| 41. |
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| 42. |
- Byröd, Martin, 1980, et al.
(författare)
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Efficient Reachability Analysis on Modular Discrete-Event Systems using Binary Decision Diagrams
- 2006
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Ingår i: 8th International Workshop on Discrete Event Systems, WODES 2006; Ann Arbor, MI; United States; 10 July 2006 through 12 July 2006. - 1424400538 ; , s. 288-293
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Konferensbidrag (refereegranskat)abstract
- A well known strategy for handling the exponential complexity of modular discrete event systems is to represent the state space symbolically, using binary decision diagrams (BBDs). In this paper, key success factors in the design of efficient BDD-based reachability algorithms for synthesis and verification are discussed. It is also shown how the modular structure of a discrete event system (DES) can be utilized by taking advantage of the process communication graph and partitioning techniques. A reachability algorithm based on these principles is discussed and a proof of correctness for the algorithm is given.
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| 43. |
- Carlsson, Henrik, 1979-, et al.
(författare)
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Automated Generation of Discrete Event System Simulation Models for Flexible Automation
- 2011
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Ingår i: The 21st International Conference on Flexible Automation and Intelligent Manufacturing. - 9789868729100 ; , s. 825-832, s. 825-832
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Konferensbidrag (refereegranskat)abstract
- Flexible automation cells with rapid product changes are an important competitive advantage for industries today. These cells can increase a company’s productivity and thereby increase their profits. A flexible cell shall be able to handle different products with none or minimal changes to the cell itself. A powerful tool, which can be used to analyse and verify such cells, is discrete event system simulation. Problems such as potential bottlenecks, deadlocks, answers to "what-if" questions and the level of resource utilisation can be gathered. The drawback of discrete event system simulation is that the modelling task is both time consuming and difficult to accomplish. Furthermore, state-of-the-art discrete event system simulation tools that are used in the industry today are not suitable for flexible automation. If the production scenario is changed, e.g. introduction of a new product, the simulation and modelling has to be redone and this is both time consuming and tedious. In this paper a new approach will be presented that enables discrete event simulation models to be generated automatically. The models are generated from information retrieved from a PLM/PDM database system, which is shared among other engineering tools such as robot simulation, CAD and process planning. Hence, when the cell and the database are updated a new model can easily be generated. The database is also connected to the real cell so up-to-date data can be retrieved from the real cell. The model generator described in this paper was implemented and tested in a discrete event system simulation tool and showed promising results. With this approach it is possible to handle flexible automation cells more effectively in a process planning stage.
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| 44. |
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| 45. |
- Carlsson, Henrik, 1979-, et al.
(författare)
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Methods for Reliable Simulation-Based PLC Code Verification
- 2012
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Ingår i: IEEE Transactions on Industrial Informatics. - 1941-0050 .- 1551-3203. ; 8:2, s. 267-278
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Tidskriftsartikel (refereegranskat)abstract
- Simulation-based programmable logic controller (PLC) code verification is a part of virtual commissioning, where the control code is verified against a virtual prototype of an application. With today's general OPC interface, it is easy to connect a PLC to a simulation tool for, e. g., verification purposes. However, there are some problems with this approach that can lead to an unreliable verification result. In this paper, four major problems with the OPC interface are described, and two possible solutions to the problems are presented: a general IEC 61131-3-based software solution, and a new OPC standard solution.
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| 46. |
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| 47. |
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| 48. |
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| 49. |
- Christiansson, Anna-Karin, 1947-, et al.
(författare)
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Low order sampled-data H∞ control
- 2003
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Ingår i: Decision and Control, 2003. Proceedings. 42nd IEEE Conference on. ; 3, s. 2308 - 2313
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Konferensbidrag (refereegranskat)abstract
- A method for obtaining low order sampled-data H∞ controllers is presented. The method is mainly based on a parametric static feedback controller for a plant that is augmented with the controller dynamics. The design of a full-order controller is a convex problem, while the optimisation problem for lower order controllers is non convex. The proposed method starts with design of a full-order sampled-data controller using Riccati equations. Then this controller is reduced by an ordinary model reduction technique, and the reduced controller is used as an initial value for an iterative procedure using linear matrix inequalities (LMIs) in the search for an optimal controller. The matrix inequalities are in fact linear in either the Lyapunov matrix or the static controller matrix, why the solution to the non convex problem fundamentally is given by a bilinear matrix inequality (BMI). The order of the controller is reduced until the closed loop performance degrades too much. Simulations are shown for the control of a time delayed SISO-plant where the controller order can be reduced from 8th to 3rd order. Results are also shown from control of a MIMO-model of a jet engine where the reduction is successful from 15th to 4th order. It is argued that the non convexity is handled efficiently since the procedure uses a model reduction of the full-order controller as initial value.
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| 50. |
- Christiansson, Anna-Karin, 1947-, et al.
(författare)
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Mixed continuous/discrete-time output feedback H∞ control : A unified approach
- 1999
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Ingår i: European Control Conference, ECC 1999 - Conference Proceedings. - 9783952417355 ; , s. 4077-4082
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Konferensbidrag (refereegranskat)abstract
- A Riccati equation (RE) based solution to the H∞ optimal control problem for mixed continuous/discrete-time systems is presented. The results unify a number of recently penetrated H∞ control problems. In the infinite-horizon case a periodic behaviour is assumed, and it is shown how the related continuous RE with jumps can be replaced by an equivalent discrete periodic RE. A related algebraic RE, which involves the system behaviour during one period, then can be formulated and solved by standard methods. Typical applications are control of continuous-time or discrete-time periodic systems, as well as multirate and sampled-data control, including mixed continuous and sampled-data measurements. © 1999 EUCA.
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