| 1. |
- Alenljung, Tord, 1977, et al.
(författare)
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Sensor Graphs for Discrete Event Modeling Applied to Formal Verification of PLCs
- 2012
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Ingår i: IEEE Transactions on Control Systems Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 1063-6536 .- 1558-0865. ; 20:6, s. 1506-1521
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces Sensor Graphs, a discrete event modeling language directed at physical systems with binary and identity sensors (e. g., RFID). The aim of Sensor Graphs is to simplify the modeling of the plant/process that is to be controlled by a discrete controller, for example a programmable logic controller (PLC); thereby making formal verification and other model-based formal methods more applicable for PLC programmers. The formal syntax and semantics of Sensor Graphs are defined and a compact graphical representation is presented. The language is exemplified by modeling a conveyor module and a lab process. For comparison, the latter is also modeled using Statecharts and Net Condition/Event systems. A controller, modeled as a discrete state equation, can be composed with a Sensor Graph of the process in order to form a model of the closed-loop system. It is demonstrated how requirements on such a closed-loop system, based on a PLC program and a Sensor Graph process model, can be formally verified using the model checker Cadence SMV.
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| 2. |
- Andersson, Kristin, 1976, et al.
(författare)
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Coordination of Operations by Relation Extraction for Manufacturing Cell Controllers
- 2010
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Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 18:2, s. 414-429
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Tidskriftsartikel (refereegranskat)abstract
- A method for generation of the control function for flexible manufacturing cells is presented in this paper. The control function is separated from the rest of the PLC program, and partitioned into a high-level part handling the operation sequence and a low-level part defining the execution process of the operations. The program structure enables high-level supervisor synthesis, which alleviates the state-space explosion problem. Information present in earlier steps of the development process is reused and processed, to automatically generate the automata needed for supervisor synthesis. An algorithm for generating automata, from the low-level safety requirements that restrict the high-level behavior, is presented. Algorithms are also presented for extracting the relations between the operations defining the work in the cell, from the synthesized supervisor. These relations give an easy-to-read representation of the control function that makes it interpretable by machine operators and maintenance personnel, an important feature to make the method applicable in an industrial setting. Hence, the control function generated by our method combines the benefits of a traditional supervisor, namely optimality and flexibility, with simplicity and clarity.
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| 3. |
- Andersson, Kristin, 1976, et al.
(författare)
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Generation of restart states for manufacturing cell controllers
- 2011
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 19:9, s. 1014-1022
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Tidskriftsartikel (refereegranskat)abstract
- A method for restart of manufacturing systems has recently been introduced. After correction of a fault. the system resumes normal production by returning to a certain restart state in the control function. and from there reexecuting parts of the work schedule. The current paper concerns automatic generation of the restart states, using discrete event systems theory. The generation process finds all possible restart states that guarantee that the execution restrictions are fulfilled during a restart, and that the production goals can be maintained. The number of restart states is minimized to reduce the number of necessary extensions to the control program. (C) 2011 Elsevier Ltd. All rights reserved.
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| 4. |
- Andersson, Kristin, 1976, et al.
(författare)
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Restarting manufacturing systems; restart states and restartability
- 2010
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 7:3, s. 486-499
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Tidskriftsartikel (refereegranskat)abstract
- A method for restart after an error in a manufacturing system is introduced. The method is able to restart systems even after nonforeseen errors that cannot be planned for, and the online part of the restart method does not require use of more powerful computers than a standard Programmable Logic Controller. It is shown what properties the control function must have to ensure that there is at least one restart state for each controller state. Sufficient conditions to guarantee the possibility to restart a system regardless of where an error occurs are given, along with indications on how the system could otherwise be rebuilt to be restartable.
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| 5. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Developing control logic using aspect-oriented programming and sequence planning
- 2013
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 21:1, s. 12-22
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental functionality of a Programmable Logic Controller (PLC) is to control and execute a set of operations. But a large part of the program code is more involved in supporting the user with concerns like alarm, HMI, communication, safety and manual control. Code related to these supporting concerns is often tangled with operation execution code, the core concerns, which makes it hard to reuse.This paper describes a method to reuse code and functionality when developing PLC programs and code libraries. The method proposes that core concerns are planned with a software tool called Sequence Planner, and the supporting concerns are integrated into the core concerns with a tool based on aspect-oriented programming.
