Sufficient Conditions For Reachability Research Articles

Modeling, Reachability and Controllability of Bounded Petri Nets Based on Semi‐Tensor Product of Matrices

AbstractIn this paper, we present a comprehensive modeling technique for bounded Petri net systems (BPNSs) in the framework of the semi‐tensor product (STP) of matrices. The two dynamic properties of BPNSs, namely, reachability and controllability, are investigated systematacially. First, the dynamics of a bounded Petri net system (BPNS), by resorting to the STP of matrices, are expressed in the form of a discrete‐time bilinear equation, which is called the marking evolution equation (MEE) of BPNSs. Second, controllability and transition‐marking adjacency matrix (TMAM) of BPNSs are defined, respectively. Further, several necessary and sufficient conditions for reachability and controllability of BPNSs are given in terms of the MEE and TMAM. Third, an efficient algorithm to verify reachability property of BPNSs, in this paper, is provided, as well as its computational complexity. Finally, an example is presented to illustrate the theoretical results in this paper. The main contribution of this paper is the presentation of a precise mathematical model for BPNSs. The main advantage of the proposed approach is that not only it can be applied to verify whether or not any given marking is reachable from the other in state space, but also it is very convenient to find all firing sequences between any two reachable markings.

Algorithms of reduced complexity to design control sequences for untimed Petri nets in varying and uncertain environments

Petri nets have been widely used for the modelling, analysis, control and optimization of discrete event systems with shared resources in the domains of engineering. This article concerns the design of control sequences for such systems modelled with untimed Petri nets. The aim of the controller is to incrementally compute sequences of transition firings with minimal size. Such sequences aim to move the marking from an initial value to a reference value. The resulting trajectory must avoid some forbidden markings and limit as possible the exploration of non-promising branches. For this purpose, the approach explores a small part of the reachability graph in the neighbourhood of the current marking. Then from the explored markings, it estimates a distance to the reference. The main contributions are (a) to reduce the explored part of the reachability graph according to a double limitation in breadth and in depth in order to provide solutions with a low computational effort; (b) to provide conditions to ensure the converge and optimality of the proposed algorithms and derive necessary and sufficient conditions for reachability; and (c) to include the firing sequence design in a global control schema suitable for reactive scheduling problems in uncertain and perturbed environments. The main application concerns deadlock-free scheduling problems in the domain of flexible manufacturing systems, but the approach is also applicable for systems in computer science and transportation.

Fractional variable order discrete-time systems, their solutions and properties

ABSTRACTIn this paper, fractional variable order discrete state-space systems based on different definitions of fractional variable order difference are investigated.The general solution of these systems is derived. Moreover, necessary and sufficient conditions for reachability and observability are given and proven. The sufficient conditions for controllability are proposed too.

Sufficient conditions for reachability in automata networks with priorities

In this paper, we develop a framework for an efficient under-approximation of the dynamics of Asynchronous Automata Networks (AANs). An AAN is an Automata Network with synchronised transitions between automata, where each transition changes the local state of exactly one automaton (but any number of synchronising local states are allowed). The work we propose here is based on static analysis by abstract interpretation, which allows to prove that reaching a state with a given property is possible, without the same computational cost of usual model checkers: the complexity is polynomial with the total number of local states and exponential with the number of local states within a single automaton. Furthermore, we address AANs with classes of priorities, and give an encoding into AANs without priorities, thus extending the application range of our under-approximation. Finally, we illustrate our method for the model checking of large-scale biological networks.

Controllability and observability of Boolean networks arising from biology.

Boolean networks are currently receiving considerable attention as a computational scheme for system level analysis and modeling of biological systems. Studying control-related problems in Boolean networks may reveal new insights into the intrinsic control in complex biological systems and enable us to develop strategies for manipulating biological systems using exogenous inputs. This paper considers controllability and observability of Boolean biological networks. We propose a new approach, which draws from the rich theory of symbolic computation, to solve the problems. Consequently, simple necessary and sufficient conditions for reachability, controllability, and observability are obtained, and algorithmic tests for controllability and observability which are based on the Gröbner basis method are presented. As practical applications, we apply the proposed approach to several different biological systems, namely, the mammalian cell-cycle network, the T-cell activation network, the large granular lymphocyte survival signaling network, and the Drosophila segment polarity network, gaining novel insights into the control and/or monitoring of the specific biological systems.

Controllability of Boolean control networks avoiding states set

In this paper, using semi-tensor product and the vector form of Boolean logical variables, the Boolean control network (BCN) is expressed as a bilinear discrete time system about state and control variables. Based on the algebraic form, the reachability and controllability avoiding undesirable states set are discussed. The reachability and controllability discussed here are under certain constraint and the definitions of reachability and controllability avoiding undesirable states set have practical meaning. Also, the necessary and sufficient conditions for reachability and controllability are given. At last, the control sequence that steers one state to another is constructed.

