A Standardized Value Stream Management Method for Supply Chain Networks

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 ▲]

Agentenbasierte Steuerung der Mensch-Roboter-Interaktion

in Automatisierungstechnische Praxis (2016), 12

Die manuelle Demontage schmälert die Wirtschaftlichkeit von Refabrikationsprozessen maßgebend und stellt in der Arbeitsplatzergonomie einen Problemprozess dar. Versuche, die zerstörungsfreie Demontage zu ... [more ▼]

Die manuelle Demontage schmälert die Wirtschaftlichkeit von Refabrikationsprozessen maßgebend und stellt in der Arbeitsplatzergonomie einen Problemprozess dar. Versuche, die zerstörungsfreie Demontage zu automatisieren, scheiterten an der Varianz der Produktgestalt oder am Produktzustand. Zur Lösung dieses Problems wird im Beitrag der Einsatz eines Softwareagenten beschrieben. Die Software steuert das Verhalten eines Roboters, um dem Menschen bei der Demontage zu assistieren. Zur Information des Agenten dienen generische Informationsmodelle die zur Prozessplanung und -steuerung verwendet werden. Die grobe Prozessplanung erfolgt mit Hilfe gerichteter Graphen und zerlegt den Gesamtprozess in eine Abfolge von Teilprozessen. In der detaillierten Prozessplanung werden die Aktionen und deren zeitliche Abfolge im Teilprozess durch eine Suche ermittelt und dann zur Steuerung des Roboters verwendet. Dies ermöglicht es dem System, in einer komplexen Umgebung zielgerichtet Assistenz zu leisten und die hierfür notwendigen eigenen Handlungen autonom zu bestimmen. Ziel des Assistenzsystems ist es, die Ergonomie der Demontagearbeitsplätze durch die Unterstützung von Handlungen zu verbessern. [less ▲]

Acoustic-Emission-Analysis of Dissimilar Laser-welds of Aluminium and Polyamide 6.6

in Universal Journal of Materials Science (2016), 4(6), 119-124

A novel laser joining process for hybrid polymer-metal structures has proven a strong bond between polyamide and aluminium. This welding technique is strongly requested by the automobile producing ... [more ▼]

A novel laser joining process for hybrid polymer-metal structures has proven a strong bond between polyamide and aluminium. This welding technique is strongly requested by the automobile producing industry for numerous applications within structure components. However, the joining quality exhibits a strong dependency on process-related variables, which highlights the need for an online inspection technique. The requirements for a chosen inspection technique are [1], [2]: 1. Showing the results on-line during the joining process; 2. Working non-destructive; 3. Working as an integral method; Being able to determine weld defects. In that case only the Acoustic Emission Analysis (AEA) as a Non-Destructive-Technique (NDT) can be used to guarantee reasonable results. During the first tests at the welding laboratory at the Laser Technology Competence Centre (LTCC) at the University of Luxembourg, AEA sensors are applied onto the surface of the test specimen which has to be welded. In this principle acoustic events, caused by welding defects, are recorded during the laser joining. The most important laser process parameters, like velocity, power and horizontal focal position of the laser spot, have been verified and evaluated by the AEA. It was observed that insufficient laser power can lead to the break of the melting bath, which is often not recognizable by non-destructive optical methods [2]. The AEA however was able to detect this lack of fusion. Using high laser power, the appearance of gas bubbles arising from the Polyamide 6.6 could be detected afterwards in a microscopic micrograph. The AEA signals related to this effect can be correlated clearly. Due to the high pressure of the gas bubbles, the aluminium weld is often interrupted, which can be traced back to the solidification of the aluminium molten mass. Due to the actual situation, the AEA is a well-working NDT online monitoring method and can be used for the correlation of acoustic events and welding defects within the mentioned joining method. Future tasks will develop some algorithms to separate the different defects by pattern recognition of the AEA signals and parameter [less ▲]

Path planning self-learning algorithm for a dynamic chaning environment

Scientific Conference (2015, December)

The relevance of Human Robot Interaction to complement human skills in a manufacturing environment with industrial robots increases the concerns over safety of human and the robot. It is necessary to ... [more ▼]

