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See detailAgentenbasierte Steuerung der Mensch-Roboter-Interaktion
Jungbluth, Jan UL; Gerke; Plapper, Peter UL

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 ▲]

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See detailDemontage von Elektroantrieben mit Assistenzrobotern zum wirtschaftlichen Recycling
Jungbluth, Jan UL; Plapper, Peter UL; Gerke, Wolfgang

in Tagungsband AALE 2016 (2016)

Die zerstörungsfreie Demontage zum Zweck der Refrabrikation oder des höherwertigem Produktrecyclings findet nur selten im industriellen Umfeld Anwendung. Allerdings ist mit einem Anstieg dieses trennenden ... [more ▼]

Die zerstörungsfreie Demontage zum Zweck der Refrabrikation oder des höherwertigem Produktrecyclings findet nur selten im industriellen Umfeld Anwendung. Allerdings ist mit einem Anstieg dieses trennenden Fertigungsverfahrens in naher Zukunft zu rechnen da die immer stärker begrenzten und zugänglichen Ressourcen durch strengere Gesetze im Rahmen der Abfallwirtschaft gesichert werden müssen. Zum Beispiel wurden durch das Kreislaufwirt-schaftsgesetz der europäischen Union [1] die Hersteller dazu verpflichtet Rücknahmesysteme für elektrische und elektronische Geräte zu schaffen um sie einer weiteren wirtschaftlichen Nutzung oder umweltgerechten Entsorgung zugänglich zu machen. Für die umweltgerechte Entsorgung ist eine wertstoffgerechte Trennung der Produktkomponenten vorgesehen. Aus wirtschaftlichen Gründen erfolgt diese Materialtrennung meist verfahrenstechnisch durch Zerkleinern und Sortieren der Wertstoffe. Die weitere wirtschaftliche Nutzung ganzer Kompo-nenten wird, trotz hoher Einsparpotenziale [2], durch den Aufwand der Refabrikation kaum in Betracht gezogen. Denn die zerstörungsfreie Trennung kann bisher meist nur manuell und damit kostenintensiv erfolgen. In der Folge werden gerade im Bereich der Elektroschrottver-wertung häufig illegale Entsorgungswege über das außereuropäische Ausland gewählt [3]. Zur Verbesserung der Wirtschaftlichkeit der Demontage bietet oft die Automatisierung Lösun-gen. Um diesen Sektor der Automatisierung zugänglich zu machen, erfolgten bereits For-schungsaktivitäten zur Automatisierung der Demontage von Fernsehgeräten [4] und PCs [5]. Das Ergebnis dieser Studien zeigt, dass durch die hohe Variation der Produktgestalt oder aufgrund von Beschädigungen der Produkte, der [less ▲]

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See detailAcoustic-Emission-Analysis of Dissimilar Laser-welds of Aluminium and Polyamide 6.6
Schiry, Marc UL; Lamberti, Christian UL; Böhm, Peter et al

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 ▲]

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See detailRobotizing of small lot production
Plapper, Peter UL

Scientific Conference (2015, December)

Industrial robots bear significant potential for increasing productivity of manufacturing operations. However, producing increasingly individualized products with an enhanced number of variants, the ... [more ▼]

Industrial robots bear significant potential for increasing productivity of manufacturing operations. However, producing increasingly individualized products with an enhanced number of variants, the flexibility of the production system poses substantial challenges in order to robotize manual tasks. Comprehensive scientific research is required to provide tailored solutions for these manufacturing processes. This is true especially for small and medium sized companies (SME). The key note discusses the challenges of automating flexible manufacturing operations with examples from specific use cases with industrial background. We present automotive powertrain assembly, which requires agile robotic joining of rigid and complaint parts. However, as automation of many low volume processes is economically not advantageous, semi-automation and Human-Robot Collaboration are key enablers for robotizing small lot production. Human-Robot Collaboration requires novel technologies for dynamic workload distribution between worker and robot. Automating 3D surface grinding process is another example how scientific research contributes to increased manufacturing efficiency. [less ▲]

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See detailPath planning self-learning algorithm for a dynamic chaning environment
Ahmad, Rafiq; Plapper, Peter UL

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 ▲]

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See detailGaussian Filtering for Enhanced Impedance Parameters Identification in Robotic Assembly Processes
Jasim, Ibrahim UL; Plapper, Peter UL; Voos, Holger UL

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

Robot interaction with the environment is normally described as a mass-spring-damping impedance model and the estimation of such interaction impedance parameters requires the computation of the joint (or ... [more ▼]

