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  • 1.
    Ahmed, Muhammad Rehan
    Örebro University, School of Science and Technology.
    Compliance Control of Robot Manipulator for Safe Physical Human Robot Interaction2011Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Inspiration from biological systems suggests that robots should demonstrate same level of capabilities that are embedded in biological systems in performing safe and successful interaction with the humans. The major challenge in physical human robot interaction tasks in anthropic environment is the safe sharing of robot work space such that robot will not cause harm or injury to the human under any operating condition.

    Embedding human like adaptable compliance characteristics into robot manipulators can provide safe physical human robot interaction in constrained motion tasks. In robotics, this property can be achieved by using active, passive and semi active compliant actuation devices. Traditional methods of active and passive compliance lead to complex control systems and complex mechanical design.

    In this thesis we present compliant robot manipulator system with semi active compliant device having magneto rheological fluid based actuation mechanism. Human like adaptable compliance is achieved by controlling the properties of the magneto rheological fluid inside joint actuator. This method offers high operational accuracy, intrinsic safety and high absorption to impacts. Safety is assured by mechanism design rather than by conventional approach based on advance control. Control schemes for implementing adaptable compliance are implemented in parallel with the robot motion control that brings much simple interaction control strategy compared to other methods.

    Here we address two main issues: human robot collision safety and robot motion performance.We present existing human robot collision safety standards and evaluate the proposed actuation mechanism on the basis of static and dynamic collision tests. Static collision safety analysis is based on Yamada’s safety criterion and the adaptable compliance control scheme keeps the robot in the safe region of operation. For the dynamic collision safety analysis, Yamada’s impact force criterion and head injury criterion are employed. Experimental results validate the effectiveness of our solution. In addition, the results with head injury criterion showed the need to investigate human bio-mechanics in more details in order to acquire adequate knowledge for estimating the injury severity index for robots interacting with humans.

    We analyzed the robot motion performance in several physical human robot interaction tasks. Three interaction scenarios are studied to simulate human robot physical contact in direct and inadvertent contact situations. Respective control disciplines for the joint actuators are designed and implemented with much simplified adaptable compliance control scheme.

    The series of experimental tests in direct and inadvertent contact situations validate our solution of implementing human like adaptable compliance during robot motion and prove the safe interaction with humans in anthropic domains.

  • 2.
    Albitar, Houssam
    Örebro University, School of Science and Technology.
    Enabling a Robot for Underwater Surface Cleaning2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biofouling build-up on submerged structures such as ships, petroleum and gas storage tanks, electric power plants, bridges, oil rigs etc. is a major problem that affects the surface material of the structure, the eventual hydrodynamic quality of the surface and in some cases the efficacy of cooling systems. Underwater cleaning is a solution to maintain submerged structures in order to assure proper functioning for as long as possible. Consequently, there has been an increased interest in the development of new technologies for robotised underwater cleaning systems.

    This thesis presents a new concept of a flexible crawling mechanism for an industrial underwater cleaning robot, which is evaluated from the viewpoint of its capability to work underwater, scanning the desired surface, and perform a cleaning task. The main research questions investigated in this thesis are: (1.) how to select the most important features in choosing the platform mechanism to fulfil the surface scanning operation, (2.) how to design the platform in order to bear the forces related to the cleaning task, (3.) how to maintain surface contact throughout cleaning, (4.) determine the significant parameters to be monitored in order to ensure stable positioning on the surface during the cleaning process and (5.) how to develop the control of actuators to realise the locomotion and to follow the desired trajectory.

    This thesis begins with a classification and discussion of the available solutions for underwater operation, taking into consideration the benefits and drawbacks, overall efficiency and environmental and human safety issues. From this survey, an underwater mobile robotic platform is designed to address the main requirements and industrial needs. Further, a study and simulation of its mobility and stability on the surface is performed and a complete scenario of the entire cleaning operation is presented. In addition, an overview of the required sensors and the control system is given. Finally, a new robotised system was developed to clean underwater surfaces with minimum active degrees of freedom. A successful simulation and real experimental results were obtained with a simplified lab-scale prototype. The thesis concludes with a summary of future works and outlook for the growing field of underwater cleaning robots.

    List of papers
    1. Underwater Robotics: Surface Cleaning Technics, Adhesion and Locomotion Systems
    Open this publication in new window or tab >>Underwater Robotics: Surface Cleaning Technics, Adhesion and Locomotion Systems
    2016 (English)In: International Journal of Advanced Robotic Systems, ISSN 1729-8806, E-ISSN 1729-8814, Vol. 13, article id 7Article in journal (Refereed) Published
    Abstract [en]

    Underwater robots are being developed for various applications ranging from inspection to maintenance and cleaning of submerged surfaces and constructions. These platforms should be able to travel on these surfaces. Furthermore, these platforms should adapt and reconfigure for underwater environment conditions and should be autonomous. Regarding the adhesion to the surface, they should produce a proper attaching force using a light-weight technics. Taking these facts into consideration, this paper presents a survey of different technologies used for underwater cleaning and the available underwater robotics solutions for the locomotion and the adhesion to surfaces.

    Place, publisher, year, edition, pages
    INTECH, 2016
    Keywords
    Underwater Robot, Underwater Cleaning, Bio-fouling, Adhesion, Locomotion
    National Category
    Computer Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-47813 (URN)10.5772/62060 (DOI)000368630700001 ()2-s2.0-85002271299 (Scopus ID)
    Available from: 2016-01-28 Created: 2016-01-28 Last updated: 2018-01-10Bibliographically approved
    2. New concept of in-water surface cleaning robot
    Open this publication in new window or tab >>New concept of in-water surface cleaning robot
    2013 (English)In: Mechatronics and Automation (ICMA), 2013 IEEE International Conference onDate 4-7 Aug. 2013, IEEE conference proceedings, 2013, p. 1582-1587Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper introduces a new concept of flexible crawling mechanism to design an industrial underwater cleaning robot, which is evaluated from the viewpoint of the capability to work underwater, scanning the desired surface, and bearing the reactions. This can be used as a robotic application in underwater surface cleaning and maintenance. We designed a robot that realizes the motion by contraction and extraction using DC-motors and vacuum technology. In this study we first focused on realizing the adhesion, bearing reactions, and achieving a stable locomotion on the surface.

    Place, publisher, year, edition, pages
    IEEE conference proceedings, 2013
    Keywords
    climbing robot; inspection
    National Category
    Computer Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-30340 (URN)10.1109/ICMA.2013.6618150 (DOI)000335375900267 ()2-s2.0-84887901379 (Scopus ID)978-1-4673-5557-5 (ISBN)
    Conference
    2013 IEEE International Conference on Mechatronics and Automation (ICMA), 4-7 aug. 2013, Takamatsu, Japan
    Available from: 2013-08-27 Created: 2013-08-27 Last updated: 2018-01-11Bibliographically approved
    3. In-water surface cleaning robot: concept, locomotion and stability
    Open this publication in new window or tab >>In-water surface cleaning robot: concept, locomotion and stability
    2014 (English)In: International Journal of Mechatronics and Automation, ISSN 2045-1067, Vol. 4, no 2, p. 104-115Article in journal (Refereed) Published
    Abstract [en]

    This paper introduces a new concept of flexible crawling mechanism in the design ofindustrial in-water cleaning robot, which is evaluated from the viewpoint of work and operationon an underwater surface. It enables the scanning and cleaning process performed by water jets,while keeping stable robot position on the surface by its capacity to bear and compensate the jetreactions. Such robotic platform can be used for cleaning and maintenance of various underwatersurfaces, including moving ships in the open sea. The designed robot implements its motions bycontraction and expansion of legged mechanism using standard motors and suction cupstechnology. In this study we focus at the conditions for achieving enough adhesion for keepingcontinuous contact between the robot and the surface and robot stability in different situations forthe basic locomotions.

    Place, publisher, year, edition, pages
    IEEE, 2014
    Keywords
    underwater robot, crawling robot, underwater surface cleaning
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:oru:diva-35987 (URN)10.1504/IJMA.2014.062338 (DOI)2-s2.0-84904859302 (Scopus ID)
    Available from: 2014-08-19 Created: 2014-08-19 Last updated: 2019-08-30Bibliographically approved
    4. Stability study of underwater crawling robot on non-horizontal surface
    Open this publication in new window or tab >>Stability study of underwater crawling robot on non-horizontal surface
    2014 (English)In: Mobile Service Robotics: Clawar 2014: 17th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines: Poznan, Poland 21 - 23 July 2014, Singapore: World Scientific, 2014, p. 511-519Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper introduces a study of a concept of exible crawling mechanism todesign an industrial underwater cleaning robot, which is evaluated from theviewpoint of the capability to work underwater, scanning the desired surface,and bearing the reactions. This can be used as a robotic application in under-water surface cleaning and maintenance. In this study we focused on realizingthe adhesion on the surface in stationary and in motion, bearing reactions,enabling the needed locomotion types for scanning, and achieving the stabilityin dierent situations on the surface.

    Place, publisher, year, edition, pages
    Singapore: World Scientific, 2014
    Keywords
    Crawling robot, underwater, locomotion, stability
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:oru:diva-35985 (URN)000342693100061 ()2-s2.0-85007347787 (Scopus ID)978-981-4623-34-6 (ISBN)
    Conference
    Clawar 2014: 17th International Conference on Climbing and Walking Robots CLAWAR, Poznan, Poland, 21 - 23 July, 2014
    Available from: 2014-08-19 Created: 2014-08-19 Last updated: 2018-01-11Bibliographically approved
    5. Layered mission control architecture and strategy for crawling underwater cleaning robot
    Open this publication in new window or tab >>Layered mission control architecture and strategy for crawling underwater cleaning robot
    2015 (English)In: International Journal of Mechatronics and Automation, ISSN 2045-1059, Vol. 5, no 2/3, p. 114-124Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the mechanical design and the control system architecture of anunderwater robot, developed for bio-fouling cleaning surfaces. The robotic system presented herehas been designed to improve the productivity, reduce the environmental impacts, and excludethe hazards for the operators. The control system has a layered structure which is distributed intotwo blocks: cleaning robot, and on-board base station connected with power and control cablesand a water hose, to facilitate different modes of operations and to increase the system reliability.A low level control has been implemented on the robotic platform. The onboard station designedto be in different layers of the control system: manual, semiautonomous and autonomous modes.A scaled prototype has been implemented and tested to prove the concept, and to make certainthat the mechanical design and the chosen control system are perfectly suited to the mainfunctions of the robotic system.

    Place, publisher, year, edition, pages
    InderScience Publishers, 2015
    Keywords
    underwater robots, layered control system, crawling robots, bio-fouling cleaning
    National Category
    Computer Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-49753 (URN)10.1504/IJMA.2015.075957 (DOI)2-s2.0-84973596360 (Scopus ID)
    Available from: 2016-04-11 Created: 2016-04-11 Last updated: 2018-01-10Bibliographically approved
  • 3.
    Alirezaie, Marjan
    Örebro University, School of Science and Technology.
    Bridging the Semantic Gap between Sensor Data and Ontological Knowledge2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The rapid growth of sensor data can potentially enable a better awareness of the environment for humans. In this regard, interpretation of data needs to be human-understandable. For this, data interpretation may include semantic annotations that hold the meaning of numeric data. This thesis is about bridging the gap between quantitative data and qualitative knowledge to enrich the interpretation of data. There are a number of challenges which make the automation of the interpretation process non-trivial. Challenges include the complexity of sensor data, the amount of available structured knowledge and the inherent uncertainty in data. Under the premise that high level knowledge is contained in ontologies, this thesis investigates the use of current techniques in ontological knowledge representation and reasoning to confront these challenges. Our research is divided into three phases, where the focus of the first phase is on the interpretation of data for domains which are semantically poor in terms of available structured knowledge. During the second phase, we studied publicly available ontological knowledge for the task of annotating multivariate data. Our contribution in this phase is about applying a diagnostic reasoning algorithm to available ontologies. Our studies during the last phase have been focused on the design and development of a domain-independent ontological representation model equipped with a non-monotonic reasoning approach with the purpose of annotating time-series data. Our last contribution is related to coupling the OWL-DL ontology with a non-monotonic reasoner. The experimental platforms used for validation consist of a network of sensors which include gas sensors whose generated data is complex. A secondary data set includes time series medical signals representing physiological data, as well as a number of publicly available ontologies such as NCBO Bioportal repository.

  • 4.
    Andreasson, Henrik
    Örebro University, Department of Technology.
    Local visual feature based localisation and mapping by mobile robots2008Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis addresses the problems of registration, localisation and simultaneous localisation and mapping (SLAM), relying particularly on local visual features extracted from camera images. These fundamental problems in mobile robot navigation are tightly coupled. Localisation requires a representation of the environment (a map) and registration methods to estimate the pose of the robot relative to the map given the robot’s sensory readings. To create a map, sensor data must be accumulated into a consistent representation and therefore the pose of the robot needs to be estimated, which is again the problem of localisation.