The relevance of Human Robot Interaction to complement human skills in a manufacturing environment with industrial robots increases the concerns over safety of human and the robot. It is necessary to identify collision risks and avoid them otherwise production stops may cost a huge amount to the industry. A robot working at manufacturing facility should be able to predict potential collisions and must be able to prevent i.e. react automatically for safe detour around obstacle/human. Currently, industrial robots are able to detect collisions after a real contact but the existing proposals for avoiding collisions are either computationally expensive or not very well adapted to human safety. The objective of this paper is to provide intelligence to the industrial robot to predict collision risks and react automatically without stopping the production in a static environment. The proposed approach using Time of Flight (TOF) camera, provides decision regarding trajectory correction and improvement by shifting robot to a secure position. The application presented in this paper is for safe KUKA robot trajectory generation in peg-in-hole assembly process in the laboratory context. [less ▲]

Model-Free Robust Adaptive Control for Flexible Rubber Objects Manipulation

in 20th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2015), Luxembourg 8-11 September 2015 (2015, September 08)

This article addresses the control problem of robots with unknown dynamics and manipulating flexible rubber objects of unknown elasticity. The manipulated rubber object is considered to be interacting ... [more ▼]

This article addresses the control problem of robots with unknown dynamics and manipulating flexible rubber objects of unknown elasticity. The manipulated rubber object is considered to be interacting with arbitrarily-switched constraints. Such a kind of robot system is shown to have switched impedance parameters during a task execution that results in an unknown hybrid nonlinear system with arbitrarily switched signal. A Model-Free Robust Adaptive Control (MFRAC) strategy is proposed for such a robot system that is proved to guarantee global stable performance with all closed loop signals are assured to be bounded. The suggested MFRAC strategy relies on the synergy of the Adaptive Fuzzy System (AFS), the Sliding Mode Control (SMC), and the notion of Common Lyapunov Functions (CLF). The AFS relaxes the need for knowing the precise robot dynamics, the SMC adds robustness against the drift of the dynamics parameters, and the CLF accommodates the arbitrary switching of the impedance parameters. The bounds of the impedance parameters are adapted online and incorporated in the MFRAC design such that a convergent performance is achieved. Experiment is conducted on a KUKA Lightweight Robot (LWR) doing flexible rubber peg-in-hole assembly process that falls in the category of systems considered in this article. From the experimental results, excellent tracking performance is reported when using the proposed MFRAC strategy for the considered robotic system despite the dynamics anonymity and the unknown impedance parameters arbitrary switching. [less ▲]

Design rules for autofrettage of an aluminium valve body

in Fatigue and Fracture of Engineering Materials and Structures (2015)

The following paper is intended to improve the fatigue behaviour of a complex aluminium valve geometry under high internal cyclic pres sure loading. The autofrettage process helps to increase the f atigue ... [more ▼]

The following paper is intended to improve the fatigue behaviour of a complex aluminium valve geometry under high internal cyclic pres sure loading. The autofrettage process helps to increase the f atigue durability and a simple, but efficient design method for this proces s is deployed. Based o n non-linear material’s behaviour, fin ite eleme nt simulations of t he crack-free geometry help to determine the minimum and maximum autofrettage pressure to be used, without iterative crack simulations , which would require higher computational effort. Material tests under inverse plastifications were performed in order to determine the correct material model. The derived design method was validated with simplified specimens subjected to different autofrettage pressure levels and su bsequent cyclic fatigue tests. [less ▲]

Value Stream Management in high variability production systems

in SSRG International Journal of Industrial Engineering (2015), 2(1), 4

Increasing customer requirements and high pressure from global competition are forcing companies to a holistic optimization of their business and production processes. To ensure the competiveness of ... [more ▼]

Increasing customer requirements and high pressure from global competition are forcing companies to a holistic optimization of their business and production processes. To ensure the competiveness of enterprises in future, it is necessary to introduce a process-oriented view instead of a departmental thinking. This paper describes the application of Value Stream Management by the University of Luxembourg in collaboration with the industrial partner Rotarex S.A., a provider of gas control solutions headquartered in Luxembourg. With the help of Value Stream Analysis and Design, relevant material and information flows are captured, analyzed and finally optimized. [less ▲]

Safe and Automated Assembly Process using Vision assisted Robot Manipulator

in Procedia CIRP (2015)

Many manufacturing industries especially small and medium size (SMEs) industries are reluctant to automatize their production using robots. This is due to the fact that mostly industrial robots are not ... [more ▼]

