Resilient event-triggered consensus control for nonlinear muti-agent systems with DoS attacks

The distributed event-triggered secure consensus control is discussed for multi-agent systems (MASs) subject to DoS attacks and controller gain variation. In order to reduce unnecessary network traffic in communication channel, a resilient distributed event-triggered scheme is adopted at each agent to decide whether the sampled signal should be transmitted or not. The event-triggered scheme in this paper can be applicable to MASs under denial-of-service (DoS) attacks. We assume the information of DoS attacks, such as the attack period and the consecutive attack duration, can be detected. Under the introduced communication scheme and the occurrence of DoS attacks, a new sufficient condition is achieved which can guarantee the security consensus performance of the established system model. Moreover, the explicit expressions of the triggering matrices and the controller gain are presented. Finally, simulation results are provided to verify the effectiveness of the obtained theoretical results.     

Fault-tolerant control for model-free networked control systems under DoS attacks

This paper studies the fault-tolerant model-free adaptive control (FT-MFAC) problem for a class of single-input single-output (SISO) nonlinear networked control systems (NCSs) under denial-of-service (DoS) attacks. A novel FT-MFAC framework is established with the consideration of DoS attacks and the sensor fault, in which DoS attacks obeying the Bernoulli distribution randomly happen in the sensor-to-controller channel and the sensor fault is approximated by the radial basis function neural network (RBFNN). Based on the proposed framework, an FT-MFAC algorithm that uses only input/output data is proposed to guarantee that the output tracking error is bounded in the sense of mean square. Finally, the effectiveness of the proposed algorithm is illustrated by a simulation.     

Switching resilient control scheme for cyber-physical systems against DoS attacks

This paper investigates the problem of resilient control for cyber-physical systems (CPSs) described by T-S fuzzy models. In the presence of denial-of-service (DoS) attacks, information transmission over the communication network is prevented. Under this circumstance, the traditional control schemes which are proposed based on perfect measurements will be infeasible. To overcome this difficulty, with the utilization of an equivalent switching control method, a novel gain-switched observer-based resilient control scheme is proposed. According to whether the DoS attack is activated, two different controller synthesis conditions are given by combining the information of the tolerable DoS attacks. In addition, a quantitative relationship between the resilience against DoS attacks and the obtained disturbance attenuation level is revealed, which is helpful for balancing the tradeoff between the abilities to tolerate DoS attacks and attenuate the influence of external disturbance. Finally, simulation results are provided to verify the effectiveness of the proposed switching control scheme.     

Quantized output feedback control for switched systems with DoS attacks and event-triggered sampling

This paper studies the event-triggered control for discrete-time switched systems under the influence of denial-of-service (DoS) attacks and output quantization. Firstly, the switching is assumed to be slow enough in the sense of average dwell time, and DoS attacks are assumed to be energy-limited by constraining DoS frequency and DoS duration. Secondly, by designing an event-triggered mechanism which integrates switching, DoS attacks and transmission error, the initial state bound is obtained at a finite time. Then, a novel quantization coding method is designed by introducing a monotonically increasing sequence, which guarantees the unsaturation of the quantizer. On the basis of this, the exponential convergence and Lyapounov stability of the closed-loop system are established. Finally, two-tanks system is illustrated to demonstrate the effectiveness of the theoretical analysis.     

Adaptive neural dissipative control for markovian jump cyber-Physical systems against sensor and actuator attacks

This work addresses the issue of adaptive neural dissipative control for Markovian Jump Cyber-Physical Systems subject to output-dependent sensor and state-dependent actuator attacks. Attackers can inject false information into feedforward and feedback signals to degrade system performance or even destabilize the system. To identify and approximate attack signals, neural network technique is employed. Attacks are successfully withstood by constructing the estimated signals of these approximate functions. New adaptive state and output feedback controllers are being developed in the meantime. Then, by adapting Lyapunov function technique, sufficient conditions are provided to achieve the stochastic stability of the considered system with extended dissipation. Last, two practical examples are applied to elucidate the effectiveness of the devised adaptive neural control approaches.     

Observer-based defense control for networked Takagi-Sugeno fuzzy systems against asynchronous DoS attacks

This article investigates the defense control problem for sampled-data Takagi-Sugeno (T-S) fuzzy systems with multiple transmission channels against asynchronous denial-of-service (DoS) attacks. Firstly, a new switching security control method is proposed to tolerate the asynchronous DoS attacks that act independently on each channel. Then, based on switching strategy, the resulting augmented sampled-data system can be converted into new switched systems including several stable subsystems and one open-loop subsystem. Besides, by applying the piecewise Lyapunov-Krasovskii (L-K) function method, membership functions (MFs) dependent sufficient conditions are derived to ensure the exponential stability of newly constructed switching systems. Moreover, quantitative relations among the sampling period, the exponential decay rate, and the rate of all channels being fully attacked and not being completely attacked are established. Finally, simulation examples show the effectiveness of the developed defense control approach.     