    The major contributions of this thesis are new methods proposed to address the registration, localisation and SLAM problems, considering two different sensor configurations. The first part of the thesis concerns a sensor configuration consisting of an omni-directional camera and odometry, while the second part assumes a standard camera together with a 3D laser range scanner. The main difference is that the former configuration allows for a very inexpensive set-up and (considering the possibility to include visual odometry) the realisation of purely visual navigation approaches. By contrast, the second configuration was chosen to study the usefulness of colour or intensity information in connection with 3D point clouds (“coloured point clouds”), both for improved 3D resolution (“super resolution”) and approaches to the fundamental problems of navigation that exploit the complementary strengths of visual and range information.

    Considering the omni-directional camera/odometry setup, the first part introduces a new registration method based on a measure of image similarity. This registration method is then used to develop a localisation method, which is robust to the changes in dynamic environments, and a visual approach to metric SLAM, which does not require position estimation of local image features and thus provides a very efficient approach.

    The second part, which considers a standard camera together with a 3D laser range scanner, starts with the proposal and evaluation of non-iterative interpolation methods. These methods use colour information from the camera to obtain range information at the resolution of the camera image, or even with sub-pixel accuracy, from the low resolution range information provided by the range scanner. Based on the ability to determine depth values for local visual features, a new registration method is then introduced, which combines the depth of local image features and variance estimates obtained from the 3D laser range scanner to realise a vision-aided 6D registration method, which does not require an initial pose estimate. This is possible because of the discriminative power of the local image features used to determine point correspondences (data association). The vision-aided registration method is further developed into a 6D SLAM approach where the optimisation constraint is based on distances of paired local visual features. Finally, the methods introduced in the second part are combined with a novel adaptive normal distribution transform (NDT) representation of coloured 3D point clouds into a robotic difference detection system.

  • 5.
    Ansheden, Caroline
    Örebro University, School of Science and Technology.
    Processförbättring för tillverkandet av specialbalk2010Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis work has been conducted for Corus Byggsystem AB. The company is located in Halmstad and manufactures profile claddings and purlins from sheet metal. The company also offers the customers professional advice and creates optimal solutions.

    In the production there is a press brake that manufactures purlins. This work station has neither efficient production or is ergonomically correct. The material and purlins are lifted manually by the workers and in some cases over the head. For heavy work, it is extremely important to apply an ergonomic approach, both to improve security for the workers and to increase the manufacturing volume. The focus was therefore on how to improve the workplace ergonomically to result in a safe workplace with efficient manufacturing results.

    The method that was mainly used in this project was David G. Ullmans The Mechanical Design Process and Fredy Olssons Primärkonstruktion and Principkonstruktion. Also SVID’s Design Process has been used as support.

  • 6.
    Asadi, Sahar
    Örebro University, School of Science and Technology.
    Towards Dense Air Quality Monitoring: Time-Dependent Statistical Gas Distribution Modelling and Sensor Planning2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis addresses the problem of gas distribution modelling for gas monitoring and gas detection. The presented research is particularly focused on the methods that are suitable for uncontrolled environments. In such environments, gas source locations and the physical properties of the environment, such as humidity and temperature may be unknown or only sparse noisy local measurements are available. Example applications include air pollution monitoring, leakage detection, and search and rescue operations.

    This thesis addresses how to efficiently obtain and compute predictive models that accurately represent spatio-temporal gas distribution.

    Most statistical gas distribution modelling methods assume that gas dispersion can be modelled as a time-constant random process. While this assumption may hold in some situations, it is necessary to model variations over time in order to enable applications of gas distribution modelling for a wider range of realistic scenarios.

    This thesis proposes two time-dependent gas distribution modelling methods. In the first method, a temporal (sub-)sampling strategy is introduced. In the second method, a time-dependent gas distribution modelling approach is presented, which introduces a recency weight that relates measurement to prediction time. These contributions are presented and evaluated as an extension of a previously proposed method called Kernel DM+V using several simulation and real-world experiments. The results of comparing the proposed time-dependent gas distribution modelling approaches to the time-independent version Kernel DM+V indicate a consistent improvement in the prediction of unseen measurements, particularly in dynamic scenarios under the condition that there is a sufficient spatial coverage. Dynamic scenarios are often defined as environments where strong fluctuations and gas plume development are present.

    For mobile robot olfaction, we are interested in sampling strategies that provide accurate gas distribution models given a small number of samples in a limited time span. Correspondingly, this thesis addresses the problem of selecting the most informative locations to acquire the next samples.

    As a further contribution, this thesis proposes a novel adaptive sensor planning method. This method is based on a modified artificial potential field, which selects the next sampling location based on the currently predicted gas distribution and the spatial distribution of previously collected samples. In particular, three objectives are used that direct the sensor towards areas of (1) high predictive mean and (2) high predictive variance, while (3) maximising the coverage area. The relative weight of these objectives corresponds to a trade-off between exploration and exploitation in the sampling strategy. This thesis discusses the weights or importance factors and evaluates the performance of the proposed sampling strategy. The results of the simulation experiments indicate an improved quality of the gas distribution models when using the proposed sensor planning method compared to commonly used methods, such as random sampling and sampling along a predefined sweeping trajectory. In this thesis, we show that applying a locality constraint on the proposed sampling method decreases the travelling distance, which makes the proposed sensor planning approach suitable for real-world applications where limited resources and time are available. As a real-world use-case, we applied the proposed sensor planning approach on a micro-drone in outdoor experiments.

    Finally, this thesis discusses the potential of using gas distribution modelling and sensor planning in large-scale outdoor real-world applications. We integrated the proposed methods in a framework for decision-making in hazardous inncidents where gas leakage is involved and applied the gas distribution modelling in two real-world use-cases. Our investigation indicates that the proposed sensor planning and gas distribution modelling approaches can be used to inform experts both about the gas plume and the distribution of gas in order to improve the assessment of an incident.

  • 7.
    Banaee, Hadi
    Örebro University, School of Science and Technology.
    From Numerical Sensor Data to Semantic Representations: A Data-driven Approach for Generating Linguistic Descriptions2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In our daily lives, sensors recordings are becoming more and more ubiquitous. With the increased availability of data comes the increased need of systems that can represent the data in human interpretable concepts. In order to describe unknown observations in natural language, an artificial intelligence system must deal with several issues involving perception, concept formation, and linguistic description. These issues cover various subfields within artificial intelligence, such as machine learning, cognitive science, and natural language generation.The aim of this thesis is to address the problem of semantically modelling and describing numerical observations from sensor data. This thesis introduces data-driven approaches to perform the tasks of mining numerical data and creating semantic representations of the derived information in order to describe unseen but interesting observations in natural language.The research considers creating a semantic representation using the theory of conceptual spaces. In particular, the central contribution of this thesis is to present a data-driven approach that automatically constructs conceptual spaces from labelled numerical data sets. This constructed conceptual space then utilises semantic inference techniques to derive linguistic interpretations for novel unknown observations. Another contribution of this thesis is to explore an instantiation of the proposed approach in a real-world application. Specifically, this research investigates a case study where the proposed approach is used to describe unknown time series patterns that emerge from physiological sensor data. This instantiation first presents automatic data analysis methods to extract time series patterns and temporal rules from multiple channels of physiological sensor data, and then applies various linguistic description approaches (including the proposed semantic representation based on conceptual spaces) to generate human-readable natural language descriptions for such time series patterns and temporal rules.The main outcome of this thesis is the use of data-driven strategies that enable the system to reveal and explain aspects of sensor data which may otherwise be difficult to capture by knowledge-driven techniques alone. Briefly put, the thesis aims to automate the process whereby unknown observations of data can be 1) numerically analysed, 2) semantically represented, and eventually 3) linguistically described.

  • 8.
    Bergsten, Pontus
    Örebro University, Department of Technology.
    Observers and controllers for Takagi-Sugeno fuzzy systems2001Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis studies analysis and design issues for observers anc controllers for Takagi-Sugeno (TS) fuzzy systems. Many physical systems are nonlinear in nature and using the well known linear techniques for such systems may result in bad performance, and even instability. On the other hand, analysis and design of observers and controllers for general nonlinear systems tend to be a quite involved procedure. It turns out, however, that a TS fuzzy system is able to represent or approximate a large class of nonlinear systems. Developing methods for observation and control for TS systems should therefore be worthwile.

    The TS fuzzy systems considered in this thesis are allowed to have an affine term. This can be an advantage, because affine TS fuzzy systems may be able to approximate nonlinear functions  to high accuracy with fewer rules than the TS fuzzy system with linear consequents only.

    It is shown that observer design is more difficult when the weights in the TS fuzzy systems depend on the estimated state, and an explicit design procedure is devised for that case. A reduced order observer is also proposed. To deal with modeling errors a fuzzy sliding mode approach is taken.

    The controller design is focused on affine TS fuzzy systems. Analysis and design of observer-based error state feedback controllers are proposed. Furthermore, it is also shown how recent results on classical gain scheduling may be used for control of affine TS fuzzy systems.

    Analysis and design for both observers and controllers are based on quadratic stability analysis, and in some cases, on robust quadratic stability analysis. Although this approach may be conservative, it often results in automatic design procedures based on optimization subject to linear matrix inequalities.

  • 9.
    Berntsson, Tomas
    Örebro University, Department of Technology.
    Replacement of lead baths with environment friendly alternative heat treatment processes in steel wire production2005Licentiate thesis, comprehensive summary (Other academic)
    List of papers
    1. Replacement of lead baths for the tempering of spring wire
    Open this publication in new window or tab >>Replacement of lead baths for the tempering of spring wire
    2003 (English)In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, no 5, p. 241-246Article in journal (Refereed) Published
    Abstract [en]

    Molten lead is used for tempering of valve-spring wire. Lead has drawbacks due to slow temperature changes. In 1991 the Swedish Parliament passed a Government Bill, in which proposals were made to phase out the use of lead in the long term, primarily through voluntary measures. Tempering of SIS 2090 (SAE 9254, DIN 55SiCr7) wire with different dimensions using induction heating was tested in a pilot process line. An induction coil for six wires and two coils with different lengths designed for single wires were tested. The results showed that an induction coil for six wires gave excessive temperature and property variations between the wires. The shorter of the single wire coils gave fluctuations in temperature and properties using a 3.00-mm wire. No such fluctuations were observed with the longer coil. One of the experiments showed that the process might need time to reach stable conditions. The results so far indicate that it is possible to produce valve-spring wire with induction tempering. The process needs more control and monitoring compared to tempering in molten lead. © Blackwell Munksgaard, 2003.

    Keywords
    Automotive engineering, Lead, Wire, Monitoring
    National Category
    Engineering and Technology
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-4615 (URN)10.1034/j.1600-0692.2003.00648.x (DOI)
    Available from: 2007-07-12 Created: 2007-07-12 Last updated: 2017-12-14Bibliographically approved
    2. Alternatives to lead bath for patenting of high carbon steel wire
    Open this publication in new window or tab >>Alternatives to lead bath for patenting of high carbon steel wire
    2004 (English)In: Wire Journal International, ISSN 0277-4275, Vol. 37, no 5, p. 82-86Article in journal (Refereed) Published
    Abstract [en]

    The alternatives to lead bath for patenting of high carbon steel wire are discussed. It is found that it is possible to achieve properties of high-speed gas patented music wire without using a soaking furnace. Laboratory experiments with patenting in a fluidized bed, showed that the process could give the required mechanical properties for the valve spring wire. It is also found that small alterations in process parameters in the industrial trials has a large impact on the mechanical properties and microstructures.

    Keywords
    Carbon steel, Furnaces, Austenite, Mufflers, Wire drawing, Molten materials, Valves (mechanical), Quenching, Process control, High temperature effects
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-4582 (URN)
    Available from: 2007-07-12 Created: 2007-07-12 Last updated: 2017-10-18Bibliographically approved
    3. Material properties of induction tempered high tensile valve spring wire
    Open this publication in new window or tab >>Material properties of induction tempered high tensile valve spring wire
    2006 (English)In: Steel Research International, ISSN 1611-3683, Vol. 77, no 11, p. 836-843Article in journal (Refereed) Published
    Abstract [en]

    Most of today's hardened valve spring wires are tempered in a lead bath. The lead bath provides a stable and accurate degree of tempering of the wire, but it has environmental disadvantages and limitations in flexibility. This paper describes how induction heating can replace lead bath and how this may affect the material properties. The study includes FEM-simulations, calculation of the tempering parameter and experiments with induction tempering of three different SiCr valve spring steels carried out under pilot production. The mechanical properties of the test samples were measured. Fatigue testing of one of the steels was performed on finished springs. The results were evaluated by comparing induction-tempered wire with the conventional lead tempered reference wire. The induction tempered wire fulfilled the product requirements and corresponded in performance with the lead tempered wire.

