Publications

元宇宙可被视为一个社会化和虚拟化的网络

This paper deals with the problem of environmental monitoring by developing an event-triggered finite-time control scheme for mobile sensor networks. The proposed control scheme can be executed by each sensor node independently and consists of two parts: one part is a finite-time consensus algorithm while the other part is an event-triggered rule. The consensus algorithm is employed to enable the positions and velocities of sensor nodes to quickly track the position and velocity of a virtual leader in finite time. The event-triggered rule is used to reduce the updating frequency of controllers in order to save the computational resources of sensor nodes. Some stability conditions are derived for mobile sensor networks with the proposed control scheme under both a fixed communication topology and a switching communication topology. Finally, simulation results illustrate the effectiveness of the proposed control scheme for the problem of environmental monitoring.

This paper addresses the set-membership filtering problem with communication constraints for a class of discrete time-varying systems in the presence of unknown-but-bounded process and measurement noises. The dynamic coder and decoder are proposed to model the digital communication channel to transmit the error between the current measurement output and the last time quantized measurement output rather than the current measurement output. This strategy will reduce the channel communication burden by transmitting fewer bits. A time-varying linear matrix inequality approach is developed to solve the set-membership filtering problem and a sufficient condition for the existence of set-membership filter is derived. A recursive convex optimization algorithm is provided to determine a state estimation ellipsoid that is a set of states compatible with quantized measurement and unknown-but-bounded process and measurement noises. Simulation results demonstrate the effectiveness of the proposed method.

This paper is concerned with event-triggered generalized dissipativity filtering for a neural network (NN) with a time-varying delay. The signal transmission from the NN to its filter is completed through a communication channel. It is assumed that the network measurement of the NN is sampled periodically. An event-triggered communication scheme is introduced to design a suitable filter such that precious communication resources can be saved significantly while certain filtering performance can be ensured. On the one hand, the event-triggered communication scheme is devised to select only those sampled signals violating a certain threshold to be transmitted, which directly leads to saving of precious communication resources. On the other hand, the filtering error system is modeled as a time-delay system closely dependent on the parameters of the event-triggered scheme. Based on this model, a suitable filter is designed such that certain filtering performance can be ensured, provided that a set of linear matrix inequalities are satisfied. Furthermore, since a generalized dissipativity performance index is introduced, several kinds of event-triggered filtering issues, such as H∞ filtering, passive filtering, mixed H∞ and passive filtering, (Q, S, R)-dissipative filtering, and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> filtering, are solved in a unified framework. Finally, two examples are given to illustrate the effectiveness of the proposed method.

This paper is concerned with event-triggered H∞ filtering for networked systems. A novel event-triggering scheme is proposed by taking network dynamics into account simultaneously. First, an information dispatching middleware is constructed to establish a novel framework for networked systems, where two modules namely information selection module and congestion avoidance module are introduced. The information selection module aims to regulate the transmission of the sampled data in terms of a predefined event-triggering condition. The congestion avoidance module is used to schedule those sampled data released by the information selection module to the filter. Second, the on-line scheduling strategy is proposed under this framework. Then the filtering error system based on network dynamics is formulated as a system with an interval time-varying delay. Third, Lyapunov-Krasovskii functional approach is employed to formulate a new sufficient condition to ensure the stability and to guarantee a prescribed H∞ noise attenuation performance for the filtering error system. Based on this condition, H∞ filtering parameters, network dynamic controllers and event-triggering parameters can be co-designed provided that a set of linear matrix inequalities are feasible. Finally, an example is given to illustrate the merits and effectiveness of the method proposed in this paper.

This paper is concerned with stability of linear discrete time-delay systems. Note that a tighter estimation on a finite-sum term appearing in the forward difference of some Lyapunov functional leads to a less conservative delay-dependent stability criterion. By using Abel lemma, a novel finite-sum inequality is established, which can provide a tighter estimation than the ones in the literature for the finite-sum term. Applying this Abel lemma-based finite-sum inequality, a stability criterion for linear discrete time-delay systems is derived. It is shown through numerical examples that the stability criterion can provide a larger admissible maximum upper bound than stability criteria using a Jensen-type inequality approach and a free-weighting matrix approach.

Global asymptotic stability is an important issue for wide applications of recurrent neural networks with time-varying delays. The Lyapunov–Krasovskii functional method is a powerful tool to check the global asymptotic stability of a delayed recurrent neural network. When the Lyapunov–Krasovskii functional method is employed, three steps are necessary in order to derive a global asymptotic stability criterion: (i) constructing a Lyapunov–Krasovskii functional, (ii) estimating the derivative of the Lyapunov–Krasovskii functional, and (iii) formulating a global asymptotic stability criterion. This paper provides an overview of recent developments in each step with insightful understanding. In the first step, some existing Lyapunov–Krasovskii functionals for stability of delayed recurrent neural networks are anatomized. In the second step, a free-weighting matrix approach, an integral inequality approach and its recent developments, reciprocally convex inequalities and S-procedure are analyzed in detail. In the third step, linear convex and quadratic convex approaches, together with the refinement of allowable delay sets are reviewed. Finally, some challenging issues are presented to guide the future research.