Robot interaction with the environment is normally described as a mass-spring-damping impedance model and the estimation of such interaction impedance parameters requires the computation of the joint (or task) space velocity and acceleration. In many cases, the velocity and acceleration are computed by numerically computing the first and second derivatives of the sensed position signal. The numerical differentiation results in approximation errors when computing the velocity and acceleration signals that would have a direct impact on the estimation of the impedance parameters. This article proposes enhancing the estimation of the impedance parameters by smoothing the velocity and acceleration signals prior to the considered estimation process. Gaussian Smoothing Filter (GSF) is employed in smoothing the considered signals. After the smoothing process, impedance parameters estimation becomes more feasible using the available strategies like the Least Mean Square (LMS) or any other estimation approach. Experiments are conducted on a KUKA Lightweight Robot (LWR) doing the assembly of the air-intake manifold of an automotive powertrain. The impedance parameters are estimated for the smoothed and unsmoothed cases in order to show the enhancement in the estimation process. [less ▲]

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See detailModel-Free Robust Adaptive Control for Flexible Rubber Objects Manipulation
Jasim, Ibrahim UL; Plapper, Peter UL; Voos, Holger UL

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 ▲]

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See detailGeneration of safe tool-path for 2.5D milling/drilling machine-tool using 3D ToF sensor
Ahmad, Rafiq UL; Plapper, Peter UL

in CIRP - Journal of Manufacturing Science and Technology (2015), 10

The complexity of multi-axis, milling and drilling CNC machines and the demand of high precision for complex parts production increase the importance of safe and efficient tool-paths generation during ... [more ▼]

The complexity of multi-axis, milling and drilling CNC machines and the demand of high precision for complex parts production increase the importance of safe and efficient tool-paths generation during manufacturing. In these machines, multi-tool working in the same area, or static un-programed machine elements, such as fixtures, another work-part may cause collision problems. It is important to know the collision risks in advance during production in order to avoid unexpected production stops, and machinery damage. This research study is focusing on automatic collision detection and avoidance for safe non-functional (rapid) tool-path generation in a static 2.5D milling or drilling machining environment, as an initial step toward complex, dynamic multi-axis machine-tool manufacturing. A 3D vision based Time of Flight (ToF) sensor provides the depth information about the manufacturing scene that are exploited by the method presented for taking an effective decision to automatically detect and avoid collisions in order to achieve safe tool-path during production. The concept presented opens up new areas for research and application of ToF camera in a CNC manufacturing environment for tool-path planning. The results obtained are for traversal safe tool-paths in a static environment, which will be adapted to more complex and dynamic real machining scenarios by integrating it with STEP-NC technology in future. [less ▲]

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See detailDesign rules for autofrettage of an aluminium valve body
Sellen, Stephan UL; Maas, Stefan UL; Andreas, Thomas et al

in Fatigue & Fracture of Engineering Materials & 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 ▲]

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See detailValue Stream Management in the "Lean Manufacturing Laboratory"
Oberhausen, Christof UL; Plapper, Peter UL

in Procedia CIRP (2015, July), 32

The University of Luxembourg has recently launched its learning factory, the “Lean Manufacturing Laboratory”. With the help of this manual assembly line, students gain valuable insights in the operation ... [more ▼]

The University of Luxembourg has recently launched its learning factory, the “Lean Manufacturing Laboratory”. With the help of this manual assembly line, students gain valuable insights in the operation of a manufacturing line as well as in buffer, waste and congestion management. Currently, one of the main research topics at the University of Luxembourg in the field of Lean Management is the further development of the method Value Stream Management (VSM). The application of VSM in the “Lean Manufacturing Laboratory” with a projected focus on industry and service sectors reveals the need for a standardized VSM approach. Thus, one of the research objectives is the development of a common VSM method accompanied by standardized software and process interfaces to ensure robust product and information flows within a company and also throughout supply chains. On the way towards a VSM method as standard, existing VSM approaches have to be investigated and validated. By a detailed comparison of existing VSM approaches, all necessary fields of action for the development of a standardized Value Stream Management approach are shown. [less ▲]

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See detailValue Stream Management in high variability production systems
Oberhausen, Christof UL; Weber, Daniel; Plapper, Peter UL

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 ▲]

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See detailImproved design of threaded connections by autofrettage in aluminium compounds for cyclic high pressure loading: design calculations and experimental verification
Sellen, Stephan; Maas, Stefan UL; Andreas, Thomas et al

