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- Flordal, Hugo, 1977, et al.
(författare)
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Automatic model generation and PLC-code implementation for interlocking policies in industrial robot cells
- 2007
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 15:11, s. 1416-1426
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Tidskriftsartikel (refereegranskat)abstract
- In industrial production lines, for example in the automotive industry, cells with multiple industrial robots are common. In such cells, each robot has to avoid running into static obstacles and when the robots work together in a shared space they must also avoid colliding with each other. Typically. the latter is enforced by manually implementing interlocks in programmable logic controllers (PLCs). This is a tedious. error-prone task that is a bottleneck in the development of production lines. The PLC-code being man-made also greatly complicates the maintenance and reconfiguration of such production lines. However, in industry today, a lot of development of robot cells is made offline in 3D simulation environments which enables the use of computers also for deciding and implementing the necessary coordination. This paper presents a method that makes use of information in a robot simulation environment in order to automatically extract finite state models. These models can be used to generate supervisors for ensuring that the deadlock situations that may arise as a consequence of the introduced interlocks are avoided. It is also possible to optimize the work cycle time for the cell. Finally, PLC-code to supervise the production cell can be automatically generated from the deadlock-free and possibly optimized system model. This approach results in a high flexibility in that the coordination function can be quickly reimplemented whenever necessary. A prototype implementation has been developed making use of a commercial 3D robot simulation tool, and a software tool for supervisor synthesis and code generation. The approach is general and should be possible to implement in most offline robot simulation tools. (c) 2007 Elsevier Ltd. All rights reserved.
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- Flordal, Hugo, 1977, et al.
(författare)
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Automatic Multi Robot Coordination
- 2003
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Ingår i: Konferensprogram för Mekatronikmötet 2003, Göteborg, Sweden.
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Konferensbidrag (refereegranskat)
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- Flordal, Hugo, 1977
(författare)
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Compositional Approaches in Supervisory Control with Application to Automatic Generation of Robot Interlocking Policies
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work presented in this thesis concerns verification and synthesis in the Ramadge and Wonham supervisory control framework. Supervisory control constitutes a formal framework for the design of supervisors for discrete event systems. These systems usually model high level descriptions of logical behaviours in applications such as flexible manufacturing processes, chemical batch processing systems and communication systems. The supervisory control framework has the potential to solve many safety and flexibility issues in such systems. Unfortunately, the analysis of discrete event systems involves an intrinsic difficulty known as the state-space explosion problem---a combinatorial explosion that soon occurs when problems of real-world complexity are analysed. The state-space explosion problem has given rise to much research and in the last decades many ingenious approaches to solving the problem have been presented. However, most of these approaches have in common that they can only be applied to special classes of supervisory control problems or that they only give partial solutions.Therefore, in a new attempt to overcome the state-space explosion problem for general supervisory control problems, this thesis develops compositional methods for verification and synthesis in the supervisory control framework. Compositional methods exploit the inherent modularity of discrete event models by using abstractions to incrementally hide already analysed behaviour of the system. A major part of the thesis concerns developing a methodology for calculating these abstractions and for applying the compositional approach to complex problems. Furthermore, a very important part of this work is the implementation of the compositional methods in a software tool for supervisory control. Experimental results from this implementation are also presented in the thesis.As a matter of fact, earlier work on computational complexity have shown that it is impossible to solve the state-space explosion problem efficiently for general problems. Even so, the results presented in this thesis show that ``large'' supervisory control problems found in the litterature typically have enough structure in them to be solved efficiently by compositional methods.Another contribution of this thesis is the development of a method to automatically generate models of the necessary interlocking requirements with respect to robot collisions in industrial robot cells. The generated models are suitable for supervisor synthesis in the supervisory control framework as well as for work-cycle optimisation. Automatic model generation and synthesis are important factors for shortening the development time and improving the flexibility for industrial robot cells.
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- Flordal, Hugo, 1977, et al.
(författare)
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Compositional Synthesis of Maximally Permissive Supervisors Using Supervision Equivalence
- 2007
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Ingår i: Discrete Event Dynamic Systems: Theory and Applications. - : Springer Science and Business Media LLC. - 0924-6703 .- 1573-7594. ; 17:4, s. 475-504
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a general framework for efficient synthesis of supervisors for discrete event systems. The approach is based on compositional minimisation, using concepts of process equivalence. In this context, a large number of ways are suggested how a finite-state automaton can be simplified such that the results of supervisor synthesis are preserved. The proposed approach yields a compact representation of a least restrictive supervisor that ensures controllability and nonblocking. The method is demonstrated on a simple manufacturing example to significantly reduce the number of states constructed for supervisor synthesis. © 2007 Springer Science+Business Media, LLC.
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- Flordal, Hugo, 1977, et al.
(författare)
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Compositional Verification in Supervisory Control
- 2009
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Ingår i: SIAM Journal on Control and Optimization. - : Society for Industrial & Applied Mathematics (SIAM). - 1095-7138 .- 0363-0129. ; 48:3, s. 1914-1938
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a compositional approach to verifying whether a large discrete event system is nonblocking. The new approach avoids computing the synchronous product of a large set of finite-state machines. Instead, the synchronous product is computed gradually, and intermediate results are simplified using conflict-preserving abstractions based on process-algebraic results about fair testing. Heuristics are used to choose between different possible abstractions. By translating the problem representation, the same method can also be applied to verify safety properties, in particular, controllability. Experimental results show that the method is applicable to finite-state machine models of industrial scale and brings considerable improvements in performance over other methods for nonblocking verification.
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