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| 3. |
- Bolmsjö, Gunnar, et al.
(författare)
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Task planning for welding applications
- 1993
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Ingår i: Systems, Man and Cybernetics : Systems Engineering in the Service of Humans - Systems Engineering in the Service of Humans. - 0780309111 ; , s. 515-519
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Konferensbidrag (refereegranskat)abstract
- Welding robots that use sensors to compensate for variations in their environment pose new requirements for programming systems and for controller architectures. Tracking sensors must be programmed with the geometry of the welds and the motions of the robot. The process monitoring system must be programmed with the required process tolerances and the type of weld. Finally, the controller must be programmed with the motion parameters, velocity and end-pose. Task planning for welding applications is the specification of the geometrical and the technological parameters that are necessary to the above subsystems. The architecture of the controller also must be process-related to allow the flow of planning information to the different subsystems and the necessary feedback to the planning level. Data from the sensors must be used with path data, process information and the geometry of the welds to adjust the process in real time. This article describes the requirements of process-related programming and real-time control of industrial robots based on sensor data.
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| 4. |
- Bolmsjö, Gunnar, et al.
(författare)
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Task Programming of Welding Robots
- 1995
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Ingår i: Proceedings of the International Conference on the Joining of Materials, JOM-7. ; , s. 573-585
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Konferensbidrag (refereegranskat)
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| 5. |
- De Backer, Jeroen, 1987-
(författare)
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Robotic Friction Stir Welding for Flexible Production
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Friction Stir Welding (FSW) is a modern welding process that joins materials by frictional heat, generated by a rotating tool. Unlike other welding processes, the material never melts, which is beneficial for the weld properties. FSW is already widely adopted in several industries but the applications are limited to simple geometries like straight lines or circular welds, mostly in aluminium. The welding operation is performed by rigid FSW machines, which deliver excellent welds but puts limitations on the system in terms of flexibility and joint geometries. Therefore, several research groups are working on the implementation of the FSW process on industrial robots. A robot allows welding of three-dimensional geometries and increases the flexibility of the whole system. The high process forces required for FSW, in combination with the limited stiffness of the robot brings some extra complexity to the system. The limitations of the robot system are addressed in this licentiate thesis.One part of the thesis studies the effect of robot deflections on the weld quality. A sensor-based solution is presented that measures the path deviation and compensates this deviation by modifying the robot trajectory. The tool deviation is reduced to an acceptable tolerance and root defects in the weld are hereby eliminated. The sensor-based method provided better process understanding, leading to a new strategy that uses existing force-feedback for path compensations of the tool. This method avoids extra sensors and makes the system less complex. Another part of this work focuses on the extra complexity to maintain a stable welding process on more advanced geometries. A model is presented that allows control of the heat input in the process by control of the downforce. Finally, the robot’s limitations in terms of maximal hardness of the materials to be welded are investigated. Parameter tuning and implementation of preheating are proposed to allow robotic FSW of superalloys.
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| 6. |
- Gao, Chuansi, et al.
(författare)
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Using a walkway with adjustable inclination to measure and assess slip and fall risks
- 2014
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Ingår i: Proceedings of CIB W099 International Conference Achieving Sustainable Construction Health and Safety. - 9789176230053 ; , s. 118-124
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Konferensbidrag (refereegranskat)abstract
- Fall is the most common cause of serious work related accidents. Falls and related injuries not only cause suffering for individuals, but also means a high economic burden to industries and society. The objective of the study was to use a walkway with in-built force plate, adjustable inclination and surface to assess how risks of slips and falls vary due to inclination and friction of the walkway surface. A walkway was designed with adjustable slopes between 0 to 30 degrees. Subject walking tests were performed on dry and wet steel sheet surfaces in two walking directions (uphill and downhill) at three inclination angles (0, 5 and 10 degrees). 3D ground reaction forces while walking were recorded using the force plate. Required coefficient of friction (RCOF) was derived to determine slip and fall risks. The main finding of this study is that the RCOF during heel strike when walking downwards on the steel plate surface increases linearly as the inclination increases. The results contribute to the understanding of slipping and falling mechanisms and the prevention of slipping and falling accidents. When ramps or sloped surfaces are used in workplaces, slip resistance between footwear and the sloped surfaces should be improved.
