Dwell Time Technique Research Articles

Non-fragile exponential synchronisation of stochastic neural networks via aperiodic intermittent impulsive control

This study aims to address the non-fragile exponential synchronisation problem of stochastic neural networks (SNNs). To cut down unnecessary control costs, a novel aperiodic intermittent-based impulsive control (APIIC) is designed in this investigation. Besides, the randomly occurring gain fluctuation (ROGF) is considered in APIIC, which satisfies certain Bernoulli distributed white noise sequences. By exploiting the Lyapunov approach and the average dwell-time technique, some sufficient criteria are derived in terms of linear matrix inequalities, which ensure that APIIC can achieve exponential synchronisation of SNNs with and without ROGF. More intriguingly, a technical definition of aperiodic window-based average impulsive interval is developed to cut back the conservativeness of these results. At last, the effectiveness of our explored results is confirmed by several numerical examples.

On exponential stability of switched functional differential equations with average dwell-time

We present a novel approach to the exponential stability of switched functional differential equations. Our approach does not involve Lyapunov functions. It is simple and based upon spectral properties of Metzler matrices, a comparison principle and the average dwell-time technique. Consequently, some new explicit criteria for the exponential stability of switched functional differential equations are derived. Some illustrative examples are given.

Protocol-Based Load Frequency Control for Power Systems With Nonhomogeneous Sojourn Probabilities

This article is concentrated on the load frequency control for interconnected multiarea power systems (IMAPSs) with nonhomogeneous sojourn probabilities (NSPs) and cyber-attacks. A generalized framework of NSPs is formulated to describe the dynamic behavior of IMAPSs. To govern variations of sojourn probabilities, a deterministic switching signal is introduced using the average dwell-time technique. Essentially, different from the existing protocols, an improved event-triggered protocol that is relevant to the dynamic quantizer parameter is presented, thereby increasing triggering intervals. Furthermore, both denial-of-service and deception attacks, which obey Bernoulli distributions, are considered during information transmission. By virtue of the Lyapunov theory, the mean-square exponential stability of the considered systems is established. Finally, the effectiveness of the obtained results is verified via a numerical example.

Minimal Leader Selection in General Linear Multi-Agent Systems With Switching Topologies: Leveraging Submodularity Ratio

In multi-agent systems with leader-follower dynamics, choosing a subset of agents as leaders is a critical step in achieving the desired coordination performance. In this study, by considering consensus tracking for general linear multi-agent systems under switching topologies, we address the problem of selecting a minimum-size set of leaders by leveraging the submodularity ratio. First, using the dwell time technique, a criterion is derived to ensure that the states of all agents can converge to a reference trajectory that is directly tracked by each leader. Second, exploiting the derived consensus tracking criterion, the metrics with a structure of the Euclidean distance between specific vectors and the space spanned by an iteratively updated matrix are established to identify a set of leaders, and then the corresponding bound of the submodularity ratio is proposed. Third, combining the derived criterion and the constructed metrics, a leader selection scheme is presented together with three polynomial-time algorithms, and the related provable optimality bound of each algorithm can be obtained by leveraging the proposed bound of the submodularity ratio. Finally, illustrative examples are provided to verify the effectiveness of the proposed leader selection scheme.

The Couple‐Group Consensus of Heterogeneous Multiagent Systems with Asynchronous Switching in Cooperative‐Competitive Networks

This paper investigates the problem of leader‐following or leaderless couple‐group consensus of heterogeneous multiagent systems (HMASs) with cooperative‐competitive interaction, asynchronous switching, and controller faults. Some novel protocols have been proposed to solve the couple‐group consensus of the two kinds of HMASs. Compared with the existing results, asynchronous control, controller faults, leaders, and the competitive‐cooperative interaction are all considered in these novel protocols. By using linear matrix inequality, graph theory, Lyapunov functional theory, and model‐dependent dwell time technique (MDADT), some sufficient conditions have been gained for the leader‐following or leaderless couple‐group consensus of these systems. The obtained results show that the couple‐group consensus of HMASs can be transformed into determining the stability of the related switching linear system. These results can also be applied to HMASs with weakly connected topology without satisfying the demand of in‐degree balance, strong connectivity, or containing a spanning tree. Some simulation experiments are given to prove the validity of the obtained results.

