| 1. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Efficient sequencing of industrial robots through optimal control
- 2014
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Ingår i: 5th CIRP Conference on Assembly Technologies and Systems, November 13-14, 2014, Dresden, Germany. - : Elsevier BV. - 2212-8271. ; 23:C, s. 194-199
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Konferensbidrag (refereegranskat)abstract
- In a production plant for complex assembled products there could be up to several hundred robots used for handling and joining operations. Thus, improvements in robot motion can have a huge impact on equipment utilization and energy consumption. By combining recent algorithms for collision free numerical optimal control and for optimal sequencing, we are able to cut down on energy consumption without sacrificing cycle time. The algorithm has been successfully applied to several industrial cases demonstrating that the proposed method can be used effectively in practical applications to find fast and energy efficient solutions.
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| 2. |
- Carlson, Johan, 1972, et al.
(författare)
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Minimizing Dimensional Variation and Robot Traveling Time in Welding Stations
- 2014
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 23:C, s. 77-82
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Konferensbidrag (refereegranskat)abstract
- Complex assembled products as an automotive car body consist of about 300 sheet metal parts joined by up to 4000 spot welds. In the body factory, there are several hundred robots organized into lines of welding stations. The distribution of welds between robots and the welding sequences have a significant influence on both dimensional quality and throughput. Therefore, this paper proposes a novel method for quality and throughput optimization based on a systematic search algorithm which exploits properties of the welding process. It uses approximated lower bounds to speed up the search and to estimate the quality of the solution. The method is successfully tested on reference assemblies, including detailed fixtures, welding robots and guns.
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| 3. |
- Carlson, Johan, 1972, et al.
(författare)
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Non-nominal path planning for robust robotic assembly
- 2013
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Ingår i: Journal of Manufacturing Systems. - : Elsevier BV. - 0278-6125. ; 32:3, s. 429-435
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Tidskriftsartikel (refereegranskat)abstract
- In manufacturing and assembly processes it is important, in terms of time and money, to verify the feasi-bility of the operations at the design stage and at early production planning. To achieve that, verificationin a virtual environment is often performed by using methods such as path planning and simulation ofdimensional variation. Lately, these areas have gained interest both in industry and academia, however,they are almost always treated as separate activities, leading to unnecessary tight tolerances and on-lineadjustments.To resolve this, we present a novel procedure based on the interaction between path planning tech-niques and variation simulation. This combined tool is able to compute robust assembly paths forindustrial robots, i.e. paths less sensitive to the geometrical variation existing in the robot links, in itscontrol system, and in the environment. This may lead to increased productivity and may limit errorsources. The main idea to improve robustness is to enable robots to avoid motions in areas with highvariation, preferring instead low variation zones. The method is able to deal with the different geometricalvariation due to the different robot kinematic configurations. Computing variation might be a computa-tionally expensive task or variation data might be unavailable in the entire state space, therefore threedifferent ways to estimate variation are also proposed and compared. An industrial test case from theautomotive industry is successfully studied and the results are presented.
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| 4. |
- Flordal, Hugo, 1977, et al.
(författare)
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Supervision of Multiple Industrial Robots - Optimal and Collision Free Work Cycles
- 2004
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Ingår i: Proceedings of the IEEE Conference on Control Applications, Taipei, Taiwan, 2-4 Sept. 2004. ; 2, s. 1404 - 1409
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Konferensbidrag (refereegranskat)abstract
- A method for automatic generation of collision free, blocking free and work cycle time optimized supervisors for industrial robot cells has been implemented. The individual robots' tasks are specified as a set of targets that the robot should visit in arbitrary order. Finite automaton models of allocation and release of critical spatial volumes that the robots share, as well as models of the robots' possible movements are automatically extracted from a 3D simulation environment. This includes explicitly calculating the intersection between the robots' work envelopes, the spatial volumes where collisions may occur, and simulating the robots' collisions with these. Each robot's different sequences of operations of factorial complexity in the number of states are efficiently represented as a set of automata using a polynomial number of states. The automatically generated system model is analyzed using the Ramadge-Wonham supervisory control theory to verify nonlocking and to synthesize supervisors. The method guarantees collision freeness, nonblocking and a flexible coordination function. The model is also used to find the time optimal work cycle for completion of the robots' tasks. To meet market demands of mass customization and shorter time to market, more flexible manufacturing systems are needed. The method presented here aims to automatize robot coordination programming which, being a tedious manual task in today's industry, is a bottleneck in the development of old and new production lines.
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| 5. |
- Hanson, Lars, et al.
(författare)
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Industrial path solutions - intelligently moving manikins
- 2019
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Ingår i: DHM and Posturography. - London : Academic Press. - 9780128167137 ; , s. 115-124
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- IPS IMMA (Industrial Path Solutions - Intelligently Moving Manikins) is a digital human modeling tool developed in close cooperation between academia and industry in Sweden. The academic consortium behind the software consists of expertise within applied mathematics, ergonomics, and engineering. The development of IMMA was initiated from the vehicle industries’ need of an effective, efficient, objective, and user-friendly software for verification of manufacturing ergonomics. The ‘Industrial path solutions - intelligently moving manikins’ chapter consists of two main sections: the first about the commercially available tool, and the second about current or recent research projects developing the software further. Commercial IPS IMMA is presented by describing the biomechanical model and appearance, anthropometrics module, motion prediction, instruction language, and ergonomics evaluation. The research projects focus on dynamic motions simulation, muscle modelling and application areas such as human-robot collaboration, occupant packaging, and layout planning.
