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See detailTowards Intelligent Robot Assistants for the non-destructive Disassembly of End of Life Products
Jungbluth, Jan UL; Plapper, Peter UL; Gerke, Wolfgang

in Plapper, Peter; Hichri, Bassem (Eds.) Robotix-Academy Conference (2017, May 06)

The effective collaboration between humans and robots in complex and task rich environments like End of Life product disassembly depends on the ability of the robot to anticipate the workflow as well as ... [more ▼]

The effective collaboration between humans and robots in complex and task rich environments like End of Life product disassembly depends on the ability of the robot to anticipate the workflow as well as the assistance the human co-worker wants. Our approach towards such an intelligent system is the development of an informed software agent that controls the robot assistance behavior. We inform the agent with procedural and declarative knowledge about the disassembly domain through models of the product structure and actor/object models. The product structure is then transformed to a directed graph and used to build, share and define a goal-orientated coarse workflow. Depending on the tasks and wanted assistance, the system can generate adaptable and detailed workflows through searching in the situation space on the basis of predefined and task dependent actions. The created detailed workflow consists of a sequence of actions that are used to call, parameterize and execute robot programs for the fulfillment of the assistance. The aim of this research is to equip robot systems with higher cognitive skills to allow them to be autonomous in the performance of their assistance to improve the ergonomics of disassembly workstations. [less ▲]

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See detailRobust BELBIC-Extension for Trajectory Tracking Control
Klecker, Sophie UL; Hichri, Bassem UL; Plapper, Peter UL

in Journal of Mechanics Engineering and Automation (2017), 7(2),

In real-life trajectory tracking applications of robotic manipulators uncertain robot dynamics, external disturbances and switching constraints which cannot be accommodated for by a conventional ... [more ▼]

In real-life trajectory tracking applications of robotic manipulators uncertain robot dynamics, external disturbances and switching constraints which cannot be accommodated for by a conventional controller affect the system performance. We suggested an additional control element combining sliding mode and bio-mimetic, neurologically-inspired BELBIC (brain emotional learning-based intelligent control). The former is invariant to internal and external uncertainties and guarantees robust behavior. The latter is based on an interplay of inputs relating to environmental information through error-signals of position and sliding surfaces and of emotional signals regulating the learning rate and adapting the future behaviour based on prior experiences and with the goal to maximize a reward function. We proofed the stability and the performance of the suggested control scheme through Lyapunov theory and numerical simulations, respectively. [less ▲]

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See detailInfluence of Material Moisture during Laser Joining of Polyamide 6.6 to Aluminum
Lamberti, C.; Peral Alonso, Inmaculada UL; Plapper, Peter UL

in Atiner's Conference Paper Series (2017), IND 2017 - 2270

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See detailPID and Biomimetic Variable Structure Path Tracking Control in Automated Surface Finishing Processes
Klecker, Sophie UL; Plapper, Peter UL; Hichri, Bassem UL

in Robotix-Academy Conference for Industrial Robotics (RACIR) 2017 (2017)

This paper addresses freeform surface following control as one of the main challenges in automating surface finishing processes. Successive changes in constraints between the tool attached to the robotic ... [more ▼]

This paper addresses freeform surface following control as one of the main challenges in automating surface finishing processes. Successive changes in constraints between the tool attached to the robotic manipulator and its surroundings are due to complex workpiece-geometries and result in a switched nonlinear system. The control problem of the latter is addressed by industrial state-of-the-art conventional PID control as well as by biomimetic variable structure control which are both applied to a benchmark path tracking problem as characteristically encountered in surface finishing. [less ▲]

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See detailAn intelligent agent-controlled and robot-based disassembly assistant
Jungbluth, Jan UL; Gerke, Wolfgang; Plapper, Peter UL

in Conference Proceedings on the 2nd International Conference on Artificial Intelligence and Robotics ( ICAIR 2017) (2017)

One key for successful and fluent human-robot-collaboration in disassembly processes is equipping the robot system with higher autonomy and intelligence. In this paper, we present an informed software ... [more ▼]

One key for successful and fluent human-robot-collaboration in disassembly processes is equipping the robot system with higher autonomy and intelligence. In this paper, we present an informed software agent that controls the robot behavior to form an intelligent robot assistant for disassembly purposes. While the disassembly process first depends on the product structure, we inform the agent using a generic approach through product models. The product model is then transformed to a directed graph and used to build, share and define a coarse disassembly plan. To refine the workflow, we formulate “the problem of loosening a connection and the distribution of the work” as a search problem. The created detailed plan consists of a sequence of actions that are used to call, parametrize and execute robot programs for the fulfillment of the assistance. The aim of this research is to equip robot systems with knowledge and skills to allow them to be autonomous in the performance of their assistance to finally improve the ergonomics of disassembly workstations. [less ▲]

