Feedback control logic synthesis for non safe Petri nets

This paper addresses the problem of forbidden states of non safe Petri Net (PN) modelling discrete events systems. To prevent the forbidden states, it is possible to use conditions or predicates associated with transitions. Generally, there are many forbidden states, thus many complex conditions are associated with the transitions. A new idea for computing predicates in non safe Petri nets will be presented. Using this method, we can construct a maximally permissive controller if it exists

Controller synthesis with very simplified linear constraints in PN model

This paper addresses the problem of forbidden states for safe Petri net modeling discrete event systems. We present an efficient method to construct a controller. A set of linear constraints allow forbidding the reachability of specific states. The number of these so-called forbidden states and consequently the number of constraints are large and lead to a large number of control places. A systematic method for constructing very simplified controller is offered. By using a method based on Petri nets partial invariants, maximal permissive controllers are determined.Comment: Dependable Control of discrete Systems, Bari : Italie (2009

Tuning the analog and digital performance of Germanene nanoribbon field effect transistors with engineering the width and geometry of source, channel and drain region in the ballistic regime

In this paper, with taking advantage of electrical properties of a germanene nanoribbon, we propose a germanene nanoribbon field effect transistor (GeNR-FET). Here by tuning the width and geometry of the germanene nanoribbon in the source, drain and channel regions, we investigate theoretically the transistor characteristics, analog and digital performances of these several different GeNR-FETs at room temperature. Our simulations are obtained usingdensity functional theory (DFT) combined withnon-equilibrium Green’s function (NEGF) method. The simulation results show that for digital applications, by tuning the width of the germanene nanoribbon a GeNR-FET with a finite band gap in the channel region and small band gap in the source and drain regions showsa better Ion/Ioff ratio in transfer characteristics. However, for the analog applications, if the band gap of the channel region has small value and the band gap of the source and drain regionshave a finite value, the output characteristic shows a higher peak to valley (PVR) ratio which is an important figure of merit in analog applications. Also from the output characteristics, we find that the T-shape channel shows more desirable (PVR) compared with otherdevices and it reaches to 17.28 in this case

Synthèse optimale d'un contrôleur par construction l'ensemble minimal de contraints

International audienceThe marking invariant in a Petri Net is known to establish an approach to synthesize a controller in a simple and elegant way. In the literature, we find numerous methods of controller's synthesis with a state approach. In general case, the number of forbidden states and then constraints is large and then a lot of control places are needed. In this article, is presented a systematic method to reduce the size and the number of constraints. This method is applicable for safe Petri Nest and allows constructing maximal permissive controller

Synthèse de contrôleurs discrets par simplification de contraintes et de conditions

In this work, we propose a systematic method for controller synthesis in discrete events systems. We model the process and the specification by safe Petri Nets (PN). Two distinct ideas are used: 1) adding the control places to prevent the reachability of forbidden states, and 2) adding conditions with the controllable transitions. The uncontrollability asks the problem of optimatlity and the large number of control places the problem of complexity.In the first idea, we use the theorem introduced by Guia, which makes it possible to pass from the set of forbidden states to the set of linear constraints. We propose original methods of simplification of the constraints. It is then possible to reduce the number and the bound of the constraints and thus to build a simple controller model. The methods of simplification presented are applicable on safe PN. We determine the necessary and sufficient conditions to have a maximal permissive controller. The principal advantage of these methods is that the controlled PN model is very close to the PN initial model. The second idea for controller synthesis is the using of conditions for controllable transitions. The methods which use this technique generally need a long calculation in real time. While applying our method of simplification, we arrive to a simple controller.Dans ce travail, nous proposons une méthode systématique et facile de mise en œuvre pour la synthèse du contrôle des systèmes à événements discrets. Nous modélisons les systèmes par des modèles RdP saufs. Deux idées distinctes sont utilisées : 1) ajout de places de contrôle pour empêcher l'atteignabilité des états interdits, et 2) ajout de conditions pour les transitions contrôlables. Nous avons alors été confrontés au problème des transitions incontrôlables pour garantir l'optimalité et à la complexité apportée par le nombre des places de contrôles qui peut être très grand. Dans la première idée, nous avons utilisé le théorème introduit par Guia, qui permet de passer d'un ensemble d'états interdits vers un ensemble de contraintes linéaires. Nous avons proposé des méthodes originales de simplification des contraintes. Il est alors possible de réduire le nombre et la borne des contraintes et ainsi de construire un modèle contrôlé simple. Les méthodes de simplification présentées sont applicables sur les RdP saufs. Nous avons déterminé les conditions nécessaires et suffisantes pour avoir un contrôleur maximal permissif. L'avantage principal de ces méthodes de synthèse de contrôleurs est que le modèle RdP contrôlé est très proche du modèle initial. La deuxième idée qui a été utilisée pour la synthèse est l'utilisation des conditions pour le franchissement des transitions contrôlables. Les méthodes qui utilisent cette technique, ont en général besoin d'un calcul long en temps réel. En appliquant notre méthode de simplification, nous arrivons à un contrôleur simple

