Consecutive Packet Dropouts Research Articles

A Sampled-Data-Based Secure Control Approach for Networked Control Systems Under Random DoS Attacks.

This article aims to analyze H∞ stability of a class of networked control systems (NCSs) under random denial of service (DoS) attacks and design a sampled-data-based state feedback security controller to mitigate the influence of attacks. Different from the existing random attacks, the information about the maximum duration time of DoS attacks can be captured by introducing a predesigned logical processor. Then, based on the periodic sampling technique, the probability of attack occurrence and the resultant number of maximum allowable consecutive packet dropouts can be calculated, which is quite significant to investigating the security problem of NCSs. A DoS-dependent security controller which makes full use of the attack probability information and the number of attack-induced packet dropouts is designed. A novel networked sampled-data system model is first established that enables us to deal with the random DoS attacks phenomena and the time-varying delay induced by attacks under a uniform framework. By structuring a suitable Lyapunov-Krasovskii functional, the relationship between mean square asymptotic stability and attack characteristics is obtained. Finally, the reliability and applicability of the presented control strategy in eliminating the influence of DoS attacks are validated by two practical engineering applications.

Consensus control and initialization region optimization for leader‐following multi‐agent systems under time‐varying communication delay and consecutive packet dropouts

AbstractThis article is to investigate the consensus control and initialization region optimization for leader‐following multi‐agent systems with time‐varying communication delay and nonidentical consecutive packet dropouts. By combining the Bernoulli distribution model of the data loss and the Hadamard product, the control protocols affected by both communication delay and packet dropouts are utilized to formulate the consensus problem into the mean‐square stability problem of the augmented error systems. Resorting to the Lyapunov function methodology and a structure separation method, a sufficient condition to ensure the consensus is built in the form of linear matrix inequality. Relying on the given Lyapunov function and set‐membership analysis, an optimization procedure is proposed to simultaneously ensure the consensus and enlarge the estimated ellipsoid of initial conditions. The validity of the provided method is illustrated through a comparative simulation.

H∞ Controller Design for Networked Systems With Two-Channel Packet Dropouts and FDI Attacks.

In this article, the stochastic analysis and H∞ controller design problems of networked systems with packet dropouts and false data injection attacks are investigated. Different from the existing literature, we focus on the linear networked systems with external disturbances and both sensor-controller channel and controller-actuator channel are studied. First, we present a discrete-time modeling framework that leads to a stochastic closed-loop system with randomly varying parameters. To facilitate the analysis and H∞ control of resulting discrete-time stochastic closed-loop system, an equivalent yet analyzable stochastic augmented model is further constructed by matrix exponential computation. Based on this model, a stability condition is derived in the form of linear matrix inequality (LMI) with the aid of a reduced-order confluent Vandermonde matrix, Kronecker product operation, and law of total expectation. Specifically, the dimension of the LMI obtained in this article does not increase as the upper bound of consecutive packet dropouts does, which is also different from the existing literature. Subsequently, a desired H∞ controller is obtained such that the original discrete-time stochastic closed-loop system is exponentially mean-square stable with a prescribed H∞ performance. Finally, a numerical example and a direct current motor system are exploited to substantiate the effectiveness and practicability of the designed strategy.

Observer‐based sampled‐data control for networked systems with consecutive packet dropouts

AbstractThis paper investigates the observer‐based sampled‐data control problem for networked systems with consecutive packet dropouts. A new consecutive packet dropout model is established to describe the phenomenon of packet dropout in both the sensor‐controller (S‐C) and controller‐actuator (C‐A) channels. First, the considered system with observer‐based control scheme is studied in the discrete‐time domain by using equivalent discretization transformation. In order to simplify subsequent analysis, matrix exponential computation is employed to transform the discrete‐time system into a more tractable form. Then, the proposed new consecutive packet dropout model is taken into consideration to establish the stochastic mean square exponential stability condition. Furthermore, a novel two‐step synthesis approach is used to design the observer‐based controller. Finally, the effectiveness of the proposed observer‐based sampled‐data control approach is verified using a numerical example. In addition, the advantages of the proposed approach are validated through comparisons.

