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Schneider, Ulrich; Drust, Manuel; Ansaloni, Matteo; Lehmann, Christian; Pellicciari, Marcello; Leali, Francesco; Gunnink, Jan; Verl, Alexander
doi: 10.1007/s00170-014-6021-2pmid: N/A
Machining using industrial robots is currently limited to applications with low geometrical accuracies and soft materials. This paper analyzes the sources of errors in robotic machining and characterizes them in amplitude and frequency. Experiments under different conditions represent a typical set of industrial applications and allow a qualified evaluation. Based on this analysis, a modular approach is proposed to overcome these obstacles, applied both during program generation (offline) and execution (online). Predictive offline compensation of machining errors is achieved by means of an innovative programming system, based on kinematic and dynamic robot models. Real-time adaptive machining error compensation is also provided by sensing the real robot positions with an innovative tracking system and corrective feedback to both the robot and an additional high-dynamic compensation mechanism on piezo-actuator basis.
Krebs, F.; Larsen, L.; Braun, G.; Dudenhausen, W.
doi: 10.1007/s00170-014-6022-1pmid: N/A
Owing to the rising demand in efficiency and sustainability in commercial aviation, aircraft manufacturers increase the usage of high-performance, lightweight materials like carbon-fibre-reinforced plastics (CFRPs). These materials pose new challenges to manufacturing processes concerning cost-effectiveness and quality requirements. To meet these challenges, the Institute of Structures and Design within the German Aerospace Center (DLR) designed a flexible robotic manufacturing cell at the Center for Lightweight Production Technology (ZLP) in Augsburg. The multifunctional cell (MFZ) can integrate processes for production and inspection on an industrial scale. Due to large workpieces like fuselage components or wing skins and low production quantities, workshop space and investment cost are major concerns for effective CFRP production. The large size of the cell (30 m × 15 m × 7 m) demands a highly reconfigurable space. The platform is composed of five ceiling-mounted robots on a gantry-like machine frame and may be divided in smaller independent cells. The multifunctional cell will improve the understanding of requirements of future production processes for lightweight components by providing a highly flexible platform on an industrial scale.
Yang, Hai; Baradat, Cédric; Krut, Sébastien; Pierrot, François
doi: 10.1007/s00170-014-6023-0pmid: N/A
REMORA aims at offering an agile robotic solution for manufacturing tasks done on very large parts (e.g., very long and slender parts found in aeronautic industries). For such tasks, classical machine tools are designed at several tens of meters. Both their construction and operation require huge infrastructure supports. REMORA is a novel lightweight concept and flexible robotic solution that combines the ability of walking and manufacturing. The robot is a mobile manufacturing system which can effectuate operations with good payload capacity and good precisions for large workspace applications. This new concept combines parallel kinematics to ensure high stiffness but low inertia and mobile robotics to operate in very large workspaces. This results in a machining center of new generation: (1) agile manufacturing system for large workspace applications, (2) heavy load and good precisions, (3) 5-axis machining and 5-axis locomotion/clamping, (4) self-reconfigurable for specific tasks (workspace and force), and (5) flexible and multifunctional.
Mendes, N.; Neto, P.; Simão, M.; Loureiro, A.; Pires, J.
doi: 10.1007/s00170-014-6024-zpmid: N/A
The relevance, importance and presence of industrial robots in manufacturing have increased over the years, with applications in diverse new and nontraditional manufacturing processes. This paper presents the complete concept and design of a novel friction stir welding (FSW) robotic platform for welding polymeric materials. It was conceived to have a number of advantages over common FSW machines: it is more flexible, cheaper, easier and faster to setup and easier to programme. The platform is composed by three major groups of hardware: a robotic manipulator, a FSW tool and a system that links the manipulator wrist to the FSW tool (support of the FSW tool). This system is also responsible for supporting a force/torque (F/T) sensor and a servo motor that transmits motion to the tool. During the process, a hybrid force/motion control system adjusts the robot trajectories to keep a given contact force between the tool and the welding surface. The platform is tested and optimized in the process of welding acrylonitrile butadiene styrene (ABS) plates. Experimental tests proved the versatility and validity of the proposed solution.
Leali, Francesco; Vergnano, Alberto; Pini, Fabio; Pellicciari, Marcello; Berselli, Giovanni
doi: 10.1007/s00170-014-6025-ypmid: N/A
Industrial robotics provides high flexibility and reconfigurability supported by a user-friendly programming, but still lacks in accuracy. An effective workcell calibration reduces errors in robot manufacturing and enables robot machining applications. A novel workcell calibration method is embedded in an integrated design framework for an in-depth exploitation of CAD-based simulations and offline programming. The method is composed of two steps: first calibration of the workpiece-independent equipment in the workcell layout and final automated online calibration of workpiece-dependent equipment. The method is finally applied to a changeable robotic workcell for finishing aluminium cast housings for aerospace gear transmissions characterised by complex shapes and by close dimensional and geometrical specifications. Experimental results prove the method effectiveness in enhancing accuracy in robot machining.
Ferreira, Marcos; Costa, Paulo; Rocha, Luís; Moreira, A.
doi: 10.1007/s00170-014-6026-xpmid: N/A
This contribution presents a new system for fast and intuitive industrial robot reprogramming. It is based on a luminous marker built with high-intensity LEDs, which are captured by a set of industrial cameras. Using stereoscopy, the marker supplies 6-DoF human wrist tracking with both position and orientation data. This marker can be efficiently attached to any working tool which then provides a way to capture human skills without further intrusion in the tasks. The acquisition technique makes the tracking very robust against lighting conditions so no environment preparation is needed. The robot is automatically programmed from the demonstrated task which delivers complete abstraction of programming concepts. The system is able to perform in real time, and is low-cost starting with a single pair of industrial cameras though more can be used for improved effectiveness and accuracy. The real-time feature means that the robot is ready to perform as soon as the demonstration is over which carries no overhead of reprogramming times. Also, there is no interference with the task itself since the marker is attached to the work tool and the tracking is contactless; the human operator can then perform naturally. The test bed is a real industrial environment: a spray painting application. A prototype has been developed and installed, and is currently in operation. The tests show that the proposed system enables transferring to the machine the human ability of manipulating a spray gun.
Rooker, Martijn; Wögerer, Christian; Angerer, Alfred; Kopf, Christoph; Capco, Jose; Olarra, Aitor; Fuentes, Elena; Zwicker, Carola; Pichler, Andreas
doi: 10.1007/s00170-014-6027-9pmid: N/A
Automated packaging is becoming more and more interesting for production sites. However, in many companies, the packaging process can only handle a limited amount of products. Most of the time for new products, the packaging system needs to be modified. One of the main components in an automated packaging process is the grasping of the objects that need to be packed. For different products, mostly a different gripping system is required. In this paper, solutions from a research project are presented which enables the flexible grasping of different products. These solutions include flexible pose recognition for different objects, path planning for the recognized objects and finally, a prototypical design for a flexible gripper, which enables handling of various objects of different weight and size.
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