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See detailLearning-While Controlling RBF-NN for Robot Dynamics Approximation in Neuro-Inspired Control of Switched Nonlinear Systems
Klecker, Sophie UL; Hichri, Bassem UL; Plapper, Peter UL

in Artificial Neural Networks and Machine Learning; ICANN 2018 part 3 (2018)

Radial Basis Function-Neural Networks are well-established function approximators. This paper presents an adaptive Gaussian RBF-NN with an extended learning-while controlling behaviour. The weights ... [more ▼]

Radial Basis Function-Neural Networks are well-established function approximators. This paper presents an adaptive Gaussian RBF-NN with an extended learning-while controlling behaviour. The weights, function centres and widths are updated online based on a sliding mode control element. In this way, the need for fixing parameters a priori is overcome and the network is able to adapt to dynamically changing systems. The aim of this work is to present an extended adaptive neuro-controller for trajectory tracking of serial robots with unknown dynamics. The adaptive RBF-NN is used to approximate the unknown robot manipulator dynamics-function. It is combined with a conventional controller and a bio-inpsired extension for the control of a robot in the presence of switching constraints and discontinuous inputs. Its learned goal-directed output results from the complementary action of an actuator, A, and a prventer, P. The trigger is an incentive, I, based on the weighted perception of the enviornment. The concept is validated through simulations and implementation on a KUKA LWR4-robot. [less ▲]

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See detailRecent Progress Toward Intelligent Robot Assistants for Non-Destructive Disassembly
Jungbluth, Jan UL; Gerke, Wolfgang; Plapper, Peter UL

in Müller, Rainer; Plapper, Peter; Brüls, Olivier (Eds.) et al Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018)

One key to successful and fluent human-robot collaboration in disassembly processes is equipping the robot systems with greater autonomy and intelligence. In this paper, we present our progress in ... [more ▼]

One key to successful and fluent human-robot collaboration in disassembly processes is equipping the robot systems with greater autonomy and intelligence. In this paper, we present our progress in developing such an intelligent robot assistant system. We present the multi-agent control architecture we developed and describe its technical implementation. Our control approach relies on two types of knowledge models: product and process models. The product model describes the structure of the product to be dismantled through a description of the parts involved and the connections between them. A connection type-related process model describes which agents and objects participate in the disassembly process and which methods of human-robot cooperation or collaboration are most useful. When supplied with a product model and a goal definition, our robotic assistant can automatically generate a partially ordered disassembly task sequence. For each disassembly task, the user can choose one of the divisions of labor defined in the process model. Using the process model, through perception and deliberation, the control system can both execute actions and coordinate and synchronize the actions of human and machine. This approach allows the system to be more autonomous when providing assistance to human coworkers in complex and one-piece disassembly processes. [less ▲]

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See detailCombining Virtual and Robot Assistants - A Case Study about Integrating Amazon's Alexa as a Voice Interface in Robotics
Jungbluth, Jan UL; Krieger, Rolf; Gerke, Wolfgang et al

in Müller, Rainer; Plapper, Peter; Brüls, Oliver (Eds.) et al Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018)

Virtual assistants such as Alexa, Siri, Cortana and Google Assistant increasingly find ways to enter our homes and everyday lives, where they serve as powerful human-machine interfaces to control devices ... [more ▼]

Virtual assistants such as Alexa, Siri, Cortana and Google Assistant increasingly find ways to enter our homes and everyday lives, where they serve as powerful human-machine interfaces to control devices through natural language. In this work, we explore the use of virtual assistants to control single components within an intelligent industrial robot assistant system for disassembly applications. Following a short introduction and an overview of commercially available virtual assistants, we present our system architecture, which integrates Amazon's Alexa through an Echo Dot device. Utilizing the Alexa Skill Kit, we build a voice user interface that contains dialogs to control various device functions and assistive system behaviors. By connecting Alexa Voice Service with Amazon’s Lambda and IoT web services, we can parametrize machine commands depending on the user's voice input and, through a Raspberry Pi, which routes messages between the internet and decoupled machine network, send them to the devices within the intelligent robot assistance system. With the reversed communication flow, we can update and store the current state of the devices in the Amazon Web Services IoT Shadow. Utilizing the IoT Shadow, we are able to inform the user upon request about the current state of the devices by synthesize speech with the Alexa Voice Services and vocalize it through the Echo Dot. One implemented assistive system behavior and the related dialog to activate the behavior is further explained in this work. In the conclusion, we address our gathered positive and negative experience to date. [less ▲]

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See detailContinuous Improvement of complex process flows by means of StreaM
Oberhausen, Christof UL; Minoufekr, Meysam UL; Plapper, Peter UL

Presentation (2017, December 11)

In numerous sectors and industries worldwide, there is a trend towards an intercompany and often international division of value creation and related work tasks. To overcome the challenges of complex ... [more ▼]