Distributed cooperative control of multi-agent systems has been one of the most active research topics in the fields of automatic control and robotics. This paper provides a survey on recent advances in distributed cooperative control under a sampled-data setting, with special emphasis on the published results since 2011. First, some typical sampling mechanisms related to this topic, such as uniform sampling, nonuniform sampling, random sampling, and event-triggered sampling, are summarized in both asynchronous and synchronous paradigms. Then, based on different coordinated tasks, recent results on distributed sampled-data cooperative control of multi-agent systems are categorized into four classes, i.e., sampled-data leaderless consensus, sampled-data leader-following consensus, sampled-data containment control, and sampled-data formation control. For each class, some explicit research lines are identified according to various sampling mechanisms. In particular, depending on definitions of event triggering conditions, some representative event-triggered sampling mechanisms are sorted out and discussed in detail. Finally, several challenging issues for future research are proposed.

This study is concerned with modelling and observer‐based H ∞ controller design for a continuous‐time networked control system with network‐induced delays and packet dropouts. A new model for an observer‐based networked control system is first established by proposing a linear estimation‐based delay compensation method. Then some controller design criteria are obtained by constructing an interval time‐varying delay decomposition‐based Lyapunov functional. A new bounding inequality is introduced to transfer non‐linear matrix inequalities into a solvable optimisation problem. A numerical example is given to illustrate the merits and effectiveness of the obtained results.

This paper is concerned with the global synchronization in Lur'e complex dynamical networks. Compared with the existing complex dynamical networks with the time delay either in every node or in coupling part, this class of Lur'e complex dynamical networks not only have the time-delayed nodes, but also have the time-delayed coupling. These two classes of time delays are different from each other. By using LMI technique, synchronization criteria of this class of Lur'e complex dynamical networks are derived. These synchronization criteria are delay-dependent not only for the time delay in every node, but also for the time delay in the coupling part. A numerical example demonstrates the effectiveness of synchronization results.

This paper investigates the problem of master-slave synchronization of two delayed Lur'e systems in the presence of parameter mismatches. First, by analyzing the corresponding synchronization error system, synchronization with an error level, which is referred to as quasi-synchronization, is established. Some delay-dependent quasi-synchronization criteria are derived. An estimation of the synchronization error bound is given, and an explicit expression of error levels is obtained. Second, sufficient conditions on the existence of feedback controllers under a predetermined error level are provided. The controller gains are obtained by solving a set of linear matrix inequalities. Finally, a delayed Chua's circuit is chosen to illustrate the effectiveness of the derived results.

This paper investigates robust stability of uncertain linear systems with interval time-varying delay. The time-varying delay is assumed to belong to an interval and is a fast time-varying function. The uncertainty under consideration includes polytopic-type uncertainty and linear fractional norm-bounded uncertainty. A new Lyapunov–Krasovskii functional, which makes use of the information of both the lower and upper bounds of the interval time-varying delay, is proposed to drive some new delay-dependent stability criteria. In order to obtain much less conservative results, a tighter bounding for some term is estimated. Moreover, no redundant matrix variable is introduced. Finally, three numerical examples are given to show the effectiveness of the proposed stability criteria.

This paper is concerned with network-based heading control and rudder oscillation reduction for an unmanned surface vehicle (USV) equipped with single rudder in network environments. A novel network-based model is first established by constructing a heading control error system and purposely dropping some control input packets, which are received by a steering machine. Then, a stabilization criterion is derived to guarantee the heading angle tracking performance and to reduce the oscillation of the rudder angle. Some algorithms for selecting the number of purposely dropped control input packets are presented. It is shown through heading control and rudder oscillation reduction performance analysis that compared with the controller design without dropping control input packets purposely, the proposed intentional packet dropouts-based controller design is more effective in improving the control performance of the USV.

This paper is concerned with the distributed H∞ filtering problem over sensor networks subject to time varying transmission delays. First, the classical Round-Robin protocol is used for the scheduling of samplers' information towards the corresponding filter. Second, a distributed event-triggering transmission scheme is introduced for information communication among distributed filters. As a result, communication and energy resources can be saved significantly while certain system performance can be preserved. Third, the resulting filtering error system is modeled as a switched system with time-varying delays. By employing Lyapunov-Krasovskii functional approach, a linear matrix inequality (LMI)-based sufficient condition is established which guarantees the filtering error system asymptotically stable with prescribed H∞ performance. An algorithm for both the distributed filters and event-triggering parameters is presented on the basis of solutions of a set of LMIs. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

No abstract is provided for this article.

Summary The problem of the stability of a linear system with an interval time‐varying delay is investigated. A new Lyapunov–Krasovskii functional that fully uses information about the lower bound of the time‐varying delay is constructed to derive new stability criteria. It is proved that the proposed Lyapunov–Krasovskii functional can lead to less conservative results than some existing ones. Based on the proposed Lyapunov–Krasovskii functional, two stability conditions are developed using two different methods to estimate Lyapunov–Krasovskii functional's derivative. Two numerical examples are given to illustrate that the two stability conditions are complementary and yield a larger maximum upper bound of the time‐varying delay than some existing results. Copyright © 2013 John Wiley &amp; Sons, Ltd.

This paper deals with the problem of distributed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> consensus filtering for a continuous-time Itô-type stochastic system with Wiener process disturbances and Markovian coupling intercommunication delays. The problem is solved based on distributed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> filters in combination with consensus strategies. The set of filter nodes form a communication network whose topology is modeled by a directed graph that describes estimates exchanged among neighboring nodes. A refined technique is provided to tackle the complicated coupling of the exchanged estimates in the presence of random coupling intercommunication delays. Moreover, a sufficient condition on the existence of desired distributed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> consensus-based filters is established such that the resultant filter error system is mean square exponentially stable with a weighting H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> consensus performance index. The filter design problem is posed in terms of linear matrix inequalities. Finally an illustrative example is given to show the effectiveness of the proposed filter design method.