    Place, publisher, year, edition, pages
    Düsseldorf: Verlag Stahleisen, 2006
    Keywords
    Wire, Valves (mechanical), Tempering, Lead, Thermoanalysis, Steel, Finite element method, Computer simulation, Induction tempering, Spring steel, Super clean steel, High strength steel, Silicon chromium steel
    National Category
    Engineering and Technology
    Research subject
    maskinteknik
    Identifiers
    urn:nbn:se:oru:diva-4387 (URN)
    Available from: 2007-07-12 Created: 2007-07-12 Last updated: 2017-10-18Bibliographically approved
  • 10.
    Biel, Lena
    Örebro University, Department of Technology.
    Modeling of perceptual systems: a sensor fusion model with active perception2002Licentiate thesis, comprehensive summary (Other academic)
    List of papers
    1. ECG analysis: a new approach in human identification
    Open this publication in new window or tab >>ECG analysis: a new approach in human identification
    2001 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In this paper a new approach in human identification is investigated, For this purpose, a standard 12-lead electrocardiogram (ECG) recorded during rest is used. Selected features extracted from the ECG are used to identify a person in a predetermined group. Multivariate analysis is used for the identification task. Experiments show that it is possible to identify a person by features extracted from one lead only. Hence, only three electrodes have to be attached on the person to be identified. This makes the method applicable without too much effort.

    Keywords
    data fusion, electrocardiogram (ECG), feature extraction, human identification, multivariate analysis
    National Category
    Computer Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-16067 (URN)000169439600022 ()
    Available from: 2011-06-22 Created: 2011-06-22 Last updated: 2018-01-12Bibliographically approved
    2. Multivariate sensor fusion by a neural network model
    Open this publication in new window or tab >>Multivariate sensor fusion by a neural network model
    (English)Manuscript (preprint) (Other academic)
    National Category
    Computer Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-16070 (URN)
    Available from: 2011-06-22 Created: 2011-06-22 Last updated: 2018-01-12Bibliographically approved
    3. Active perception for autonomous sensor systems: an emerging paradigm?
    Open this publication in new window or tab >>Active perception for autonomous sensor systems: an emerging paradigm?
    2000 (English)Manuscript (preprint) (Other academic)
    National Category
    Computer Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-16068 (URN)000165444800008 ()
    Available from: 2011-06-22 Created: 2011-06-22 Last updated: 2018-01-12Bibliographically approved
    4. Active perception in a sensor fusion model
    Open this publication in new window or tab >>Active perception in a sensor fusion model
    2002 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    During the last decades the research in the sensor fusion area has mainly been focused on fusion methods and feature selection methods. A possible further development in this area is to incorporate a process referred to as active perception. This means that the system is able to manipulate the sensing mechanisms to create a focus on selected information in the surrounding environment. This process may also be able to handle the feature selection process with respect to which features to be used and/or the number of features to use. This paper presents a model that contains a decision system based on active perception integrated with previous sensor fusion algorithms. The human body has perhaps one of the most advanced perceptual processing systems. The human perception process can be divided into sensation (measurement collection) and perception (interpret the surroundings). During the sensation process a huge amount of data is collected from different sensors that reflect the environment. The information has to be interpreted in an effective way, i.e. in the fusion process. The interpretation together with a decision system to control the sensors to focus on important information will correspond to the (active) perception process. The model presented in this paper capitalizes on the properties presented by the biological counterpart to achieve more human-like processes for a sensor fusion. Finally, the paper presents the testing of the model in two examples. The applications used have a safety approach of fire indication, identification and decision-making. The goal is to enlarge a conventional fire alarm system to not only detect fire, but also to propose different actions for a human in a dangerous area for example.

    National Category
    Computer Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-16066 (URN)000176995000017 ()
    Available from: 2011-06-22 Created: 2011-06-22 Last updated: 2018-01-12Bibliographically approved
  • 11.
    Bouguerra, Abdelbaki
    Örebro University, Department of Technology.
    Robust execution of robot task-plans: a knowledge-based approach2008Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Autonomous mobile robots are being developed with the aim of accomplishing complex tasks in different environments, including human habitats as well as less friendly places, such as distant planets and underwater regions. A major challenge faced by such robots is to make sure that their actions are executed correctly and reliably, despite the dynamics and the uncertainty inherent in their working space. This thesis is concerned with the ability of a mobile robot to reliably monitor the execution of its plans and detect failures.

    Existing approaches for monitoring the execution of plans rely mainly on checking the explicit effects of plan actions, i.e., effects encoded in the action model. This supposedly means that the effects to monitor are directly observable, but that is not always the case in a real-world environment. In this thesis, we propose to use semantic domain-knowledge to derive and monitor implicit expectations about the effects of actions. For instance, a robot entering a room asserted to be an office should expect to see at least a desk, a chair, and possibly a PC. These expectations are derived from knowledge about the type of the room the robot is entering. If the robot enters a kitchen instead, then it should expect to see an oven, a sink, etc.

    The major contributions of this thesis are as follows.

    • We define the notion of Semantic Knowledge-based Execution Monitoring SKEMon, and we propose a general algorithm for it based on the use of description logics for representing knowledge.

    • We develop a probabilistic approach of semantic Knowledge-based execution monitoring to take into account uncertainty in both acting and sensing. Specifically, we allow for sensing to be unreliable and for action models to have more than one possible outcome. We also take into consideration uncertainty about the state of the world. This development is essential to the applicability of our technique, since uncertainty is a pervasive feature in robotics.

    • We present a general schema to deal with situations where perceptual information relevant to SKEMon is missing. The schema includes steps for modeling and generating a course of action to actively collect such information. We describe approaches based on planning and greedy action selection to generate the information-gathering solutions. The thesis also shows how such a schema can be applied to respond to failures occurring before or while an action is executed. The failures we address are ambiguous situations that arise when the robot attempts to anchor symbolic descriptions (relevant to a plan action) in perceptual information. The work reported in this thesis has been tested and verified using a mobile robot navigating in an indoor environment. In addition, simulation experiments were conducted to evaluate the performance of SKEMon using known metrics. The results show that using semantic knowledge can lead to high performance in monitoring the execution of robot plans.

  • 12.
    Boustedt, Katarina
    Örebro University, Department of Technology.
    Flip chip for high frequency applications: materials aspects2007Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Flip chip has since decades been the primary choice for chip interconnect for high performance circuits. Over the last few years, interest from the microwave arena has increased, and at this point in time microwave flip chip is a possible option for volume production.

    This thesis is based on an extensive literature survey in combination with experiments done in collaboration with Ericsson, Flextronics in Linköping and Chalmers University of Technology in Gothenburg. The backbone of the literature survey was published as a chapter on high frequency interconnects in the reference book “Area Array Interconnection Handbook” (2002), edited by Karl Puttlitz and Paul A. Totta, who are known as the fathers of flip chip. This literature study has since then been expanded and the latest search was

    done in June 2007.

    Four groups of experiments are reported in this thesis. The fi rst experiments are on stud bumping thin film substrates for subsequent fl ip-chip bonding. The wire was 17-μm diameter Au1Pd and bumping was uniform and successful, after some initial equipment problems.

    The second is a set of tests on flip-chip bonding using gold stud bumps, gold tin solder-on-substrate, and plated gold pillars on alumina carriers. To evaluate the joining process using these different bumps, chips made of alumina

    with coplanar waveguide transmission lines were thermocompression bonded to the bumped carriers. Bonder parameters were assessed related to the different bump types and materials. The bonding results were analyzed using shear tests, transmissive x-ray and scanning electron microscopy on

    cross-sections.

    The third experiment lot contains early results on reliability of stud-bump flip chip of gallium arsenide microstrip chips. Since the sample availability was very low and the joining process still under development, the results are vague, although it was fruitful to establish adequate methods of analysis and test.

    The fourth set of experiments involved the same alumina on alumina assembly, and flip-chip underfill and its impact measured up to 70 GHz. Three different underfill materials were applied to the test vehicles described above. Before and after underfilling, the test vehicles were measured for S parameters and compared.

    This study concludes that for flip chip on gold pads, the preferred joining process is soldering, just as for silicon chips with aluminum or copper pads. Since solder bumping on gold pads is hard to come by, the second best choice is plated pillars, on carrier or chip, and thirdly, gold wire stud bumping.

    Underfill for microwave applications should not necessarily be dreaded to the extent that it is today. This study has proven that the matching of lines isnot affected and the changes in dips can be considered in the early phases of the design process for chip and carrier.

  • 13.
    Brax, Christoffer
    Örebro University, School of Science and Technology.
    Anomaly detection in the surveillance domain2011Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In the post September 11 era, the demand for security has increased in virtually all parts of the society. The need for increased security originates from the emergence of new threats which differ from the traditional ones in such a way that they cannot be easily defined and are sometimes unknown or hidden in the “noise” of daily life.

    When the threats are known and definable, methods based on situation recognition can be used find them. However, when the threats are hard or impossible to define, other approaches must be used. One such approach is data-driven anomaly detection, where a model of normalcy is built and used to find anomalies, that is, things that do not fit the normal model. Anomaly detection has been identified as one of many enabling technologies for increasing security in the society.

    In this thesis, the problem of how to detect anomalies in the surveillance domain is studied. This is done by a characterisation of the surveillance domain and a literature review that identifies a number of weaknesses in previous anomaly detection methods used in the surveillance domain. Examples of identified weaknesses include: the handling of contextual information, the inclusion of expert knowledge and the handling of joint attributes. Based on the findings from this study, a new anomaly detection method is proposed. The proposed method is evaluated with respect to detection performance and computational cost on a number datasets, recorded from real-world sensors, in different application areas of the surveillance domain. Additionally, the method is also compared to two other commonly used anomaly detection methods. Finally, the method is evaluated on a dataset with anomalies developed together with maritime subject matter experts. The conclusion of the thesis is that the proposed method has a number of strengths compared to previous methods and is suitable foruse in operative maritime command and control systems.

  • 14.
    Buschka, Pär
    Örebro University, Department of Technology.
    An investigation of hybrid maps for mobile robots2005Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Autonomous robots typically rely on internal representations of the environment, or maps, to plan and execute their tasks. Several types of maps have been proposed in the literature, and there is general consensus that different types have different advantages and limitations, and that each type is more suited to certain tasks and less to others. Because of these reasons, it is becoming common wisdom in the field of mobile robotics to use hybrid maps that integrate several representations, usually of different types. Hybrid maps provide scalability and multiple views, allowing for instance to combine robot-centered and human-centered representations. There is, however, little understanding of the general principles that can be used to combine different maps into a hybrid one, and to make it something more than the sum of its parts. There is no systematic analysis of the different ways in which different maps can be combined, and how they can be made to cooperate. This makes it difficult to evaluate and compare different systems, and precludes us from getting a clear understanding of how a hybrid map can be designed or improved.

    The investigation presented in this thesis aims to contribute to fill this foundational gap, and to get a clearer understanding of the nature of hybrid maps. To help in this investigation, we develop two tools: The first one is a conceptual tool, an analytical framework in which the main ingredients of a hybrid map are described; the second one is an empirical tool, a new hybrid map that allows us to experimentally verify our claims and hypotheses.

    While these tools are themselves important contributions of this thesis, our investigation has resulted in the following additional outcomes:

    • A set of concepts that allow us to better understand the structure and operation of hybrid maps, and that help us to design them, compare them, identify their problems, and possibly improve them;

    • The identification of the notion of synergy as the fundamental way in which component maps inside a hybrid map cooperate.

    To assess the significance of these outcomes, we make and validate the following claims:

    1. Our framework allows us to classify and describe existing maps in a uniform way. This claim is validated constructively by making a thorough classification of the hybrid maps reported in the literature.

    2. Our framework also allows us to enhance an existing hybrid map by identifying spots for improvement. This claim is verified experimentally by modifying an existing map and evaluating its performance against the original one.

    3. The notion of synergy plays an important role in hybrid maps. This claim is verified experimentally by testing the performance of a hybrid map with and without synergy.

  • 15.
    Canelhas, Daniel Ricão
    Örebro University, School of Science and Technology.
    Truncated Signed Distance Fields Applied To Robotics2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis is concerned with topics related to dense mapping of large scale three-dimensional spaces. In particular, the motivating scenario of this work is one in which a mobile robot with limited computational resources explores an unknown environment using a depth-camera. To this end, low-level topics such as sensor noise, map representation, interpolation, bit-rates, compression are investigated, and their impacts on more complex tasks, such as feature detection and description, camera-tracking, and mapping are evaluated thoroughly. A central idea of this thesis is the use of truncated signed distance fields (TSDF) as a map representation and a comprehensive yet accessible treatise on this subject is the first major contribution of this dissertation. The TSDF is a voxel-based representation of 3D space that enables dense mapping with high surface quality and robustness to sensor noise, making it a good candidate for use in grasping, manipulation and collision avoidance scenarios.

