimization for tandem press lines2012Licentiate thesis, comprehensive summary (Other academic)
  • 43.
    Rohdin, Patrik
    et al.
    Linköpings universitet.
    Johansson, M
    Saab Automobile AB.
    Löfberg, J
    Automatic Control, Linköping University, Sweden.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Energy efficient process ventilation in paint shops in the car industry: Experiences and an evaluation of a full scale implementation at Saab Automobile in Sweden.2012In: Ventilation 2012, 2012, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Support processes in industrial energy systems, such as heating, ventilation and cooling systems, are important processes in industrial premises as they are related to energy cost, product quality as well as the indoor environment.

    In the vehicle production process the paint shop is the most energy intensive part, and about 75% of the energy is used in the ovens and spray booths. The spray booth line, which includes paint application and the oven, uses large quantities of air in order to keep the air quality in an optimal range to achieve the desired paint quality. The approach used in paint shops has up to now been to keep as much of steady state conditions as possible to avoid paint defects due to disturbances in the balance. This means that these high air flows are used also at low and non production hours. There is thus a large potential to increase energy efficiency by controlling the air flow and heating without losing the critical balances. This paper will present an initial post-implementation evaluation of the energy efficiency potential and experiences after running this type of system. CFD has been used to investigate the control strategy.

  • 44.
    Runnemalm, Anna
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Appelgren, Anders
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Evaluation of non-destructive testing methods for automatic quality checking of spot welds2012Report (Other academic)
    Abstract [en]

    Car bodies are today more often made of high strength steel. In high strength steel spot welds are more friable and it is necessary to have higher demands on the inspections of spot welds. Quality control of spot weld can be either destructive or non-destructive. Destructive testing is still the most common method to test spot weld. The non-destructive methods that are investigete in this project are visual inspektion (VT), penetrant testing (PT), eddy current testing (ET), ultrasonic testing (UT), magnetic paticle testing (MT) and X-ray testing (RT). Other NDT methods are acoustic emission (AE), digital sheargraphy and IR-termography (IRT). These methods are investigated with focus on the possibility to detect Lens Diameter, stick welds, expulsions, porosity and cracks. And the possibility to automation of the method with focus on size and weight of the system, protection equipment, contact or contactless, one or two sided, position accuracy, and result in real-time.

    Only tree NDT methods, UT, RT and IRT, can detect all discontinuities that we looking for in RSW. The thermography system has the largest potential to be a NDT system for spot weld in the future, mainly because the method is non-contact, which helps when you have the opportunity to searching on a surface instead of a specific position. The main problem with this method is that there is no software for analysing the results to obtain lens diameter.

  • 45.
    Runnemalm, Anna
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Appelgren, Anders
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Ahlberg, Jörgen
    Termisk Systemteknik AB.
    Lundevall, Åsa
    SWEREA IVF.
    Albinsson, Ola
    Automated NDT cell for quality checking of spot welds2013Report (Other academic)
    Abstract [en]

    This report is written within Spotlight WP5 financed by the FFI programme within Vinnova.

    Thermography is a non-destructive testing method based on measurement of the heat distribution by an infrared camera. The method is suitable for automatic inspection since it is a full filed and non-contact method.

    A thermography system with an analysis tool developed by Termisk Systemteknik AB is investigated as an inspection method for spot weld. The system is able to detect spot welds, measure the diameter and separate a spot weld from a stick weld. The algorithms used in the analysis are rather simplified and the development opportunities are significant.

    A fully automated NDT-cell for spot weld inspection is presented. The automation includes a six axis industrial robot and communication for handling the information flow. This comprised the identification of the inspected spot weld and the reporting to the overall system as to the operator.

    A failure modes and effects analysis (FMEA) of the automated NDT-cell is accomplished and the most important actions are reported

    A business case for implementing a automated NDT-cell was included in the project. In this business case the most promising quality check concepts for NDT spot weld will be presented and compared with the other identified methods.

