Finite-horizon optimal secure tracking control under denial-of-service attacks

The finite-horizon optimal secure tracking control (FHOSTC) problem for cyber-physical systems under actuator denial-of-service (DoS) attacks is addressed in this paper. A model-free method based on the Q-function is designed to achieve FHOSTC without the system model information. First, an augmented time-varying Riccati equation (TVRE) is derived by integrating the system with the reference system into a unified augmented system. Then, a lower bound on malicious DoS attacks probability that guarantees the solutions of the TVRE is provided. Third, a Q-function that changes over time (time-varying Q-function, TVQF) is devised. A TVQF-based method is then proposed to solve the TVRE without the need for the knowledge of the augmented system dynamics. The developed method works backward-in-time and uses the least-squares method. To validate the performance and features of the developed method, simulation studies are conducted in the end.

Finite-time tolerant containment control for IT2 T-S fuzzy network multi-agent systems with actuator faults, packet dropouts and DoS attacks

This article studies finite-time tolerant containment control issue for uncertain nonlinear networked multi-agent systems (MASs) with actuator faults, denial-of-service (DoS) attacks and packet dropouts, under the framework of interval type-2 (IT2) Takagi-Sugeno (T-S) fuzzy method. Firstly, based on establishing the actuator fault models and introducing Bernoulli random distribution to represent the packet dropouts phenomenon, the IT2 T-S fuzzy network MASs under actuator faults and packet dropouts are constructed as switchable systems according to the attack situations on the communication channels. Secondly, the slack matrix with more information of lower and upper membership functions is introduced in the stability analysis to reduce conservatism. And on basis of Lyapunov stability theory and average dwell-time method, finite-time tolerant containment control protocol is proposed, which makes the follower' states converge to the convex hull controlled by the leaders in finite time. Finally, the effectiveness of the control protocol designed in this article is verified by numerical simulation.

Event-based fuzzy resilient control of nonlinear DC Microgrids under denial-of-service attacks

This paper focuses on designing an event-triggered fuzzy resilient controller for networked nonlinear DC microgrid (MG) with constant power loads (CPLs) in the presence of denial-of-service (DoS) attacks. First, an attack-resilient event-triggered communication scheme is introduced to reduce the communication overhead of the DC MG while achieving the desired performance despite the presence of the DoS attacks. Second, the nonlinear event-triggered DC MG system with CPLs is modeled as a T-S fuzzy system with artificial delay through the sector nonlinearity approach combined with time-delay system modeling method. Then, by employing the noncontinuous piecewise Lyapunov-Krasovskii functional (NPLKF) approach, the asymptotic stability criterion of the built event-triggered T-S fuzzy DC MG is obtained in the form of linear matrix inequalities (LMIs), and a design method of fuzzy controller is proposed. Finally, case studies are presented to validate the efficiency of our proposed method.

Observer-based state feedback H∞ control for offshore steel jacket structures under denial-of-service attacks

This article focuses on observer-based state feedback H_∞ control for a jacket structure against DoS attacks and external wave loads. First, a networked model of the structure is formulated as a switched delay system, in which DoS attacks and network-induced delays are considered simultaneously. A matching switched observer is developed for estimating states of the networked jacket structure system. Then, some new sufficient conditions are provided for the observer-based networked H_∞ controller for the resultant switched system. Finally, it is shown from several case studies that the provided mechanism can maintain desired performance of the jacket structure against attacks and wave loads. In addition, the developed control schemes can save the control cost significantly.

Event-triggered active disturbance rejection control for nonlinear network control systems subject to DoS and physical attacks

This paper investigates the problem of event-triggered active disturbance rejection control of nonlinear network control system in simultaneous presence of unknown dynamics, physical attacks and denial-of-service attacks. Considering the network congestion, an event-triggered communication mechanism is adopted, where the measurements are transmitted only when an 'event' occurs. An indicator obeying the Markov jump rule is introduced to characterize the randomly occurring denial-of-service attacks. In virtue of the extended state observer (ESO), the states and the total disturbance which involves both unknown dynamics and physical attacks are estimated. Then, the composite controller is designed which could stabilize the overall controlled system and eliminate the so-called total disturbance. Sufficient conditions are established to guarantee the stability of the observer system and overall controlled system. The cone-complementarity linearization algorithm is adopted to obtain the parameters of the extended state observer and the controller. Finally, both numerical and application design examples demonstrate the feasibility and efficacy of the proposed method. Simulation results show that the steady-state error within 0.02 can be achieved within 3 s.