    The second main contribution of this thesis deals with the way in which information can be efficiently encoded in TSDF maps. The redundant way in which voxels represent continuous surfaces and empty space is one of the main impediments to applying TSDF representations to large-scale mapping. This thesis proposes two algorithms for enabling large-scale 3D tracking and mapping: a fast on-the-fly compression method based on unsupervised learning, and a parallel algorithm for lifting a sparse scene-graph representation from the dense 3D map.

    The third major contribution of this work consists of thorough evaluations of the impacts of low-level choices on higher-level tasks. Examples of these are the relationships between gradient estimation methods and feature detector repeatability, voxel bit-rate, interpolation strategy and compression ratio on camera tracking performance. Each evaluation thus leads to a better understanding of the trade-offs involved, which translate to direct recommendations for future applications, depending on their particular resource constraints.

  • 16.
    Cielniak, Grzegorz
    Örebro University, Department of Technology.
    People tracking by mobile robots using thermal and colour vision2007Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis addresses the problem of people detection and tracking by mobile robots in indoor environments. A system that can detect and recognise people is an essential part of any mobile robot that is designed to operate in populated environments. Information about the presence and location of persons in the robot’s surroundings is necessary to enable interaction with the human operator, and also for ensuring the safety of people near the robot.

    The presented people tracking system uses a combination of thermal and colour information to robustly track persons. The use of a thermal camera simplifies the detection problem, which is especially difficult on a mobile platform. The system is based on a fast and efficient samplebased tracking method that enables tracking of people in real-time. The elliptic measurement model is fast to calculate and allows detection and tracking of persons under different views. An explicit model of the human silhouette effectively distinguishes persons from other objects in the scene. Moreover the process of detection and localisation is performed simultaneously so that measurements are incorporated directly into the tracking framework without thresholding of observations. With this approach persons can be detected independently from current light conditions and in situations where other popular detection methods based on skin colour would fail.

    A very challenging situation for a tracking system occurs when multiple persons are present on the scene. The tracking system has to estimate the number and position of all persons in the vicinity of the robot. Tracking of multiple persons in the presented system is realised by an efficient algorithm that mitigates the problems of combinatorial explosion common to other known algorithms. A sequential detector initialises an independent tracking filter for each new person appearing in the image. A single filter is automatically deleted when it stops tracking a person. While thermal vision is good for detecting people, it can be very difficult to maintain the correct association between different observations and persons, especially where they occlude one another, due to the unpredictable appearance and social behaviour of humans. To address these problems the presented tracking system uses additional information from the colour camera. An adaptive colour model is incorporated into the measurement model of the tracker to improve data association. For this purpose an efficient integral image based method is used to maintain the real-time performance of the tracker. To deal with occlusions the system uses an explicit method that first detects situations where people occlude each other. This is realised by a new approach based on a machine learning classifier for pairwise comparison of persons that uses both thermal and colour features provided by the tracker. This information is then incorporated into the tracker for occlusion handling and to resolve situations where persons reappear in a scene.

    Finally the thesis presents a comprehensive, quantitative evaluation of the whole system and its different components using a set of well defined performance measures. The behaviour of the system was investigated on different data sets including different real office environments and different appearances and behaviours of persons. Moreover the influence of all important system parameters on the performance of the system was checked and their values optimised based on these results.

  • 17.
    Cirillo, Marcello
    Örebro University, School of Science and Technology.
    Planning in Inhabited Environments: Human-Aware Task Planning and Activity Recognition2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Promised some decades ago by researchers in artificial intelligence and robotics as an imminent breakthrough in our everyday lives, a robotic assistant that could work with us in our home and our workplace is a dream still far from being fulfilled. The work presented in this thesis aims at bringing this future vision a little closer to realization. Here, we start from the assumption that an efficient robotic helper should not impose constraints on users' activities, but rather perform its tasks unobtrusively to fulfill its goals and to facilitate people in achieving their objectives.  Also, the helper should be able to consider the outcome of possible future actions by the human users, to assess how those would affect the environment with respect to the agent's objectives, and to predict when its support will be needed. In this thesis we address two highly interconnected problems that are essential for the cohabitation of people and service robots: robot task planning and human activity recognition. First, we present human-aware planning, that is, our approach to robot high-level symbolic reasoning for plan generation. Human-aware planning can be applied in situations where there is a controllable agent, the robot, whose actions we can plan, and one or more uncontrollable agents, the human users, whose future actions we can only try to predict. In our approach, therefore, the knowledge of the users' current and future activities is an important prerequisite. We define human-aware as a new type of planning problem, we formalize the extensions needed by a classical planner to solve such a problem, and we present the implementation of a planner that satisfies all identified requirements. In this thesis we explore also a second issue, which is a prerequisite to the first one: human activity monitoring in intelligent environments. We adopt a knowledge driven approach to activity recognition, whereby a constraint-based domain description is used to correlate sensor readings to human activities. We validate our solutions to both human-aware planning and activity recognition both theoretically and experimentally, describing a number of explanatory examples and test runs in a real environment.

  • 18.
    Dahlbom, Anders
    Örebro University, School of Science and Technology.
    Petri nets for situation recognition2011Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Situation recognition is a process with the goal of identifying a priori defined situations in a flow of data and information. The purpose is to aid decision makers with focusing on relevant information by filtering out situations of interest. This is an increasingly important and non trivial problem to solve since the amount of information in various decision making situations constantly grow. Situation recognition thus addresses the information gap, i.e. the problem of finding the correct information at the correct time. Interesting situations may also evolve over time and they may consist of multiple participating objects and their actions. This makes the problem even more complex to solve. This thesis explores situation recognition and provides a conceptualization and a definition of the problem, which allow for situations of partial temporal definition to be described. The thesis then focuses on investigating how Petri nets can be used for recognising situations. Existing Petri net based approaches for recognition have some limitations when it comes to fulfilling requirements that can be put on solutions to the situation recognition problem. An extended Petri net based technique that addresses these limitations is therefore introduced. It is shown that this technique can be as efficient as a rule based techniques using the Rete algorithm with extensions for explicitly representing temporal constraints. Such techniques are known to be efficient; hence, the Petri net based technique is efficient too. The thesis also looks at the problem of learning Petri net situation templates using genetic algorithms. Results points towards complex dynamic genome representations as being more suited for learning complex concepts, since these allow for promising solutions to be found more quickly compared with classical bit string based representations. In conclusion, the extended Petri net based technique is argued to offer a viable approach for situation recognition since it: (1) can achieve good recognition performance, (2) is efficient with respect to time, (3) allows for manually constructed situation templates to be improved and (4) can be used with real world data to find real world situations.

  • 19.
    Dandan, Kinan
    Örebro University, School of Science and Technology.
    Enabling Surface Cleaning Robot for Large Food Silo2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Working conditions in the dry cleaning and sanitation of confined interior spaces are often extreme, and workers need overall protection with tight clothing, helmets, face mask, earmuffs, and respirators. The environment is dirty, noisy with bad visibility and heavy with a high static work load. Dry cleaning is mainly practised in silos for grain, foodstuff and flour, etc. The inside of the silo is a hazardous environment due to many factors such as an unsafe oxygen level, engulfment, biological, mechanical, electrical, and atmospheric hazards. The requirements of the EU norms related to hygiene and food quality indicate that silos should be cleaned frequently and cleaning is obligatory after a silo is totally emptied. Therefore, there is an increased societal need for silo cleaning and a natural necessity to replace humans by robot manipulators in executing this risky and dangerous job.

    This thesis presents a new concept of a flexible crawling mechanism for an industrial food cleaning robot, which is evaluated from the viewpoint of the capability to work inside a large food silo, scanning the desired surface, and performing the cleaning task. The main research questions investigated in this thesis are about: how to select the most important characteristics in designing a robot to fulfil the surface cleaning operation of a large confined space; how the crawling movement affects the dynamic behaviour of the robot mechanism; how the cleaning process affects the dynamic behaviour of the robot mechanism; how to develop the control of the robot to realize the locomotion and the cleaning process.

    The structure of the robot and the cleaning technology are well defined after an overview of the existing technologies and solutions for cleaning large confined spaces. The robot design is based on a suspension and crawling system, using minimal actuators, where the force of gravity is well used to simplify the control system and to stabilise the robot. Further, the static and dynamic analysis of the mechanical system is studied. In addition, the control architecture of the system is performed, where the required sensors and control algorithm are given. A scale model testing has also been used to verify the locomotion of the concept, while simple controllers and algorithms are used to manage the motions of the prototype.

    List of papers
    1. SIRO: the silos surface cleaning robot concept
    Open this publication in new window or tab >>SIRO: the silos surface cleaning robot concept
    2013 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    A concept of a suspended robot for surface cleaning in silos is presented in this paper. The main requirements and limitations resulting from the specific operational conditions are discussed. Due to the large dimension of the silo as a confined space, specific kinematics of the robot manipulator is proposed. The major problems in its design are highlighted and an approach to resolve them is proposed. The suggested concept is a reasonable compromise between the basic contradicting factors in the design: small entrance and large surface of the confined space, suspension and stabilization of the robot

    Place, publisher, year, edition, pages
    IEEE conference proceedings, 2013
    National Category
    Robotics Computer Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-30689 (URN)10.1109/ICMA.2013.6617994 (DOI)000335375900111 ()2-s2.0-84887856459 (Scopus ID)978-1-4673-5560-5 (ISBN)
    Conference
    The 2013 IEEE International Conference on Mechatronics and Automation (ICMA), 4-7 aug. 2013, Takamatsu, Japan
    Available from: 2013-09-04 Created: 2013-09-04 Last updated: 2019-01-14Bibliographically approved
    2. Modeling and simulation of a silo cleaning robot
    Open this publication in new window or tab >>Modeling and simulation of a silo cleaning robot
    2014 (English)In: Mobile Service Robotics / [ed] Krazystof Kotowski, Mohammad O Tokhi and Gurvinder S Virk, Singapore: World Scientific, 2014, p. 627-635Conference paper, Published paper (Refereed)
    Abstract [en]

    A suspended robot for surface cleaning in silos is presented in this paper. Thesuggested concept is a reasonable compromise between the basic contradictingfactors in the design: small entrance and large surface of the confined space,suspension and stabilization of the robot. A dynamic study for the suspendedrobot is presented in this paper. A dynamic simulation in MSC ADAMS iscarried out to confirm the results from the theoretic study.

    Place, publisher, year, edition, pages
    Singapore: World Scientific, 2014
    Keywords
    Suspended robot, Cleaning robot, Dynamic model, Dynamic simulation
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:oru:diva-35878 (URN)000342693100074 ()2-s2.0-85007393142 (Scopus ID)978-981-4623-34-6 (ISBN)
    Conference
    the 17th international conference on climbing and walking robots
    Available from: 2014-08-08 Created: 2014-08-07 Last updated: 2019-01-14Bibliographically approved
    3. Motion Control of Siro: The Silo Cleaning Robot
    Open this publication in new window or tab >>Motion Control of Siro: The Silo Cleaning Robot
    2015 (English)In: International Journal of Advanced Robotic Systems, ISSN 1729-8806, E-ISSN 1729-8814, Vol. 12, article id 184Article in journal (Refereed) Published
    Abstract [en]

    Both the principle of operation and the motion-control system of a suspended robot for surface cleaning in silos are presented in this paper. The mechanical design is a reasonable compromise between basically contradictory factors in the design: the small entrance and the large surface of the confined space, and the suspension and the stabilization of the robot. The design consists of three main parts: a support unit, the cleaning robot and a cleaning mechanism. The latter two parts enter the silo in a folded form and, thereafter, the robot’s arms are spread in order to achieve stability during the cleaning process. The vertical movement of the robot is achieved via sequential crawling motions.

    The control system is divided into two separate subsystems, the robot’s control subsystem and a support-unit control subsystem, in order to facilitate different operational modes. The robot has three principle motion-control tasks: positioning the robot inside the silo, holding a vertical position during the cleaning process and a crawling movement.

    A scaled prototype of the robot has been implemented and tested to prove the concept, in order to make certain that the mechanical design suits the main functions of the robotic system, to realize the robot’s design in an industrial version and to test it in a realistic environment.

    Place, publisher, year, edition, pages
    InTech, 2015
    Keywords
    Suspended Robot, Silo Cleaning, Motion-control System, Control Algorithm
    National Category
    Computer and Information Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-47132 (URN)10.5772/61812 (DOI)000366622700002 ()
    Available from: 2015-12-18 Created: 2015-12-18 Last updated: 2019-02-15Bibliographically approved
    4. Dynamical Analysis of Silo Surface Cleaning Robot using Finite Element Method
    Open this publication in new window or tab >>Dynamical Analysis of Silo Surface Cleaning Robot using Finite Element Method
    2016 (English)In: International Journal of Mechanical Engineering & Technology (IJMET), ISSN 0976-6340, Vol. 07, no 01, p. 190-202, article id IJMET_07_01_020Article in journal (Refereed) Published
    Abstract [en]

    All mechanical systems are subjected to dynamic forces when they are in functioning. Thus a dynamical analysis has to be studied to determine the system behaviour. The vibration is of interest to study, due to its destructive or constructive effect. In the present era computational techniques are quite common and are very reliable as far as the modal analysis is concerned. In this work, the robot of silo cleaning is analysed for its vibration behaviour using finite element method (FEM).The robot was modelled and meshed in ANSYS. Modal analysis was conducted to calculate few initial natural frequencies. After carrying out the modal analysis, harmonic and transient analysis were done to see the response of the robot under dynamic loading. It was observed that robot is safe in its entire range of operation.