  • 46.
    Runnemalm, Anna
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Broberg, Patrik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Appelgren, Anders
    University West, Department of Engineering Science, Division of Automation and Computer Engineering. University West, Department of Engineering Science, Division of Production System.
    Possibilities and Limitations of Automated Non-Destructive Testing of Welds2012In: Proceedings of the 5th International Swedish Production Symposium: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping, 2012, p. 3-9Conference paper (Refereed)
  • 47.
    Runnemalm, Anna
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Liu, Tongwein
    Ericsson, Mikael
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Appelgren, Anders
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Influence of Vibration Induced Disturbances in an Automatic Inspection Cell2013In: Robotics in Smart Manufacturing / [ed] Pedro Neto,António Paulo Moreira, 2013, p. 191-202Conference paper (Refereed)
    Abstract [en]

    In the modern manufacturing industry, quality assurance is important. Over the last few years, the interest in automatic inspection has increased and automatic non-destructive testing (NDT) has been introduced. A general automated inspection cell consists of a mechanized system for scanning and a computer system for automatic analysis of the data. In the manufacturing industry, it is preferable to use industrial robots as the scanning equipment since they offer great flexibility, excellent support organization and the in-house know-how is normally high. Another benefit is that a robot can carry different inspection equipment and an inspection cell can therefore include more than one NDT method. For an automatic analysis, high quality of the resulting data is essential. However, a non-stable condition of the NDT sensor mounted on the robotic arm may influence the results. This paper focuses on the influence of the vibration induced disturbances on the results from an NDT system. Vibration amplitude of a point to point robot movement on the robotic arm is measured. The influence of vibration disturbances on the inspection results are evaluated on the thermal images from a thermography system mounted on a six axis industrial robot. The thermal images taken by the system during the movement and after the stop of the robot are evaluated, and the influence of the vibration in these two situations is considered.

  • 48.
    Svensson, Bo
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    A new Combined Optimisation Algorithm for Sheet-Metal Press Line Tuning2012In: Proceedings of the 5th International Swedish Production Symposium, SPS12: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping: Produktionsakademien, The Swedish Production Academy , 2012, p. 479-485Conference paper (Refereed)
    Abstract [en]

    This paper shows how a new combined optimisation algorithm can improve the efficiency in simulation-based parameter tuning of sheet-metal press lines. In automotive tandem sheet-metal press lines there are a number of critical interactions between moving parts to consider during the loading and unloading motions. All these interactions, both within each station and between the stations, are time-critical and must be synchronised to reach high production rates and avoid collisions. This cause conditions such as a highly non-linear objective functions with multiple local optima, considerable number of parameters, and long evaluation times. It is a great challenge to obtain an efficient direct search algorithm for global multi-criteria optimisation fulfilling all these conditions.

    The new combined algorithm starts with the Lipschitzian algorithm DIRECT as global search and then switches over to the Nelder-Mead simplex algorithm for local convergence. Furthermore, during the switch over, the algorithm determines all local candidates of the set of points evaluated by DIRECT, and starts multiple Nelder-Mead local searches in each of these.

  • 49.
    Svensson, Bo
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Improving Performance in Flexible Manufacturing by a P-sop Approach2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    This paper present a Part oriented Sequence of Operation (P-SOP) approach that address flexibility, robustness and deployment in manufacturing cells up to plant level. A P-SOP description language has been formulated where the control strategy based on actual circumstances easily can be defined. Furthermore, a P-SOP multi-agent generator has been created that compiles the strategy description to multi-agents that control the manufacturing. Deadlock free IEC 61131-3 PLC code are directly generated from the description language. The code is not optimised for a specific scenario since the general description contains all possible routing paths and all resources available.

  • 50.
    Svensson, Bo
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Automation and Computer Engineering. University West, Department of Engineering Science, Division of Production System.
    An efficient algorithm for press line optimisation2013In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 68, no 5, p. 1627-1638Article in journal (Refereed)
    Abstract [en]

    Automated manufacturing processes such as automotive tandem press lines include time dependent complex control functions. All motions and critical interactions between moving parts must be synchronised to avoid collisions and reach high production rate. It is even for a skilled operator hard to optimise these processes on-line. Therefore, a hardware-in-the-loop simulation including real industrial control systems and its control code establish an essential tool for optimisation. Additionally, an efficient optimisation algorithm is required to reach a useful simulation-based optimisation method. This paper proposes a new optimisation algorithm starting with the Lipschitzian algorithm DIRECT as global search and then switches over to the Nelder-Mead simplex algorithm for local convergence. During the switch over, the new algorithm determines all local candidates of the set of points evaluated by DIRECT and starts multiple Nelder-Mead local searches in each of these. An optimisation study for an automotive press line shows that the proposed algorithm combines the benefits of the Lipschitzian and the simplex algorithms in an efficient way. The importance of multiple local searches from all local candidates found is also shown in the study. Based on the same number of function evaluations, it is also shown that this algorithm reaches improved press line performances compared to the stochastic differential evolution algorithm.

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