Resilient Control Problem Research Articles

Resilient control of cyber‐physical systems under sensor and actuator attacks driven by adaptive sliding mode observer

AbstractThe problem of resilient control of linear cyber‐physical systems with cyber‐attacked sensor measurements and actuator commands is studied in this article. Online reconstruction of unknown cyber‐attacks is accomplished by an adaptive sliding mode observer with a novel injection term in the form of a dynamically extended equivalent control. Then, the attacked/corrupted sensor's measurements and the actuators are proposed to be cleaned up using the reconstructed attacks. The performance of the system prior to the attacks is shown to be retained after a transient response required for the attack reconstruction/estimation. The efficacy of the proposed algorithms is validated on an electrical power network.

Event-triggered resilient control for cyber-physical systems under periodic DoS jamming attacks

This paper considers the event-triggered resilient control problem for cyber-physical systems against periodic denial-of-service (DoS) attacks. Firstly, a novel event-triggered scheme without Zeno behaviors is presented to save network resources and eliminate the occurrence of invalid events during periodic DoS attacks. Subsequently, by constructing a predictor-based event-triggered control framework, the upper bound of the prediction error related to periodic DoS attack parameters is given. Furthermore, sufficient conditions related to periodic DoS attack parameters are established to ensure the input-to-state stability. It is shown that the proposed design method can achieve better system performances than the existing ones when the system suffers the same degree of periodic DoS attacks. Finally, the theoretical research results are validated through a batch reactor system model.

MAS-Based Distributed Resilient Control for a Class of Cyber-Physical Systems With Communication Delays Under DoS Attacks.

In this article, we investigate the distributed resilient control problem for a class of cyber-physical systems with communication delays under denial-of-service (DoS) attacks. In contrast to the previous DoS attacks results based on multiagent systems (MASs), a new distributed resilient control approach is proposed for more general heterogeneous linear MASs with nonuniform communication delays. Two types of sampled-based observers are, respectively, proposed. Namely, adaptive distributed observers are designed by introducing a buffer mechanism to eliminate the heterogeneous behavior caused by communication delays while adaptive distributed resilient observers are designed by introducing resilient mechanisms to resist the DoS attacks. Furthermore, a time-varying sampling period sequence is provided to prevent the attacker from identifying the sampling period of the system. Based on the developed resilient observers, a controller is developed. It is proved that the considered problem can be solved by the developed method. Finally, a numerical example is given to illustrate the effectiveness of the obtained result.

Robust adaptive estimation and tracking control for perturbed cyber-physical systems against denial of service

This paper is concerned with the adaptive state observation and resilient control problem for a class of perturbed cyber-physical system against denial of service (DoS) attacks. An adaptive observer is firstly constructed to observe the compromised states under DoS attacks. Then based on the estimated sates, a resilient control strategy is developed to remedy the negative influence of DoS attacks and perturbations. By employing linear matrix inequality and Lyapunov stability theory, one can guarantee that the system states can track the desired signals of reference systems with time going to infinity. Furthermore, the state observation errors are guaranteed to remain a high accuracy. An aircraft system with different attack forms and attack modes is given to verify the effectiveness of designed adaptive observer and control methods.

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.

Observer-Based Adaptive Hybrid Fuzzy Resilient Control for Fractional-Order Nonlinear Systems With Time-Varying Delays and Actuator Failures

This article investigates the adaptive output feedback resilient control problem for a class of incommensurate fractional-order (FO) nonlinear systems in the presence of time-varying delays and actuator faults by combining with an adaptive backstepping technique and a modified FO dynamic surface control (FODSC) method. Considering that the information of system states is not fully available, a hybrid fuzzy observer is designed to estimate the unmeasurable system states, where the neuro-fuzzy network system is introduced to handle the unknown nonlinear functions existing in the system. Furthermore, in order to overcome the problem of the explosion of complexity caused by traditional backstepping design procedure, an FO filter is constructed to pass the virtual control signal based on the FODSC scheme. Moreover, according to an indirect Lyapunov stability method, an adaptive hybrid fuzzy output feedback controller is designed to guarantee that all the signals of the closed-loop systems are bounded. Finally, three examples are given to verify the validity and superiority of the presented control scheme.