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

Threaded connections in an aluminium valve body under high internal swelling pressure are investigated. A static straining process called autofrettage leads to an improved fatigue behaviour of the ... [more ▼]

Threaded connections in an aluminium valve body under high internal swelling pressure are investigated. A static straining process called autofrettage leads to an improved fatigue behaviour of the aluminium component, while normally the threaded connections are unloaded during this autofrettage. But by unloading the thread during autofrettage the first loaded thread flank became the weakest point of this valve component. This effect is analyzed with non-linear finite element simulations, FKM guideline for fatigue assessment and by experimental testing. The analytical and experimental parts match very well and it can be shown that a well-designed autofrettage without unloading the threaded connection is helpful for the aluminium thread and extends its fatigue lifetime, as compressive residual stresses and an equalized stress distribution over the thread flanks can be generated. Finally different materials were chosen for the plug or screw and this effect for cyclic loading is shortly analyzed. [less ▲]

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See detailSafe and Automated Assembly Process using Vision assisted Robot Manipulator
Ahmad, Rafiq UL; Plapper, Peter UL

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 ▲]

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See detailAdaptive sliding mode fuzzy control for unknown robots with arbitrarily-switched constraints
Jasim, Ibrahim UL; Plapper, Peter UL; Voos, Holger UL

in Mechatronics (2015), 30C

This article addresses the control problem of robots with unknown dynamics and arbitrarily-switched unknown constraints. Such kind of robots will be shown to be unknown hybrid systems with arbitrary ... [more ▼]

This article addresses the control problem of robots with unknown dynamics and arbitrarily-switched unknown constraints. Such kind of robots will be shown to be unknown hybrid systems with arbitrary switching and an Adaptive Sliding Mode Fuzzy Control (ASMFC) strategy is proposed that handles the unknown dynamics of the robot along with the unknown constraints arbitrary switching. The ASMFC is a synergy of finding a Common Lyapunov Function (CLF) between the resulted switched subsystems of the considered robots, employing the Fuzzy Logic Systems (FLS), and the use of the Sliding Mode Control (SMC). The CLF accommodates the constraints arbitrary switching, the SMC adds robustness against possible parameters drift, and the FLS approximates the unknown robot dynamics. All unknown parameters are adapted online and all closed loop signals are guaranteed to be bounded. The proposed strategy is validated by conducting an experiment on a KUKA Lightweight Robot (LWR) doing a typical force-guided peg-in-hole assembly task that falls in the category of robot systems under consideration. Excellent tracking performance is obtained when using the ASMFC strategy. Comparison is conducted with the performance of a PD controller that is widely used in commanding industrial robots and the superiority of the proposed strategy is shown. [less ▲]

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See detailContact-State Modelling in Force-Controlled Robotic Peg-in-Hole Assembly Processes of Flexible Objects Using Optimised Gaussian Mixtures
Jasim, Ibrahim UL; Plapper, Peter UL; Voos, Holger UL

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 ▲]

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See detailAnt-Air self-learning algorithm for path planning in a cluttered environment
Ahmad, Rafiq UL; Plapper, Peter UL

in Applied Mechanics and Materials Journal (2014, December)

Path planning in unstructured area while dealing with narrow spaces is an area of research which is receiving extensive interest. Many existing algorithms are able to produce safe paths but the presented ... [more ▼]

Path planning in unstructured area while dealing with narrow spaces is an area of research which is receiving extensive interest. Many existing algorithms are able to produce safe paths but the presented concepts are either not adapted to narrow spaces or they are unable to learn from the past experience to improve repeated movements from the same agent or followed trajectories by other agents. This paper introduces an original concept based on Ant-Air phenomenon for safe path planning in a cluttered environment where narrow passages are treated. The algorithm presented is able to learn from the past experience and hence improve the already generated trajectory further by using some lessons learned from the past experience. The concept is applicable in various domains such as mobile robot path planning, manipulator trajectory generation and part movement in narrow passages in real or virtual assembly/disassembly process. [less ▲]

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See detailHuman-Robot Collaboration: Twofold strategy algorithm to avoid collisions using ToF sensor
Ahmad, Rafiq UL; Plapper, Peter UL

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 ▲]

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See detailSafe and Automated Tool-Path Generation for Multi-Axis Production Machines
Ahmad, Rafiq UL; Plapper, Peter UL

in Transactions of the American Society of Mechanical Engineers (2014, November 14), 2B(Advanced Manufacturing), 0202034-7

