Reconfigurable Discrete Event Systems Research Articles

On Quantitative Properties Preservation in Reconfigurable Generalized Stochastic Petri Nets

Generalized stochastic Petri nets (GSPNs) have been extended to several dynamic-structure formalisms providing suitable tools for the modeling and verification of reconfigurable discrete-event systems (R-DESs). However, analyzing the performance of large-complex R-DESs remains a big challenging issue. Indeed, dynamic-structure GSPNs still rely on old-fashioned techniques often causing the state-space explosion problem. In this article, we present a new technique for the quantitative analysis of a dynamic-structure formalism called reconfigurable GSPNs without computing the whole state space. This work describes new reconfiguration forms used to preserve desired quantitative properties of parts of interest after each reconfiguration. Therefore, it is only required to verify the examined properties at an initial configuration. The proposed technique is proven to effectively reduce the state space and shorten the computation time in such cases. Finally, some experimental results are provided to illustrate that, from a computational perspective, the developed approach outperforms the existing tools.

Reconfiguration Control of Dynamic Reconfigurable Discrete Event Systems Based on NCESs

In order to satisfy system specifications persistently in the cases of component failure, partial communication blocks, or energy deficiency, safety-critical systems need to apply system reconfigurations at runtime. Such systems can be considered as dynamic reconfigurable discrete event systems (DRDESs) if their logic behaviors are concerned only. A reconfiguration of a DRDES includes the switch of system structures and the update of system states. Based on the assumption that all configurations of a DRDES are designed in advance and dynamic reconfigurations can be implemented only at a few predefined reconfigurable states, a novel reconfiguration control method is proposed in this paper. The aim is to implement a required dynamic reconfiguration smoothly and rapidly. A DRDES is modeled by net condition/event systems (NCESs) under the firing rule “maximal single spontaneous transition steps.” An integer linear programming-based method is developed to compute a shortest legal firing sequence (SLFS) from the state where a reconfiguration requirement arises to a reconfigurable state. Accordingly, a virtual controller for guiding the system to evolve along the obtained SLFS is proposed. The proposed method is able to implement a required reconfiguration before the maximum permissible reconfiguration delay if an SLFS exists. A simple reconfigurable assembly system is adopted to illustrate the method.

On Reconfiguration Theory of Discrete-Event Systems: From Initial Specification Until Final Deployment

This paper presents an overview on different research activities that we did in the recent decade for developing reconfigurable discrete-event systems (RDESs) from initial high-level specification according to user requirements until final low-level deployment in target hardware components. A reconfiguration is any run-time scenario that adapts the system’s behavior to any evolution in the related environment by adding or removing services or also configuring their parameters, i.e., their frequency, execution time, or also their location in the considered hardware architecture. Since the development of distributed RDESs under functional and extra-functional constraints is required by experts, we propose a complete methodology that deals first with their initial design with a new general profile named R-UML extending unified modeling language (UML) or also with new specific technology-oriented profiles, the validation of the related models with a new language R-OCL extending object constraint language (OCL), before their transformation to formal formalisms, such as Petri nets, timed automata, or B method for simulation or also formal verification of different properties. The checked models are transformed into OS reconfigurable tasks in the operational level, before applying a co-design methodology under functional, real-time, memory, and energy constraints for minimizing redundancies in tasks and for optimizing the composition of software and hardware parts together. We describe technology-oriented solutions for the scheduling of distributed RDESs by parameterizing tasks and their exchanged messages between multi-speed networked processors. We finish with the real low-level deployment on target hardware devices before applying useful software and hardware tests for checking the delivered system quality. These contributions, published in different journal and conference papers, are applied to different applications in medicine, wireless sensor networks, transportation systems, manufacturing industry, smart grids and microgrids, embedded technologies, and so on. We find significant gains in terms of the system reactivity and flexibility under related constraints.

Simulation and analysis of reconfigurable assembly systems based on R-TNCES

ABSTRACTRecent research indicates that dynamic reconfiguration techniques can be applied to manufacturing systems to reduce energy consumption by switching energy-intensive components in a timely manner between their working and idle modes during system runtime because these components consume less energy in their idle modes than in their working modes. The current work studies reconfigurable assembly systems with such dynamic reconfiguration techniques by abstracting them as reconfigurable discrete event systems, considering only their logic behavior and properties. The formalism, R-TNCES (reconfigurable timed net condition/event systems), a modular extension of the well-known Petri nets, is used as a system modeling and analysis tool. The simulation of system global reconfigurations is guided by command inserting, whereas the simulation of local reconfigurations is automatic because their execution time is computed a priori by a proposed algorithm. Finally, qualitative properties specified by computation tree logic and quantitative analysis regarding energy-efficiency are performed by using the software SESA.

Modeling, Simulation and Verification of Probabilistic Reconfigurable Discrete-Event Systems Under Energy and Memory Constraints

Adaptive probabilistic systems have ability to modify their behaviors to cope with unpredictable significant changes at run-time such as component failures or resources depletion. Reconfiguration is often a major task for systems, i.e., it may violate the memory usage, the required energy and the concerned real-time constraints. It might also make the system’s functions unavailable for some time and make potential harm to human life or large financial investments. Thus, updating a system with any new configuration requires that the post-reconfigurable system fully satisfies the related constraints. Formal modeling and verification could avoid the resources and constraints violation. Thus, the paper proposes a new formalism to specify such systems. We also develop a new visual environment named ZIZO which helps in modeling, constructive simulation and CTL-based verification of adaptive probabilistic systems. The contributions are used to guarantee the resources and correctness of an IPv4 ZeroConf protocol.

State-space supervisory control of reconfigurable discrete event systems

The discrete event theory of supervisory and state feedback control offers many advatages for implementing supervisory systems. Algorithmic concepts have been introduced to ensure that the supervising algorithms are correct and meet the specifications. In the current methodology, it is, in general, assumed that the supervisory specifications are invariant during the operation of the system or, at least, until a given supervisory task is completed. However, there are many practical applications where the supervising specifications need to be updated in real time. For example, when dealing with complex processes, the tasks of supervisory systems analysis and synthesis can be facilitated by partitioning the controlled Discrete-Event System (DES) into several subprocesses. This partitioning is based on operational or physical considerations and a unique supervisor is assigned to control each subprocess at a given instant of time. When a decision maker at a higher level of hierarchy decides to change the super...