| 1. |
- Christiansson, Anna-Karin, 1947-, et al.
(author)
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Automation of a robotised metal deposition system using laser melting of wire
- 2008
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In: 18th International Conference on<em> </em>Flexible Automation and Intelligent Manufacturing (FAIM 2008). - 9789163327575 ; , s. 122-129
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Conference paper (other academic/artistic)abstract
- This paper presents a system for full automation of free-form-fabrication of fully dense metal structures using robotized laser melting of wire. The structure is built of beads of melted wire laid side by side and layer upon layer governed by synchronized robot motion. By full automation is here meant that the process starts with a product specification of a component, and ends in a geometrically validated dense metal component fulfilling industrial material requirements. Due to the complexity of this flexible manufacturing system, a number of different disciplines are involved. This paper discusses mainly the system design, which includes how off-line programming is used for automatic generation of code and how feedback control is used for on-line adjustment of parameters based on desired building properties. To meet industrial needs, the project is carried out in a close cooperation between research and development activities in academy and industry.
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| 2. |
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| 3. |
- Heralic, Almir, 1981-, et al.
(author)
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Automation of Robotized Laser Metal-Wire Deposition
- 2007
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In: Proceedings of the ninth IASTED International Conference on Control and Applications. - : ACTA Press. - 9780889866652 ; , s. ID 658-075-
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Conference paper (peer-reviewed)
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| 4. |
- Heralic, Almir, 1981-, et al.
(author)
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Control Design for Automation of Robotized Laser Metal-Wire Deposition
- 2008
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In: Proceedings of the 17th IFAC World Congress. - : International Federation of Automatic Control. ; , s. 14785-14791
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Conference paper (other academic/artistic)abstract
- In this paper a novel approach towards automation of robotized laser metal-wire deposition (RLMwD) is described. The RLMwD technique is being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully dense metal structures. The process utilizes robotized fibre laser welding and metal wire filler material, together with a layered manufacturing method, to create metal structures directly from a CAD drawing. The RLMwD process can also be used for repair or modification of existing components. This paper faces the challenge of designing a control system for maintaining stable process variables, such as a constant layer height and a stable component temperature, during the entire manufacturing process. Several problems are identified and discussed in the paper, e.g. the difficulty of obtaining the bead height in the weld pool environment. The case study is a repair application for stamping tools, where worn out trim edges are to be repaired. Issues regarding the control design, system identification, and the practical implementation of this application are discussed.
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| 7. |
- Ryberg, Anders, 1973-, et al.
(author)
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A new Camera Model and Algorithms for higher Accuracy and better Convergence in Vision-based Pose Calculations
- 2006
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In: Mechatronics and Automation, Proceedings of the 2006 IEEE International Conference on. - 1424404657 ; , s. 194-199
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Conference paper (peer-reviewed)abstract
- This paper presents novel strategies for better calibration and pose calculations of a system for determining the pose, i.e. position and orientation, of a camera. The system in question has a camera aimed to be placed on the hand of an industrial robot for welding, but is useful for any application with a need for measuring position and/or orientation. To calculate the pose of the camera circular reference points that can be recognized in the images are distributed in the working area. From their 2D image coordinates the 6D pose of the camera can be calculated. First the system is calibrated, i.e. the positions of the reference points and the camera parameters are determined. This is done by first taking images of the reference points from different locations, and then do a "total calibration" procedure to calculate the unknown parameters. For a specific system, called PosEye, it was concluded that the accuracy needs to be improved for welding applications. Also a method for making the calculations converge more easily, was needed. To meet these demands a new camera model is proposed, and three preprocessing calculation steps are presented. The new camera model increases accuracy by considering more distortion effects. The preprocessing steps give better initial values for more robust convergence of the algorithms and increased accuracy
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| 8. |
- Ryberg, Anders, 1973-, et al.
(author)
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A new Camera Model for Higher Accuracy Pose Calculations
- 2006
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In: Industrial Electronics, 2006 IEEE International Symposium on Industrial Electronics. - 1424404967 ; , s. 2798-2802
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Conference paper (peer-reviewed)abstract
- A position and orientation (pose) measurement system is being developed. The system, called PosEye, is based on a camera and by using the information in the image, the pose of the camera taking the image can be calculated. The system is aimed to be placed on an industrial robot for welding, but it is flexible and can also be used in many other applications. The accuracy has been measured, and it is concluded that the accuracy needs to be improved for welding applications. To make the pose measurement, reference points, that can be recognized in the image, are distributed in the working area. The positions of the reference points and the parameters in a camera model are initially computed automatically from sample images from a number of directions to the reference points. After this calibration, the pose can be calculated at each sample image. For high accuracy there is a need to have a camera model that takes into account a number of distortion effects, which are further developed in this paper. The new model is used to express an optimization cost function that can be used for both the pose calculation, and the extensive calibration, that determines camera parameters in the camera model and the positions of the reference points
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| 9. |
- Ryberg, Anders, 1973-, et al.