    Place, publisher, year, edition, pages
    India: IAME, 2016
    Keywords
    Silo, Suspended Robot, Finite Element, Modal Analysis, Dynamic Analysis
    National Category
    Computer Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-48415 (URN)
    Available from: 2016-02-19 Created: 2016-02-19 Last updated: 2019-03-22Bibliographically approved
  • 20.
    Daoutis, Marios
    Örebro University, School of Science and Technology.
    Knowledge based perceptual anchoring: grounding percepts to concepts in cognitive robots2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A successful articial cognitive agent needs to integrate its perception of the environment with reasoning and actuation. A key aspect of this integration is the perceptual-symbolic correspondence, which intends to give meaning to the concepts the agent refers to { known as Anchoring. However, perceptual representations alone (e.g., feature lists) cannot entirely provide sucient abstraction and enough richness to deal with the complex nature of the concepts' meanings. On the other hand, neither plain symbol manipulation appears capable of attributing the desired intrinsic meaning.

    We approach this integration in the context of cognitive robots which operate in the physical world. Specically we investigate the challenge of establishing the connection between percepts and concepts referring to objects, their relations and properties.We examine how knowledge representation can be used together with an anchoring framework, so as to complement the meaning of percepts while supporting linguistic interaction. This implies that robots need to represent both their perceptual and semantic knowledge, which is often expressed in dierent abstraction levels and may originate from dierent modalities.

    The solution proposed in this thesis concerns the specication, design and implementation ofa hybrid cognitive computational model, which extends a classical anchoring framework, in order to address the creation and maintenance of the perceptual-symbolic correspondences. The model is based on four main aspects: (a) robust perception, by relying on state-of-the art techniques from computer vision and mobile robot localisation; (b) symbol grounding, using topdown and bottom-up information acquisition processes as well as multi-modal representations; (c) knowledge representation and reasoning techniques in order to establish a common language and semantics regarding physical objects, their properties and relations, that are to be used between heterogeneous robotic agents and humans; and (d) commonsense information in order to enable high-level reasoning as well as to enhance the semantic

    descriptions of objects.

    The resulting system and the proposed integration has the potential to strengthen and expand the knowledge of a cognitive robot. Specically, by providing more robust percepts it is possible to cope better with the ambiguity and uncertainty of the perceptual data. In addition, the framework is able to exploit mutual interaction between dierent levels of representation while integrating dierent sources of information. By modelling and using semantic & perceptual knowledge, the robot can: acquire, exchange and reason formally about concepts, while prior knowledge can become a cognitive bias in the acquisition of novel concepts.

    List of papers
    1. Using Knowledge Representation for Perceptual Anchoring in a Robotic System
    Open this publication in new window or tab >>Using Knowledge Representation for Perceptual Anchoring in a Robotic System
    2008 (English)In: International Journal on Artificial Intelligence Tools, ISSN 0218-2130, Vol. 17, no 5, p. 925-944Article in journal (Refereed) Published
    Abstract [en]

    In this work we introduce symbolic knowledge representation and reasoning capabilities to enrich perceptual anchoring. The idea that encompasses perceptual anchoring is the creation and maintenance of a connection between the symbolic and perceptual description that refer to the same object in the environment. In this work we further extend the symbolic layer by combining a knowledge representation and reasoning (KRR) system with the anchoring module to exploit a knowledge inference mechanisms. We implemented a prototype of this novel approach to explore through initial experimentation the advantages of integrating a symbolic knowledge system to the anchoring framework in the context of an intelligent home. Our results show that using the KRR we are better able to cope with ambiguities in the anchoring module through exploitation of human robot interaction.

    National Category
    Engineering and Technology Computer and Information Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-5175 (URN)
    Available from: 2009-02-24 Created: 2009-01-29 Last updated: 2018-01-13Bibliographically approved
    2. Grounding commonsense knowledge in intelligent systems
    Open this publication in new window or tab >>Grounding commonsense knowledge in intelligent systems
    2009 (English)In: Journal of Ambient Intelligence and Smart Environments, ISSN 1876-1364, E-ISSN 1876-1372, Vol. 1, no 4, p. 311-321Article in journal (Refereed) Published
    Abstract [en]

    Ambient environments which integrate a number of sensing devices and actuators intended for use by human users need to be able to express knowledge about objects, their functions and their properties to assist in the performance of everyday tasks. For this to occur perceptual data must be grounded to symbolic information that in its turn can be used in the communication with the human. For symbolic information to be meaningful it should be part of a rich knowledge base that includes an ontology of concepts and common sense. In this work we present an integration between ResearchCyc and an anchoring framework that mediates the connection between the perceptual information in an intelligent home environment and the reasoning system. Through simple dialogues we validate how objects placed in the home environment are grounded by a network of sensors and made available to a larger KB where reasoning is exploited. This first integration work is a step towards integrating the richness of a KRR system developed over many years in isolation, with a physically embedded intelligent system.

    Place, publisher, year, edition, pages
    Amsterdam: IOS Press, 2009
    Keywords
    Physical Symbol Grounding, Commonsense Knowledge Representation, Human Robot Interaction, Intelligent Home
    National Category
    Computer Sciences
    Research subject
    Computer Science; Information technology
    Identifiers
    urn:nbn:se:oru:diva-8485 (URN)10.3233/AIS-2009-0040 (DOI)000207842000002 ()2-s2.0-78651496919 (Scopus ID)
    Available from: 2009-11-09 Created: 2009-11-09 Last updated: 2018-01-12Bibliographically approved
    3. Cooperative knowledge based perceptual anchoring
    Open this publication in new window or tab >>Cooperative knowledge based perceptual anchoring
    2012 (English)In: International journal on artificial intelligence tools, ISSN 0218-2130, Vol. 21, no 3, article id 1250012Article in journal (Refereed) Published
    Abstract [en]

    In settings where heterogenous robotic systems interact with humans, information from the environment must be systematically captured, organized and maintained in time. In this work, we propose a model for connecting perceptual information to semantic information in a multi-agent setting. In particular, we present semantic cooperative perceptual anchoring, that captures collectively acquired perceptual information and connects it to semantically expressed commonsense knowledge. We describe how we implemented the proposed model in a smart environment, using different modern perceptual and knowledge representation techniques. We present the results of the systemand investigate different scenarios in which we use the common sense together with perceptual knowledge, for communication, reasoning and exchange of information.

    Place, publisher, year, edition, pages
    World Scientific, 2012
    Keywords
    Cognitive robotics; physical symbol grounding; commonsense information; multi-agent perception; object recognition
    National Category
    Computer Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-24226 (URN)10.1142/S0218213012500121 (DOI)000305795900008 ()2-s2.0-84863086324 (Scopus ID)
    Funder
    Swedish Research Council
    Available from: 2012-08-06 Created: 2012-08-05 Last updated: 2018-01-12Bibliographically approved
    4. Towards concept anchoring for cognitive robots
    Open this publication in new window or tab >>Towards concept anchoring for cognitive robots
    2012 (English)In: Intelligent Service Robotics, ISSN 1861-2784, Vol. 5, no 4, p. 213-228Article in journal (Refereed) Published
    Abstract [en]

    We present a model for anchoring categorical conceptual information which originates from physical perception and the web. The model is an extension of the anchoring framework which is used to create and maintain over time semantically grounded sensor information. Using the augmented anchoring framework that employs complex symbolic knowledge from a commonsense knowledge base, we attempt to ground and integrate symbolic and perceptual data that are available on the web. We introduce conceptual anchors which are representations of general, concrete conceptual terms. We show in an example scenario how conceptual anchors can be coherently integrated with perceptual anchors and commonsense information for the acquisition of novel concepts.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2012
    Keywords
    Anchoring; Categorical perception; Near sets; Knowledge representation; Commonsense information
    National Category
    Robotics Computer Vision and Robotics (Autonomous Systems) Computer Sciences
    Research subject
    Computer Science
    Identifiers
    urn:nbn:se:oru:diva-26831 (URN)10.1007/s11370-012-0117-z (DOI)000208947900002 ()2-s2.0-84867580722 (Scopus ID)
    Funder
    Swedish Research Council
    Available from: 2013-01-10 Created: 2013-01-10 Last updated: 2018-01-11Bibliographically approved
  • 21.
    Erlandsson, Tina
    Örebro University, School of Science and Technology.
    A combat survivability model for evaluating air mission routes in future decision support systems2014Doctoral thesis, comprehensive summary (Other academic)
    List of papers
    1. Modeling fighter aircraft mission survivability
    Open this publication in new window or tab >>Modeling fighter aircraft mission survivability
    2011 (English)In: Proceedings of the 14th International Conference on Information Fusion (FUSION 2011), New York: IEEE conference proceedings, 2011, p. 999-1006Conference paper, Published paper (Other academic)
    Abstract [en]

    A fighter aircraft flying a mission is often exposed to ground-based threats such as surface-to-air missile (SAM) sites.The fighter pilot needs to take actions to minimize the risk of being shot down, but at the same time be able to accomplish the mission. In this paper we propose a survivability model, which describes the probability that the aircraft will be able to fly a given route without being hit by incoming missiles. Input to this model can consist of sensor measurements collected during flight as well as intelligence data gathered before the mission.This input is by nature uncertain and we therefore investigate the influence of uncertainty in the input to the model. Finally we propose a number of decision support functions that can be developed based on the suggested model such as countermeasure management, mission planning and sensor management

    Place, publisher, year, edition, pages
    New York: IEEE conference proceedings, 2011
    Keywords
    Survivability, fighter aircraft, decision support, threat model
    National Category
    Computer and Information Sciences
    Research subject
    Computer and Systems Science
    Identifiers
    urn:nbn:se:oru:diva-20538 (URN)978-1-4577-0267-9 (ISBN)
    Conference
    14th International Conference on Information Fusion (FUSION 2011), 5-8 July, Chicago
    Note

    This research has been supported by the Swedish Governmental Agency for Innovation Systems (Vinnova) through the National Aviation Engineering Research Program (NFFP5- 2009-01315), Saab AB and the University of Skovde.

    Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2018-01-12Bibliographically approved
    2. Calculating uncertainties in situation analysis for fighter aircraft combat survivability
    Open this publication in new window or tab >>Calculating uncertainties in situation analysis for fighter aircraft combat survivability
    2012 (English)In: 2012 15th International Conference on Information Fusion (FUSION), 9-12 July 2012, IEEE, 2012, p. 196-203Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    IEEE, 2012
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:oru:diva-34573 (URN)978-0-9824438-4-2 (ISBN)
    Conference
    2012 15th International Conference on Information Fusion (FUSION), 9-12 July 2012
    Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2018-05-13Bibliographically approved
    3. An air-to-ground combat survivability model
    Open this publication in new window or tab >>An air-to-ground combat survivability model
    (English)Article in journal (Refereed) Epub ahead of print
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:oru:diva-34572 (URN)10.1177/1548512913484399 (DOI)
    Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-10-17Bibliographically approved
    4. Automatic evaluation of air mission routes with respect to combat survival
    Open this publication in new window or tab >>Automatic evaluation of air mission routes with respect to combat survival
    (English)In: Information Fusion, ISSN 1566-2535, E-ISSN 1872-6305Article in journal (Refereed) In press
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:oru:diva-34571 (URN)10.1016/j.inffus.2013.12.001 (DOI)
    Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-12-05Bibliographically approved
    5. Route planning for air missions in hostile environments
    Open this publication in new window or tab >>Route planning for air missions in hostile environments
    (English)In: Journal of defense modeling and simulation, ISSN 1557-380XArticle in journal (Refereed) Submitted
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:oru:diva-34570 (URN)
    Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-10-17Bibliographically approved
    6. Threat assessment for missions in hostile territory: from the aircraft perspective
    Open this publication in new window or tab >>Threat assessment for missions in hostile territory: from the aircraft perspective
    2013 (English)In: 16th International Conference on Information Fusion Istanbul, Turkey, July 9-12, 2013, IEEE, 2013, p. 1856-1862Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    IEEE, 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:oru:diva-34569 (URN)978-605-86311-1-3 (ISBN)
    Conference
    16th International Conference on Information Fusion Istanbul, Turkey, July 9-12, 2013
    Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-10-18Bibliographically approved
  • 22.
    Gillström, Peter
    Örebro University, Department of Technology.
    Alternatives to pickling: preparation of carbon and low alloyed steel wire rod2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A well established method for scale removal on hot rolled wire rod is pickling. To avoid pollution problems, the wire rod can be mechanically descaled. By this method, the removed scale can be recirculated to the blast furnace.