A cyber-resilient control approach for islanded microgrids under hybrid attacks

Microgrids (MGs) are cyber–physical systems (CPSs) where electrical and communication systems are coupled by networked control systems. The secondary control functions of MGs via communications could confront various cyber-attacks from vulnerable components. This paper proposes a cyber-resilient control approach for islanded MG systems with distributed generators (DGs) and energy storage systems (ESSs), which are subject to hybrid false data injection (FDI) and denial-of-service (DoS) attacks. The proposed control is designed based on the adaptive method to compensate for the bounded FDI attacks on secondary controllers while tolerating certain DoS attacks on communication links. The stability of the error systems is proved by using the dwell time technique and the Lyapunov stability theory. The proposed control can maintain frequency restoration, fair power sharing, as well as energy balancing among DGs and ESSs under the hybrid cyber-attack. The proposed cyber-resilient control approach is realized in a 13-bus MG system with 3 ESSs and 3 DGs. Real-time test is conducted by using OPAL-RT simulator to validate the effectiveness of the proposed approach under successive, time-varying and hybrid FDI and DoS attacks scenarios.

Cooperative Output Regulation of T–S Fuzzy Multiagent Systems Under Switching Directed Topologies and Event-Triggered Communication

In this article, the event-triggered cooperative output regulation problem of T–S fuzzy multiagent systems under jointly connected switching directed topologies is investigated. A distributed sampled-data event-triggered scheme is proposed such that the estimator, which estimates the exosystem, transmits the data information to its neighbors under the switching directed topologies at its triggering instants. The continuous event detection and triggering Zeno behavior are avoided via aperiodic sampling. Then, the time-dependent Lyapunov functional approach together with the dwell time technique is utilized, such that the estimation errors converge to zero exponentially. Furthermore, the observer-based fuzzy controllers are developed to ensure the solvability of the cooperative output regulation. Besides, the advantage of the distributed sampled-data event-triggered scheme is that the data transmissions caused by triggerings and switchings are autocephalous, which avoids the situation that triggering must occur at the switching points. Finally, an example is given to show the validity of results.

Stability analysis of delayed fractional-order switched systems

This paper discusses stability of delayed fractional-order switched systems. First, two useful propositions are proposed based on Razumikhin approach together with properties of fractional calculus and analytical techniques, which can well solve the difficulties caused by distributed and discrete delays and fractional-order derivatives. Then, with the help of multiple Lyapunov function approach and dwell time technique, an effective way is developed to overcome the trouble caused by switching rules. A delay-dependent dwell time is derived to guarantee asymptotic stability under the hypothesis that each subsystem of delayed fractional-order switched systems is asymptotically stable. Finally, two illustrative examples further clarify the obtained conclusions.

New Results of Observer Design for Continuous-Time Fuzzy Systems: A Switching Technique

It is observed that if the premise variables are differentiable, the time derivatives of membership functions are positive or nonpositive. Based on the above fact, the switching observer gains and controller gains are designed to guarantee that the fuzzy system is globally exponentially asymptotically stable by applying the average dwell-time (ADT) technique. In addition, two methods are proposed to find the controller gains and observer gains by dividing the matrices into <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times 1$ </tex-math></inline-formula> blocks or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> blocks. Finally, two examples are given to verify the conclusion.

Exploring Gaze for Assisting Freehand Selection-based Text Entry in AR

With eye-tracking increasingly available in Augmented Reality, we explore how gaze can be used to assist freehand gestural text entry. Here the eyes are often coordinated with manual input across the spatial positions of the keys. Inspired by this, we investigate gaze-assisted selection-based text entry through the concept of spatial alignment of both modalities. Users can enter text by aligning both gaze and manual pointer at each key, as a novel alternative to existing dwell-time or explicit manual triggers. We present a text entry user study comparing two of such alignment techniques to a gaze-only and a manual-only baseline. The results show that one alignment technique reduces physical finger movement by more than half compared to standard in-air finger typing, and is faster and exhibits less perceived eye fatigue than an eyes-only dwell-time technique. We discuss trade-offs between uni and multimodal text entry techniques, pointing to novel ways to integrate eye movements to facilitate virtual text entry.