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| 7. |
- Heralic, Almir, 1981-
(författare)
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Towards full Automation of Robotized Laser Metal-wire Deposition
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metal wire deposition by means of robotized laser welding offers great saving potentials, i.e. reduced costs and reduced lead times, in many different applications, such as fabrication of complex components, repair or modification of high-value components, rapid prototyping and low volume production, especially if the process can be automated. Metal deposition is a layered manufacturing technique that builds metal structures by melting metal wire into beads which are deposited side by side and layer upon layer. This thesis presents a system for on-line monitoring and control of robotized laser metal wire deposition (RLMwD). The task is to ensure a stable deposition process with correct geometrical profile of the resulting geometry and sound metallurgical properties. Issues regarding sensor calibration, system identification and control design are discussed. The suggested controller maintains a constant bead height and width throughout the deposition process. It is evaluated through real experiments, however, limited to straight line deposition experiments. Solutions towards a more general controller, i.e. one that can handle different deposition paths, are suggested.A method is also proposed on how an operator can use different sensor information for process understanding, process development and for manual on-line control. The strategies are evaluated through different deposition tasks and considered materials are tool steel and Ti-6Al-4V. The developed monitoring system enables an operator to control the process at a safe distance from the hazardous laser beam.The results obtained in this work indicate promising steps towards full automation of the RLMwD process, i.e. without human intervention and for arbitrary deposition paths.
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| 8. |
- Kihlman, Henrik
(författare)
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Affordable automation for airframe assembly : developing of key enabling technologies
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Building aircraft is a challenging field. An aircraft has a life expectancy of 40 years, compared to just 10 years for a car. Given the vibrations of flying at close to Mach one at an altitude of 10,000 meters, these machines must function flawlessly in a tough environment. This demands high quality in the assembly processes. The typical part joining process in the automotive industry is welding, whereas in the aircraft industry, assembly is made through drilling, followed by fastening. The typical tolerances for part location in aircraft assembly, as well as for hole drilling, is +/- 0.2 mm.This dissertation discusses the use of industrial robots, widely used for welding and pick-and-place operation for automotive industry, in the automation of the aircraft industry, and specifically for the drilling of holes in the assembly process of airframe parts. The dissertation presents how a new drilling technology called orbital drilling is incorporated with and industrial robot. Orbital drilling reduces the cutting forces up to ten times compared to conventional drilling using a spiral cutter.The robot is also utilized for performing changeovers between different airframe structure types. A novel jointed reconfigurable tooling system called Affordable Reconfigurable Tooling (ART) is presented, which uses the robot to reconfigure flexible fixture modules. The ART system can also be rebuilt, which means that the tool is dismantled and reused for a completely different product family (e.g. wings, fins or fuselage sections). This is made possible through a modular framework, i.e. not welded as with conventional tooling, but rather jointed by screws.Robots, originally developed for the automotive industry, have an accuracy which is ten times less accurate than that required for aerospace applications. To help meet this limitation in the use of robots in aircraft assembly, an additional metrology system, used in the aircraft industry for calibrating assembly tooling, is integrated into the robot controller. The feedback loop enables the robot to be positioned to ±0.05 mm absolute accuracy. This integration is made possible by existing embedded software packages for the robot and the metrology system.The processes in the system are programmed in a software package with an intuitive user interface in a 3D-environment, normally used for the offline-programming of robots in automotive industry. The planning is intuitive, and an approach towards a process planning abstraction level is presented where processes are defined directly on the coordinate frames constituting the robot trajectories and manual operations. Tolerance on accuracy requirements are dynamically programmed in the same environment. The metrology system, working online with the robot controller, eliminates most of the calibration work required in traditional robot programming. Changes in the operation planning take less than a minute to run physically with the best tolerance.
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| 9. |
- Nikoleris, Giorgos
(författare)
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A programming system for welding robots
- 1990
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Ingår i: International Journal for the Joining of Materials. - 0905-6866. ; 2:2, s. 55-61
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Nikoleris, Giorgos, et al.
(författare)
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Graphical robot programming: requirements and existing systems
- 1992
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Ingår i: Robotic Systems : Advanced Techniques and Applications - Advanced Techniques and Applications. - 9789401125260 ; 10, s. 451-458
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Bokkapitel (refereegranskat)abstract
- The use of a graphical system for the programming of industrial robots offers a number of advantages. Graphical systems employ an interface that is much easier to use. The resulting motion trajectories can be simulated and tested for collisions or singular points. Contemporary graphical systems use the geometry of the objects that are to be handled or processed in order to generate robot motion trajectories. Robot motions are however constrained by the process requirements which should be one of the main sources of the generation of robot motion trajectories. In this article the methodology of the generation of the robot motion trajectories in three commercial systems is examined as well as the requirements of process-related robot programming with special emphasis on high-quality arc welding.
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