The safety region-based model predictive control for discrete-time systems under deception attacks

In this paper, a resilient control problem is investigated for the discrete-time linear system subjected to both input constraint and additive disturbances. In addition, deception attacks are also taken into consideration which could compromise the communication channels. To deal with the mentioned complexities, the so-called safety region-based defense strategy (SRDS) is designed in the context of the robust model predictive control (RMPC) method. The original constraints of the system are used to establish the safety region. Sufficient conditions are established for the proposed SRDS such that the recursive feasibility and stability of the overall closed-system are guaranteed. Finally, two numerical examples are conducted to verify the effectiveness of the proposed methodology.

A Novel Resilient Control Scheme for a Class of Markovian Jump Systems With Partially Unknown Information.

In the complex practical engineering systems, many interferences and attacking signals are inevitable in industrial applications. This article investigates the reinforcement learning (RL)-based resilient control algorithm for a class of Markovion jump systems with completely unknown transition probability information. Based on the Takagi-Sugeno logical structure, the resilient control problem of the nonlinear Markovion systems is converted into solving a set of local dynamic games, where the control policy and attacking signal are considered as two rival players. Combining the potential learning and forecasting abilities, the new integral RL (IRL) algorithm is designed via system data to compute the zero-sum games without using the information of stationary transition probability. Besides, the matrices of system dynamics can also be partially unknown, and the new architecture requires less transmission and computation during the learning process. The stochastic stability of the system dynamics under the developed overall resilient control is guaranteed based on the Lyapunov theory. Finally, the designed IRL-based resilient control is applied to a typical multimode robot arm system, and implementing results demonstrate the practicality and effectiveness.

Memory-Based Continuous Event-Triggered Control for Networked T–S Fuzzy Systems Against Cyberattacks

This article investigates the problem of resilient control for the Takagi–Sugeno (T–S) fuzzy systems against bounded cyberattack. A novel memory-based event triggering mechanism (ETM) is developed, by which the past information of the physical process through the window function is utilized. Using such an ETM cannot only lead to a lower data-releasing rate but also reduce the occurrence of wrong triggering event. Furthermore, the frequency of event generation is relatively smoother than existing ETMs. From the current releasing instant to the next, two periods are designed. The ETM works only when the first period ends, thereby avoiding the Zeno behavior that commonly exists in continuous ETM designs. The control system is then formulated as a switched fuzzy control system with two modes in each releasing period. Based on an assumption of secure control, and the proposed ETM, sufficient conditions are obtained to guarantee the exponential stability of networked T–S fuzzy systems in the presence of deception attacks in secure sense. Finally, a single-link rigid robot is taken as an example to illustrate the advantages of theoretical results.

A dynamic event-triggered resilient control approach to cyber-physical systems under asynchronous DoS attacks

In this paper, the resilient control problem for cyber-physical systems in the presence of denial-of-service (DoS) attacks which are characterized by frequency and duration properties is investigated. We consider the case that information transmission between measurement and control channels may be attacked asynchronously. A novel model is established to describe the asynchronous attack signals by a recursive characterization. Based on this model, a dynamic event-triggered resilient control approach is presented with the aim of resisting the DoS attacks. The stability criterion is derived via the Lyapunov stability theory. In contrast to the existing results on the static event-triggered mechanism, the developed method is more flexible and generates fewer events. Finally, simulation results are provided to verify the effectiveness of the proposed approach.