Incremental stability of stochastic time‐varying impulsive and switching systems

AbstractIn this article, the incremental stability problem is addressed for stochastic time‐varying impulsive and switching systems. Both cases of stable continuous subsystems with destabilizing impulses and unstable continuous subsystems with stabilizing impulses are fully considered. By resorting to contraction theory and the Lyapunov function approach together with the dwell time technique, sufficient criteria are established to achieve practical incrementally globally asymptotic stability. Finally, the feasibility of these results is verified by a numerical example.

Periodic event‐triggered consensus control for multi‐agent systems with switching jointly connected topologies

The consensus problem for a class of multi-agent systems with switching jointly connected topologies via periodic event-triggered control is studied. The distinguishing feature of such system is that the eigenvalues of system matrix can contain positive real parts. Due to the coexistence of unstable system matrix and disconnected topologies, the agents can diverge from each other across some periods even if the control input is imposed on them. To overcome this difficulty, a periodic-sampling time unit (PSTU) approach is introduced to analyse the local convergence or divergence property within each sampling time unit based on the periodic event-triggering control. Then the stabilisation property of switching behaviours is utilised to compensate the divergence within each switching interval via the dwell time technique. It is interesting to see that each switching period is considered to consist of finite number of PSTUs. Then by confining a pair of lower and upper bounds on the dwell time, the overall consensus can be reached. Further, a novel class of event-dependent discretised Lyapunov functions are utilised to describe the error characteristics and computable conditions for the overall consensus can be derived. Finally, the effectiveness of the proposed result is illustrated by a numerical example.

Delay-Dependent Stability Analysis for Switched Stochastic Networks With Proportional Delay.

In this article, the issue of exponential stability (ES) is investigated for a class of switched stochastic neural networks (SSNNs) with proportional delay (PD). The key feature of PD is an unbounded time-varying delay. By considering the comparison principle and combining the extended formula for the variation of parameters, we conquer the difficulty in consideration of PD effects for such networks for the first time, where the subsystems addressed may be stable or unstable. New delay-dependent conditions with respect to the mean-square ES of systems are established by employing the average dwell-time (ADT) technique, stochastic analysis theory, and Lyapunov approach. It is shown that the acquired minimum average dwell time (MADT) is not only relevant to the stable subsystems (SSs) and unstable subsystems (USs) but also dependent on the decay ratio (DR), increasing ratio (IR), as well as PD. Finally, the availability of the derived results under an average dwell-time-switched regulation (ADTSR) is illustrated through two numerical simulation examples.

Cooperative Output-Feedback Secure Control of Distributed Linear Cyber-Physical Systems Resist Intermittent DoS Attacks.

This article studies a cooperative output-feedback secure control problem for distributed cyber-physical systems over an unreliable communication interaction, which is to achieve coordination tracking in the presence of intermittent denial-of-service (DoS) attacks. Under the switching communication network environment, first, a distributed secure control method for each subsystem is proposed via neighborhood information, which includes the local state estimator and cooperative resilient controller. Second, based on the topology-dependent Lyapunov function approach, the design conditions of secure control protocol are derived such that cooperative tracking errors are uniformly ultimately bounded. Interestingly, by exploiting the topology-allocation-dependent average dwell-time (TADADT) technique, the stability analysis of closed-loop error dynamics is presented, and the proposed coordination design conditions can relax time constraints on interaction topology switching. Finally, two numerical examples are presented to demonstrate the effectiveness of the theoretical results.