Event-triggered H∞ control for network-based uncertain Markov jump systems under DoS attacks

This paper investigates the event-triggered $H_{\infty }$ control problem for network-based Markov jump systems subject to denial-of-service (DoS) attacks. In order to reduce the amount of signal transmission, the event-triggering scheme (ETS) is adopted between sensor and controller. Due to DoS attacks invalidating data over networks, a new switched time-delay Markov jump model with unstable subsystems is developed based on state feedback controller. Then with the help of piecewise Lyapunov-Krasovskii functional method, a set of sufficient conditions incorporating constraints of DoS attacks are provided, which guarantees that the resulting switched time-delay Markov jump system is stochastically stable with a certain $H_{\infty }$ performance. Subsequently, we present criterions to obtain the parameters of state feedback gain and ETS. Finally, an example is provided to show the effectiveness of the proposed method.     

Resilient control of double-integrator stochastic multi-agent systems under denial-of-service attacks

The resilient control problem of double-integrator stochastic multi-agent systems under denial-of-service (DoS) attack is studied in this paper. We neutralize the effects of DoS attacks by introducing a hidden layer that has no physical significance. Compared with previous works, this method requires less computation, does not require a high degree of connectivity of communication topology, and does not need to know any information about attacks, such as attack frequency and attack duration. It is proved that the introduction of hidden layer will not affect the consensus of the original system and can improve its robustness. Besides, we also verify the effectiveness of event-triggered mechanism for systems with the hidden layer.     

Resilient sliding mode control for a class of cyber-physical systems with multiple transmission channels under denial-of-service attacks

This paper investigates the resilient sliding mode control problem for cyber-physical systems (CPSs) with multiple transmission channels under denial-of-service (DoS) attacks. A set of finite-time observers is designed, and a switched integral-type sliding surface is introduced. Thus, the impact of unreliable state estimating channels is reduced, and the disturbance rejection performance is also improved. The number of linear matrix inequalities (LMIs) decreases compared with some existing results in designing the observer-based controller, and the input-to-state stability (ISS) is guaranteed. Moreover, the input saturation and event-triggering scheme are considered in the controller and handled by an auxiliary system. The network congestion in the control channel is thus relieved, and the Zeno behavior is excluded simultaneously. Finally, an example of an unmanned stratospheric airship is given to demonstrate effectiveness of the proposed resilient control approach.     

Distributed event-triggered control co-design for large-scale systems via static output feedback

This work investigates the problem of distributed control for large-scale systems, in which a communication network is available to exchange information. To avoid the unnecessary communication, an event-triggered control (ETC) mechanism is introduced, in which the transmission occurs only when a certain event is triggered. Under the assumption that only the output signal is available, the static output feedback (SOF) is considered in this work. The aim of the co-design is to design an SOF controller and an ETC condition simultaneously such that the overall closed-loop system is stabilized with a certain level of performance. To this end, an event-triggering scheme based on output signals is proposed to determine when the event is triggered. Then the closed-loop system is modeled as a linear perturbed system. The distributed control co-design is formulated as a convex optimization problem with linear matrix inequalities (LMIs) constraints. Finally, a numerical example is presented to show the effectiveness of the proposed design method.     

Stabilization of networked singular control systems under double-channel quantization and DoS attacks

This paper is concerned with the asymptotic stabilization of discrete singular systems over a bandwidth limited digital network, when the state measurements are periodically sampled and encoded using a finite alphabet, and the control input signals are subject to finite-alphabet encoding and Denial-of-Service attacks. It is assumed that the attack signals are uniform for all sampling periods and have been identified. A dynamic controller is designed based on a restricted equivalent model of the controlled plant. Two types of finite-level quantizers are designed for encoding: uniform and logarithmic. For both types of quantizers, dynamic encoding-decoding strategies for the plant state and the control input are proposed, which exploit the controller’s state and the origin, respectively, as the quantization centers. Sufficient conditions for asymptotic stabilizability involving the sampling period, the numbers of the state and input quantization levels, the beginning time and corresponding duration of the attack signals are established by propagating reachable sets during sampling interval. Finally, several numerical examples are given to illustrate the design procedures and the efficacy of the theoretical results.     

Interval state estimation for positive linear systems under DoS attacks

This paper is concerned with the interval state estimation problem for continuous-time positive linear systems under intermittent denial-of-service (DoS) attacks. To solve the problem, two types of estimate strategies are proposed. One is using the interval observer at all times, the other is using the interval observer in the absence of attacks but using, instead, the interval predictor otherwise. To facilitate the analysis, the interval state estimation problem is reformulated into the positivity and stability analysis of the associated error system. Then, stability conditions and disturbance attenuation characterization of the error systems for the two strategies are established via a mode-dependent Lyapunov approach. Roughly speaking, it is shown that the interval estimation accuracy of the former strategy is higher than the latter when the open loop system is stable. Finally, several numerical examples are provided to illustrate the ascendancy of the proposed estimation strategies.     