Resilient Control Design for Lateral Motion Regulation of Intelligent Vehicle

This article studies the state-feedback resilient control problem for lateral motion regulation of an intelligent vehicle in the presence of randomly occurring uncertainties. First, the uncertain disturbance in an external yaw moment is compensated by the randomly occurring uncertainty when modeling the vehicle system, and a resilient controller by considering the randomly occurring uncertainty is developed, which is a more general case, but increases complexity of regulation design. Then, the resilient control condition is proposed to guarantee the sideslip angle and yaw rate satisfying the prescribed $\mathcal {H}_{\infty }$ and $\mathcal {L}_2-\mathcal {L}_\infty$ performance indexes. Moreover, $\mathcal {H}_{\infty }$ and $\mathcal {L}_2-\mathcal {L}_\infty$ performance indexes of control outputs are merged into one linear matrix inequality. Finally, an illustrative simulation is given to show the effectiveness of the proposed resilient control design.

Adaptive synchronization of multi-agent systems with resilience to communication link faults

The resilience of multi-agent systems (MAS) measures the capability of recovering the cooperative performance after experiencing faults or uncertainties. In this paper, we seek the improvement of the synchronization resilience for MAS by means of addressing unknown faults on communication links. To this end, we first transform the resilient control problem into designing distributed state observers. In addition, we show that the proposed state observers are resilient to communication link faults. Finally, we provide the main result of this paper as a synchronization protocol for MAS even in the presence of communication link faults.

Robust resilient control for parametric strict feedback systems with prescribed output and virtual tracking errors

SummaryThis paper investigates the robust resilient control problem for a class of parametric strict feedback nonlinear systems with prescribed output and virtual tracking errors performance. The resilience is governed by a continuously nonlinear control gains function, which endows the virtual and actual controllers with self‐adjusting abilities with respect to transformed error surfaces. The proposed control scheme is adaptation, estimation, and approximation‐free in the presence of unknown parameters and nonlinearities, and only a number of control gains, which is equal to the relative degree of the considered plants, need to be selected in applications. It is proved by rigorous analysis that the output tracking errors are confined in predefined prescribed performance functions under some nonrestrictive initial conditions, and the bounds of states are obtained characterized as control gains and systemic function‐associated constants. Finally, comparative illustrative examples are given to demonstrate the effectiveness of the proposed control scheme.

Robust event‐triggered model predictive control for cyber‐physical systems under denial‐of‐service attacks

SummaryThis paper investigates the resilient control problem for constrained continuous‐time cyber‐physical systems subject to bounded disturbances and denial‐of‐service (DoS) attacks. A sampled‐data robust model predictive control law with a packet‐based transmission scheduling is taken advantage to compensate for the loss of the control data during the intermittent DoS intervals, and an event‐triggered control strategy is designed to save communication and computation resources. The robust constraint satisfaction and the stability of the closed‐loop system under DoS attacks are proved. In contrast to the existing studies that guarantee the system under DoS attacks is input‐to‐state stable, the predicted input error caused by the system constraints can be dealt with by the input‐to‐state practical stability framework. Finally, a simulation example is performed to verify the feasibility and efficiency of the proposed strategy.

Resilient Observer-Based Control for Cyber-Physical Systems With Multiple Transmission Channels Under Denial-of-Service.

This paper investigates the resilient control problem for cyber-physical systems (CPSs) with multiple transmission channels under denial-of-service (DoS). First, a set of partial observers is designed to estimate partial states corresponding to different channels. Second, by combining the proposed partial observers, the finite-time observer technique and a switching scheme, a modified finite-time partial observer-based controller is proposed to stabilize the system in the presence of DoS. Compared with the existing results for the CPSs with multiple transmission channels, the computational burden of designing observer-based controller is reduced, and the resilience against DoS is improved by adopting the proposed finite-time partial observers. Especially, besides stability, the proposed resilient observer-based controller also provides better disturbance rejection performance.