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See detailResistance Measurement of Laser Welded Dissimilar AlCu Joints
Schmalen, Pascal Guy UL; Plapper, Peter UL

in Journal of Laser Micro/Nanoengineering (2017), 12(3), 189-194

Aluminum and Copper were joined using the laser-based braze-welding process. By avoiding the intermixture of both conductive materials, the formation of brittle intermetallic compounds is strongly reduced ... [more ▼]

Aluminum and Copper were joined using the laser-based braze-welding process. By avoiding the intermixture of both conductive materials, the formation of brittle intermetallic compounds is strongly reduced. This results in a tough, ductile connection with reduced electric resistance. This paper describes a method, which is based on the 4-wire method, to measure the resistance of the weld seam. The arrangement of the conductive electrodes directly on top and bottom of the weld seam significantly increases the accuracy of the measured resistances, thus offers a direct estimation of the inter-metallic layer thickness. The electric measuring of the layer thickness is a non-destructive method, which assists in the reduction of the post-process effort (cross sections, pull tests, hardness measurements) and decreases the lead-time by reducing the time needed for the identification of suitable laser process parameters. [less ▲]

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See detailStandardized Value Stream Management Method to Visualize, Analyze and Optimize Cross-Enterprise Value Stream Data
Oberhausen, Christof UL; Minoufekr, Meysam UL; Plapper, Peter UL

in International Journal of Standardization Research (2017), 15(2), 25-36

This article describes how on the way towards a reliable and efficient collaboration in global supply chain networks, organizations are seeking for suitable methods and tools to enhance product and ... [more ▼]

This article describes how on the way towards a reliable and efficient collaboration in global supply chain networks, organizations are seeking for suitable methods and tools to enhance product and information flows. Based on the evolving Lean Manufacturing methodology in combination with the increased exploitation of ICT, new and diverse Value Stream Management (VSM) approaches are currently used. Thus, a common VSM standard is sought to analyze and visualize valuable data and to synchronize capacities and flows. In this article, the authors present a review of existing VSM approaches, patents and software solutions. Furthermore, a classification comprising four categories that serve as a basis for the ongoing VSM standard development within ISO/TC 154 and a case study of an administrative value stream are shown. [less ▲]

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See detailCross-enterprise value stream assessment
Oberhausen, Christof UL; Plapper, Peter UL

in Journal of Advances in Management Research (2017), 14(2), 182-193

Purpose – In most cases, the conventional assessment of value streams is based on key performance indicators (KPIs) like the share of added value, the degree of flow or a comprehensive lead time analysis ... [more ▼]

Purpose – In most cases, the conventional assessment of value streams is based on key performance indicators (KPIs) like the share of added value, the degree of flow or a comprehensive lead time analysis. To evaluate cross-enterprise value streams of manufacturing, business or service processes in detail, a holistic methodology is needed. The paper aims to discuss this issue. Design/methodology/approach – In this research paper, the assessment of value streams within complex cross-company networks is described. After a presentation of relevant KPIs in the fields of value stream management (VSM) and supply chain management (SCM), an approach for a cross-enterprise evaluation of value streams on different levels of detail is shown. In addition, the use of an absolute VSM evaluation, in contrast to a relative VSM assessment, is examined. Findings – Based on a uniform and well-balanced set of KPIs and other VSM and SCM parameters, a performance assessment on different levels of value stream detail is enabled. Further investigations reveal the advantages of a relative compared with an absolute VSM assessment. Research limitations/implications – In addition to a comprehensive overview of existing KPIs for a value stream assessment beyond company borders, a holistic and multi-level VSM approach is presented in this paper. In contrast to existing VSM approaches, the described method allows an evaluation and subsequent improvement of value streams within supply chain networks. Up to now, the presented approach for the assessment of cross-enterprise value streams has only been tested in specific industrial environments. In future, the proposed methodology shall also be validated for other process types like business, service or further manufacturing processes. Practical implications – The described cross-company performance measurement approach shows a high practical relevance for organizations operating in supply chain networks. Due to the integrated use of different VSM parameters, the evaluation of highly interconnected value streams across corporate boundaries is facilitated. By means of a case study, the proposed methodology is validated under real industry conditions and proves its practical applicability. Originality/value – One of the novel features of this research is the extension of the traditional VSM method with respect to a relative evaluation of value streams based on a set of significant KPIs. In addition, the allocation of these KPIs to different value stream layers and categories leads to an innovative approach for a multi-level assessment according to the needs of the specific VSM application, e.g. a more standardized use of VSM in complex supply chain networks. [less ▲]

