Discrete-time Nonlinear Networked Control Systems Research Articles

Learning-Based Model-Free Adaptive Control for Nonlinear Discrete-Time Networked Control Systems Under Hybrid Cyber Attacks.

A novel learning-based model-free adaptive control (LMFAC) approach is presented in this article for a class of unknown nonaffine nonlinear discrete-time networked control systems (NCSs) subject to hybrid cyber attacks. The aperiodic denial-of-service (DoS) attacks and persistent deception attacks are assumed to arise in feedback channels, which could result in the absence or authenticity lackness of system signals sent to the controller. With the aid of dynamic linearizaton technology, the equivalent dynamic linearized data models of considered NCSs are first established only based on I/O information instead of the knowledge of mathematical models that are commonly used under the model-based control framework. Then, an LMFAC scheme is designed on the basis of occurred maximum DoS attacks interval to adaptively tune the attenuation coefficient of the input signal for improving system performance during the next DoS attacks interval. Finally, the boundedness of tracking error is rigorously proved through the contraction mapping principle and the effectiveness of the proposed pure data-driven LMFAC method is demonstrated via simulations.

Novel asynchronous premise reconstruction based adaptive event-triggered control for fuzzy systems with actuator failure

This paper explores the adaptive event-triggered (AET) based variable gains controller design problem for a category of discrete-time nonlinear networked control systems (NCSs) with actuator failure. An AET communication scheme is applied for NCSs to reduce the utilization of limited network bandwidth. For overcoming the asynchronous issue of premise variable caused by AET scheme, a novel asynchronous premise reconstruction technique is introduced. Meanwhile, a new variable gains controller is designed subject to AET approach, where the controller gains will be automatically updated by executing the online iteration algorithm. According to a discontinuous Lyapunov function, sufficient conditions are given to ensure that the closed-loop system is asymptotically stable and satisfies H∞ performance. Finally, in the simulation results, the validity of the proposed control method is verified and it is shown that the proposed scheme can achieve better system performances than the existing design technique with fixed threshold.

Nonfragile peak-to-peak filtering for discrete-time Takagi-Sugeno fuzzy systems with dynamic quantizations

This paper investigates the problem of nonfragile peak-to-peak filtering for a class of discrete-time nonlinear networked control systems with dynamic quantizations. The Takagi-Sugeno fuzzy model is applied to approximate the considered nonlinear networked control systems. The perturbations are also considered in the peak-to-peak filter to be designed. Unlike most work about the peak-to-peak filtering for dynamic systems with quantization, both the performance output signal and measurement output signal are quantized by two different dynamic quantizers in our work. The main attention is to design the nonfragile peak-to-peak filter which guarantees the filtering error system to be asymptotically stable and possess a peak-to-peak performance index. By employing the fuzzy basis-dependent Lyapunov function approach and the S-procedure, new sufficient conditions about designing the nonfragile peak-to-peak filter have been established, which are expressed in the form of linear matrix inequalities. In the end, a numerical example is offered to verify the effectiveness of the designed nonfragile peak-to-peak filter.

Quantized Guaranteed Cost Output Feedback Control for Nonlinear Networked Control Systems and Its Applications

The quantized guaranteed cost static output feedback control problem is investigated for a class of discrete-time nonlinear networked control systems in this article. In this article, the Takagi–Sugeno fuzzy model is put to use for the representation of considered nonlinear networked control systems, where local nonlinear models instead of local linear models are used in the Takagi–Sugeno fuzzy model. Two different dynamic quantizers are applied to quantize the control input and measurement output, respectively. Different from some previous work, a novel guaranteed cost performance function including the quantized control input is used in this article. Through using the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$S$</tex-math></inline-formula> -procedure and introducing some auxiliary scalars, sufficient conditions for the design of guaranteed cost static output feedback controller and dynamic quantizers are obtained in the form of linear matrix inequalities. Finally, the applicability of the proposed method is illustrated through the application in nonlinear mass-spring-damper mechanical system.

Dissipative-based non-fragile filtering for fuzzy networked control systems with switching communication channels

The problem of finite-time dissipative-based non-fragile filter design for a class of discrete-time nonlinear networked control systems subject to randomly occurring parameter uncertainties, external disturbances as well as packet dropouts due to unreliable communication channels and networked induced time-varying delay is discussed. The randomly occurring uncertainties are assumed to satisfy Bernoulli distribution and the considered stochastic variables are mutually independent. Multiple communication channel scenario is taken into account to enhance the data transmission performance and the channel switching phenomena is governed by a Markov chain. The intention here is to design a dissipative-based non-fragile filter for the filtering error system such that it is stochastically finite-time bounded and attains a prescribed dissipative performance attenuation level. Lyapunov stability theory and linear matrix inequality approach are exploited to develop a set of sufficient criterion for the existence of the desired filter. Finally, the filter design framework is applied to the truck-trailer model to demonstrate its effectiveness.