Distributed Resilient Observer-Based Fault-Tolerant Control for Heterogeneous Multiagent Systems Under Actuator Faults and DoS Attacks

In this article, we investigate the distributed resilient observer-based fault-tolerant control problem for heterogeneous linear multiagent systems in the presence of actuator faults and denial-of-service (DoS) attacks. In order to estimate the system matrix and the state of the exosystem, novel resilient adaptive distributed observers are proposed. By using the dwell time technique and the Lyapunov stability theory, the observer error system is shown to be exponentially stable even under the influence of DoS attacks. Then, an algorithm is proposed to determine observer parameters with the aim of maximizing the ability to resist attacks. Besides, a novel fault-tolerant controller without causing chattering behaviors is designed to compensate for actuator faults. Moreover, it is proved that the developed controller solves the cooperative fault-tolerant output regulation problem by using a newly derived lemma. Finally, an illustrative example is provided to verify the effectiveness of the proposed method.

Exponential state estimation for competitive neural network via stochastic sampled-data control with packet losses

This paper investigates the exponential state estimation problem for competitive neural networks via stochastic sampled-data control with packet losses. Based on this strategy, a switched system model is used to describe packet dropouts for the error system. In addition, transmittal delays between neurons are also considered. Instead of the continuous measurement, the sampled measurement is used to estimate the neuron states, and a sampled-data estimator with probabilistic sampling in two sampling periods is proposed. Then the estimator is designed in terms of the solution to a set of linear matrix inequalities (LMIs), which can be solved by using available software. When the missing of control packet occurs, some sufficient conditions are obtained to guarantee that the exponentially stable of the error system by means of constructing an appropriate Lyapunov function and using the average dwell-time technique. Finally, a numerical example is given to show the effectiveness of the proposed method.

Asymptotic Stability Analysis for Switched Stochastic Nonlinear Systems Using Mode-dependent Uniformly Stable Functions

In this paper, we intend to investigate uniform global asymptotic stability in probability (UGAS-P) for a class of time-varying switched stochastic nonlinear systems. Conventional criteria on stability for switched stochastic systems are based on the negativity of the infinitesimal generator of Lyapunov functions, it is demonstrated that these criteria are conservative. Taking this fact into account, the infinitesimal generator for each active subsystem acting on Lyapunov functions is relaxed to be indefinite with the help of uniformly stable function (USF). Subsequently, improved criteria on asymptotic stability are proposed by applying the weakened condition and mode-dependent average dwell time (MDADT) technique. In addition, numerical examples are presented to verify the effectiveness of the obtained results.

Sampled-data based asynchronous stabilization for switched systems with stochastic perturbations

This paper studies the sampled-data based asynchronous control problem for switched nonlinear systems subject to stochastic perturbations. Applying the T-S fuzzy model, the sampled-data based asynchronous stabilization is studied for switched nonlinear systems subject to stochastic perturbations. Combining the sampled-data dependent Lyapunov functional with the mode-dependent average dwell-time technique, a fuzzy controller is obtained to stabilize switched nonlinear systems in the mean-square sense. No more than one switching and multiple switchings are both discussed in one sampling interval to achieve more common results. At last, a simulation example about nonlinear mass-spring mechanical systems subject to stochastic perturbations is given to illustrate the effectiveness of proposed results.

On stability analysis of random impulsive and switching neural networks

The problem of stability analysis for a general class of random impulsive and switching neural networks is studied in this paper, in which both the continuous dynamics and the impulsive jumps are subject to random disturbances. First, a result concerning with the existence and uniqueness of solutions to random impulsive and switching neural networks is developed under some general conditions. Then, by means of time-varying discretized Lyapunov function approach and dwell time technique, some criteria guaranteeing global asymptotic stability and noise-to-state stability are established, in which the impulse and switching effects are characterized in an aggregated form. Two numerical examples are employed to explain and illuminate the efficiency of the developed results.

Stability analysis and robust stabilisation for a class of switched nonlinear systems with input delay

ABSTRACT This paper investigates stability analysis and robust model reference tracking control problem for a class of switched nonlinear systems with input delay and disturbance. Using a new Lyapunov–Krasovskii functional, free-weighting matrices and average dwell-time technique, new input-to-state stability conditions are derived in terms of linear matrix inequalities under a certain bound of delay. Then, based on the proposed Lyapunov–Krasovskii functional, robust model reference tracking control problem is studied. Finally, a kind of state feedback control law is proposed to guarantee robust model reference tracking performance. In addition, some examples are given to illustrate the effectiveness and feasibility of the proposed method.