فهرست مطالب sobhi bani ardalani

This paper deals with fault diagnosis of a linear continuous variable dynamical system represented by a discrete state space model. The proposed fault diagnoser is based on a special Petri Net called Continuous Time Delay Petri Net (CTDPN). Thanks to the theorem presented in this paper, an exact correspondence between discrete-state space equations and fundamental equations of the CTDPN can be established. Based on this theorem, a systematic method is presented for realization of classical parity equations by a CTDPN that plays the role of the fault diagnoser. By integrating the concept of state space models and Petri Nets in this paper, new and effective methods can be proposed for analyzing and fault diagnosis of hybrid systems. Finally, the performance of the proposed method is investigated for fault diagnosis of a DC motor. The results show that with the help of proposed Petri net, fault diagnosis can be done well and traditional diagnoser can be replaced with this network.

The state estimation of a quantized system (Q.S.) is a challenging problem for designing feedback control and model-based fault diagnosis algorithms. The core of a Q.S. is a continuous variable system whose inputs and outputs are represented by their corresponding quantized values. This paper concerns with state estimation of a Q.S. by a qualitative observer. The presented observer in this paper uses a non-deterministic automaton as its qualitative model and estimates quantized values of the system state. Observer inputs are on-line measured input and output signals of Q.S. The previous proposed qualitative observers use dynamics of the continuous variable system of Q.S., whereas, in this paper, the qualitative observer model is built by a quantitative observer. The main theorem of the paper shows that if the parameters of quantitative observer and sampling time are chosen correctly, then qualitative estimation error will be uniformly ultimate bounded, i.e. it will converge to a bounded convex set. In addition, simulation results show that reducing bounds of the convex set results in less additional generated spurious states.

Digital switches are one of the main components of the data transmission networks, and their modeling in applications such as traffic measurement, fault diagnosis, and operator training,have significant importance. In this paper, signaling of a digital switch is modeled and simulatedusing Colored Petri Nets. Colored PetriNet can support various data types and due to its intuitive graphical representationis known as an efficient tool for modeling of Discrete Event Systems (DES). In this papera digital switch is considered as a DES and its signaling is modeled using a CPN. Signalingis a sustainable and comprehensiveprotocol that can integrate various communication services into digital and analog telephone subscribers. The protocol cited in this paper,meets all the requirements for communication between digital databases and its role in the communications system is the same as one in computer networks. In this paper the signaling state is limited to a successful call between twosubscribers. In addition, the reachability graph is extracted for the CPN which contains all possible events in the DES and can be used for supervisory control tasks such as fault diagnosis process.

Modeling and diagnosis of signaling faults in digital telecommunication switches is very important. Providing practical approaches to this issue can be effective in increasing the speed and security of traffic information in the telecommunications network. In this paper, the signaling of the NEAX digital switch, which is a commonly used switch in the Iran telecommunication network, is simulated using the concept of Petri Nets (PNs), and then based on this model, a new algebraic method is proposed for detecting fault signaling. Unlike most of the methods presented in this field, the method proposed in this paper, without using of the reachability graph, uses algebraic approaches to detect the faults. The low complexity of computations, the needles of observablity of transitions, possibility of fault detection both in places and transitions of PN are the advantages of this method. Here, for more illustration, signaling in a successful single-call mode and busy mode is simulated and faults such as incomplete sending of destination phone numbers are detected.

Supervisory control and fault diagnosis of hybrid systems need to have complete information about the discrete states transitions of the underling system. From this point of view, the hybrid system should be abstracted to a Discrete Trace Transition System (DTTS) and represented by a discrete mode transition graph. In this paper an effective method is proposed for generating discrete mode transition graph of a hybrid system. This method can be used for a general class of industrial hybrid plants which are defined by Polyhedral Invariant Hybrid Automata (PIHA). In these automata there are no resetting maps, while invariant sets are defined by linear inequalities. Therefore, based on the continuity property of the state trajectories in a PIHA, the problem is reduced to finding possible transitions between all two adjacent discrete modes. In the presented method, the possibility and the direction of such transitions are detected only by computing the angle between the vector field and the normal vector of the switching surfaces. Thus, unlike the most other reachability methods, there is no need to solve differential equations and to do mapping computations. In addition, the proposed method, with some modifications can be applied for extracting Stochastic or Timed Discrete Trace Transition Systems.