Coordinated Distributed Predictive Control for Voltage Regulation of DC Microgrids With Communication Delays and Data Loss

This paper is concerned with the voltage tracking problem of DC microgrids subject to communication delays and packet losses, for which existing work commonly adopts passive fault-tolerant approaches. To accurately compensate for the above communication constraints experienced by DC microgrids, a coupled discrete microgrid model is developed on the basis of the physical laws of actual DC microgrids. Unlike the practice of passively tolerating communication delays, through the physical model established, this paper suggests a consensus-based proportional-integral predictive control strategy, which can actively compensate for communication delays and consecutive packet dropouts encountered by DC microgrids. Under the observer-based distributed networked predictive control framework, each distributed generation subsystem in the microgrid exchanges its own measurements over the network and integrates information from controllers of other units to achieve output voltage consensus in the presence of time delays and packet losses. Furthermore, to demonstrate the generality of the proposed method, the sufficient and necessary conditions for the DC microgrid system to accomplish voltage tracking are given. These conditions are rendered in the form of matrix eigenvalues associated with the physical connections and communication couplings between distributed generation units. Besides, the stability and convergence of the closed-loop microgrid system are given in the form of linear matrix inequality based on the Lyapunov function. Finally, the performance of the proposed control scheme is evaluated in terms of its convergence, robustness to load variations, and plug-and-play functionality through the built photovoltaic cell-based (with battery banks) DC microgrid hardware system.

Stabilization of Networked Control Systems Subject to Consecutive Packet Dropouts: The Random Clock Offsets Case

In this article, the stabilization problem is investigated for a class of networked control systems with random clock offsets and consecutive packet dropouts. Different from the existing literature, the consecutive packet dropouts occurring in communication networks are subject to clock offsets, and the clock offsets between the sensor and the controller are described by a random variable with a certain probability distribution. First, we construct a closed-loop discrete-time stochastic system by considering the random clock offsets and the consecutive packet dropouts in a unified framework. To render the discrete-time system suitable for analysis, an equivalent yet tractable stochastic augmented model is then established, where the system matrix is characterized by high nonlinearity and dual randomness, which poses substantial difficulties for the expectation operation in the controller design process. In order to deal with the difficulties, the law of total expectation, confluent Vandermonde matrix, and Kronecker product operation are introduced and then a stability condition in the form of linear matrix inequality is obtained. Based on this, a desired controller is designed, such that the closed-loop stochastic system is stochastically stable. Finally, a numerical example with two cases and an example using batch reactor are provided to demonstrate the effectiveness of the proposed design approach.

Decentralized Resilient Output-Feedback Control Design for Networked Control Systems Under Denial-of-Service

This article deals with the problem of decentralized resilient observer-based output-feedback control design for networked control systems (NCSs). The proposed scheme considers both network imperfections and security issues. It is assumed that the NCS is suffering from time-varying network-induced delays and time-varying transmission intervals. Moreover, data transmission is performed over a nonsecure network that suffers from a denial-of-service (DoS) attack. The DoS jamming attack has affected the network by the occurrence of consecutive packet dropouts, which result in attack-induced packet dropouts. Based on the fact that packet dropouts caused by DoS attacks naturally do not follow a specific statistical pattern, the attack-induced packet dropouts are modeled as an extension of time-varying intervals with no probability distribution. Sufficient conditions are provided to guarantee the uniformly globally exponential stability of the NCS in the form of linear matrix inequalities. Finally, the effectiveness and applicability of the proposed method are demonstrated by simulation results.

Stability Analysis and Controller Design of Networked Active Vehicle Suspension System Subject to Delays and Packet Losses

In this paper, the stability analysis and control design of networked control systems (NCS) subject to network induced delay and packet dropouts, the study is aiming to maximize the allowable upper bound of network induced delay together with the number of consecutive packet dropouts, The analysis method utilizes a new Lyapunov-Krasovskii (LKF) functional to provide less conservative results. The delay-dependent stability criteria based on improved Wirtinger inequality and reciprocally convex combination inequality are derived in terms of linear matrix inequalities (LMI). Finally, numerical examples are given to show the effectiveness of the proposed analysis method compared to other existing methods.

A Probability Theory Approach to Stability Analysis of Networked Sampled-Data Systems With Consecutive Packet Dropouts

In this brief note, a probability theory approach is proposed to investigate the stability analysis issue for a class of networked sampled-data systems with packet dropouts. The continuous-time linear system under consideration is first transformed into a discrete-time system, where the system matrix of the discrete-time system is characterized by stochastic characteristic. Then, by the matrix exponential computation, an equivalent discrete-time stochastic system is established. Based on this, a controller is designed by the law of total expectation, which guarantees the stochastic stability of the closed-loop stochastic system. Finally, a numerical example and an example using power grid with IEEE 4-bus line are used to verify the effectiveness and applicability of the proposed design algorithm.

