Now showing 1 - 10 of 1856
  • Publication
    Material-adapted and process-reliable multi-wire submerged arc welding of large-diameter pipes
    ( 2022-03-07) ; ; ; ;
    Lichtenthäler, Frank
    ;
    Stark, Michael
    Ensuring the required mechanical-technological properties of welds is a critical issue in the application of multi-wire submerged arc welding processes in the manufacture of largediameter pipes made of high-strength fine-grained steels of grade X70 and higher according to API 5L. Excessive heat input of up to 10 kJ/mm is one of the main causes of the formation of microstructural areas in the heat-affected zone with deteriorated mechanical properties, such as impact toughness and tensile strength. In this work, a variant of a five-wire submerged arc welding process is proposed that reduces the weld volume and the heat input, while retaining the high process stability and production speed of multi-wire submerged arc welding. By adapting the welding wire configuration of a five-wire submerged arc welding process and the energetic parameters of the arcs, the high penetration depth of approx. 24 mm and a 10 % reduction in the weld cross-section could be achieved compared to the usual process configuration. This effect was transformed into a higher welding speed, which led to a reduction in the heat input. A concept for process monitoring is proposed in order to maintain constant manufacturing quality in large-diameter pipe production. In addition to the analysis of electrical process signals such as welding current and welding voltage, acoustic process monitoring using vibro-acoustic sensors provides reliable information on the stability of the welding process.
  • Publication
    Redundancy Concepts for Real-Time Cloud- and Edge-based Control of Autonomous Mobile Robots
    ( 2022)
    Nouruzi-Pur, Jan
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    Lambrecht, Jens
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    Nguyen, The Duy
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    ;
    Deploying navigation algorithms on an edge or cloud server according to the Software-as-a-Service paradigm has many advantages for autonomous mobile robots in indus-trial environments, e.g. cooperative planning and less onboard energy consumption. However, outsourcing corresponding real-time critical control functions requires a high level of reliability, which cannot be guaranteed either by modern wireless networks nor by the outsourced computing infrastructure. This work introduces redundancy concepts, which enable real-time capability within these uncertain infrastructures by providing redundant computation nodes, as well as robot-controlled switching between them. Redundancies can vary regarding their physical location, robot behavior during the switchover process and degree of activeness while quality of service concerning the primary controller is sufficient. In the case that fallback redun-dancies are not continuously active, when a disturbance occurs an initial state estimation of the robot pose has to be provided and an activation time has to be anticipated. To gain some insights on expected behavior, redundant computation nodes are deployed locally on the robot and on an outsourced computation node and consequently evaluated empirically. Quantitative and qualitative results in simulation and a real environment show that redun-dancies help to significantly improve the robot-trajectory within an unreliable network. Moreover, resource-saving redundancies, which are not continuously active, can robustly take over control by using an estimated state.
  • Publication
    Potentials of Design Thinking for knowledge transfer of Model-Based Systems Engineering
    ( 2022)
    Manoury, Marvin Michael
    ;
    Horländer, Toni
    ;
    Zimmermann, Thomas
    Industrial products are becoming increasingly complex due to the use and development of mechatronic systems. This increasing complexity is addressed by virtual representations of the systems in the form of interdisciplinary models. Model-Based Systems Engineering (MBSE) supports product development from the early development phase through validation, verification and integration up to later life cycle phases of the product by means of system modeling.Typical drivers for innovations in the industrial environment are business viability, technology driven feasibility and human driven desirability. While business viability and feasibility are considered in most product development processes and innovation driven projects, the human factor is often neglected in this context. This is addressed by a MBSE Capability and Maturation Matrix (CMM), which consists of capabilities for the acquisition and mastering of the MBSE competencies. The authors have considered Design Thinking as a feasible approach to transfer MBSE knowledge and thus support this acquisition MBSE competencies. This publication shall present the first findings on the application of Design Thinking for the creation of a user-centered MBSE introduction event. This event shall be used in further iterative steps to teach non-experts in the MBSE field the required competencies for their work and thus support the CMM development capability.
  • Publication
    Design and Validation of an Adaptive Force Control Algorithm with Parameter Estimation Unit for Electromechanical Feed Axis
    ( 2022)
    Sewohl, André
    ;
    Norberger, Manuel
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    Sigg, Stefan
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    Schlegel, Holger
    ;
    Dix, Martin
    Production technology is characterized by the use of electromechanical feed axes, for which the concept of cascade control has become established. The concept is based on linear control engineering. It is not suitable for the control of process forces, which is associated with nonlinearities. Here, adaptive control algorithms from the field of higher control engineering represent a promising approach for improvements of manufacturing strategies and processes in terms of stability, quality, and efficiency. This can also ensure in reducing the number of parts rejected due to bad quality and thus aiding as a significant economic benefit. In this paper, the development of an adaptive control concept that automatically reacts to different and changing environmental conditions during the process is presented. The digital, parameter-adaptive controller consists of a recursive online parameter estimation unit, the controller design procedure, which is based on the setting rule for the symmet ric optimum, and the control algorithm. The functionality of the adaptive control concept is demonstrated in simulation and validated by means of experiments on a test setup. It is real-time capable and implemented directly on the machine control together with all calculation algorithms.