Many manufacturing industries especially small and medium size (SMEs) industries are reluctant to automatize their production using robots. This is due to the fact that mostly industrial robots are not properly equipped to recognize their surrounding and take intelligent decisions regarding path planning especially for low volume, flexible production with versatile production lines. The proposed idea is that a robot manipulator performing assembly or disassembly tasks should be able to predict potential collisions even with unknown obstacles and must be able to prevent i.e. react automatically for safe detour around obstacle. Currently, industrial robots have tactile sensing abilities, which detect collisions after a real contact but the existing proposals for its avoidance are either computationally expensive, need prior information about the obstacles or not very well adapted to the safety standards. Therefore, this paper introduces a ToF sensor based information collection and intelligent decision methodology in order to localize the un-known, un-programmed obstacles and propose a safe peg-in-hole automated assembly process. In the case of collisions, the proposed method will provide various solutions and decides for the best solution according to the scenario on-hand. The proposed solution is quick and robust and currently applied for static environment, whereas dynamic obstacles will be treated in future. [less ▲]

Contact-State Modelling in Force-Controlled Robotic Peg-in-Hole Assembly Processes of Flexible Objects Using Optimised Gaussian Mixtures

in Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture (2015)

This article proposes the distribution similarity measure–based Gaussian mixtures model for the contact-state (CS) modelling in force-guided robotic assembly processes of flexible rubber parts. The wrench ... [more ▼]

This article proposes the distribution similarity measure–based Gaussian mixtures model for the contact-state (CS) modelling in force-guided robotic assembly processes of flexible rubber parts. The wrench (Cartesian force and torque) signals of the manipulated object are captured for different states of the given assembly process. The distribution similarity measure–based Gaussian mixtures model CS modelling scheme is employed in modelling the captured wrench signals for different CSs. The proposed distribution similarity measure–based Gaussian mixtures model CS modelling scheme uses the Gaussian mixtures model in modelling the captured signals. The parameters of the Gaussian mixtures models are computed using expectation maximisation. The optimal number of Gaussian mixtures model components for each CS model is determined by considering the classification success rate as an index for the similarity measure between the distribution of the captured signals and the developed models. The optimal number of Gaussian mixtures model components corresponds to the highest classification success rate; hence, object elasticity variation would be accommodated by properly choosing the optimal number of Gaussian mixtures model components. The performance of the proposed distribution similarity measure–based Gaussian mixtures model CS modelling strategy is evaluated by a test stand composed of a KUKA lightweight robot doing peg-in-hole assembly processes for flexible rubber objects. Two rubber objects with different elasticity are considered for two experiments; in the first experiment, an elastic peg of 30 Shore A hardness is considered and that of the second experiment has hardness of 6 Shore A which is even softer than the one used in experiment 1. Employing the proposed distribution similarity measure–based Gaussian mixtures model CS modelling strategy excellent classification success rate was obtained for both experiments. However, more Gaussian mixtures model components are required for the softer one that gives a strong impression of the non-stationarity behaviour increment for softer materials. Comparison is performed with the available CS modelling schemes and the distribution similarity measure–based Gaussian mixtures model is shown to provide the best classification success rate performance with a reduced computational time. [less ▲]

Human-Robot Collaboration: Twofold strategy algorithm to avoid collisions using ToF sensor

in Applied Mechanics and Materials Journal (2014, December)

The importance of Human Robot Interaction to complement human skills in a manufacturing environment with industrial robots increases the concerns over safety of human and the robot. It is necessary to ... [more ▼]

The importance of Human Robot Interaction to complement human skills in a manufacturing environment with industrial robots increases the concerns over safety of human and the robot. It is necessary to identify collision risks and avoid them otherwise production stops may cost a huge amount to the industry. A robot working at manufacturing facility should be able to predict potential collisions and must be able to prevent i.e. react automatically for safe detour around obstacle/human. Currently, industrial robots are able to detect collisions after a real contact but the existing proposals for avoiding collisions are either computationally expensive or not very well adapted to human safety. The objective of this paper is to provide intelligence to the industrial robot to predict collision risks and react automatically without stopping the production in a static environment. The proposed approach using Time of Flight (TOF) camera, provides decision regarding trajectory correction and improvement by shifting robot to a secure position. The application presented in this paper is for safe KUKA robot trajectory generation in peg-in-hole assembly process in the laboratory context. [less ▲]