Modeling and analysis using hybrid Petri nets

This paper is devoted to the use of hybrid Petri nets (PNs) for modeling and control of hybrid dynamic systems (HDS). Modeling, analysis and control of HDS attract ever more of researchers' attention and several works have been devoted to these topics. We consider in this paper the extensions of the PN formalism (initially conceived for modeling and analysis of discrete event systems) in the direction of hybrid modeling. We present, first, the continuous PN models. These models are obtained from discrete PNs by the fluidification of the markings. They constitute the first steps in the extension of PNs toward hybrid modeling. Then, we present two hybrid PN models, which differ in the class of HDS they can deal with. The first one is used for deterministic HDS modeling, whereas the second one can deal with HDS with nondeterministic behavior. Keywords: Hybrid dynamic systems; D-elementary hybrid Petri nets; Hybrid automata; Controller synthesi

Modeling and Analysis of Hybrid Dynamic Systems Using Hybrid Petri Nets

International audienceWe consider in this paper the extensions of the PN formalism in the direction of hybrid modeling. We briefly presents hybrid dynamic systems. Then the hybrid automata model. Is introduced and we discuss continuous Petri nets. These models are obtained from discrete PNs by the fluidification of the markings. They constitute the first steps in the extension of PNs toward hybrid modeling. Two hybrid PN models, which differ in the class of HDS they can deal with, are studied. The first one is used for deterministic HDS modeling, whereas the second one can deal with HDS with nondeterministic behavior. The general control structure based on hybrid PNs is briefly described

Modelling & analysis of hybrid dynamic systems using a bond graph approach

Hybrid models are those containing continuous and discontinuous behaviour. In constructing dynamic systems models, it is frequently desirable to abstract rapidly changing, highly nonlinear behaviour to a discontinuity. Bond graphs lend themselves to systems modelling by being multi-disciplinary and reflecting the physics of the system. One advantage is that they can produce a mathematical model in a form that simulates quickly and efficiently. Hybrid bond graphs are a logical development which could further improve speed and efficiency. A range of hybrid bond graph forms have been proposed which are suitable for either simulation or further analysis, but not both. None have reached common usage. A Hybrid bond graph method is proposed here which is suitable for simulation as well as providing engineering insight through analysis. This new method features a distinction between structural and parametric switching. The controlled junction is used for the former, and gives rise to dynamic causality. A controlled element is developed for the latter. Dynamic causality is unconstrained so as to aid insight, and a new notation is proposed. The junction structure matrix for the hybrid bond graph features Boolean terms to reflect the controlled junctions in the graph structure. This hybrid JSM is used to generate a mixed-Boolean state equation. When storage elements are in dynamic causality, the resulting system equation is implicit. The focus of this thesis is the exploitation of the model. The implicit form enables application of matrix-rank criteria from control theory, and control properties can be seen in the structure and causal assignment. An impulsive mode may occur when storage elements are in dynamic causality, but otherwise there are no energy losses associated with commutation because this method dictates the way discontinuities are abstracted. The main contribution is therefore a Hybrid Bond Graph which reflects the physics of commutating systems and offers engineering insight through the choice of controlled elements and dynamic causality. It generates a unique, implicit, mixed-Boolean system equation, describing all modes of operation. This form is suitable for both simulation and analysis