Improved robust H ∞ stability analysis and stabilisation of uncertain and disturbed networked control systems with network-induced delay and packets dropout

This paper is concerned with stability analysis and stabilisation of uncertain Networked Control Systems (NCS) with network-induced delay and packet dropouts. This proposal aims at maximising the allowable upper bound of network-induced delay, together with the number of consecutive packet dropouts, from which uncertain and disturbed NCS plants are stable. A novel augmented Lyapunov–Krasovskii functionals (LKF), dependent on both the lower and upper bounds of the network-induced time-varying delay, is considered to derive the proposed delay-dependent LMI-based stability conditions. Relaxation of these conditions are obtained by exploiting simple and double integral Wirtinger's inequalities to introduce more degrees of freedom from the LKF terms than existing related conditions in the literature. Finally, numerical examples and simulation results are presented to illustrate the effectiveness and the conservatism improvement raised by this proposal compared to previous related results.

Networked control for linear systems with forward and backward channels in presence of data transmission delays, consecutive packet dropouts and disordering

This paper investigates networked control for discrete-time systems with communication imperfections including data transmission time-varying delays, consecutive packet dropouts and packet disordering. The system states, which are measured by a sensor with periodic sampling period, will be directly transmitted to a sender and further delivered to a remote controller with aperiodic sending time-intervals. Only when the controller receives valid state information, the control signals are calculated and sent to the actuator. Because the data transmission imperfections are simultaneously allowed in the forward and backward communication channels (i.e., sender-to-controller and controller-to-actuator networks), the data transmission procedure from the sensor to the actuator is analyzed in details and the actuator received control command is presented in a time-delay description. Meanwhile, the qualitative relationships between the non-periodical sampling period, time-delay bound, consecutive packet dropout number and disordering are given as well. A delay-independent Lyapunov functional is employed while the sufficient delay-dependent stability condition is obtained. By the proposed method, not only system asymptotical stability of the closed-loop system can be achieved but also the network imperfections can be tolerated. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed method.

Static Output Feedback Predictive Control for Cyber-Physical System under Denial of Service Attacks

This paper addresses the static output feedback predictive (SOFP) control problem with cyber-physical system (CPS) subject to Denial-of-Service (DoS) attacks. The effects of DoS attacks are reasonably assumed to the bounded consecutive packet dropouts by considering the energy constraints of an attacker. Then, a novel predictive control sequence, in which only the latest successfully received output is employed, is designed to compensate such packet dropouts caused by DoS attacks. Furthermore, the stability criterion and predictive control design are carefully derived by using the switching Lyapunov functional approach and linear matrix inequality. Compared with the previous works, the proposed predictive control strategy can compensate arbitrary packet dropouts under DoS attacks while only the latest successfully received output is available. At last, a simulation example illustrates the effectiveness of the SOFP control strategy.

A Hybrid Controller for DOS-Resilient String-Stable Vehicle Platoons

This paper deals with the design of resilient Cooperative Adaptive Cruise Control (CACC) for homogeneous vehicle platoons in which communication is vulnerable to Denial-of-Service (DOS) attacks. We consider DOS attacks as consecutive packet dropouts. We present a controller tuning procedure based on linear matrix inequalities (LMI) that maximizes the resiliency to DOS attacks, while guaranteeing performance and string stability. The design procedure returns controller gains and gives a lower bound on the maximum allowable number of successive packet dropouts. A numerical example is employed to illustrate the effectiveness of the proposed approach.

Synchronization of Stochastic Complex Dynamical Networks Subject to Consecutive Packet Dropouts.

This paper studies the modeling and synchronization problems for stochastic complex dynamical networks subject to consecutive packet dropouts. Different from some existing research results, both probability characteristic and upper bound of consecutive packet dropouts are involved in the proposed approach of controller design. First, an error dynamical network with stochastic and bounded delay is established by step-delay method, where the randomness of the bounded delay can be verified later by the probability theory method. A new modeling method is introduced to reflect the probability characteristic of consecutive packet dropouts. Based on the proposed model, some sufficient conditions are proposed under which the error dynamical network is globally exponentially synchronized in the mean square sense. Subsequently, a probability-distribution-dependent controller design procedure is then proposed. Finally, two numerical examples with simulations are provided to validate the analytical results and demonstrate the less conservatism of the proposed model method.

