Nonlinear Networked Control Systems Research Articles

A discrete-time framework for stability analysis of nonlinear networked control systems

In this paper we develop a prescriptive framework for the stabilising controller design based on approximate discrete-time models for nonlinear Networked Control Systems (NCSs) with time-varying sampling intervals, large time-varying delays and packet dropouts. As opposed to emulation-based approaches where the effects of sampling-and-hold and delays are ignored in the phase of controller design, we propose an approach in which the controller design is based on approximate discrete-time models constructed for a set of nominal (non-zero) sampling intervals and nominal delays while taking into account sampling-and-hold effects. Subsequently, sufficient conditions for the global exponential stability of the closed-loop NCS are provided.

Robust stability of nonlinear model-based networked control systems with time-varying transmission times

Robust stability of a class of model-based networked control systems (MB-NCSs, for short) with nonlinear perturbation is analyzed. Based on the model-based networked control algorithm, a linear model of the plant is used to estimate the plant state behavior between transmission times. The case that the nonlinear plant and the linear plant model are connected via a network channel with transmission times that are varying within a time interval is of particular interest. Sufficient condition on stability of MB-NCSs with nonlinear perturbation is given. One advantage of the proposed method is that the maximum transmission interval and the robustness bound on nonlinear perturbation can be computed. Finally, numerical simulation is worked out to show our main result.

Mode-independent fuzzy fault-tolerant variable sampling stabilization of nonlinear networked systems with both time-varying and random delays

This paper develops a fault-tolerant variable sampling control (VSC) scheme for a class of nonlinear networked control systems (NCSs) with time-varying state and random network delays. An uncertain continuous Takagi–Sugeno (T–S) fuzzy system with both state and input varying delays, in the presence of possible actuator faults, is obtained equivalently on the basis of the input delay methodology. A tighter bounding lemma is proposed so as to gain less conservative closed-loop stability criteria. Delay-dependent conditions in terms of linear matrix inequalities are derived for the mode-independent fault-tolerant stabilizing controller of the resulting Markovian network-based system by employing a novel stochastic Lyapunov–Krasovskii (L–K) functional. An illustrative example is simulated to show the validity of the obtained results.

Exponential Stability Control for T-S fuzzy Nonlinear Stochastic Networked Control Systems

Exponential Stability Control for T-S fuzzy Nonlinear Stochastic Networked Control Systems

Computation of an optimal communication schedule in a nonlinear networked control system using sum-of-squares

In this paper, we consider the design of a control optimal communication schedule in nonlinear networked control with nonlinear affine plant systems. We focus here on periodic communication schedules in control systems with time-triggered control communication and assume the existence of predesigned controllers which need to be optimally integrated via the control communication system. For this, we formulate a quadratic cost function for the nonlinear affine plant. The system and the cost are first discretized using an exact mixed discretization approach which allows to lift the problem from the continuous-discrete domain into a purely discrete-time representation. Periodicity due to the fixed communication schedule is dealt with the discrete lifting technique. To allow for the computation of the cost, nonlinearities are approximated in terms of a Taylor series which allows the use of the sum-of-squares framework. Once a cost function of the networked control system for a given fixed communication schedule is defined, it is then possible to compare and choose those sequences that minimize this cost for optimal controller integration.

Fault detection for nonlinear networked control systems based on fuzzy observer

Security and reliability must be focused on control systems firstly, and fault detection and diagnosis (FDD) is the main theory and technology. Now, there are many positive results in FDD for linear networked control systems (LNCSs), but nonlinear networked control systems (NNCSs) are less involved. Based on the T-S fuzzy-modeling theory, NNCSs are modeled and network random time-delays are changed into the unknown bounded uncertain part without changing its structure. Then a fuzzy state observer is designed and an observer-based fault detection approach for an NNCS is presented. The main results are given and the relative theories are proved in detail. Finally, some simulation results are given and demonstrate the proposed method is effective.