Event-Triggered Suboptimal Tracking Controller Design for a Class of Nonlinear Discrete-Time Systems

In this paper, using the state-dependent Riccati equation approach, an event-triggered technique is proposed to solve the tracking problem for a broad class of nonlinear discrete-time networked control systems. It is shown that the proposed tracking controller leads to an asymptotically stable system, while the information exchange between the controller and the actuator can be directly affected with predictable results by changing a parameter of the controller called the triggering factor. The proposed method is experimentally validated on a laboratory three-tank system. The obtained results demonstrate the effectiveness of the proposed event-triggered technique for solving the tracking problem of a nonlinear system in a networked control framework.

Event-Triggered Control for Nonlinear Systems Under Unreliable Communication Links

This paper is concerned with the event-triggered $H_{\infty }$ control problem for discrete-time nonlinear networked control systems with unreliable communication links. First, an event-triggered scheme is proposed to determine whether the sampled data should be released into the network or not. Second, when the released data is transmitted in the network, a Bernoulli process is employed to model the phenomenon of data losses. Third, considering the instants at which the sampled data is not released or data losses occur, a new random process is first developed to model the input data sequence of the controller under the effect of the buffer. Consequently, a novel method is presented to address the stability analysis and control synthesis problems based on the polynomial fuzzy model approach. Finally, some simulation results are given to illustrate the effectiveness of the proposed method.

Event-triggered fault detection observer design for affine fuzzy systems

This paper is concerned with the event-based fault detection observer design problem for a class of discrete-time nonlinear networked control systems with output saturation. The system is represented by the T–S affine fuzzy models, and it is assumed that the premise variables of these models are not necessarily measurable. Different from the existing results, an adaptive event-triggered mechanism is introduced to reduce the burden of communication by judging whether the measured data should be transmitted. Based on the piecewise Lyapunov function and free-weighting matrices technique, the design conditions are given in terms of linear matrix inequalities, which can ensure the residual is sensitive to faults. Finally, a numerical example verifies the validity of the proposed method.

Fuzzy Tracking Control for Nonlinear Networked Systems.

This paper studies the observer-based tracking control problem for discrete-time nonlinear networked control systems with parameter uncertainties and unmeasurable state variables. A network-induced constraint, i.e., the intermittent measurement loss, is considered in the controller design. The uncertain nonlinear system is described by an interval type-2 (IT2) fuzzy Takagi-Sugeno model, in which the lower and the upper membership functions with corresponding coefficients are used to capture and express uncertainties existing in the system. A premise-variables-independent IT2 fuzzy observer is constructed to estimate the unmeasurable state variables, and then a novel IT2 fuzzy tracking controller is designed. Furthermore, sufficient criteria are established to guarantee the resulting closed-loop system to be stochastically stable. Finally, two examples are provided to show the effectiveness of the proposed approach.

Mixed H 2/H ∞ control for a class of nonlinear networked control systems

In this paper, the mixed H 2/H ∞ control problem is investigated for a class of nonlinear discrete-time networked control systems with random network-induced delays, stochastic packet dropouts and probabilistic sensor faults. The packet dropouts process is modeled as a homogeneous Markov chains taking values in a finite state space. Network-induced delays occur in a random way with known upper bound. A set of stochastic variables are exploited to describe sensor faults with different probabilistic density functions. By using a delay-dependent Lyapunov functional, a mode-dependent mixed H 2/H ∞ controller is designed to guarantee both stochastic stability of the closed-loop system and the prescribed H2, H¥ control performances. Sufficient conditions for the existence of the mixed H 2/H ∞ controller are presented in terms of a series of LMIs. If these LMIs are feasible, then the modedependent mixed H 2/H ∞ controller can be obtained. A numerical example is given to demonstrate the effectiveness of the developed method.

