A survey: Scheduling of Automated Guided Vehicles in Flexible (Re-)Manufacturing Systems

in Müller, Rainer; Brüls, Oliver; Abba, Gabriel (Eds.) et al Robotix-Academy Conference for Industrial Robotics (RACIR) 2019 (2019, June)

This work gives a state-of-the-art overview regarding the scheduling of Automated Guided Vehicles (AGV) in Flexible (Re-)Manufacturing Systems (FMS/FRMS). Different, general approaches are available to ... [more ▼]

This work gives a state-of-the-art overview regarding the scheduling of Automated Guided Vehicles (AGV) in Flexible (Re-)Manufacturing Systems (FMS/FRMS). Different, general approaches are available to solve this task. In this regard an overview of currently available fleet management software and research in this field as well as the simultaneous scheduling of machines and AGVs is given. Production scheduling and transport scheduling have been vastly studied by many researchers, but most of the works address these both problems separately. However, these two problems are closely linked and influence each other. By looking at them together, it is possible to achieve an improvement in the overall scheduling. The different works are examined regarding the consideration of one available machine for each tasks, or if alternative machines are available and if the approaches are static or dynamic. Especially the appropriability of the presented works regarding the use in remanufacturing systems is examined. Remanufacturing is a process for used products to make them “as good as new or better”. Due to unknown condition of the used products many challenges occur during the remanufacturing process which are special to the domain of remanufacturing and not know from manufacturing. The resulting stochastic routing of products and material in particular places special demands on the flexibility and dynamic of the scheduling and control of the remanufacturing system. In order to meet the challenges of a real remanufacturing system, the scheduling algorithm should consider alternative machines as well as be dynamic. None of the approaches examined can meet these requirements, which is why new methods have to be developed. [less ▲]

Entwicklung eines intelligenten, robotergestützten Assistenzsystems für die Demontage industrieller Produkte

Doctoral thesis (2019)

Technical assistance systems are used in many aspects of our private environment to simplify our daily lives. Such assistance would also be desirable in our working environment, especially in physically ... [more ▼]

Technical assistance systems are used in many aspects of our private environment to simplify our daily lives. Such assistance would also be desirable in our working environment, especially in physically demanding activities such as dismantling products for maintenance, corrective maintenance, or remanufacturing. However, the use of robot-supported assistance systems is prevented by the imponderabilities in the dismantling process of different products due to the lack of autonomy of the technical systems. In the course of this dissertation, the development of intelligent, robot-supported assistance systems that can support people in such complex processes in a target-oriented manner are considered, and the following research question is posed: What are the technical requirements for such assistance systems and how can they be implemented? In the reviewed scientific literature, no holistic approach has been identified for the development of these systems, but many approaches to partial aspects of such a system have been collected across several research disciplines. In order to address the research question, this dissertation discusses the theoretical fields of technical assistance systems, human-robot systems, and the field of application in order to define technical requirements. A demonstrator for experimental validation is implemented in the form of a multi-agent system in which various technical systems are integrated and interconnected by software. The function of the developed robot-based assistance system could be verified in concrete dismantling processes in conjunction with suitable man-machine communication interfaces. Finally, this dissertation identifies further research questions that must be addressed before such systems can be introduced in the industrial environment. [less ▲]

Elucidation of influencing parameters of the laser butt welding process of dissimilar steel to tungsten alloy sheets

in Proceedings of International Conference on Competitive Manufacturing COMA'19 (2019, January)

Laser welding of steel - tungsten alloy joints requires deep understanding of the impact of the laser parameters on the welding process. Due to the dissimilar thermal and metallurgical properties of both ... [more ▼]

Laser welding of steel - tungsten alloy joints requires deep understanding of the impact of the laser parameters on the welding process. Due to the dissimilar thermal and metallurgical properties of both materials, a defined heat input and a precise temperature control in the weld interface is required. In the presented work, the influence of different laser parameter (e.g. laser power, focal position, scanner speed etc.) on the joint quality of laser welded steel / tungsten alloy butt-joints were investigated. By using statistical methods, the influencing process parameters were defined and optimized. It is shown that the horizontal focal position is the main parameter for the welding process in a butt-joint configuration. Additionally, manipulation of the heat input leads to modifications of the weld bead profile. By obtaining vertical seam boundaries in the sheet metal, a homogenous temperature profile at the interface of the materials to be welded was achieved. Due to the complete bonding and low amount of intermetallic phases, high shear strength accompanied with a low variance were the result. [less ▲]

Robotic trajectory tracking: Bio-inspired position and torque control

in Procedia CIRP (2019)

As far as complex contact-based manufacturing tasks are concerned, humans outperform machines. Indeed, conventionally controlled robotic manipulators are limited to basic applications in close to ideal ... [more ▼]