(author)
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Accuracy Investigation of a Vision Based System for Pose Measurements
- 2006
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In: Control, Automation, Robotics and Vision, 2006. ICARCV '06. 9th International Conference on. - 1424403413 ; , s. 1-6
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Conference paper (other academic/artistic)abstract
- The accuracy of a pose measurement system, called PosEye, is investigated. PosEye is a system for real time measurement of the position and orientation, the pose, of a camera (sensor) using the information in its image. This sensor is aimed to be mounted on an industrial robot for welding. The investigation was done by comparing the PosEye system position output to that of a coordinate measuring machine. Sources of errors are identified, and suggestions for improvements are made
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| 11. |
- Sikström, Fredrik, 1971-, et al.
(author)
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3D-Scanning for Weld Distortion Measuring
- 2006
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In: Instrumentation and Measurement Technology Conference, 2006. IMTC 2006. Proceedings of the IEEE. - : IEEE conference proceedings. - 0780393600 - 0780393597 ; , s. 2132-2137
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Conference paper (peer-reviewed)abstract
- Optical three dimensional scanning for weld distortion measurements have been performed for validation, inspection, general visualization and documentation of a robotized welding process. The planning, preparing and processing of the weld is done in a simulation-based concept where computer aided robotics software simulations are integrated with finite element analysis simulations with the objective to reduce global geometrical deformation during welding. The off-line programmed robot paths were used as an input for finite element calculations of temperature fields and distortion in the work piece. In order to validate the finite element model 3D-scannings have been performed before and after every single welding sequence. This paper describes a validation experiment with non-contact measurements of weld distortion and discusses limitations in optical 3D-scanning techniques used for this purpose
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| 12. |
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| 13. |
- Sikström, Fredrik, 1971-, et al.
(author)
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Simulated Feedback Control of Metal Fusion Welding
- 2007
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In: Proceedings of the ninth IASTED International Conference on Control and Applications. - : ACTA Press. - 9780889866652 ; , s. 2263-2270
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Conference paper (peer-reviewed)
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| 14. |
- Sikström, Fredrik, 1971-, et al.
(author)
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Simulation for Design of Automated Welding
- 2007
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In: EUROCON, 2007. The International Conference on "Computer as a Tool". - : IEEE Explore. - 142440813X - 9781424408139 ; , s. 2263-2270
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Conference paper (peer-reviewed)abstract
- This paper describes a promising approach where simulations were used in the design of real-time control for automated welding. A finite element method has been used for thermal modelling of gas tungsten arc welding on a simplified test object. Measurement data for model calibration and validation was acquired through thermal imaging during weld experiments on test objects of the alloy Fe-316. An optimisation scheme for inverse modelling was employed in the calibration of the distributed weld process model. Frequency weighted model reduction and parametric system identification were applied and evaluated to get a low order model of the single-input single-output dynamics between a simulated weld heat source (actuator) and a sensor. This low order model was then successfully used for controller design where the control signal was weld current and the measured output was a moving spot temperature. Finally, the closed-loop performance was evaluated by simulation of the weld process model showing improved temperature stability relative to open loop.
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| 15. |
- Sikström, Fredrik, 1971-, et al.
(author)
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Tools for simulation based fixture design to reduce deformation in advanced fusion welding
- 2008
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In: Intelligent Robotics and ApplicationsLecture Notes in Computer Science Volume 5315, 2008. - Berlin, Heidelberg : Springer. ; , s. 398-407
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Conference paper (peer-reviewed)abstract
- The traditional fusion welding and fixture simulations are performed using advanced finite element simulation tools, commonly used are e.g. MSC.Marc, ANSYS, ABACUS and COMSOL Multiphysics. These simulations are made one at a time and separately due to heavy calculation load for each case. Such an approach does not give a full description of the integrated work piece and fixture behaviour. We propose a strategy to decrease the computational time and solve the problem accurately enough for industrial needs. Focus of the simulation result is on residual deformation. The work piece is a simplified component composed by metal sheets, and rigid and loose clamping was investigated. Simulation results give the size of forces and deformations in the clamped edge. Deformation measurements are performed using 3D-scanning of the work piece after cooling and released from fixture, same situation as in the FE-simulations. The proposed strategy has shown to be useful and is industrially competitive due to reduced engineering manpower, computation time, and need for practical experiments. The strategy is to use full off-line programming where computer aided robotics for weld sequencies is integrated with finite element modelling in order to obtain weld parameters and fixture design.
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| 16. |
- Yücel, Baris, et al.
(author)
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Automatic Generation of Multivariable Sampled-data Controllers for Jet-engines
- 2006
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In: Proceedings of Reglermöte 2006.
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Conference paper (other academic/artistic)abstract
- In this contribution, it is shown how multivariable sampled-data controllers can be generated for a set of linearized models. The size of this set makes an automatic generation of controllers more practical and less time consuming. The control strategy is robust loopshaping according to Glover/McFarlane. The generated controllers are to be used for the military turbofan engine F404-RM12 which is currently used in the Swedish air fighter JAS39 Gripen.
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