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See detailTrajectory Tracking for Robotic Freeform Grinding
Klecker, Sophie UL; Plapper, Peter UL

in Cahier Scientifique - Revue Technique Luxembourgeoise (2016), 1(2016), 6-7

Unergonomic working conditions, a decline in available labour force and uncompetitively high salaries make automation an attractive solution for a variety of manufacturing processes. To achieve successful ... [more ▼]

Unergonomic working conditions, a decline in available labour force and uncompetitively high salaries make automation an attractive solution for a variety of manufacturing processes. To achieve successful automation of even complex, contact-based manufacturing processes, inspiration is more and more found in nature. In this work, a biomimetic approach is chosen to address the grinding process of freeform geometries by industrial robots. [less ▲]

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See detailBELBIC-Sliding Mode Control of Robotic Manipulators with Uncertainties and Switching Constraints
Klecker, Sophie UL; Plapper, Peter UL

in Proceedings of the ASME 2016 International Mechanical Engineering Congress and Exposition (2016, November)

This paper addresses the control problem for trajectory tracking of a class of robotic manipulators presenting uncertainties and switching constraints using a biomimetic approach. Uncertainties, system ... [more ▼]

This paper addresses the control problem for trajectory tracking of a class of robotic manipulators presenting uncertainties and switching constraints using a biomimetic approach. Uncertainties, system-inherent as well as environmental disturbances deteriorate the performance of the system. A change in constraints between the robot’s end-effector and the environment resulting in a switched nonlinear system, undermines the stable system performance. In this work, a robust adaptive controller combining sliding mode control and BELBIC (Brain Emotional Learning-Based Intelligent Control) is suggested to remediate the expected impacts on the overall system tracking performance and stability. The controller is based on an interplay of inputs relating to environmental information through error-signals of position and sliding surfaces and of emotional signals regulating the learning rate and adapting the future behaviour based on prior experiences. The proposed control algorithm is designed to be applicable to discontinuous freeform geometries. Its stability is proven theoretically and a simulation, performed on a two-link manipulator verifies its efficacy. [less ▲]

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See detailValue Stream Management zur Synchronisation im Unternehmensverbund
Plapper, Peter UL

Scientific Conference (2016, October)

Das Thema „Wertstrom Management“ wird in Luxemburg bereits in der Bachelor Ausbildung vermittelt und für die Master vertieft. In der Forschung erweist dieses Werkzeug großes Potential zur Synchronisation ... [more ▼]

Das Thema „Wertstrom Management“ wird in Luxemburg bereits in der Bachelor Ausbildung vermittelt und für die Master vertieft. In der Forschung erweist dieses Werkzeug großes Potential zur Synchronisation und Optimierung der Wertschöpfung im Unternehmensverbund, das wir hier vorstellen möchten: Mit der Methode VSM lässt sich Verschwendung erkennen und Wertschöpfungspotentiale heben. Die Verschwendung wird damit nicht nur in den produktiven Unternehmensbereichen, sondern auch in indirekten Bereichen und ebenso in Verwaltungsfunktionen und administrativen Abteilungen visualisiert. Man erkennt Möglichkeiten, die Verschwendung abzubauen und die Wertschöpfung zu erhöhen. Bei der praktischen Anwendung dieses leistungsfähigen Werkzeugs erwiesen sich die Schnittstellen zwischen den Unternehmen als immerwährende Quellen von Verschwendung und Ineffizienzen. Hier sind die unterschiedlichen Ausprägungen der Methode VSM hinderlich für eine durchgängige Anwendung dieser Methode. Aus dieser Erkenntnis heraus schlagen wir eine Vereinheitlichung der „Best Practices“ als Industrie Standard bzw. als internationale Norm vor. Im Rahmen der aktuell laufender Forschungsprojekte an der Universität Luxemburg werden Methoden entwickelt, um das Wertstrom Management international zu standardisieren und allgemein zu vereinheitlichen. [less ▲]

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See detailEngineering Education at the University of Luxembourg - Hand in hand with national industry
Plapper, Peter UL

Scientific Conference (2016, September)

Speech on how industry and university educate students together on Bachelor, Master and PhD level. The presenter answered questions of his peers during the discussion.