Multi-axis machines are growing rapidly their precision and complexity with the increasing importance of machine intelligence, automation, optimization and safety. It is necessary to identify collision ... [more ▼]

Multi-axis machines are growing rapidly their precision and complexity with the increasing importance of machine intelligence, automation, optimization and safety. It is necessary to identify collision risks and avoid them in manufacturing otherwise production stops may cost a huge amount to the manufacturing company. This study has focused on safe trajectory generation for CNC machines especially focusing on high risked non-functional trajectories. These machines should be able to see any unwilling situation (i.e. collisions) in their vicinity and must be able to detect and react automatically in real-time for safe tool movements. Currently CAM software and some multi-axis machines are able to detect collisions but they do not have any solution to avoid such collisions automatically. The main objective is to make multi-axis machine vision system effective enough that it can see all its activities regarding collisions and can react or command automatically online as well as off-line for real and virtual productions. In presence of obstacles during manufacturing, the proposed approach will provide decisions regarding trajectory correction and improvement automatically. The proposed vision concept is able to take into account the evolution of the scene i.e. the aspects of changes to the obstacle like shape, size or presence during production. The application presented in this paper is for 2D traversal safe online trajectories generation in virtual simulated dynamic environment, which will be adapted to the real-time real machining scenarios at shop-floor by integrating it with STEP-NC technology in future. [less ▲]

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See detailPosition Identification in Force-Guided Robotic Peg-in-Hole Assembly Tasks
Jasim, Ibrahim UL; Plapper, Peter UL; Voos, Holger UL

in Procedia CIRP (2014), 22

Position uncertainty is inevitable in many force-guided robotic assembly tasks. Such uncertainty can cause a significant delay, extra energy expenditure, and may even results in detriments to the mated ... [more ▼]

Position uncertainty is inevitable in many force-guided robotic assembly tasks. Such uncertainty can cause a significant delay, extra energy expenditure, and may even results in detriments to the mated parts or the robot itself. This article suggests a strategy for identifying the accurate hole position in force-guided robotic peg-in-hole assembly tasks through employing only the captured wrench (the Cartesian forces and torques) signals of the manipulated. In the framework of using the Contact-State (CS) modeling for such robotic tasks, the identification of the hole position is realized through detecting the CS that corresponds for the phase of the peg-on-hole, that is the phase in which the peg is located precisely on the hole. Expectation Maximization-based Gaussian Mixtures Model (EM-GMM) CS modeling scheme is employed in detecting the CS corresponding for the peg-on-hole phase. Only the wrench signals are used in modeling and detecting the phases of the assembly process. The considered peg-in-hole assembly process starts from free space and as soon as the peg touches the environment with missing the hole, a spiral search path is followed that would survey the whole environment surface. When the CS of the peg-on-hole is detected, the hole position is identified. Experiments are conducted on a KUKA Lightweight Robot (LWR) doing typical peg-in-hole assembly tasks. Multiple hole positions are considered and excellent performance of the proposed identification strategy is shown. [less ▲]

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See detailEnhanced Decentralized Robust Adaptive Control of Robots With Arbitrarily-Switched Unknown Constraints
Jasim, Ibrahim UL; Plapper, Peter UL

in 2014 IEEE International Conference on Systems, Man, and Cybernetics (SMC2014) (2014, October 05)

In this article, we propose an Enhanced Decentralized Robust Adaptive Control (EDRAC) strategy that guarantees global stable performance for robots under arbitrarily-switched and unknown constraints. The ... [more ▼]

In this article, we propose an Enhanced Decentralized Robust Adaptive Control (EDRAC) strategy that guarantees global stable performance for robots under arbitrarily-switched and unknown constraints. The EDRAC strategy is a synergy of the concepts of the decentralized control, finding a Common Lyapunov Function (CLF), and the Sliding Mode Control (SMC). The decentralization in the control action is realized through decomposing the joints dynamics into two parts; a function of the specific joint variables and another one in term of the all joints variables. The first term is assumed to be known and the latter is compensated through adapting its upper bound in the control loop hence relaxing the need for knowing part of the robot dynamics and simplifying the control strategy. The CLF guarantees global stable performance under arbitrary constraints switching, and the SMC makes the EDRAC strategy robust against possible parameters drift. Simulation is performed for a two link robot interacting with two switching constraints and the efficiency of the EDRAC strategy is shown. [less ▲]

Detailed reference viewed: 37 (10 UL)