A new compensation for fuzzy static output-feedback control of nonlinear networked discrete-time systems

This paper investigates the problem of static output-feedback control of discrete-time nonlinear networked control systems with data packet dropouts on the basis of the fuzzy-model-based Takagi-Sugeno (T-S) approach. The nonlinear system is modeled via T-S fuzzy model. Both imperfect sensor-to-controller (S/C) and controller-to-actuator (C/A) links are considered via a novel data model. Some slack matrices are introduced to reduce the conservativeness. By constructing fuzzy Lyapunov function, the sufficient conditions are derived to guarantee the resulting closed-loop system to be stochastically stable as well as the predefined H∞ performance index. Finally, some simulation results are given to demonstrate the effectiveness of the proposed results.

On Feedback Passivity of Discrete-Time Nonlinear Networked Control Systems With Packet Drops

We analyze the feedback passivity of a networked control system in which the control packets may be dropped by the communication channel. Specifically, we consider a discrete-time switched nonlinear system with relative degree zero that switches between two modes. At the instants when the communication link transmits the packet successfully, the system evolves in closed-loop and the increase in storage function is bounded below the energy supplied by the control input. At the instants when a packet drop occurs, the system evolves in open loop according to the free dynamics of the closed-loop mode and the increase in storage function is not necessarily bounded by the supplied energy. The literature on passivity of switched systems seems to consider only the case when all the modes are passive, which is not the case here. We prove that if the ratio of time steps for which the system evolves in closed-loop versus in open loop is lower bounded by a critical number, the system is locally feedback passive in a suitably defined sense. This generalized definition of feedback passivity is useful since it preserves two important properties of classical passivity—that feedback passivity implies asymptotic stabilizability for zero state detectable systems and that feedback passivity is preserved in parallel and negative feedback interconnections.

Fault detection for a class of non‐linear networked control systems in the presence of Markov sensors assignment with partially known transition probabilities

In this study, the problem of fault detection for a class of discrete-time non-linear networked control systems is investigated. An event modelled as a Markov chain taking matrix values in a certain set with partially known transition probabilities is utilised to characterise the phenomenon of the sensors assignment. A full-order mode-dependent fault detection filter is constructed and the corresponding fault detection problem is converted into an H ∞ filtering problem of a Markov jump system with partially known transition probabilities. Sufficient conditions for the existence of the fault detection filter are formulated as a linear matrix inequality-based convex optimisation problem. If the convex optimisation problem has a feasible solution, the corresponding fault detection filter parameters are determined. A numerical example with four cases of transition probability matrices is presented to show the usefulness of the developed method.

Fault detection for a class of non‐linear networked control systems with data drift

In this paper, the fault detection problem is studied for a class of non-linear discrete-time networked control systems (NCSs). An individual stochastic variable satisfying a certain probabilistic distribution is utilised to describe the data drift of each sensor. The random transmission delays with the upper bound and the data drift phenomena are taken into account in a unified framework. By augmenting the states of the original non-linear NCS and the constructed full-order fault detection filter, the resulting fault detection dynamics is converted into an H ∞ filtering problem of a non-linear time-delay system. A sufficient condition for the existence of the designed fault detection filter is given in terms of a feasible linear matrix inequality, guaranteeing that the fault detection dynamics is stochastically stable and attains the prescribed H ∞ attenuation level. Finally, a numerical example is presented to show the effectiveness of the proposed method.

Event-triggered controller design of nonlinear discrete-time networked control systems in T-S fuzzy model

This article is concerned with event-triggered fuzzy control design for a class of discrete-time nonlinear networked control systems (NCSs) with time-varying communication delays. Firstly, a more general mixed event-triggering scheme (ETS) is proposed. Secondly, considering the effects of the ETS and communication delays, based on the T-S fuzzy model scheme and time delay system approach, the original nonlinear NCSs is reformulated as a new event-triggered networked T-S fuzzy systems with interval time-varying delays. Sufficient conditions for uniform ultimately bound (UUB) stability are established in terms of linear matrix inequalities (LMIs). In particular, the quantitative relation between the boundness of the stability region and the triggering parameters are studied in detail. Thirdly, a relative ETS is also provided, which can be seen as a special case of the above proposed mixed ETS. As a difference from the preceding results, sufficient conditions on the existence of desired fuzzy controller are derived to ensure the asymptotic stability of the closed-loop system with reduced communication frequency between sensors and controllers. Moreover, a co-design algorithm for simultaneously determining the gain matrices of the fuzzy controller and the triggering parameters is developed. Finally, two illustrative examples are presented to demonstrate the advantage of the proposed ETS and the effectiveness of the controller design method.