Fault Detection for Nonlinear Networked Control Systems with Markov Data Transmission Pattern

This paper is concerned with the fault-detection problem of nonlinear multiple channels data transmission networked control systems (NCSs). Two irrelevant Markov chains are introduced to describe the data transmission characterization of nonlinear delayed NCSs with data loss in both from sensors to controller and from controller to actuators, and a nonlinear Markovian jump system model is established. Based on this novel model, employing a mode-dependent fault-detection filter as residual generator, a fault-detection filter design of nonlinear NCSs is formulated as a nonlinear H ∞-filtering problem. Then an appropriate Lyapunov functional is chosen to derive the sufficient condition which satisfies the stochastic stability and prescribes the H ∞ attenuation level simultaneously. Especially, the desired mode-dependent fault-detection filters are constructed in terms of certain linear matrix inequalities (LMIs), and explicit parameters are characterized if these LMIs are feasible. The effectiveness of the proposed method is demonstrated by a simulation example.

Adaptive Output Tracking for Nonlinear Network Control Systems with Time-Delay

The problem of adaptive output tracking is researched for a class of nonlinear network control systems with parameter uncertainties and time-delay. In this paper, a new program is proposed to design a state-feedback controller for this system. For time-delay and parameter uncertainties problems in network control systems, applying the backstepping recursive method, and using Young inequality to process the time-delay term of the systems, a robust adaptive output tracking controller is designed to achieve robust control over a class of nonlinear time-delay network control systems. According to Lyapunov stability theory, Barbalat lemma and Gronwall inequality, it is proved that the designed state feedback controller not only guarantees the state of systems is uniformly bounded, but also ensures the tracking error of the systems converges to a small neighborhood of the origin. Finally, a simulation example for nonlinear network control systems with parameter uncertainties and time-delay is given to illustrate the robust effectiveness of the designed state-feedback controller.

Robust fault detection filter for non-linear state-delay networked control system

A robust fault detection filter (RFDF) problem is investigated for a non-linear state-delay networked control system (NCS) with model uncertainty and data packet dropout. In both sensor-to-controller link and controller-to-actuator link, the random data packet dropouts are described by two variables, which obey the Bernoulli distribution. An observer-based RFDF is presented as a residual generator, and the residual dynamical system is modelled as a novel stochastic non-linear NCS with state-delay, model uncertainty, external disturbance. A performance index is proposed to deal with the robustness issue, which is to enhance the robustness of the residual generator against network-induced uncertainties and disturbances, without significant loss of the sensitivity of faults. Sufficient condition for asymptotically mean-square stable of this residual dynamical system is derived. Then, the desired RFDF is obtained, which is constructed in terms of certain linear matrix inequality. Finally, two numerical examples are employed to illustrate that the proposed approach performs better than the existing approaches.

An entropy approach to filtering for networked control systems

This paper is concerned with minimum error entropy filter design for non-linear Networked Control Systems (NCSs) with multiple-packet transmission mechanism. Since the error of the filter in NCSs is generally non-Gaussian, the filter is designed under the information theoretic learning frame. The convergent condition of the proposed filter is established. A simulation example shows that the proposed approach is feasible and effective.

Modeling and Simulation of Nonlinear Networked Control System Based on Fuzzy Control

In the nonlinear networked control system (NCS), the conventional control method is difficult to achieve good control performance, due to the nonlinear problem associated with the disturbance factors, such as network induced time delay and data packet dropout. Considering this situation, this paper is aimed to propose a nonlinear networked control system based on T-S fuzzy model, which does not rely on specific network parameters or mathematical model. The nonlinear problem and the uncertainties of network can be both processed by the designed fuzzy controller. Then this approach is applied to nonlinear motor servo system, simulation of the example model is implemented in Matlab/Simulink associated with True Time toolbox. The results show that the proposed method not only is convenient for modeling, but also upgrade the performance of control system.