    In batch pickling considerable energy is necessary; e.g. for heating of the pickling baths, ventilation of acid fumes and application of lubricant carrier. Energy consumption of the alternative descaling methods has been assessed and compared to pickling

    A method was developed to evaluate the remaining scale on mechanically descaled wire rod. Stretching experiments were used to evaluate adhesion of scale to the wire rod surface of different steel grades. Most of the scale was removed on the carbon steel grades and Cr/V alloyed steel grades. More scale remained on silicon alloyed steel grades.

    Shot blasting with steel shots was studied as an alternative to pickling. This method removed the scale on all studied steel grades, even the silicon alloyed grades. The wire rod surface was much rougher compared to the pickled wire rod surface. The shot blast power consumption was measured and evaluated. The PC strand wire gave more wear of dies otherwise the shot blasted wire rod showed no difference in the wire drawing process compared to pickled wire rod. Downstream problems such as cleaning and adherence of copper were observed.

    Reverse bending and brushing with steel brushes and brushes with SiC abrasives were studied on wire rod of low carbon and silicon chromium alloyed steel grades. Scale remained in surface valleys after brushing of the low carbon steel grade. The silicon steel grades were not possible to descale by bending and brushing. Surface defects from brushing were observed on wire rods brushed by steel brushes, but not on wire rod brushed by SiC-nylon brushes.

    A study of shot blasting with recycled glass was done. Due to the lower density, the shot velocity must be higher than for steel shots. Recycled glass gives an irregular surface of the wire, including chip formation, which can improve the lubricant carrying ability of the wire rod surface, but also increase the risk for reduction of the fatigue strength of the wire.

    The differences of die wear using wire rods descaled by two treatments; pickling and reversed bending has been studied. The study gave a background of wear mechanism and described a method to estimate die wear in wire drawing. The conclusions of the experiments indicate that the method for wire rod preparation seems to be of minor importance for the wear of die. The wear rate of a die used in the sixth draft was one order of magnitude lower than the wear rate of the die in the first draft. Abrasive wear is present presumably from the WC grains, torn out in the adhesive wear, on both dies used on pickled wire rod and reverse bent and steel wool cleaned wire rod.

    In order to evaluate new methods to descale wire rod, the effect of thermal shock has been studied. An estimation of the stresses, developed in the oxide during cooling after hot rolling and a FEM-simulation during cooling from ambient temperature down to 77 K, has been made. Experiments using liquid nitrogen, flame and steam to descale wire rod have been performed with mild steel and silicon and chromium steel wire rod. The experiments have shown that thermal shock cannot descale the wire rod. Only a descaling effect from the flame has been found.

    List of papers
    1. Determination of scale amount on wire of carbon steels and low alloyed steels
    Open this publication in new window or tab >>Determination of scale amount on wire of carbon steels and low alloyed steels
    2003 (English)In: Wire Journal International, ISSN 0277-4275, Vol. 36, no 9, p. 73-77Article in journal (Refereed) Published
    Abstract [en]

    Scale amount on wire of carbon steels and low alloyed steels was discussed. Metal microscopy and scanning electron microscopy were used. It was found that this method can determine the scale determinations after the material has been stretched.

    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-3063 (URN)
    Available from: 2006-03-17 Created: 2006-03-17 Last updated: 2017-10-18Bibliographically approved
    2. Replacement of pickling with shot blasting for wire rod preparation
    Open this publication in new window or tab >>Replacement of pickling with shot blasting for wire rod preparation
    2004 (English)In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 5, p. 269-278Article in journal (Refereed) Published
    Abstract [en]

    An oxide scale layer covers steel wire rod produced by hot rolling. This oxide is often removed by pickling before wire drawing; otherwise, hard oxides will be impressed into the wire surface and give an inferior surface quality. Stricter pollution regulations increase the incentive to replace pickling with mechanical descaling. This paper gives results from tests on carbon steels by using shot blasting to descale wire rod. The tests include: (i) shot blasting experiments in an industrial full-scale in-line shot blasting machine, (ii) laboratory drawing experiments on shot blasted wire rod, (iii) industrial trials on shot blasted wire rod at the drawing plants. There are differences in the appearance of surfaces between shot blasted and pickled wires, but no differences in the drawing process were observed in the laboratory experiment. In the industrial trials the wear of dies were more severe when drawing shot blasted wire of one of the steel grades. In the downstream processes, problems were recorded with the cleanness of the surface of another grade and adhesion of copper coating on a third grade.

    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-3064 (URN)10.1111/j.1600-0692.2004.00692.x (DOI)
    Available from: 2006-03-17 Created: 2006-03-17 Last updated: 2017-12-14Bibliographically approved
    3. Mechanical descaling of wire rod using reverse bending and brushing
    Open this publication in new window or tab >>Mechanical descaling of wire rod using reverse bending and brushing
    2006 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 172, no 3, p. 332-340Article in journal (Refereed) Published
    Abstract [en]

    Wire rods are covered with an oxide layer, which must be removed before wire drawing. This paper presents an investigation of mechanical descaling by reverse bending and brushing as replacement for pickling. Steel grades studied were low carbon steel and silicon chromium steel. Brushing was done with steel brushes and nylon brushes with SiC. The amount of scale remaining after reverse bending of the low carbon steel depended on the roller diameter. After brushing traces of scale remained in valleys on the surface. Surface damage was observed after brushing with steel brushes but not after SiC-nylon brushing. Silicon chromium alloyed steel was not possible to clean by bending and brushing with the roller diameters studied. The electrical energy required for the mechanical descaling of low C steel may be estimated to be 7kWh/tonne with SiC-nylon brushes and 14kWh/tonne with steel brushes. [All rights reserved Elsevier]

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2006
    Keywords
    bending, carbon steel, drawing (mechanical), pickling (materials processing), rods (structures), rollers (machinery), wires
    National Category
    Engineering and Technology
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-4438 (URN)10.1016/j.jmatprotec.2005.10.014 (DOI)
    Available from: 2007-07-12 Created: 2007-07-12 Last updated: 2017-12-14Bibliographically approved
    4. Shot blasting of billets and wire rod
    Open this publication in new window or tab >>Shot blasting of billets and wire rod
    2005 (English)In: Metallurgy and new materials researches, ISSN 1221-5503, Vol. 13, no 4, p. 1-21Article in journal (Refereed) Published
    Abstract [en]

    A model for work and power in shot blasting is derived. A study is made to use recycled glass as a shot blasting media. The theoretical model must be adjusted for strain hardening material. The experiments indicate that the average shear yield stress is more than twice the initial value for austenitic stainless steels. Soft materials get rough surfaces in shot blasting, which can be advantageous for the ability to carry the wire drawing lubricant. Recycled glass is a possible shot material. Due to the lower density, the shot velocity must be higher than for steel shots. This effect becomes larger by rotation of the glass shots during operation. Recycled glass gives irregular surface, including chip formation, which can improve the lubricant carrying ability of the wire rod surface, but also increase the risk for reduction of the fatigue strength of the wire.

    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-3066 (URN)
    Note
    Tidskriftens parallelltitel: Cercetari Metalurgice si de noi MaterialeAvailable from: 2006-03-17 Created: 2006-03-17 Last updated: 2017-10-18Bibliographically approved
    5. Wear of die after drawing of pickled or reverse bent wire rod
    Open this publication in new window or tab >>Wear of die after drawing of pickled or reverse bent wire rod
    2007 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 262, no 7-8, p. 858-867Article in journal (Refereed) Published
    Abstract [en]

    The object of this paper was to evaluate the difference of die wear by using wire rods descaled by two different treatments; pickling or reversed bending. The paper gives a background of wear mechanism and describe a method to estimate die wear in wire drawing. The conclusions of the experiments were that the wire rod preparation seems to be of minor importance for the wear of die. A die in the sixth draft had a magnitude lower wear, compared to the die in the first draft. Abrasive wear is present from the WC grains, torn out in the adhesive wear, on both dies used on pickled wire rod and reverse bent and steel wool cleaned wire rod. © 2006 Elsevier B.V. All rights reserved.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2007
    Keywords
    Descaling, Drawing dies, Pickling, Wire drawing, Wire rods, Adhesive wear
    National Category
    Engineering and Technology
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-4354 (URN)10.1016/j.wear.2006.08.016 (DOI)
    Available from: 2007-07-12 Created: 2007-07-12 Last updated: 2017-12-14Bibliographically approved
    6. Descaling of wire rod by using the effect of thermal shock: liquid nitrogen, steam or flame
    Open this publication in new window or tab >>Descaling of wire rod by using the effect of thermal shock: liquid nitrogen, steam or flame
    (English)Manuscript (preprint) (Other academic)
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-3068 (URN)
    Available from: 2006-03-17 Created: 2006-03-17 Last updated: 2017-10-18Bibliographically approved
  • 23.
    Gorgoglione, Gianni
    Örebro University, School of Science and Technology.
    GRUNDLÄGGNING AV VILLOR - EN JÄMFÖRELSE MELLAN VARMGRUND OCH PLATTA PÅ MARK2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Avsikten med detta examensarbete är att närmare studera några av de grundläggningskonstruktioner som idag används för villor. Det finns många byggtekniska lösningar men här studeras endast platta på mark och varmgrund. Faktorer som byggtider, byggkostnader, fuktsäkerhet och energianvändning samverkar vid utformning, dimensionering och byggande av grundläggningar. I princip är det svårt att veta exakt vilken lösning som är den lämpligaste även om ett projekt skräddarsys med avseende på byggmaterial, fuktsäkra byggtekniska lösningar och energidimensionering.

    Tack till Jan Sundqvist för goda råd och intressanta diskussioner. Jag vill tacka också Lennart Jagemar, min interna handledare på Örebro Universitet för ditt stöd och goda synpunkter

  • 24.
    Helldin, Tove
    Örebro University, School of Science and Technology.
    Transparency for future semi-automated systems: effects of transparency on operator performance, workload and trust2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    More and more complex semi-automated systems are being developed, aiding human operators to collect and analyze data and information and even to recommend decisions and act upon these. The goal of such development is often to support the operators make better decisions faster, while at the same time decrease their workload. However, these promises are not always fulfilled and several incidents have highlighted the fact that the introduction of automated technologies might instead increase the need for human involvement andexpertise in the tasks carried out.

    The significance of communicating information regarding an automated system's performance and to explain its strengths and limitations to its operators is strongly highlighted within the system transparencyand operator-centered automation literature. However, it is not common that feedback containing system qualifiers is incorporated into the primary displays of the automated system, obscuring its transparency. In this thesis, we deal with the investigation of the effects of explaining and visualizing system reasoning and performance parameters in different domains on the operators' trust, workload and performance. Different proof-of-concept prototypes have been designed with transparency characteristics in mind, and quantitative and qualitative evaluations together with operators of these systems have been carried out.

    Our results show that the effects of automation transparency can positively influence the performance and trust calibration of operators of complex systems, yet possibly at the costs of higher workload and longer decision-making times. Further, this thesis provides recommendations for designers and developers of automated systems in terms of general design concepts and guidelines for developing transparent automated systems for the future.

  • 25.
    Hernández Bennetts, Victor Manuel
    Örebro University, School of Science and Technology.
    Mobile robots with in-situ and remote sensors for real world gas distribution modelling2015Doctoral thesis, monograph (Other academic)
  • 26.
    Hällgren, Sebastian
    Örebro University, School of Science and Technology.
    Some aspects on designing for metal Powder Bed Fusion2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive Manufacturing (AM) using the Powder Bed Fusion (PBF) is a relatively new manufacturing method that is capable of creating shapes that was previously practically impossible to manufacture. Many think it will revolutionize how manufacturing will be done in the future. This thesis is about some aspects of when and how to Design for Additive Manufacturing (DfAM) when using the PBF method in metal materials. Designing complex shapes is neither easy nor always needed, so when to design for AM is a question with different answers depending on industry or product. The cost versus performance is an important metric in making that selection. How to design for AM can be divided into how to improve performance and how to improve additive manufacturability where how to improve performance once depends on product, company and customer needs. Using advanced part shaping techniques like using Lattices or Topology Optimization (TO) to lower part mass may increase customer value in addition to lowering part cost due to faster part builds and less powder and energy use. Improving PBF manufacturability is then warranted for parts that reach series production, where determining an optimal build direction is key as it affects many properties of PBF parts. Complex shapes which are designed for optimal performance are usually more sensitive to defects which might reduce the expected performance of the part. Non Destructive Evaluation (NDE) might be needed to certify a part for dimensional accuracy and internal defects prior use. The licentiate thesis covers some aspects of both when to DfAM and how to DfAM of products destined for series production. It uses design by Lattices and Topology Optimization to reduce mass and looks at the effect on part cost and mass. It also shows effects on geometry translation accuracies from design to AM caused by differences in geometric definitions. Finally it shows the effect on how different NDE methods are capable of detecting defects in additively manufactured parts.