As far as complex contact-based manufacturing tasks are concerned, humans outperform machines. Indeed, conventionally controlled robotic manipulators are limited to basic applications in close to ideal circumstances. However, tedious work in hazardous environments, make some tasks unsuitable for humans. Therefore, the interest in expanding the application-areas of robots arose. This paper employs a bottom-up approach to develop robust and adaptive learning algorithms for trajectory tracking: position and torque control in the presence of uncertainties and switching constraints. The robotic manipulators mimicking the human behavior based on bio-inspired algorithms, take advantage of their know-how. Simulations and experiments validate the concept-performance. [less ▲]

Rule-Based Supervisory Control-Extension for Automated Manufacturing Processes

in International Journal of Mechanical Engineering and Robotics Research (2019)

Before performing a surface finishing process, human operators analyze the workpiece-conditions and react accordingly, i.e. they adapt the contact-situation of the tool with respect to the surface. This ... [more ▼]

Before performing a surface finishing process, human operators analyze the workpiece-conditions and react accordingly, i.e. they adapt the contact-situation of the tool with respect to the surface. This first step is ignored in most suggested automation concepts. Although their performance is satisfactory for the general process thanks to adaptive position- and force-/torque-control algorithms, they are unable to address specific problematic cases as often encountered in practice because of variations in workpiece-dimensions or -positioning. In this work, a human mimicking element is developed to overcome this limitation of current control concepts and to translate human expertise to the robotic manipulator. A rule-based system is designed where human knowledge is encoded as if-then rules. This system is integrated with a previously suggested control strategy in a hierarchical manner. The developed concept is experimentally validated on a KUKA LWR 4+-robotic manipulator. [less ▲]

Laser welding of polyamide-6.6 and titanium: a chemical bonding story

Scientific Conference (2019)

Hybrid materials are more and more common in biomedical applications, such as implants. However, assembling the materials is still challenging. Mechanical fastening solutions present durability problems ... [more ▼]

Hybrid materials are more and more common in biomedical applications, such as implants. However, assembling the materials is still challenging. Mechanical fastening solutions present durability problems, and adhesive solutions rarely combine strong mechanical properties and biocompatibility. To address these difficulties laser welding is a promising solution. It is a fast process with great design freedom that requires no additional material at the interface. Since the process is quite recent, the involved fundamental mechanism are not well understood. Hence this work aims at exploring the existence of a chemical bond between two materials: titanium and polyamide-6.6. Samples composed of a block of polyamide-6.6 welded to a titanium sheet were broken and analysed using XPS and ToF-SIMS. Results show more polymer in the weld and the chemical bond seems to be a complexation of titanium with the amide function. [less ▲]

Metallographic Studies of Dissimilar Al-Cu Laser-Welded Joints Using Various Etchants

in Metallography, Microstructure, and Analysis (2018)

The welding of Al and Cu is considered as difficult due to the formation of intermetallic compounds, which cause a brittle joint with increased electrical resistance. This paper investigates etching ... [more ▼]

The welding of Al and Cu is considered as difficult due to the formation of intermetallic compounds, which cause a brittle joint with increased electrical resistance. This paper investigates etching techniques that were used to contrast the intermetallic compounds for optical microscope analysis. A 0.5 mm AA-1050 sheet was welded to a 0.5 mm SF-Cu sheet in overlap configuration. The cross sections were etched by using 17 different reagents, including common Al-grade 2xxx etchants, Al-bronze etchants, and specific IMC etchants. A complete microstructural characterization, including the formation of intermetallic compounds, is presented. The experimental result showed that a clear distinction of metallurgic structures is possible, thus enabling a more detailed analysis of Al-Cu welds. It was found that etchants #09, #14, and #16 revealed best the four different intermetallic compounds θ-Al2Cu, η-AlCu, ζ-Al3Cu4, and γ-Al4Cu9. [less ▲]

FLEXCAP – Cost competitive flexible process for highly aesthetic closures manufacturing

in Kakogiannos, Ioannis; Hichri, Bassem; Plapper, Peter (Eds.) Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018, November)

Industry 4.0 – Implementation of an automated assembly line in a wooden modular house production plant: The case Leko Labs

in De vincenzo, Vincenzo; Hichri, Bassem; Plapper, Peter (Eds.) Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018, November)

Laser micro-welding of wire to flat geometry for dissimilar materials in an electromechanical application

Poster (2018, September 11)

In the presented study, the laser welding of wire to flat geometry for miniature electromechanical hybrid components has been investigated. Laser welding offers variety of advantages compared to the ... [more ▼]

In the presented study, the laser welding of wire to flat geometry for miniature electromechanical hybrid components has been investigated. Laser welding offers variety of advantages compared to the current joining processes for this application however, considering the geometry of parts to be welded also mechanical properties requirement, an accurate spatial modulation of laser beam should be implemented to achieve a sound joint. Tensile shear test and optical microscopy were employed to represent the mechanical properties and melt pool geometry of the joint. All welds were done by power modulation of the laser beam to better control the energy input at several feed rates and three different beam trajectories. Results show that the shear load of the joint can be controlled by feed rate and the trajectory of the laser beam. The material combination of the study (Nickel and CuSn6), represents solubility in solid state therefore, by defining a proper spatial modulation of the laser beam a joint stronger than base wire metal is achievable. Figure 1 represents schematics of weld components. [less ▲]