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See detailAdaptive SMC For Trajectory Tracking In FreeForm Grinding
Klecker, Sophie UL; Plapper, Peter UL

in 2016 IEEE International Conference on Industrial Informatics, Poitiers, 18th-21st July 2016 (2016, July)

This work is a first step to the automation of freeform surface grinding. A control strategy for a robotic manipulator following a path which includes switching between different surfaces, constant depths ... [more ▼]

This work is a first step to the automation of freeform surface grinding. A control strategy for a robotic manipulator following a path which includes switching between different surfaces, constant depths of cut and system-inherent as well as environmental uncertainties is presented. The sliding mode control scheme with adaptive parameter update law is verified through simulation. [less ▲]

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See detailInnovations enabled by laser joining of dissimilar materials
Plapper, Peter UL

Scientific Conference (2016, June 29)

The key-note presents latest scientific findings of the Laser Technology Competence Center (LTCC) of the University of Luxembourg and illustrate them with real use cases. see attached text of abstract

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See detailValue Stream Management Training
Plapper, Peter UL; Oberhausen, Christof UL

Learning material (2016)

The VSM workshop deals with concepts in the area of Value Stream Management, comprising the analysis, design and optimization of internal material and information flows. The VSM workshop was held by Prof ... [more ▼]

The VSM workshop deals with concepts in the area of Value Stream Management, comprising the analysis, design and optimization of internal material and information flows. The VSM workshop was held by Prof. Dr.-Ing. Peter Plapper and M.Sc. Christof Oberhausen, who contribute a profound knowledge in Value Stream Management based on their ongoing research in this field. The one-day VSM workshop is targeted at an audience of 8-12 participants with a background in Lean Engineering or Operational Excellence. [less ▲]

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See detailProcess Robustness of Laser Braze-Welded AlCu Connectors
Schmalen, Pascal Guy UL; Plapper, Peter; Cai, Wayne

in SAE International Journal of Alternative Powertrains (2016), 5(1),

Laser welding of dissimilar metals such as Aluminum and Copper, which is required for Li-ion battery joining, is challenging due to the inevitable formation of the brittle and high electrical-resistant ... [more ▼]

Laser welding of dissimilar metals such as Aluminum and Copper, which is required for Li-ion battery joining, is challenging due to the inevitable formation of the brittle and high electrical-resistant intermetallic compounds. Recent research has shown that by using a novel technology, called laser braze-welding, the Al-Cu intermetallics can be minimized to achieve superior mechanical and electrical joint performance. This paper investigates the robustness of the laser braze-welding process. Three product and process categories, i.e. choice of materials, joint configurations, and process conditions, are studied. It is found that in-process effects such as sample cleanness and shielding gas fluctuations have a minor influence on the process robustness. Furthermore, many pre-process effects, e.g. design changes such as multiple layers or anodized base material can be successfully welded by process adaption. The minimization of the interface gap is identified as the most significant influence of process stability. The specimen were validated by mechanical lap shear tests and metallographic analysis. [less ▲]

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See detailForce-Guided Robotic Assembly Process: Control and Contact-State Recognition
Jasim, Ibrahim UL

Doctoral thesis (2016)

This thesis addresses developing novel Contact-State (CS) modeling, control strategy, and environment position localization (position searching) for force-guided robotic assembly processes of rigid and ... [more ▼]

