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We consider the inherent attack tolerance properties of resilient model predictive control (R-MPC) for cyber–physical systems (CPSs) modeled by discrete linear time-invariant (LTI) systems subjected to limited disruptions. In this paper, the relationship between the maximum allowable duration of Denial-of-Service (DoS) attacks, namely attacks that disrupt both sensor to controller (S–C) and controller to actuator (C–A) communication channels, and the upper bound of disturbances is deduced at length. Moreover, to achieve robust recursive feasibility and closed-loop stability of the system, we discuss that MPC with state, control and terminal constraints has a certain degree of inherent attack tolerance concerning the DoS attack duration and parameters like system matrices and the nominal terminal set. Finally, numerical simulation is given to substantiate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The paper focuses on the asynchronous filter design based on hidden Markovian model for Markovian jump systems with time-delay and external disturbances. Cyber nonlinearities in the communication environment are also considered. To further reduce the network bandwidth usage, an internal dynamic variable is introduced based on the previously extensively studied (static) event-triggered method, which is called dynamic event-triggered approach. The hidden Markovian model is utilized to characterize the asynchronous phenomenon caused by clock signals out of sync between system and filter mode. Then, according to the augmented filtering error system dynamics, some less conservative sufficient conditions are proposed to guarantee the stochastic stability with H ∞ performance. Consecutively, the filter parameter-solving problem is synthesized by a convex optimization problem. Finally, two numerical simulations are presented to demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper applies variational Bayesian to the stochastic system filtering problem for arbitrary measurement disturbances. Considering the system's robustness when confronted with disturbances, we model its dynamics with a random walk model. Afterward, by assuming an inverse-Gamma distribution, the newly introduced covariance is estimated under a variational Bayesian (VB) framework. The proposed filter improves robustness against additive disturbance and degrades automatically into a Kalman filter when without disturbance. Moreover, this filter avoids the labor-intensive process of tuning parameters. A numerical simulation and an on-site vehicle navigation experiment are given to illustrate the effectiveness of the proposed filter. [ABSTRACT FROM AUTHOR]

This paper is concerned with the design of stabilizing event-triggered controllers for nonlinear systems subject to dynamic quantization. The plant state is assumed to be partially known, and the feedback signal is transmitted to the controller at discrete-time instants via a digital channel. To that end, an event-triggered controller is synthesized based solely on the available plant measurement. In addition, to better adapt it to practical implementation, the event-triggering law we construct is only verified at periodic time instants, i.e., periodic event-triggering mechanism. Since the network is digital, the transmitted output signal must be quantized to be encoded using a finite number of bits. Furthermore, the initial output value is assumed to be unknown, and the plant is affected by external disturbance, which can result in quantizer saturation. To overcome these challenges, a dynamic quantization policy is developed for the output measurement such that the quantization regions are dynamically updated according to the value of the quantized signal. The combined approach of periodic event-triggering mechanism and dynamic quantization ensures the stability of the networked control system under mild conditions. The stability is studied using appropriate Lyapunov functions. Numerical simulations have been conducted to justify the proposed technique. [ABSTRACT FROM AUTHOR]

This paper proposes a fixed-time anti-saturation adaptive sliding mode control (FxASASMC) methodology to solve the challenge of attitude tracking control in morphing aircraft under actuator faults, saturation and external disturbances. The proposed control algorithm consists of three key components: a novel nonsingular fixed-time sliding mode surface, a fixed-time anti-saturation compensator, and a continuous fixed-time adaptive control law. The novel nonsingular fixed-time sliding mode surface is developed based on the arctan function, enabling not only the confinement and independence of the sliding modes' convergence time from the initial states but also the benefit of a smaller initial value, thereby assisting in saturation avoidance. To mitigate the saturation issue, a fixed-time anti-saturation compensator is employed. Moreover, throughout the control process, the anti-saturation compensator ensures that the output is bounded. And once the actuator saturation stops, its output converges to zero in a fixed time, which effectively minimizes the impact of the anti-saturation compensator on the control system performance in the absence of system saturation. Based on the sliding mode surface and anti-saturation compensator, the continuous fixed-time adaptive control law ensures that the attitude tracking errors converge toward the neighborhood of the origin in a fixed time, even if the boundaries of the complex disturbance are not known in advance. Moreover, the convergence time boundary remains unaffected by the initial errors. In parallel, the control command remains continuous and free of chattering. Ultimately, the proposed control scheme's effectiveness and enhanced performance are demonstrated through various numerical simulations. [ABSTRACT FROM AUTHOR]

