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- Adlemo, Anders, 1957, et al.
(author)
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Towards a True Flexible Manufacturing System
- 1994
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In: Proc of the 10th ISPE/IFAC Int. Conference on CAD/CAM, Robotics and Factories of the Future, CARS & FOF '94, Ottawa, Canada. ; , s. 401-410
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Conference paper (peer-reviewed)
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- Alenljung, Tord, 1977, et al.
(author)
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Semantics of sensor activation graphs
- 2006
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In: Proceedings of the 2006 IEEE Conference on Automation Science and Engineering, Shanghai, China.
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Conference paper (peer-reviewed)
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| 8. |
- Alenljung, Tord, 1977, et al.
(author)
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Sensor Graphs for Discrete Event Modeling Applied to Formal Verification of PLCs
- 2012
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In: 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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Journal article (peer-reviewed)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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- Alenljung, Tord, 1977, et al.
(author)
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Simplified modeling of manufacturing systems: an introduction to sensor activation graphs
- 2005
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In: Automation Science and Engineering, 2005. IEEE International Conference on. ; , s. 261- 266
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Conference paper (peer-reviewed)abstract
- This paper presents a graphical modeling formalism, sensor activation graphs, which simplifies the design of discrete event models for a class of physical systems common within manufacturing industry. Sensor activation graphs captures, in an intuitive way, the relations between binary sensors, the physical entities that activate them, and the actuators of the system. Models expressed as sensor activation graphs are in most cases significantly simpler than corresponding automata or Petri net models. The presented formalism support two levels of detail, one that gives the general view on the order of sensor activation, and one with full control semantics that incorporates guard conditions on transitions. In addition, an algorithm for converting sensor activation graphs into a number of small deterministic finite state automata is presented.
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| 10. |
- Andersson, Kristin, 1976, et al.
(author)
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Coordination of Operations by Relation Extraction for Manufacturing Cell Controllers
- 2010
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In: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 18:2, s. 414-429
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Journal article (peer-reviewed)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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