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| 6. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Flexible Specification of Operation Behavior Using Multiple Projections
- 2014
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 11:2, s. 504 - 515
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Tidskriftsartikel (refereegranskat)abstract
- The execution behavior of a system or a product can often be specified by a set of operations (sometimes called tasks, actions or activities). The process to specify these operations seems to be a real challenge in various situations, for example when designing automation systems or keeping track of the work at an emergency department. To be flexible during design and development, is about coping with uncertainty. However, in practice, specifying operation behavior is often quite inflexible because every possible execution route is explicitly defined. This approach is sometimes refereed to as point-based engineering, which is characterized by the early selection and approval of a single "best" specific solution. This approach can result in neither a robust nor a flexible design process with many rework iterations.
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| 7. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Operation Behavior Modeling using Relation Identification and Visualization Algorithms
- 2013
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; , s. 368 - 373
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Konferensbidrag (refereegranskat)abstract
- The behavior of a system can be described by a set of operations - sometimes called activities or tasks. The process to specify these operation seems to be a real challenge in various situations, for example when designing automation systems or keeping track of the work at an emergency department. In practice, operation behavior specification is often quite inflexible because every possible execution route is explicitly defined. In this paper, a modeling method and a relation identification and visualization algorithm is introduced that does not explicitly specify operation routes, where instead the operation behavior is specified using the execution restrictions in transition conditions for each operation. This enables the possibility to create multiple projections of the operation relations to enable better understanding.
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| 8. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Patient coordination in emergency departments using an event-based information architecture
- 2014
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Ingår i: The 19th IEEE International Conference on Emerging Technologies and Factory Automation. - 9781479948451 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- It is challenging to get an overview and understanding of the activities and their relations at an emergency department (ED). This is due to the complicated relations among activities - called operations in this paper - and the always changing system behavior. Two key enablers to get this overview are the transformation of real-time events into understandable information and an operation-based behavior description. This paper presents an event-based information architecture for healthcare (EVAH) for gathering state changing events in real-time at an ED and how these are transformed into an operation-based representation. EVAH together with the tool Sequence Planner, will be used for visualization, online prognosis and optimization.
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| 9. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Patient coordination in emergency departments using visualization of operation behavior
- 2013
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Ingår i: Proceedings of the 2013 IEEE Symposium on Computational Intelligence in Healthcare and e-Health, CICARE 2013 - 2013 IEEE Symposium Series on Computational Intelligence, SSCI 2013. - 9781467358835 ; , s. 58-63
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Konferensbidrag (refereegranskat)abstract
- It is challenging to get an overview and understanding of the activities and their relations at an emergency department (ED). This is due to the complicated relations among activities called operations in this paper and the always changing system behavior. This paper presents a method to represent and visualize operations during the actual work at the ED that enables flexibility during modeling and actual care. By specifying operation behavior using only execution restrictions in transition conditions for each operation instead of fixed sequences, the method and related visualization tool can describe the ever changing and complex ED flows. Using the proposed approach, the ED staff will therefore have the possibility to in a better way coordinate the operations due to the increased overview.
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| 10. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Relations Identification and Visualization for Sequence Planning and Automation Design
- 2010
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Ingår i: In Proc. IEEE Conference on Automation Science and Engineering, Toronto. - 9781424454471 ; , s. 841 - 848
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Konferensbidrag (refereegranskat)abstract
- The sequential behavior of a manufacturing system results from a number of constraints introduced both in product, manufacturing and control logic development. Sequence planning is therefore an important activity throughout the complete development process. This paper proposes a sequence planning approach using self-contained manufacturing operations that model actions and relevant execution conditions. These operations can have temporal relations with each other, due to execution constraints expressed by operation pre- post- and reset conditions. The operation relations can for example be parallel, sequence, arbitrary order, alternative or hierarchy. Based on a formal operation model, the relations among operations are identified and visualized with a graphical language called Sequences of Operations, SOP.
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