Hybrid dynamic systems- analysis and modeling

V této práci je řešena problematika popisu, modelování a analýzy hybridních dynamických systémů. Cílem práce je vybrat vhodnou metodu pro řešení hybridních dynamických systémů a zaměřit se na řešení otázek stanovení řiditelnosti, pozorovatelnosti a stability hybridních dynamických systémů. Práce se zabývá dvěmi typy hybridních systémů. V první části je uveden popis a modelování hybridních systémů složených ze spojité části a diskrétní části tvořené systémem diskrétních událostí. Pro popis a modelování těchto hybridních systémů jsou použity hybridní automaty a hybridní Petriho sítě. Uvedené možnosti popisu a modelování jsou ukázány na jednoduchých vzorových příkladech. Druhá část práce je zaměřena na popis, modelování a analýzu hybridních dynamických systémů, které jsou tvořeny spojením spojitého dynamického systému a diskrétního dynamického systému. Pro popis, modelování a analýzu hybridních dynamických systémů je použito stavového prostoru. Jsou zde uvedeny obecné stavové rovnice, pomocí nichž je možné provést popis hybridního systému, a jim odpovídající obecné struktury matic A, B, C, D. Dále zde jsou zde odvozeny vztahy a základní postupy pro analýzu hybridních dynamických systémů. Z hlediska analýzy se jedná o obecné postupy, jakými je možné rozhodnout o řiditelnosti, pozorovatelnosti, stabilitě a ustálených stavech hybridních dynamických systémů. Pro veškeré uvedené postupy a vztahy jsou řešeny vzorové příklady hybridních regulačních systémů. Pokud je to možné, tak jsou rovněž výsledky získané výpočtem ověřeny pomocí simulace v prostředí MATLAB Simulink.In this thesis the issue with the description, modeling and analysis of hybrid dynamic systems is solved. The main goal is to select appropriate method for solving hybrid dynamic systems and to aim to question on solving controllability, observability and stability of these systems. Two types of hybrid systems are covered in this work. In the first part, the description and simulation of hybrid systems that are compiled of continous and discrete parts with the systems of discrete affair are specified. For the description and modeling of hybrid automata and hybrid Petri nets have been used. The possibilities mentioned above are showned on the simple examples. Second part of this work covers the description, modeling and analysis of hybrid systems that are compiled of links continous and discreate dynamic system. The state space has been used. The universal state equations are mentioned and have been used for the description of the hybrid system and the structure of the matrixes A, B, C, D. The relation and basic method are spin off for the analysis of hybrid dynamic systems. From the analysis point of view, these are general methods for the controllability, observability, stability and steady state of hybrid dynamic systems. The examples of hybrid control systems for mentioned methods are specified. If it is allowed, the results are verified by the simulation in MATLAB Simulink background.

Total Stability Properties Based on Fixed Point Theory for a Class of Hybrid Dynamic Systems

Es reproducción del documento publicado en http://dx.doi.org/10.1155/2009/826438Robust stability results for nominally linear hybrid systems are obtained from total stability theorems for purely continuous-time and discrete-time systems by using the powerful tool of fixed point theory. The class of hybrid systems dealt consists, in general, of coupled continuous-time and digital systems subject to state perturbations whose nominal (i.e., unperturbed) parts are linear and, in general, time-varying. The obtained sufficient conditions on robust stability under a wide class of harmless perturbations are dependent on the values of the parameters defining the over-bounding functions of those perturbations. The weakness of the coupling dynamics in terms of norm among the analog and digital substates of the whole dynamic system guarantees the total stability provided that the corresponding uncoupled nominal subsystems are both exponentially stable. Fixed point stability theory is used for the proofs of stability. Ageneralization of that result is given for the case that sampling is not uniform. The boundedness of the state-trajectory solution at sampling instants guarantees the global boundedness of the solutions for all time. The existence of a fixed point for the sampled state-trajectory solution at sampling instants guarantees the existence of a fixed point of an extended auxiliary discrete system and the existence of a global asymptotic attractor of the solutions which is either a fixed point or a limit n globally stable asymptotic oscillation.Ministerio de Educación (Projecto DPI2006-00714); Gobierno Vasco (GIC07143-IT-269-07 y SAIOTEK S-PE08UN15

Dynamic state reconciliation and model-based fault detection for chemical processes

In this paper, we present a method for the fault detection based on the residual generation. The main idea is to reconstruct the outputs of the system from the measurements using the extended Kalman filter. The estimations are compared to the values of the reference model and so, deviations are interpreted as possible faults. The reference model is simulated by the dynamic hybrid simulator, PrODHyS. The use of this method is illustrated through an application in the field of chemical processe

Model based fault diagnosis for hybrid systems : application on chemical processes

The complexity and the size of the industrial chemical processes induce the monitoring of a growing number of process variables. Their knowledge is generally based on the measurements of system variables and on the physico-chemical models of the process. Nevertheless, this information is imprecise because of process and measurement noise. So the research ways aim at developing new and more powerful techniques for the detection of process fault. In this work, we present a method for the fault detection based on the comparison between the real system and the reference model evolution generated by the extended Kalman filter. The reference model is simulated by the dynamic hybrid simulator, PrODHyS. It is a general object-oriented environment which provides common and reusable components designed for the development and the management of dynamic simulation of industrial systems. The use of this method is illustrated through a didactic example relating to the field of Chemical Process System Engineering

Integration of an object formalism within a hybrid dynamic simulation environment

PrODHyS is a general object-oriented environment which provides common and reusable components designed for the development and the management of dynamic simulation of systems engineering. Its major characteristic is its ability to simulate processes described by a hybrid model. In this framework, this paper focuses on the "Object Differential Petri Net" (ODPN) formalism integrated within PrODHyS. The use of this formalism is illustrated through a didactic example relating to the field of Chemical Process System Engineering (PSE)