Interval observer based event-triggered consensus control of networked multi-agent systems under DoS attacks

This paper presents an interval observer (IO) based event-triggered control strategy for networked multi-agent systems (MASs) under denial of service (DoS) attacks. The most significant contribution is the proposal of a new event-triggered controller based on distributed IO. Toward this, first, a new distributed IO based on output information is first constructed to estimate the state interval of each agent in the networked MASs. Then a novel distributed IO based event-triggered control (ETC) protocol is constructed using only the information observed by IO. Moreover, it turns out that based on the designed IO based ETC protocol, all agents can reach secure consensus exponentially and Zeno behavior is excluded. Finally, simulation example is used to verify the feasibility of the constructed IO based ETC protocol.     

Dynamic event-triggered control for nonlinear NCSs subject to DoS attacks

In this study, a dynamic event-triggered control problem is addressed for nonlinear networked control systems (NCSs) subject to denial-of-service (DoS) attacks. Assume that data from the plant to the controller is transmitted via a wireless transmission channel under malicious DoS attacks characterized by frequency and duration properties. On the premise of ensuring the stability and minimum inter-event time (MIET) of the systems, dynamic event-triggered mechanisms (DETMs) are proposed for the hybrid dynamic system to withstand a certain degree of DoS attacks. Three event-triggered schemes are designed for the most existing state-based control systems which further enlarge the inter-event times, and the stabilization conditions of hybrid dynamic system are given. Finally, illustrative examples are provided to verify the effectiveness of the presented theoretical results.     

Security control for two-time-scale cyber physical systems with multiple transmission channels under DoS attacks: The input-to-state stability

This paper investigates the security control problem for a class of two-time-scale cyber-physical systems (TTSCPSs) with multiple transmission channels under the denial-of-service (DoS) attacks. A linear TTSCPSs model is first proposed with slow and fast transmission channels, which correspond to slow and fast physical components in terms of their communicating capacities and sampling rates. The measurement data-packets are transmitted via slow and fast transmission channels which are compromised by asynchronous DoS attacks. A novel composite controller depending on the singular perturbation parameter (SPP) is formulated and corresponding switching laws are designed to achieve certain resilience against DoS attacks. Then, by establishing a SPP-dependent Lyapunov function, sufficient conditions are obtained on the duration and frequency of the DoS attacks, such that, for any SPP less than or equal to a predefined upper bound, the input-to-state stability can be guaranteed for the closed-loop TTSCPSs. Finally, a networked DC motor control system is employed to demonstrate the effectiveness of the proposed security control algorithm.     

Schedule and control co-design for networked control systems with bandwidth constraints

A new solution of networked control systems with bandwidth constraints is proposed in this paper. First, at the smart sensor side, a new stochastic communication logic scheduling strategy is designed based on a Poisson Process with time-dependent intensity. Under this strategy, the system only needs a finite-time state update. Hence the quantity of transmission of message is reduced. With the proof that the stochastic communication logic is essentially a Markov chain, the NCS is modeled as a jump system and the necessary and sufficient condition of stability for the state feedback system is presented as well. With the proposed stochastic communication logic, based on the update time, the controller is given in terms of a LMI. The simulation result shows that the scheduling strategy can decrease the network traffic, while the controller can guarantee certain good system performance.     

Scaled consensus design for multiagent systems under DoS attacks and communication-delays

This paper aims to solve scaled consensus problem for general linear multiagent systems under denial-of-service (DoS) attacks. Firstly, we propose a new scaled disagreement vector and investigate its properties under switching and undirected graphs. Secondly, we establish sufficient conditions in terms of linear matrix inequalities in order to guarantee that the multiagent system achieves scaled consensus under DoS attacks. Contrary to most existing studies where DoS attacks on all the channels are same, in this note, we formulate the problem such that the adversary compromises each agent independently. Moreover, the distributed consensus protocol is investigated for networks with time-varying delay. Finally, two simulation examples are given to demonstrate effectiveness of the proposed design methodologies.     

Resilient observer-based sliding mode control of connected vehicles with denial-of-service attacks

This paper investigates an observer-based sliding mode control (SMC)) for connected vehicles under denial-of-service attacks. The attacks refer to interrupting communication channels between vehicles. Firstly, a reduced order observer is used to estimate the relative acceleration between neighbor vehicles, and a switching communication topology is introduced to model the attack. Then, an observer based sliding mode controller is proposed to achieve desired stability performance. Moreover, a quadratic cost performance is also defined and the cost upper bound is proved. Some sufficient conditions are provided such that the connected vehicles can achieve robust tracking performance, and input-to-state string stability is guaranteed under zero initial errors. Finally, numerical simulations are given to illustrate the validity of the designed controller.