  • Publication
    PowerGrasp: Development Aspects for Arm Support Systems
    ( 2022)
    Goppold, J.-P.
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    Kuschan, J.
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    Schmidt, H.
    ;
    Krüger, J.
    Exoskeletons can support workers on physically demanding tasks, but in industry they lack of acceptance. This contribution gives an insight into design aspects for upper body exoskeletons, especially how active exoskeletons for industrial applications differ from military and medical use-cases. To overcome typical rigid exoskeleton problems, we suggest the use of modular soft-exosuit support systems and therefore checked different types of soft actuation principles for their eligibility for the use on upper body joints. Most promising approach is using two-layered actuators sting of robust fabric with embedded rubber tubes as pressure chambers. By inflating the tubes, it is possible to vary the stiffness of the chambers, which can be effectively used to generate assisting forces and moments at human joints (shoulder, elbow, wrist, finger).
  • Publication
    OptTopo: Automated set-point optimization for coupled systems using topology information
    ( 2022)
    Thiele, Gregor
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    Johanni, Theresa
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    Sommer, David
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    Eigel, Martin
    ;
    Krüger, Jörg
    The manufacturing sector has witnessed a rapid rise in the importance of energy-efficient operation. For finding optimal set-points for industrial facilities, optimization problems of increasing complexity occur. Key challenges are the leak of derivative information and the curse of dimensionality. For systematic reduction of the search-space by decomposition of the model, a methodology for the inclusion of topology knowledge in the optimization procedure is developed. An implementation of OptTopo (Optimization based on Topology), embedded in a testbed, demonstrates its advantages compared to popular out-of-the-box-optimization. OptTopo could be integrated in energy management software offering advanced set-point control for complex facilities.
  • Publication
    Application of Uncertainty-Aware Sensor Fusion in Physical Sensor Networks
    (IEEE, 2022)
    Gruber, Maximilian
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    Pilar von Pilchau, Wenzel
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    Koutrakis, Nikolaos-Stefanos
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    Schönborn, Nicolas
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    Eichstädt, Sascha
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    Hähner, Jörg
    ;
    ; ; ;
    Modern industrial processes often collect redundant information from multiple sensors. It is of interest to leverage this information to form a more accurate or robust estimate of an observed quantity utilizing a sensor fusion operation. To be able to comply with quality requirements on the fused value, preservation of traceability is required. Moreover, the sensor fusion needs to be implemented within suitable digital architectures for Industrial Internet of Things (IIoT) environments. In a continuation of previous work, this is achieved by the usage of digital twins that represent the entities of two IIoT testbeds and the adoption of a method for uncertainty-aware homogeneous sensor fusion, which is presented in full detail. Metrological traceability of the fused value is established by propagating the measurement uncertainty of the input sensor according to metrological standards. The method is implemented as a modular service connected to an existing IIoT architecture. The flexibility of the method is shown by application to two different scenarios with only minimal adaption efforts. The fused sensor values are (as indicated by earlier work) robust to outliers and perform well in practical scenarios within the chosen IIoT architecture.
  • Publication
    Simulating flow behaviour of wet particles within the immersed tumbling process
    ( 2021)
    Uhlmann, E.
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    Polte, J.
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    Kuche, Y.
    ;
    Landua, F.
    For many production chains, it is mandatory to involve special finishing of the manufactured parts for the chipping of the edges as well as the polishing of surfaces. One commonly used method is the immersed tumbling process, where any workpiece is dragged through a particle filled container. In many cases, the immersed tumbling process operates in environments with added liquids, leading to changes in particle-tool interaction and general flow behaviour of the used particles. Whilst the discrete element method for simulating particles is mainly limited to dry particles, the used software ROCKY DEM from ESSS, Florianópolis, Brasil, comes with a built-in liquid-bridge model to simulate water-covered particles and granulate and furthermore an extension for system couplings with Ansys Fluent of the company ANSYS, INC., Canonsburg, Pennsylvania. The latter can be used to create from both software one three-phase-model with higher amounts of actually simulated water. In thi s study, small amounts of water were added to differently shaped particles using the build-in liquid-bridge model, to analyse and compare the particles flow characteristics in both, wet and dry environments. To gather significant information leading towards precise comparisons, the particles trajectories, velocities and resulting forces against the workpieces can be specifically observed and analysed, whilst this kind of process knowledge could previously never been taken into account without simulation.
  • Publication
    Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support
    ( 2021)
    Üstündag, Ö.
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    Bakir, N.
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    Gumenyuk, A.
    ;
    Rethmeier, M.
    One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds.