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Theses

Aide à la conception des systèmes embarqués sûrs de fonctionnement

Abstract : Embedded systems run the computing devices hidden inside another larger system or product. Embedded systems have the charge of controlling various types of sub-systems; they are also in charge of the monitoring of the whole system and coordination with other systems. This means that when some event affecting the safety of the system occurs, a reconfiguration action is executed in order to maintain the system in a safe degraded state. If the reconfiguration fails then the system will reach a feared (dangerous) state with dramatic consequences for users. So it is important to understand how the system reaches such feared states to set up the reconfiguration actions. In our approach for safety analysis of dynamic systems, feared scenarios are derived from Petri net model. Based on linear logic as new representation (using the causality relations) of the Petri net model, a qualitative analysis allows to determine a partial order of transition firings and thus, to extract feared scenarios. The analysis is focalized on the parts of the model that are interesting for the reliability analysis, avoiding exploration of the global system and the problem of the state space explosion. The final objective is to determine all minimal scenarios. Indeed, one scenario can lead to a feared state and contain events which are not strictly necessary to reach the final feared state. By analogy with the concept of minimal cutsets for the fault trees, we define the concept of minimal scenario in Petri net model. To take into account the hybrid nature of systems, we developed a hybrid simulator which combines the deriving feared scenarios algorithm and differential equations solver. The algorithm is in the charge of the discrete part modelled by Petri net and the solver of the continuous part modelled by a set of differential equations. In order to have a system approach for dependability analysis, we propose an approach which allows taking into account the safety requirements in the require ment engineering process. It makes possible the establishment of the traceability in order to make sure of taking into account of the safety requirements throughout the life cycle of the system. The approach is based on EIA-632 engineering system standard.
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Submitted on : Monday, November 26, 2007 - 2:29:12 PM
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  • HAL Id : tel-00192045, version 1

Citation

Nabil Sadou. Aide à la conception des systèmes embarqués sûrs de fonctionnement. Automatique / Robotique. INSA de Toulouse, 2007. Français. ⟨tel-00192045⟩

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