This paper considers the robust output regulation and output constraints of the flexible wing system, under an output disturbance, distributed disturbances, boundary disturbances and a reference. The measurable outputs are merely the in-domain tracking error and the in-domain displacement perturbed by an unknown output disturbance that is used to define the uncertain output constraint. All the above disturbances and reference are supposed to be from an exosystem with unknown initial values. Under the guideline of internal model principle, a PDE-ODE coupled observer is designed to exponentially estimate the states of the wing system and exosystem, and meanwhile guarantee the robustness to the unknown coefficients of the disturbances, reference and output constraint. Observer-based nonlinear controllers are then proposed for the flexible wing system so that the in-domain tracking error is regulated toward zero. Furthermore, the approximately known endpoint tracking errors are further restrained by the estimation of the constraint. A numerical simulation is used to indicate the effectiveness of the designed observer-based dynamic controls. This paper also presents the advantages over the adaptive control and active disturbance rejection control. • A PDE-ODE coupled observer is designed to exponentially estimate the states of the wing system and exosystem, and further gives the approximate values of the endpoint tracking errors and output constraint. • Observer-based nonlinear controllers are proposed to guarantee the robust ourpur regulation of the in-domain tracking error of the flexible wing system. • The approximately known endpoint tracking errors are further restrained by the estimation of the unknwon constraint, which is further proved to be robust to unknown disturbances and references. [ABSTRACT FROM AUTHOR]

In this paper, the problem of localizing and circumnavigating an unknown stationary target by multiple autonomous agents using bearing-only measurements is studied. We assume that all agents are anonymous in the sense that they are indistinguishable from each other, and each agent is not permitted to exchange its local measurements or state information. A novel collision avoidance mechanism is proposed to ensure collision-free system evolution, and a distributed control algorithm is developed to steer the group of agents to circumnavigate the target at a desired distance with any prescribed angular spaced formation. Global finite-time stability of the system is rigorously derived. The performance of the proposed algorithms is verified through numerical simulations. [ABSTRACT FROM AUTHOR]

In most existing studies, formation tracking algorithms are generally based on state feedback strategies and assume that agents are treated as points. However, in practical scenarios, directly obtaining the state of the target can often be challenging, and agents may have their own shapes. In this paper, we model agents as rectangles, allowing each agent to establish a safety zone to avoid collisions during formation. Based on these rectangular agents, we design formation tracking algorithms for a mobile target using only local output information. Specifically, two layers of control algorithms are designed for each agent. (1) Upper-level algorithm: two types of fully distributed mobile observers are constructed based on only a portion of the target's output information. This is achieved by applying node-based adaptive coupling gains and edge-based adaptive gains to the consensus-based term in the state estimation algorithm, respectively. (2) Lower-level algorithm: a leader-following formation tracking algorithm is constructed. By cascading these two layers of algorithms, all agents track the target in formation at the same speed as the target. Finally, numerical simulations are presented to demonstrate the effectiveness of the proposed theoretical results. [ABSTRACT FROM AUTHOR]