This thesis addresses developing novel Contact-State (CS) modeling, control strategy, and environment position localization (position searching) for force-guided robotic assembly processes of rigid and flexible objects. For the CS modeling, the wrench (Cartesian force and torque) signals of the manipulated object are captured for different phases of the considered assembly processes and using the Expectation Maximization-based Gaussian Mixtures Model (EM-GMM), a recognizer is developed for each CS of the assembly. The suggested EM-GMM CS modeling scheme is shown to have excellent Classification Success Rate (CSR) with reduced computational efforts. For the control part, it is shown throughout the thesis that a force-guided robotic assembly process is a hybrid nonlinear system with arbitrary switching signal resulted from the constraints arbitrary switching during the assembly. Furthermore, the robot dynamics is frequently unknown, which is the case in many industrial robots, that would make the force-guided robotic assembly process to be an unknown hybrid nonlinear system with arbitrary switching. In order to overcome such a control challenge, a Decentralized Robust Adaptive Fuzzy Control (DRAFC) strategy is derived that guarantees stable performance under constraints arbitrary switching and unknown dynamics. For the environment position localization, the EM-GMM CS modeling scheme is integrated with a spiral search path and the precise hole position is identified for cases of position uncertainty. Experiments are conducted on a KUKA Lightweight Robot (LWR) doing different force-guided assembly tasks for rigid and flexible objects. Excellent performance is reported for the proposed EM-GMM CS recognition scheme, the DRAFC strategy, and the suggested position searching algorithm. The suggested EM-GMM CS recognition, DRAFC strategy, and position localization schemes are compared with the availably corresponding schemes and the superiority of the suggested schemes is shown. The reasons behind the superiority of the EM-GMM CS recognition scheme are the accommodation of the captured signals non-stationary behavior, employing optimized number of GMM components in the modeling process, and employing the EM algorithm that iteratively increases the log-likelihood. The causes behind the superiority of the DRAFC strategy are addressing the unknown nonlinear dynamics of the robot, accommodating the constraints arbitrary switching, and the robustness against possible dynamics parameters drift. The reasons behind the surpassing of the suggested position localization strategy are the robustness against the surface roughness and reduced computational efforts. The proposed EM-GMM CS modeling scheme, DRAFC strategy, and position searching scheme are applied to the entire peg-in-hole assembly processes of rigid and flexible objects. Excellent Localization Success Rate (LSR) was resulted when using the suggested schemes. Furthermore, the proposed CS modeling scheme, control strategy, and localization approach are applied to a couple of applications in automotive industry; the first one is the camshaft caps assembly of a cylinder head and the other is the air-intake manifold assembly of a powertrain. Efficient force-guided robotic assembly processes are obtained for both considered applications. [less ▲]

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See detailEditorial
Plapper, Peter UL

in Cahier Scientifique - Revue Technique Luxembourgeoise (2016), 1

Editorial comment at the start of the scientific edition of the Revue Technique, reflecting the needs of the country and the content of the journal.

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See detailA Standardized Value Stream Management Method for Supply Chain Networks
Oberhausen, Christof UL; Plapper, Peter UL

in Dimitrov, Dimiter; Oosthuizen, Tiaan (Eds.) Proceedings - International Conference on Competitive Manufacturing (2016)

In a globalized market environment, almost all companies operate in complex supply chain networks. A high degree of product diversification in combination with rapidly changing customer needs require ... [more ▼]

In a globalized market environment, almost all companies operate in complex supply chain networks. A high degree of product diversification in combination with rapidly changing customer needs require cross-enterprise supply chain collaboration, which causes communication problems. A way to cope with this complexity is to optimize both internal as well as external processes in a holistic manner and to define standards for interaction, collaboration and communication procedures. An established method for process analysis and optimization is Value Stream Management (VSM). Despite a variety of promising VSM approaches, there is a lack of a standardized VSM method, especially with regard to complex supply chain networks. Thus, a review of methods for process visualization and their suitability for different process types shall be discussed. A common VSM method with integrated features according to the specific needs of the applying organization will help to optimize the value creation in cross-enterprise supply chains. [less ▲]

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See detailEvaluation of laser braze-welded dissimilar Al-Cu joints
Schmalen, Pascal Guy UL; Plapper, Peter UL

in Physics Procedia (2016), 83

The thermal joining of Aluminum and Copper is a promising technology towards automotive battery manufacturing. The dissimilar metals Al-Cu are difficult to weld due to their different physicochemical ... [more ▼]

The thermal joining of Aluminum and Copper is a promising technology towards automotive battery manufacturing. The dissimilar metals Al-Cu are difficult to weld due to their different physicochemical characteristics and the formation of intermetallic compounds (IMC), which have reduced mechanical and electric properties. There is a critical thickness of the IMCs where the favored mechanical properties of the base material can be preserved. The laser braze welding principle uses a position and power oscillated laser-beam to reduce the energy input and the intermixture of both materials and therefore achieves minimized IMCs thickness. The evaluation of the weld seam is important to improve the joint performance and enhance the welding process. This paper is focused on the characterization and quantification of the IMCs. Mechanical, electrical and metallurgical methods are presented and performed on Al1050 and SF-Cu joints and precise weld criteria are developed. [less ▲]

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