Event-triggered resilient control for cyber-physical system under denial-of-service attacks

In this paper, we research the resilient control problem for cyber-physical system (CPS) under denial-of-service (DoS) attacks. These malicious DoS attacks aim to impede the communication of measurement data or control data in order to endanger the functionality of the closed-loop system. Meanwhile, in order to save network resources, event-triggered mechanism has been introduced into this CPS. By exploiting the relationship between cyber system and physical system, we aim to design the resilient controller and resilient control strategy to tolerate a class of DoS signals characterised by probability without serious hazard to the stability and performance of CPS. Furthermore, considering that the transition probability of cyber state is unknown, the on-policy reinforcement learning method – SARSA (State-Action-Reward-State-Action) – is used to solve this problem. Thus a resilient control algorithm that integrates game theory, robust control theory, event-triggered control method and SARSA learning method is presented to enhance the security and robustness of the CPS. At last, the numerical simulation and experimental results are given to demonstrate the validity and applicability of the proposed algorithm.

Resilient Control of Wireless Networked Control System Under Denial-of-Service Attacks: A Cross-Layer Design Approach.

The resilient control refers to the control methodology which provides an interdisciplinary solution to secure the control system. In this paper, the resilient control problem is investigated for a class of wireless networked control systems (WNCS) under a denial-of-service (DoS) attack. In the presence of the DoS attacker, the control command sent by the transmitter may be interfered, which can cause the degradation of the signal-to-interference-plus-noise ratio and further lead to packet dropout phenomenon. Such a packet dropout phenomenon is described by a two-state Markov-chain. A cross-layer view is adopted toward the security issue of the considered WNCS. The Nash power strategies and optimal control strategy in the delta-domain are obtained in the cyber- and physical-layer, respectively. Based on the obtained strategies, the coupled-design problem is solved which aims to drive the underlying control performance to the desired security region by dynamically manipulating the cyber-layer pricing parameters. Finally, a numerical simulation is conducted to verify the validity of the proposed methodology.

Resilient control for wireless networked control systems under DoS attack via a hierarchical game

SummaryIn this paper, the resilient control problem is investigated for a wireless networked control system (WNCS) under denial‐of‐service (DoS) attack via a hierarchical game approach. In the presence of a wireless network, a DoS attacker leads to extra packet dropout in the cyber layer of WNCS by launching interference power. A zero‐sum Markov game is exploited to model the interaction between the transmitter and the DoS attacker under dynamic network environment. Additionally, with the attack‐induced packet loss, an H∞ minimax controller is designed in the physical layer by using a delta operator approach. Both value iteration and Q‐learning methods are used to solve the hierarchical game problem for the WNCS. The proposed method is applied to a load frequency control system to illustrate the effectiveness.

Event-triggered finite-time resilient control for switched systems: an observer-based approach and its applications to a boost converter circuit system model

Under an event-triggered communication scheme (ETCS), this note focuses on the observer-based finite-time resilient control problem for a class of switched systems. Different from the existing finite-time problems, not only the problem of finite-time boundedness (FTBs) but also the problem of input-output finite-time stability (IO-FTSy) are considered in this paper. To effectively use the network resources, an ETCS is formulated for switched systems. Considering that not all the states could be measured, thus an event-triggered observer is constructed, and then, an observer-based resilient controller is devised, which robustly stabilizes the given systems in the meaning of finite-time control. Based on time-delay method and Lyapunov functional approach, interesting results are derived to verify the properties of the FTBs and the IO-FTSy of the event-triggered (ET) closed-loop error switched systems. All the matrix inequalities can be converted to linear matrix inequalities (LMIs) so as to simultaneously obtain the controller gain and observer gain. Finally, the applicability of the proposed control scheme is verified via a boost converter circuit system.

Resilient Control of Networked Control System Under DoS Attacks: A Unified Game Approach

We consider the problem of resilient control of networked control system (NCS) under denial-of-service (DoS) attack via a unified game approach. The DoS attacks lead to extra constraints in the NCS, where the packets may be jammed by a malicious adversary. Considering the attack-induced packet dropout, optimal control strategies with multitasking and central-tasking structures are developed using game theory in the delta domain, respectively. Based on the optimal control structures, we propose optimality criteria and algorithms for both cyber defenders and DoS attackers. Both simulation and experimental results are provided to illustrate the effectiveness of the proposed design procedure.