Practical time-varying formation-containment tracking (TVFCT) issue for nonlinear multi-agent systems with general noise is researched in this paper. A neuro-adaptive practical TVFCT protocol is put forward, where neural networks (NNs) and parameter adaptive laws are developed for estimating the nonlinearities and compensating the upper bound of the time-varying formation (TVF) condition, respectively. Leaders are expected to achieve the predetermined TVF and followers are driven to move into the formation structure confined by leaders simultaneously. The whole formation position depends on the desired trajectory produced by a virtual-leader. General noise rather than white noise is investigated in the multi-agent systems. The noise-to-state-practically stability in probability (NSPS-P) criteria can be guaranteed by employing the Lyapunov theories combined random differential equations (RDEs). Numerical simulation results reveal the effectiveness of the developed protocols. [ABSTRACT FROM AUTHOR]

From the micro-level perspective of individuals, this paper proposes a node-based SIRS epidemic model on two-layer networks, and investigates the stability of the equilibrium in the model as well as the influence of network structures and infected or recovered rate on disease propagation. By using the stability theory, we give the accurate sufficient condition for the stability as well as the threshold of disease prevalence, showing the threshold of such two-layer network is less than that of isolated single-layer network. Also, an easy-to-use approximate criterion for stability of disease-free equilibrium is provided for the two-layer network with general intra-layer structures when the infected rate across layers is far less than that within layers. Further, extensive numerical simulations on several classical network structure models verify the theoretical results, and show some new interesting results: (1) for the duplex network with equivalent number of connections each layer, the infected rate across layers has more significant effect on epidemic spreading than that within layers; (2) when fixing the whole network edge density, the same number of connections each layer always be the most conductive to propagate of the disease for the duplex network of ER structures, but it is the most/worst conductive to propagate at large/small infected rate for the duplex network of small-world structures. [ABSTRACT FROM AUTHOR]

This study considers tracking an underwater transmitter using a linear array sonar. The linear array sonar measures both the transmitter's frequency and the conic angle with respect to the array's direction. By analyzing the transmitter's conic angle and frequency, the array sonar sensor estimates the transmitter's three-dimensional position and (constant) velocity. This tracking problem is termed the conic angle-frequency tracking (CAFT) problem in our paper. We first consider tracking a transmitter which moves with a constant velocity. Then, we extend the tracking filter, so that one can track a transmitter which changes its heading occasionally. For tracking a transmitter which changes its heading in three-dimensional space, we propose a filter restart scheme. As the transmitter's heading change is observed, one restarts all filter tracks so that the transmitter can be tracked continuously after its abrupt heading change. To the best of our knowledge, this study is unique in solving the three-dimensional CAFT problem for a constant velocity transmitter or a transmitter which changes its heading occasionally. The effectiveness of the proposed three-dimensional CAFT filter is demonstrated utilizing computer simulations. [ABSTRACT FROM AUTHOR]

This paper presents a cooperative approach combining a prescribed-distance inverse-optimal guidance law with balanced control for intercepting a maneuvering target, while considering input saturation. By employing a distance-dependent scale transformation, the guidance interception problem is converted into a prescribed-distance regulation form. A prescribed-distance guidance law is then implemented building upon the inverse problem of optimal control theory to minimize a specific quadratic performance index. To address the challenges posed by input saturation, a performance safety evaluation (PSE) function is introduced. This function assesses the system's safety and determines whether compensation for saturation is necessary. As a result, a balance between performance and saturation is achieved. The effectiveness of our proposed guidance law is evaluated through numerical simulations. [ABSTRACT FROM AUTHOR]

This paper aims to achieve fixed-time flocking with collision-avoidance by providing a periodic intermittent control strategy. A modified singular Cucker–Smale model with periodic intermittent control is proposed. To match our intermittent control strategy, a novel lemma about fixed-time synchronization is established through mathematical induction, and fixed-time flocking is achieved by the lemma. Moreover, based on the singular communication rate, the collision avoidance and uniform estimate of minimal inter-particle distance are proved by imposing appropriate restrictions on the initial states. Finally, three numerical simulations are given to verify the correctness of the main results. • A novel lemma of fixed-time synchronization is proposed. • An intermittent control method is used to realize the fixed-time flocking of multiple agents. • The speed of flocking convergence can be adjusted by the intermittent control. [ABSTRACT FROM AUTHOR]