Synthèse de contrôleurs discrets par simplification de contraintes et de conditions

In this work, we propose a systematic method for controller synthesis in discrete events systems. We model the process and the specification by safe Petri Nets (PN). Two distinct ideas are used: 1) adding the control places to prevent the reachability of forbidden states, and 2) adding conditions with the controllable transitions. The uncontrollability asks the problem of optimatlity and the large number of control places the problem of complexity.In the first idea, we use the theorem introduced by Guia, which makes it possible to pass from the set of forbidden states to the set of linear constraints. We propose original methods of simplification of the constraints. It is then possible to reduce the number and the bound of the constraints and thus to build a simple controller model. The methods of simplification presented are applicable on safe PN. We determine the necessary and sufficient conditions to have a maximal permissive controller. The principal advantage of these methods is that the controlled PN model is very close to the PN initial model. The second idea for controller synthesis is the using of conditions for controllable transitions. The methods which use this technique generally need a long calculation in real time. While applying our method of simplification, we arrive to a simple controller.Dans ce travail, nous proposons une méthode systématique et facile de mise en œuvre pour la synthèse du contrôle des systèmes à événements discrets. Nous modélisons les systèmes par des modèles RdP saufs. Deux idées distinctes sont utilisées : 1) ajout de places de contrôle pour empêcher l'atteignabilité des états interdits, et 2) ajout de conditions pour les transitions contrôlables. Nous avons alors été confrontés au problème des transitions incontrôlables pour garantir l'optimalité et à la complexité apportée par le nombre des places de contrôles qui peut être très grand. Dans la première idée, nous avons utilisé le théorème introduit par Guia, qui permet de passer d'un ensemble d'états interdits vers un ensemble de contraintes linéaires. Nous avons proposé des méthodes originales de simplification des contraintes. Il est alors possible de réduire le nombre et la borne des contraintes et ainsi de construire un modèle contrôlé simple. Les méthodes de simplification présentées sont applicables sur les RdP saufs. Nous avons déterminé les conditions nécessaires et suffisantes pour avoir un contrôleur maximal permissif. L'avantage principal de ces méthodes de synthèse de contrôleurs est que le modèle RdP contrôlé est très proche du modèle initial. La deuxième idée qui a été utilisée pour la synthèse est l'utilisation des conditions pour le franchissement des transitions contrôlables. Les méthodes qui utilisent cette technique, ont en général besoin d'un calcul long en temps réel. En appliquant notre méthode de simplification, nous arrivons à un contrôleur simple

Reduction of Constraints for Controller Synthesis based on Safe Petri Nets

International audiencen this paper, we present an efficient method based on safe Petri nets to construct a controller. A set of linear constraints al-lows forbidding the reachability of specific states. The number of these so-called forbidden states and consequently the number of constraints are large and lead to a large number of control places. A systematic method to reduce the size and the number of constraints for safe Petri Nets is offered. By using a method based on Petri nets invariants, maximal permissive controllers are determined

From forbidden state to linear constraints for the optimal supervisory control

International audienceThe place invariant method is well known as an elegant way to construct a Petri net controller. It is possible to use the constraint for preventing forbidden states. But in general case, there are many of the forbidden states, thus there is many control places. In this paper is presented a systematic method to reduce the size and the number of constraints. This method is applicable for safe and conservative Petri nets. By this method we can construct a maximally permissive controlle