Global Stabilization of Nonlinear Networked Control System with System Delays and Packet Dropouts via Dynamic Output Feedback Controller

The stabilization problem is investigated for a class of nonlinear discrete-time networked control systems (NCSs). Nonideal network Quality of Services (QoS) are considered, more specifically data packet dropouts and network-induced delays. A state feedback controller for a class of NCSs is proposed. Subsequently, an observer is designed to estimate the state space. Based on the Lyapunov-Krasovskii functional, sufficient conditions (expressed in terms of LMIs) for the existence of a dynamic output feedback controller are derived. The stabilization is achieved without mathematical transformations or fuzzy logic approximations and without state space augmentation. Finally, illustrative examples are provided to show the effectiveness of the proposed method.

MixedH2/H∞control for a class of nonlinear discrete-time networked control systems with random delays and stochastic packet dropouts

The paper studies the problem of mixed H2/H∞ control for a class of nonlinear discrete-time networked control systems. By using the indicator function method, random network-induced delays and stochastic packet dropouts are taken into account in a unified framework in the designed mixed H2/H∞ controller. In the presences of random transmission delays, stochastic packet dropouts and all admissible disturbances, the resulting closed-loop system is stochastically stable in mean square and attains the prescribed H2 and H∞ performances. The designed mixed H2/H∞ controller can be obtained by solving a set of feasible linear matrix inequalities. Finally, a numerical example is provided to show the usefulness and effectiveness of the developed method. Copyright © 2014 John Wiley & Sons, Ltd.

Robust [formula omitted]∞ fuzzy control of discrete nonlinear networked control systems: A SOS approach

The paper presents a methodology for designing a robust mode delay dependent H∞ controller for nonlinear discrete-time networked control systems (NCSs). The nonlinear systems are modelled by a Takagi–Sugeno fuzzy model, and network induced delays between sensors and controllers are modelled by a finite state Markov process. The fuzzy controller׳s membership functions are allowed to be different from the plant׳s membership functions, and also the controller׳s premise variables are allowed to be the delayed plant׳s premise variables to accommodate the fact that the plant׳s premise variables are transmitted via the network. To reduce the conservatism of the controller design, the membership functions of the plant and the fuzzy controller are incorporated into the controller design. Based on the Sum Of Square (SOS) approach, sufficient conditions for the existence of the controller are derived in terms of SOS inequalities, which are then solved by YALMIP. Comparisons between the proposed design methodology and the existing controller designs are made using a numerical example.

Further results on memory control of nonlinear discrete-time networked control systems with random input delay

This paper is concerned with the problem of memory state feedback stabilization for a class of nonlinear discrete-time networked control systems with partly known probability distribution of input delay. Different from the common assumptions on the delay in the existing literatures, it is assumed that the probabilities of the delay taking values in a finite set are partly known or fully known in advance. In terms of the information about the occurrence probabilities of the delay taking values in the two finite sets, a new stochastic delay model is proposed, where the probability information of the delay is included in the parameter matrices of the transformed system. Based on the new model, a delay-dependent stabilization criterion is derived using a combination of the Lyapunov functional method, convexity of matrix inequalities, and linear matrix inequality technique. Finally, three illustrative examples are provided to show the effectiveness and applicability of the developed theoretical results.

Discrete-Time Event-Triggered Control of Nonlinear Wireless Networked Control Systems

This paper investigates the problem of stabilization of nonlinear discrete-time networked control systems (NCSs) with event-triggering communication scheme in the presence of signal transmission delay. A Takagi-Sugeno (T-S) fuzzy model and parallel-distributed compensation (PDC) scheme are first employed to design a nonlinear fuzzy event-triggered controller for the stabilization of nonlinear discrete-time NCSs. The idea of the event-triggering communication scheme (i.e., a soft computation algorithm) under consideration is that the current sensor data is transmitted only when the current sensor data and the previously transmitted one satisfy a certain state-dependent trigger condition. By taking the signal transmission delay into consideration and using delay system approach, a T-S fuzzy delay system model is established to describe the nonlinear discrete-time NCSs with event-triggering communication scheme. Attention is focused on the design of fuzzy event-triggered controller which ensures asymptotic stability of the closed-loop fuzzy systems. Linear matrix inequality- (LMI-) based conditions are formulated for the existence of admissible fuzzy event-triggered controller. If these conditions are feasible, a desired fuzzy event-triggered controller can be readily constructed. A nonlinear mass-spring-damper mechanical system is presented to demonstrate the effectiveness of the proposed method.