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- Flordal, Hugo, 1977, et al.
(author)
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Automatic Multi Robot Coordination
- 2003
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In: Konferensprogram för Mekatronikmötet 2003, Göteborg, Sweden.
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Conference paper (peer-reviewed)
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- Flordal, Hugo, 1977, et al.
(author)
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Supervision of Multiple Industrial Robots - Optimal and Collision Free Work Cycles
- 2004
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In: Proceedings of the IEEE Conference on Control Applications, Taipei, Taiwan, 2-4 Sept. 2004. ; 2, s. 1404 - 1409
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Conference paper (peer-reviewed)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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- Hellgren, Anders, 1970, et al.
(author)
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Modelling and PLC-based Implementation of Modular Supervisory Control
- 2002
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In: Proceedings of the 6th Workshop on Discrete Event Systems, Zaragoza, Spain, OCT 02-04, 2002. ; , s. 371-376
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Conference paper (peer-reviewed)abstract
- Implementation of supervisory control in Programmable Logic Controllers (PLCs) typically requires that the underlying discrete event models of plant, specification as well as the supervisor itself fulfil a number of properties. These properties are discussed and methods for solving related problems are given. In particular, determinism and synchronisation issues are investigated.In a manufacturing system, for instance, there are typically a set of processes using a set of shared resources. Uncareful modelling may cause the system model to become nondeterministic. This can be circumvented by relabelling the relevant models. For industrial-sized models, though, this must be done automatically, something that we achieve by parameterising the models.Given a deterministic model, consisting of several interacting entities, we discuss its PLC-based implementation. In addition to the synchronisation of plant and supervisor, a modular supervisor must be internally synchronised. However, synchronisation of the submodules is not well defined in the PLC-world. This may be achieved by using event monitors and an immediate transit/immediate action execution model.
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- Hellgren, Anders, 1970, et al.
(author)
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Modular Implementation of Discrete Event Systems as Sequential Function Charts Applied to an Assembly Cell
- 2001
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In: Proceedings of the 2001 IEEE Conference on Control Applications, SEP 05-07, 2001 Mexico City, Mexico. - 0780367332 ; , s. 453-458
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Conference paper (peer-reviewed)abstract
- Modular implementation of discrete event models in Programmable Logic Controllers (PLCs) using Sequential Function Charts (SFCs) is investigated. Synchronisation of such models, typically finite state automata of Petri nets, is not well defined in the synchronous PLC-world. We develop an algorithm that computes event monitors for synchronising concurrently executing SFCs. The methodology is applied to an assembly cell.
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