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| 6. |
- Kobetski, Avenir, 1977, et al.
(författare)
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Scheduling Algorithms for Optimal Robot Cell Coordination - a Comparison
- 2006
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Ingår i: Proc. of IEEE Conference on Automation Science and Engineering. - 1424403103 ; , s. 381-386
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Konferensbidrag (refereegranskat)abstract
- Flexibility is the keyword in the modern industrial world. Automatic generation of collision- and blocking free, time optimal schedules for industrial robot cells is thus motivated. While a lot of attention has been paid to the control of industrial systems, as well as to the development of general optimization algorithms, there is still a need to properly combine these two research areas. This paper discusses two scheduling algorithms, designed for industrial robot cells, in terms of performance. A novel heuristic to an A*-based algorithm, operating on Discrete Event Systems, is proposed and benchmarked against the well-known MILP algorithm.
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| 7. |
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| 8. |
- Spensieri, Domenico, 1978, et al.
(författare)
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An Iterative Approach for Collision Free Routing and Scheduling in Multirobot Stations
- 2016
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 13:2, s. 950-962
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Tidskriftsartikel (refereegranskat)abstract
- This work is inspired by the problem of planning sequences of operations, as welding, in car manufacturing stations where multiple industrial robots cooperate. The goal is to minimize the station cycle time, i.e., the time it takes for the last robot to finish its cycle. This is done by dispatching the tasks among the robots, and by routing and scheduling the robots in a collision-free way, such that they perform all predefined tasks. We propose an iterative and decoupled approach in order to cope with the high complexity of the problem. First, collisions among robots are neglected, leading to a min–max Multiple Generalized Traveling Salesman Problem (MGTSP). Then, when the sets of robot loads have been obtained and fixed, we sequence and schedule their tasks, with the aim to avoid conflicts. The first problem (min–max MGTSP) is solved by an exact branch and bound (B&B) method, where different lower bounds are presented by combining the solutions of a min–max set partitioning problem and of a Generalized Traveling Salesman Problem (GTSP). The second problem is approached by assuming that robots move synchronously: a novel transformation of this synchronous problem into a GTSP is presented. Eventually, in order to provide complete robot solutions, we include path planning functionalities, allowing the robots to avoid collisions with the static environment and among themselves. These steps are iterated until a satisfying solution is obtained. Experimental results are shown for both problems and for their combination. We even show the results of the iterative method, applied to an industrial test case adapted from a stud welding station in a car manufacturing line.
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| 9. |
- Spensieri, Domenico, 1978
(författare)
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Collision-free path coordination and cycle time optimization of industrial robot cells
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In industry, short ramp-up times, product quality, product customization and high production rates are among the main drivers of technological progress. This is especially true for automotive manufacturers whose market is very competitive, constantly pushing for new solutions. In this industry, many of the processes are carried out by robots: for example, operations such as stud/spot welding, sealing, painting and inspection. Besides higher production rates, the improvement of these processes is important from a sustainability perspective, since an optimized equipment utilization may be achieved, in terms of resources used, including such things as robots, energy, and physical prototyping. The achievements of such goals may, nowadays, be reached also thanks to virtual methods, which make modeling, simulation and optimization of industrial processes possible. The work in this thesis may be positioned in this area and focuses on virtual product and production development for throughput improvement of robotics processes in the automotive industry. Specifically, the thesis presents methods, algorithms and tools to avoid collisions and minimize cycle time in multi-robot stations. It starts with an overview of the problem, providing insights into the relationship between the volumes shared by the robots' workspaces and more abstract modeling spaces. It then describes a computational method for minimizing cycle time when robot paths are geometrically fixed and only velocity tuning is allowed to avoid collisions. Additional requirements are considered for running these solutions in industrial setups, specifically the time delays introduced when stopping robots to exchange information with a programmable logic controller (PLC). A post-processing step is suggested, with algorithms taking into account these practical constraints. When no communication at all with the PLC is highly desirable, a method of providing such programs is described to give completely separated robot workspaces. Finally, when this is not possible (in very cluttered environments and with densely distributed tasks, for example), robot routes are modified by changing the order of operations to avoid collisions between robots. In summary, by requiring fewer iterations between different planning stages, using automatic tools to optimize the process and by reducing physical prototyping, the research presented in this thesis (and the corresponding implementation in software platforms) will improve virtual product and production realization for robotic applications.
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| 10. |
- Spensieri, Domenico, 1978, et al.
(författare)
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Collision-free robot coordination and visualization tools for robust cycle time optimization
- 2021
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Ingår i: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents novel algorithms and visualization tools for avoiding collisions and minimizing cycle time in multi-robot stations by velocity tuning of robot motions. These tools have the potential to support product/manufacturing engineers in the practical task of adding synchronization instructions to robot programs to overcome the challenges in terms of product design, cycle time, quality control, and maintenance including re-usability of coordination schemes. We propose a range of techniques to achieve that, when additional requirements make the best coordination strategy hard to be chosen. Indeed, our main contributions are (i) considering and minimizing delays introduced by limitation in hardware synchronization mechanisms, (ii) highlighting insights on the relationship between a 3D working space and a path coordination space, and (iii) a computational tool for visualization of shared areas in both work space and path coordination space. Different strategies based on the developed algorithms are evaluated by successfully automatically solving industrial test cases from inspection measurement applications in the automotive industry. A study about how cycle time robustness is significantly influenced by variation in the robot motion execution times is also given.
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