Stabilization of discrete-time stochastic systems via sliding mode technique

This paper considers the problem of sliding mode control for discrete-time stochastic systems with parameter uncertainties and state-dependent noise perturbation. An integral-like sliding surface is chosen and a discrete-time sliding mode controller is designed. The key feature in this work is that both the reachability of the quasi-sliding mode and the stability of system states are simultaneously analyzed, due to the existence of state-dependent noise perturbation. By utilizing an Lyapunov function involving system states and sliding mode variables, the sufficient condition for reachability is obtained. Finally, numerical simulation results are provided.

Reachability Properties of Single-Input Continuous-Time Positive Switched Systems

In this paper, two reachability properties for single-input positive switched systems are introduced: monomial reachability and reachability. Monomial reachability, which represents a necessary but not sufficient condition for reachability, is fully characterized. Necessary and sufficient conditions for reachability are provided for the class of n-dimensional systems, switching among n subsystems. Several necessary or sufficient conditions are also provided. Moreover, the definition of k-switching reachability set is given, and an equivalent condition for the existence of an upper bound on the number of switchings required to reach any reachable vector is given. Finally, it is shown that, for reachable systems of low dimension (n = 2 or n = 3), each vector of the positive orthant can be reached by resorting to a switching sequence which switches no more than n - 1 times.

Necessary and sufficient conditions for reachability on a simplex

In this paper we solve the general problem of designing a feedback controller to reach a set of facets of an n-dimensional simplex in finite time, for a system evolving with linear affine dynamics. Necessary and sufficient conditions are presented in the form of bilinear inequalities on the vertices of the simplex. By exploiting the structure of the problem, the bilinear inequalities are converted to a series of linear programming problems.

A Sufficient Condition for Reachability in a General Petri Net

Necessary and sufficient conditions for reachability exist only for special classes of Petri nets, acyclic Petri nets being one among them. We present a net transformation procedure that converts a general Petri net into an acyclic Petri net to utilize the available sufficient condition. We show the relationship between the reachable markings of the original Petri net and the associated acyclic Petri net. Given a firing count vector, we discuss how the sufficient condition for reachability in an acyclic Petri net could be utilized for a general Petri net. We also discuss the utility of the acyclic transformed net in determining the transition firing sequences of the reachable markings with known firing count vectors.

A simple graph theoretic characterization of reachability for positive linear systems

In this paper we consider discrete-time linear positive systems, that is systems defined by a pair ( A, B) of non-negative matrices. We study the reachability of such systems which in this case amounts to the freedom of steering the state in the positive orthant by using non-negative control sequences. This problem was solved recently [Canonical forms for positive discrete-time linear control systems, Linear Algebra Appl., 310 (2000) 49]. However we derive here necessary and sufficient conditions for reachability in a simpler and more compact form. These conditions are expressed in terms of particular paths in the graph which is naturally associated with the system.

Sufficient conditions for reachability and controllability of discrete systems with phase constraints

The paper gives sufficient conditions for local reachability and local controllability in the following discrete-time dynamical system with phase constraints where Fk is a closed set-valued map from a finite-dimensional Euclidean space X into itselfMk is closed subset of X and K is a fixed positive integer. The main tools one uses are different notions of coderivatives of set-valued maps and normal cones of sets

Hierarchical reachability graph of bounded Petri nets for concurrent-software analysis

Petri nets have been proposed as a promising tool for modeling and analyzing concurrent-software systems such as Ada programs and communication protocol software. Among analysis techniques available for Petri nets, the most general approach is to generate all possible states (markings) of the system in a form of a so-called reachability graph. However, this conventional reachability graph approach is inefficient or intractable, even for a bounded Petri net, due to state explosion in many practical applications. To cope with this problem, this paper proposes a method for constructing a hierarchically organized state space called the hierarchical reachability graph (HRG). Using the HRG, we obtain necessary and sufficient conditions for reachability and deadlock, as well as algorithms to test whether a given state or marking is reachable from the initial state and whether there is a deadlock state (a state with no successor states). >

On structural conditions for weak persistency and semilinearity of Petri nets

A necessary and sufficient condition for a Petri net to be weakly persistent for every initial marking is obtained. Moreover, a necessary and sufficient condition for reachability is obtainable for this class of Petri nets. As a sufficient condition for a Petri net to have a semilinear reachability set the notion of sinklessness has been proposed, where a marked Petri net is said to be sinkless if the total number of tokens in each minimal circuit is not decreased to 0 by firing transitions. We show that the reachability set is semilinear if the total number of times that sinklessness is violated is finite during each firing, and define a new subclass of Petri nets which have this property for every initial marking.

可達性の必要十分条件を求めることが可能なペトリネットのクラス

可達性の必要十分条件を求めることが可能なペトリネットのクラス

Even More States Reachable by Boundary Control for the Heat Equation

In this note we show how both known and new sufficient conditions for reachability in boundary control for the heat equation can easily be derived from null controllability. A characterisation of reachable states remains elusive.