In numerous sectors and industries worldwide, there is a trend towards an intercompany and often international division of value creation and related work tasks. To overcome the challenges of complex cross-enterprise supply chain networks, innovative approaches to visualize, assess and enhance value streams are sought. The StreaM method, which is described in this paper, enables a comprehensive analysis, design and planning of cross-company product and information flows on different levels of value stream detail. At the same time, the entire methodology is based on a common understanding of key symbols, parameters and calculation procedures. In addition, the use of the developed StreaM method and the associated model in a case study proves its practical applicability in an industrial setting. In further validation projects, the transfer of the “Standardized cross-enterprise Value Stream Management Method” to other industry sectors is envisaged to continuously improve energy, trade or service processes. [less ▲]

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See detailContinuous Improvement of Complex Process Flows by Means of StreaM as the “Standardized Cross-Enterprise Value Stream Management Method”
Oberhausen, Christof UL; Minoufekr, Meysam UL; Plapper, Peter UL

in Proceedings of 2017 IEEE International Conference on Industrial Engineering and Engineering Management (IEEM) (2017, December)

In numerous sectors and industries worldwide, there is a trend towards an intercompany and often international division of value creation and related work tasks. To overcome the challenges of complex ... [more ▼]

In numerous sectors and industries worldwide, there is a trend towards an intercompany and often international division of value creation and related work tasks. To overcome the challenges of complex cross-enterprise supply chain networks, innovative approaches to visualize, assess and enhance value streams are sought. The StreaM method, which is described in this paper, enables a comprehensive analysis, design and planning of cross-company product and information flows on different levels of value stream detail. At the same time, the entire methodology is based on a common understanding of key symbols, parameters and calculation procedures. In addition, the use of the developed StreaM method and the associated model in a case study proves its practical applicability in an industrial setting. In further validation projects, the transfer of the “Standardized cross-enterprise Value Stream Management Method” to other industry sectors is envisaged to continuously improve energy, trade or service processes. [less ▲]

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See detailNeuro-Inspired Reward-Based Tracking Control for Robotic Manipulators with Unknown Dynamics
Klecker, Sophie UL; Hichri, Bassem UL; Plapper, Peter UL

in Proceedings of the 2017 2nd International Conference on Robotics and Automation Engineering (ICRAE) (2017, December)

Tracking control for robotic manipulators is required for numerous automation tasks in manufacturing engineering. For this purpose, model-free PD-controllers are largely implemented by default in ... [more ▼]

Tracking control for robotic manipulators is required for numerous automation tasks in manufacturing engineering. For this purpose, model-free PD-controllers are largely implemented by default in commercially available robot arms and provide satisfactory performance for simple path following applications. Ever more complex automation tasks however ask for novel intelligent and adaptive tracking control strategies. In surface finishing processes, discontinuous freeform paths as well as changing constraints between the robotic end-effector and its surrounding environment affect the tracking control by undermining the stable system performance. The lacking knowledge of industrial robot dynamic parameters presents an additional challenge for the tracking control algorithms. In this paper the control problem of robotic manipulators with unknown dynamics and varying constraints is addressed. A robust sliding mode controller is combined with an RBF (Radial Basis Function) Neural Network-estimator and an intelligent, biomimetic BELBIC (Brain Emotional Learning-Based Intelligent Control) term to approximate the nonlinear robot dynamics function and achieve a robust and adaptive tracking performance. [less ▲]

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See detailInfluence of laser ablation and plasma surface treatment on the joint strength of laser welded aluminum-polyamide assemblies
Al Sayyad, Adham UL; Bardon, Julien; Hirchenhahn, Pierre et al

Scientific Conference (2017, September 14)

Laser assembly of a metal with a polymer is an innovative process for the development of hybrid lightweight structures. It was already demonstrated that surface treatment of aluminum prior to laser ... [more ▼]

Laser assembly of a metal with a polymer is an innovative process for the development of hybrid lightweight structures. It was already demonstrated that surface treatment of aluminum prior to laser joining has a critical influence on joint strength of laser assembly with polyamide. In this work, further investigation of the influence of surface treatment prior to laser assembly is carried out. In particular, two kind of surface modification pretreatments of aluminum, laser ablation and plasma surface modification, in combination with plasma surface pretreatment of polyamide, were investigated. Surface properties of aluminum and polyamide after pretreatment are compared to their untreated state. More precisely, surface chemistry, surface energy and roughness characteristics are evaluated by X-ray photoelectron spectroscopy (XPS), sessile drop tests and 3D profilometry, respectively. Joint strength of laser assembly of treated aluminum and polyamide is reported. The more influential surface characteristics for the improvement of joint strength are determined, paving the way to significant advances in metal-polymer laser assembly technology. [less ▲]

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See detailRobotix-Academy Conference for Industrial Robotics (RACIR) 2017
Müller, Rainer; Plapper, Peter UL; Brüls, Olivier et al

Book published by Shaker Verlag - 1st ed (2017)

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See detailResistance measurement of dissimilar Al/Cu laser welds
Schmalen, Pascal Guy UL; Plapper, Peter UL

in Proceedings of LPM2017 - the 18th International Symposium on Laser Precision Microfabrication (2017)

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 de-scribes 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 signifi-cantly 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 measure-ments) and decreases the lead-time by reducing the time needed for the identification of suitable laser process parameters. [less ▲]

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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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