A New Predictive Sliding Mode Control Approach for Networked Control Systems With Time Delay and Packet Dropout

This paper investigates the predictive sliding mode control problem of networked control system with long-time delay and consecutive packet dropout in both sensor-controller link and controller-actuator link. A new modeling method that uses only one Markov chain to describe the time delay and packet dropout in a unified model is proposed. As a modification of the original law, a new chattering-free reaching law that is suitable for multiple-input systems is proposed and is later used as the reference trajectory of the designed predictive sliding mode controller. To overcome the influence of time delay and packet dropout, a novel predictive sliding mode controller equipped with a logic zero-order-holder and delay compensator is proposed, and the proposed compensation strategy is theoretically proven to be able to make the system completely free from the influence of long-time delay and consecutive packet dropout. Finally, a simulation example is given to illustrate the validity of the proposed controller.

Chattering‐Free Sliding Mode Control for Networked Control System with Time Delay and Packet Dropout Based on a New Compensation Strategy

This paper addresses the sliding mode control problem for a class of networked control systems with long time delay and consecutive packet dropout. A new modeling method is proposed, through which time delay and packet dropout are modeled in a unified model described by one Markov chain. To avoid the chattering problem of classic reaching law, a new chattering‐free reaching law is proposed. Then with a focus on the problem that controller‐actuator channel network condition cannot be foreseen by the controller, a new compensation strategy is proposed, which can effectively compensate for the effect of time delay and packet dropout in controller‐actuator channel. Finally, a simulation example is presented to demonstrate the effectiveness of the proposed approach.

Distributed fault-tolerant strategy for electric swing system of hybrid excavators under communication errors

A distributed fault-tolerant strategy for the controller area network based electric swing system of hybrid excavators is proposed to achieve good performance under communication errors based on the adaptive compensation of the delays and packet dropouts. The adverse impacts of communication errors are effectively reduced by a novel delay compensation scheme, where the feedback signal and the control command are compensated in each control period in the central controller and the swing motor driver, respectively, without requiring additional network bandwidth. The recursive least-squares algorithm with forgetting factor algorithm is employed to identify the time-varying model parameters due to pose variation, and a reverse correction law is embedded into the feedback compensation in consecutive packet dropout scenarios to overcome the impacts of the model error. Simulations and practical experiments are conducted. The results show that the proposed fault-tolerant strategy can effectively reduce the communication-error-induced overshoot and response time variation.

Data-based predictive control for networked nonlinear systems with packet dropout and measurement noise

In this paper, the data-based control problem is investigated for a class of networked nonlinear systems with measurement noise as well as packet dropouts in the feedback and forward channels. The measurement noise and the number of consecutive packet dropouts in both channels are assumed to be random but bounded. A data-based networked predictive control method is proposed, in which a sequence of control increment predictions are calculated in the controller based on the measured output error, and based on the control increment predictions received by the actuator, a proper control action is obtained and applied to the plant according to the real-time number of consecutive packet dropouts at each sampling instant. Then the stability analysis is performed for the networked closed-loop system. Finally, the effectiveness of the proposed method is illustrated by a numerical example.

A Wide-Area Damping Controller Considering Network Input and Output Delays and Packet Drop

This paper presents the development of a novel synchrophasor measurement-based wide-area centralized damping controller to improve the stability of a power system in presence of time-varying delay and packet dropout in the communication network. Two different strategies have been adopted to deal with the input and the output delays. In the first strategy, the system output delay has been compensated by predicting the dynamics of the signals. In the second strategy, a wide-area controller, based on delay-range-dependent stability criteria, has been designed for the time-varying delays in the input signals. The network induced delays and the maximum amount of the consecutive packet dropout are assumed to be bounded. The controller parameters are optimally obtained using a trace minimization of certain matrix variables by formulating Linear Matrix Inequalities problem. The system has been identified by applying Prediction-Error-Minimization methodology, and proposing a new type of probing test input-signal. A new methodology has been proposed to obtain the feedback channel latency in real time. The proposed methodology has been simulated on New England 39-bus test system and also validated on a hardware testbed consisting of physical Phasor Measurement Units connected, in feedback loop, to a Real-Time Digital Simulator.

Robust stability of a class of Networked Control Systems

Networked Control Systems (NCSs) affected with packet dropouts and scheduling are considered. The undesirable effects of packet dropouts and scheduling, such as instability or deteriorated performance, are addressed by application of a protocol and controller co-design method. The used method exploits Model Predictive Control (MPC) framework and the flexible NCS architecture which allows for distributed computation. Uniform Global Asymptotic Stability (UGAS) is established by assuming a finite bound on the number of consecutive packet dropouts and appropriate modifications to often adopted MPC stability-related assumptions. Two approaches that demonstrate UGAS are provided. The proof of one approach consists of finding an appropriate Lyapunov candidate function, while the other uses a cascade stability idea.