    List of papers
    1. Additive Manufacturing and High Speed Machining - Cost comparison of short lead time manufacturing methods
    Open this publication in new window or tab >>Additive Manufacturing and High Speed Machining - Cost comparison of short lead time manufacturing methods
    2016 (English)In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 384-389Conference paper, Published paper (Refereed)
    Abstract [en]

    Additive Manufacturing (AM) using Powder Bed Fusion (PBF) allows part with abstract shapes, that otherwise would need costly tooling, to be manufactured with short lead time. In this study AM build time simulations are used to predict series part cost for eight parts that are possible to cut from rod blanks using High Speed Machining (HSM). Results indicate that when the part shape can be cut from rod blanks, AM is more expensive than HSM even for series of one. If post processing machining is added to the printed AM blank part, the cost difference increases further. Finally, the model is used to predict part-cost in series production if print speed increases, if machine cost is reduced or if part mass is reduced as a result of redesign for AM.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2016
    Series
    Procedia CIRP, ISSN 2212-8271 ; 50
    Keywords
    Additive manufacturing, Powder Bed Fusion, High speed machining, cost, series production, AISI MR
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-53931 (URN)10.1016/j.procir.2016.05.049 (DOI)000387666600064 ()2-s2.0-84986576762 (Scopus ID)
    Conference
    26th CIRP Design Conference, KTH Royal Institute of Technology, Stockholm, Sweden, June 15-17, 2016
    Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-07-17Bibliographically approved
    2. (Re)Design for Additive Manufacturing
    Open this publication in new window or tab >>(Re)Design for Additive Manufacturing
    2016 (English)In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 246-251Conference paper, Published paper (Refereed)
    Abstract [en]

    3D-printing has been used to create prototypes during the development phase for more than 20 years. Now, functional parts can be printed directly in specific metal powders using similar layer-by-layer techniques. The additive method is unlike traditional mass production manufacturing methods in many ways, creating new possibilities for designers to realise new and different design ideas previously impossible to manufacture. When products are mass produced, there is a desire to improve manufacturability. This is traditionally done by a designer with knowledge about certain manufacturing methods altering design choices to make it cheaper to manufacture.

    This paper shows different design for AM (DfAM) methods where performance and part cost are both of interest. It adds to existing research by classifying design for additive manufacturing in two different classes; process-driven and designer-driven shaping of parts. A cost-prediction model for Selective Laser Melting (SLM) printed parts is suggested as an initial step to choose parts for redesign from an economical perspective. A case study of a missile launcher beam redesigned for additive manufacturing using three different approaches is presented. Differences and similarities in design methods are discussed and the redesigned parts are compared for mass and cost. It is shown that redesigning for AM can reduce mass but depending on part size and print speed, the part can become more expensive than the original design, creating a need to know the customer value of what the redesigned part provides, in this case, the value of reduced mass.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2016
    Series
    Procedia CIRP, ISSN 2212-8271 ; 50
    Keywords
    Additive manufacturing, Powder Bed Fusion, design, topology optimisation, lattices, DfAM
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-53930 (URN)10.1016/j.procir.2016.04.150 (DOI)000387666600041 ()2-s2.0-84986631521 (Scopus ID)
    Conference
    26th CIRP Design Conference, KTH Royal Institute of Technology, Stockholm, Sweden, June 15-17, 2016
    Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-07-17Bibliographically approved
    3. 3D data export for Additive Manufacturing - improving geometric accuracy
    Open this publication in new window or tab >>3D data export for Additive Manufacturing - improving geometric accuracy
    2016 (English)In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 518-523Conference paper, Published paper (Refereed)
    Abstract [en]

    3D data exchange between different CAD systems and from design to manufacturing has largely moved to ISO STEP based formats. The Additive Manufacturing (AM) process today requires an approximate, planar triangle tessellated 3D model as an input. Improving accuracy in STL file exports is done differently in different CAD systems. Poor tessellation accuracy results in built parts with poor geometric accuracy because of errors in source data. In this study, results of tessellation from six different CAD systems are compared. Roundness accuracy for the different settings is calculated. Results show that tessellation effects may be visible even when roundness requirements are fulfilled. A method for 3D data exchange for AM using STEP and geometric requirements is proposed until better accuracy AM formats can be used.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2016
    Series
    Procedia CIRP, ISSN 2212-8271 ; 50
    Keywords
    Additive manufacturing, 3D printing, STL, STEP, tessellation, accuracy, roundness
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-53932 (URN)10.1016/j.procir.2016.05.046 (DOI)000387666600087 ()2-s2.0-84986558119 (Scopus ID)
    Conference
    26th CIRP Design Conference, KTH Royal Institute of Technology, Stockholm, Sweden, June 15-17, 2016
    Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-07-17Bibliographically approved
    4. Non-destructive evaluation of internal defects in additive manufactured aluminium
    Open this publication in new window or tab >>Non-destructive evaluation of internal defects in additive manufactured aluminium
    2016 (English)Conference paper, Published paper (Refereed)
    Keywords
    additive manufacturing, selective laser melting, aluminium, computed tomography, ultrasonic inspection, eddy current
    National Category
    Mechanical Engineering Materials Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-51003 (URN)
    Conference
    World PM 2016, Powder Metallurgy World Congress, Hamburg, Germany, October 9-13, 2016
    Available from: 2016-06-21 Created: 2016-06-21 Last updated: 2017-12-05Bibliographically approved
  • 27.
    Iliev, Boyko
    Örebro University, Department of Technology.
    Minimum-time sliding mode control of robot manipulators2002Licentiate thesis, monograph (Other academic)
  • 28.
    Iliev, Boyko
    Örebro University, Department of Technology.
    Minimum-time sliding mode control of robot manipulators2004Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Robot manipulators have a complex and highly nonlinear dynamics, accompanied with a high degree of uncertainty. These properties make them difficult for time-optimal control. The theory of sliding mode control can provide methods, able to cope with the uncertainty and nonlinearity in the system. However, besides the chattering problem it does not provide

    time-optimal behavior. The optimal control theory provides the appropriate design methodology for minimum-time control, but the designed system lacks robustness. In this thesis we combine these two approaches to obtain new control techniques, which have the robust properties of the sliding mode control and a performance, close to the time-optimal control. Two methods for minimum-time sliding mode control based on the concept of maximum slope sliding line are developed with a theoretical proof of their properties.

    In the time-optimal sliding mode control we prove that the time-optimal switching line of a simple linear system (double integrator) can be used as a sliding surface for a complex second order nonlinear system (robot manipulator) if the control gain is sufficiently high. Optimal

    performance is achieved by scaling the surface in such way that the maximum control action is efficiently used.

    The fuzzy minimum-time sliding mode control is developed employing a Takagi-Sugeno

    fuzzy model for the sliding surface. We demonstrate that designs, based on a single sliding line tend to be conservative, due to the nonlinearities in the robot's dynamics. The Takagi-Sugeno model represents the maximum slope sliding lines for different values of the joint angles taking into account the variation in the gravity and inertia terms. This gives a convenient way to provide adaptation and incorporate additional knowledge in the controller design.

    Design procedures for all the methods are developed and evaluated in simulation and in experiments with real robot manipulators.

  • 29.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    More Than a Shadow: Computed Tomography Method Development and Applications Concerning Complex Material Systems2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The complexity of the components fabricated in today's industry is ever increasing. This is partly due to market pressure, but it is also a result from recent progress in fabrication technologies that open up new design possibilities. The increased use of additive manufacturing and multi-material systems, especially, has driven the complexity of parts to new heights. The new complex material systems bring benets in many areas such as; mechanical properties, weight reduction, and multifunctions. However, the increased complexity also makes inspection and dimensional control more dicult. In additive manufacturing, for example, internal features can be fabricated which cannot be seen or measured with conventional tools. There is thus a need for non-destructive inspection methods that can measure these geometries. Such a method is X-ray computed tomography. Computed tomography utilizes the X-rays ability to penetrate material to create 3D digital volumes of components. Measurements and material investigations can be performed in these volumes without any damage to the investigated component. However, industrial computed tomography is still not a fully mature method and there are many uncertainties associated with the investigation technique. In this work, a dual-energy computed tomography tool has been developed with the aim to increase the performance of computed tomography when investigating complex geometries and material combinations. This method has been applied to various phantoms and an industrial case. Also, in this work, complex lattice structures fabricated with additive manufacturing have been investigated and analysed using computed tomography. The results show that the new DECT method improves measurement results and can be utilized to inspect multi-material components. The results also show that computed tomography can be used successfully to gain knowledge about complex lattices.

    List of papers
    1. Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements
    Open this publication in new window or tab >>Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements
    2016 (English)In: iCT 2016, NDT.net , 2016, p. 143-150Conference paper, Published paper (Refereed)
    Abstract [en]

    The complexity of today’s products and materials is ever increasing. There is a demand on the industry to produce lighter, stronger, and more precise products. A common practice to achieve such products is to combine different materials to enhance strengths and reduce weaknesses; multi material products. Fabricating complex parts using multi materials does, however, lead to an increased difficulty in metrological verification and material characterisation. The use of computed tomography is today widespread within the industry, providing new possibilities for internal measurements, but there are still many uncertainties associated with the method. It is well known that large variations in density of multi materials greatly affects the contrast obtained by computed tomography, resulting in difficulties to scan and acquire reliable data from certain material setups.In this work the effects on internal measurements as a consequence of differences in X-ray penetration depth have been studied with regards to multi material setups. The main interest was the ability to acquire measurements from internal features of material compositions that are commonly used in the industry. In the result, difficulties and uncertainties associated with computed tomography of multi materials are highlighted and suggestions on how to reduce problems and obtain a more reliable test method are discussed.

    Place, publisher, year, edition, pages
    NDT.net, 2016
    Keywords
    Multi-materials, computed tomography, X-ray penetration depth, dual-energy computed tomography
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47802 (URN)
    Conference
    6th Conference on Industrial Computed Tomography (iCT 2016), Wels, Austria, February 9-12, 2016
    Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2019-06-13Bibliographically approved
    2. A dual-energy approach for improvement of the measurement consistency in computed tomography
    Open this publication in new window or tab >>A dual-energy approach for improvement of the measurement consistency in computed tomography
    2016 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 27, no 11, article id 115013Article in journal (Refereed) Published
    Abstract [en]

    Computed tomography is increasingly adopted by industries for metrological and material evaluation. The technology enables new measurement possibilities, while also challenging old measurement methods in their established territories. There are, however, uncertainties related with the computed tomography method. Investigation of multi-material components with, in particular, varying material thickness can result in unreliable measurements. In this paper the effects of multi-materials, and differing material thickness, on computed tomography measurement consistency has been studied. The aim of the study was to identify measurement inconsistencies and attempt to correct these with a dual-energy computed tomography approach. In this pursuit, a multi-material phantom was developed, containing reliable measurement points and custom-ability with regards to material combinations. A dual-energy method was developed and implemented using sequential acquisition and pre-reconstruction fusing of projections. It was found that measurements made on the multi-material phantom with a single computed tomography scan were highly inconsistent. It was also found that the dual-energy approach was able to reduce the measurement inconsistencies. However, more work is required with the automation of the dual-energy approach presented in this paper since it is highly operator dependant.

    Place, publisher, year, edition, pages
    Bristol, United Kingdom: Institute of Physics (IOP), 2016
    Keywords
    Multi-materials, computed tomography, dual-energy, metrology, measurement consistency, varying material thickness
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-52976 (URN)10.1088/0957-0233/27/11/115013 (DOI)000385929400008 ()2-s2.0-84992365816 (Scopus ID)
    Available from: 2016-10-14 Created: 2016-10-14 Last updated: 2019-05-13Bibliographically approved
    3. Non-linear dual-energy method development and evaluation for industrial computed tomography
    Open this publication in new window or tab >>Non-linear dual-energy method development and evaluation for industrial computed tomography
    2019 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 30, no 6, article id 065006Article in journal (Refereed) Published
    Abstract [en]

    Industrial computed tomography of multi-material objects can be problematic due to difficulties in optimising the x-ray spectra of the scan. A possible solution to the problem is to use two x-ray spectra when scanning objects. The results from such scans can be fused into a single data-set that contains enhanced information. This practice is known as dual-energy computed tomography (DECT). In this work, the aim was to investigate two DECT methods ability to improve measurements in multi-material phantoms. To determine the performance of the methods three different phantoms containing precision spheres as measurement objects were investigated. To improve measurements in this work was defined as improving the measurement consistency of diameter measurements. The phantoms were also scanned with a single setting for comparison. The fusion of the data-sets was done using two methods, a linear fusion, and a novel non-linear fusion. Both of the methods relies on pre-reconstruction fusion of data-sets. The results show that both of the DECT methods improved measurement results significantly compared to the reference method. Further, the results show that the novel non-linear DECT method produces more accurate measurement results compared to the linear method.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2019
    Keywords
    Industrial computed tomography, dual-energy, metrology, multi-material, measurement consistency
    National Category
    Engineering and Technology Mechanical Engineering
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-74031 (URN)10.1088/1361-6501/ab10cc (DOI)000466894300001 ()
    Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-06-19Bibliographically approved
    4. Multi-material gap measurements using dual-energy computed tomography
    Open this publication in new window or tab >>Multi-material gap measurements using dual-energy computed tomography
    2018 (English)In: Precision engineering, ISSN 0141-6359, E-ISSN 1873-2372, Vol. 54, p. 420-426Article in journal (Refereed) Published
    Abstract [en]

    X-ray computed tomography is a highly versatile investigation method with applications in a wide range ofareas. One of the areas where the technique has seen an increased usage, and an increased interest from industry,is in dimensional metrology. X-ray computed tomography enables the measurement of features and dimensionsthat are difficult to inspect using other methods. However, there are issues with the method when it comes tomeasurements of objects that consist of several materials. In particular, it is difficult to obtain accurate computedtomography results for all materials when the attenuation of materials differs significantly. The aim of this workwas to measure small air gaps between different materials using dual-energy X-ray computed tomography. Thedual-energy method employed in this work uses two energy spectra and fuses the data in the projections spaceusing non-linear fusion. The results from this study show that the dual-energy method used in this work was ableto capture more measurements than regular absorption computed tomography in the case of specimens withhighly different attenuation, enabling, in particular, the measurement of smaller gaps. The contrast-to-noise ratiowas also increased significantly with the use of dual-energy.

    Place, publisher, year, edition, pages
    Elsevier, 2018
    Keywords
    Metrology, Computed tomography, Dual-energy, Multi-material measurements
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-68991 (URN)10.1016/j.precisioneng.2018.07.012 (DOI)000452579900046 ()2-s2.0-85051065309 (Scopus ID)
    Funder
    EU, FP7, Seventh Framework Programme, 607817
    Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2019-05-13Bibliographically approved
    5. Characterisation of additive manufacturing metal: carbon-fibre composite bond by dual-energy computed tomography
    Open this publication in new window or tab >>Characterisation of additive manufacturing metal: carbon-fibre composite bond by dual-energy computed tomography
    2017 (English)In: EUSPEN, Conference Proceedings, Special Interest Group: Dimensional Accuracy and Surface Finish in Additive Manufacturing, Octrober 2017, KU Leuven, Belgium: EUSPEN , 2017, p. 189-192Conference paper, Published paper (Refereed)
    Abstract [en]

    Joining of dissimilar materials is a topic of high interest for the industry. The ability to seamlessly join materials with significant differences in properties would advance the development of efficient designs and concepts within many fields. In this work, bonds between aluminium and carbon-fibre reinforced plastic have been studied. The aluminium side of the bonds were fabricated using classical methods (milling) and additive manufacturing. Two types of bonds were fabricated using additive manufacturing, one flat, relying on the rough surface for adhesion in the bond, and the other with surface features designed to hook into the carbon-fibre plies. All the bonds were fabricated using wet layup of carbon-fibre, the idea was that the aluminium parts would bond to the plastic composite in one step. The bonds were characterised using dual-energy computed tomography. The method used in this work was non-linear and based around fusing of projections acquired with different energy spectra. The mechanical strength of the bonds was also evaluated, both through tensile tests and four-point bending.It was found that the bonds including additive manufactured aluminium was stronger than the milled samples in general. In the computed tomography data, it could be seen that the adhesion in those bonds were better, most likely due to the rough surface. The strongest bonds were those with additive manufacturing surface features. However, the computed tomography data revealed that these bonds have difficulties with integration between the surface features and the carbon-fibre plies.

    Place, publisher, year, edition, pages
    KU Leuven, Belgium: EUSPEN, 2017
    Keywords
    Additive manufacturing, Dual-energy computed tomography, carbon-fibre composite, joining
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-61550 (URN)978-0-9957751-1-4 (ISBN)
    Conference
    EUSPEN, Conference Proceedings, Special Interest Group: Dimensional Accuracy and Surface Finish in Additive Manufacturing, Katholieke Universiteit Leuven, October 2017
    Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2019-05-13Bibliographically approved
    6. Dual-energy computed tomography investigation of additive manufacturing aluminium: carbon-fibre composite joints
    Open this publication in new window or tab >>Dual-energy computed tomography investigation of additive manufacturing aluminium: carbon-fibre composite joints
    2019 (English)In: Heliyon, ISSN 2405-8440, Vol. 5, no 2, article id e01200Article in journal (Refereed) Published
    Abstract [en]

    In this work, aluminium–carbon-fibre reinforced plastic joints have been studied. Three types of samples were designed as double lap joints where the aluminium inserts were fabricated using both classical methods (milling) and additive manufacturing. Two versions of the joint were fabricated using additive manufacturing, one flat, and the other with small teeth designed to hook into the carbon-fibre plies. The joints were characterised using a non-linear, dual-energy computed tomography method to evaluate the bond between the composite and the metal inserts. The mechanical strength of the bonds was evaluated, both through tensile tests and four-point bending. A simple finite element model was used to discuss the joints behaviour. It was found that the joints fabricated using additive manufactured inserts were more resistant to peel stress than the milled inserts. In four-point bending tests the moment that the joint could withstand was increased by roughly 300% with the use of additive manufacturing and 400% with the use of additive manufacturing and small teeth. However, in tensile tests it was found that the teeth design reduced the maximum load capacity of the joints by roughly 30% due to porosity. Further, it was found that the additive manufactured samples did not add to the capability of withstanding shearstress. The information gained with the dual-energy computed tomography method was highly valuable as the behaviour of the joints would have been difficult to explain without the porosity information.

    Place, publisher, year, edition, pages
    Elsevier, 2019
    Keywords
    Mechanical engineering, Materials science
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-72142 (URN)10.1016/j.heliyon.2019.e01200 (DOI)000460082200023 ()30839940 (PubMedID)2-s2.0-85061013958 (Scopus ID)
    Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-06-19Bibliographically approved
    7. Surface vs Truss lattice networks, benefits and limitations
    Open this publication in new window or tab >>Surface vs Truss lattice networks, benefits and limitations
    2018 (English)In: NAFEMS nordic: Exploring the Design Freedom of Additive Manufacturing through Simulation, NAFEMS , 2018, p. 217-218Conference paper, Published paper (Refereed)
    Abstract [en]

    The use of additive manufacturing is growing rapidly among industries within many different fields of fabrication. The benefits of applying additive manufacturing can be many and an application that have received special interest is the ability to design lightweight components. Lightweight components can be fabricated with additive manufacturing with the use of lattices that have a high stiffness to weight ratio and topology optimised, complex, designs. The most commonly used lattices today are based on trusses, however, there is also the possibility to generate lattices based around continuous surfaces. In this study, the properties of the popular body-centred-cubic lattice are compared the properties of the lesser known Schwartz diamond surface lattice. The mechanical compression properties, the fabrication processes, and the possibilities of the lattices are discussed and analysed.

    Place, publisher, year, edition, pages
    NAFEMS, 2018
    National Category
    Engineering and Technology Composite Science and Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-70704 (URN)
    Conference
    NAFEMS Nordic 2018, Göteborg, Sweden, 24-25 April, 2018
    Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2019-06-13Bibliographically approved
    8. In-situ computed tomography investigation of the compression behaviour of strut, and periodic surface lattices
    Open this publication in new window or tab >>In-situ computed tomography investigation of the compression behaviour of strut, and periodic surface lattices
    2019 (English)In: iCT 2019 / [ed] Rolf Diederichs, NDT.net , 2019, p. 221-227Conference paper, Published paper (Refereed)
    Abstract [en]

    In this work the effects of fabrication errors in the Body Centered Cubic strut lattice, and the periodic surface lattice Schwarz Diamond has been investigated. The lattices were both fabricated as-is and with induced errors to evaluate the lattices response to fabrication errors. The behaviour of the lattices were studied using compression test and in-situ computed tomography investigation. The results show that the Schwarz Diamond lattices in general are stronger than the Body Centered Cubic lattices in all of the measured aspects. Often up to five times stronger. It was also found that the elastic behaviour of the Schwarz Diamond lattices were mainly unaffected by fabrication errors while the Body Centered Cubic lattices experienced severe losses in performance. The behaviour of the lattices under compression could be followed using computed tomography which aided in the understanding of their behaviour.

    Place, publisher, year, edition, pages
    NDT.net, 2019
    Keywords
    Additive manufacturing, computed tomography, periodic surface lattices, in-situ compression, fabrication error
    National Category
    Engineering and Technology Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-72514 (URN)
    Conference
    9th Conference on Industrial Computed Tomography (iCT) 2019, 13-15 Feb, 2019, Padova, Italy
    Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2019-06-13
  • 30.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Only a Shadow: Industrial computed tomography investigation, and method development, concerning complex material systems2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The complexity of components fabricated in today's industry is ever increasing. This increase is partly due to market pressure but it is also a result from progress in fabrication technologies that opens up new possibilities. The increased use of additive manufacturing and multi-material systems, especially, has driven the complexity of parts to new heights. The new complex material systems brings benefits in many areas such as; mechanical properties, weight optimisation, and sustainability. However, the increased complexity also makes material integrity investigations and dimensional control more difficult. In additive manufacturing, for example, internal features can be fabricated which cannot be seen or measured with conventional tools. There is thus a need for non-destructive inspection methods that can measure these geometries. Such a method is X-ray computed tomography. Computed tomography utilizes the X-rays ability to penetrate material to create 3D digital volumes of components. Measurements and material investigations can be performed in these volumes without any damage to the investigated component. However, computed tomography in material science is still not a fully mature method and there are many uncertainties associated with the investigation technique. In the work presented in this thesis geometries fabricated by various additive manufacturing processes have been investigated using computed tomography. Also in this work, a dual-energy computed tomography tool has been developed with the aim to increase the measurement consistency of computed tomography when investigating complex geometries and material combinations.

    List of papers
    1. Characterisation of carbon fibre-reinforced polyamide manufactured by selective laser sintering
    Open this publication in new window or tab >>Characterisation of carbon fibre-reinforced polyamide manufactured by selective laser sintering
    2016 (English)In: Additive Manufacturing, ISSN 2214-8604, Vol. 9, p. 7-13Article in journal (Refereed) Published
    Abstract [en]

    Polymers and reinforced plastics are employed in various load-bearing applications, from household objects to aerospace products. These materials are light, strong, and relatively cheap but can be difficult to form into complex geometries. However, the development of additive manufacturing processes has made it easier to manufacture reinforced plastics in complex shapes. The aim of this work was to study the internal features and mechanical properties of carbon fibre-reinforced polyamide (CF/PA12) fabricated with the additive manufacturing technique of selective laser sintering. The test specimens were studied using computed tomography to analyse the internal geometry, and the material proved to be highly porous. Moreover, the test specimens revealed an internal layered structure, which was found to have a great effect on the tensile properties of the material. The results highlight that there is room for further optimisation of the manufacturing parameters for CF/PA12, because the layered structure makes it challenging to design end user parts with acceptable mechanical properties.

    Place, publisher, year, edition, pages
    Amsterdam, Netherlands: Elsevier, 2016
    Keywords
    Computed tomography, carbon fibre–reinforced polymer, selective laser sintering, additive manufacturing
    National Category
    Materials Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47800 (URN)10.1016/j.addma.2015.12.003 (DOI)000435752300002 ()2-s2.0-84952789063 (Scopus ID)
    Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2018-11-27Bibliographically approved
    2. Measurement of internal features in additive manufactured components by the use of computed tomography
    Open this publication in new window or tab >>Measurement of internal features in additive manufactured components by the use of computed tomography
    2015 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Additive manufacturing (AM) is a set of manufacturing processes currently in rapid development providing designersnew freedoms in their designs. One distinct difference from other manufacturing methods is the ability to makecomplex internal features which can be of great benefit for applications in many industries. These features can bechannels, cavities, filled or not filled with powder, parts in parts etc. In order for these advantages to be industriallyapplicable there is a need for robust verification methods for these internal features. X-ray computed tomography (CT)holds the promise of being one of the few powerful tools for non-destructive imaging of internal features. In this work,selective laser sintering (SLS) has been used to manufacture parts of a complex geometry containing internal cavities.The test specimens were manufactured in two different materials; Polyamide12 and Titanium (Ti6Al4V). In order toinvestigate the limitations and controllability of the process, the dimensions of the internal cavities were determinedby a correlation of tactile measurements on external features and CT-data. The results were also compared to computeraided design (CAD) data. This work provides some insight concerning part accuracy of today’s frontier of AM systemsand the ability to measure and characterize internal features using CT.

    Place, publisher, year, edition, pages
    German Society for Non-Destructive Testing, 2015
    Keywords
    Computed tomography, additive manufacturing, internal features, selective laser melting
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47801 (URN)
    Conference
    Digital Industrial Radiology and Computed Tomography (DIR 2015), Ghent, Belgium, June 22-25, 2015