Observer design for classes of non-linear networked control systems

Assuming a class of continuous-time observers is known for a given non-linear system, an observation structure is derived when sensors information is subject to network-induced communication constraints. The approach is based on the recent results on hybrid observers for sampled-data systems by Karafyllis and Kravaris (2009). Considering two classes of protocols, some asymptotic stability properties are shown to hold for the observation error, under some conditions, and explicit bounds on the maximum allowable transmission interval are given.

Reliable Fuzzy Control for a Class of Nonlinear Networked Control Systems with Time Delay

Reliable Fuzzy Control for a Class of Nonlinear Networked Control Systems with Time Delay

H ∞ filter design for nonlinear networked control systems with uncertain packet-loss probability

This paper is concerned with the problem of designing H ∞ filters for a class of nonlinear networked control systems (NCSs) with transmission delays and packet losses. This problem is investigated under the following assumptions: (i) the delay is constant and known, (ii) the packet-loss process is described by a Bernoulli distributed white sequence, and (iii) the probability of the packet-loss process is unknown but bounded. The first two assumptions are well known in the literature of NCSs, while the last one may often arise in practical networks due to modeling or measurement errors. Under the aforementioned assumptions, delay-dependent conditions for the solvability of the addressed problem are presented in terms of linear matrix inequalities. Numerical examples are also included to illustrate the effectiveness of the proposed method.

Asynchronous Output-Feedback Control of Networked Nonlinear Systems With Multiple Packet Dropouts: T–S Fuzzy Affine Model-Based Approach

This paper investigates the problem of robust output-feedback control for a class of networked nonlinear systems with multiple packet dropouts. The nonlinear plant is represented by Takagi-Sugeno (T-S) fuzzy affine dynamic models with norm-bounded uncertainties, and stochastic variables that satisfy the Bernoulli random binary distribution are adopted to characterize the data-missing phenomenon. The objective is to design an admissible output-feedback controller that guarantees the stochastic stability of the resulting closed-loop system with a prescribed disturbance attenuation level. It is assumed that the plant premise variables, which are often the state variables or their functions, are not measurable so that the controller implementation with state-space partition may not be synchronous with the state trajectories of the plant. Based on a piecewise quadratic Lyapunov function combined with an S-procedure and some matrix inequality convexifying techniques, two different approaches to robust output-feedback controller design are developed for the underlying T-S fuzzy affine systems with unreliable communication links. The solutions to the problem are formulated in the form of linear matrix inequalities (LMIs). Finally, simulation examples are provided to illustrate the effectiveness of the proposed approaches.

H<inf>∞</inf>-based fault detection for nonlinear networked systems with random packet dropout and probabilistic interval delay

The fault detection problem for the nonlinear networked control system (NCS) with packet dropout and delay is inves- tigated. A nonlinear stochastic system model is proposed to account for the NCS with random packet dropout and network- induced non-uniformly distributed time-varying delay in both from sensor to controller (S/C) and from controller to actuator (C/A). Based on the obtained NCS model, employing an observer-based fault detection filter as the residual generator, the addressed fault detection problem is converted into an auxiliary nonlinear H∞ control problem. Then, with the help of Lyapunov functional ap- proach, a sufficient condition for the desired fault detection filter is constructed in terms of certain linear matrix inequalities, which depend on not only the delay interval but also the delay interval occurrence rate and successful packet communication rate. Es- pecially, a trade-off phenomenon between the maximum allowable delay bound and successful data packet transmission rate is found, which is typically resulted from the limited bandwidth of commu- nication networks. The effectiveness of the proposed method is demonstrated by a simulation example.

Reliable H ∞ filter design for T–S fuzzy model‐based networked control systems with random sensor failure

SUMMARYThis paper investigates robust and reliable H ∞ filter design for a class of nonlinear networked control systems: (i) a T‐S fuzzy model with its own uncertainties is used to approximate the nonlinear dynamics of the plant, (ii) a new sensor failure model with uncertainties is proposed, and (iii) the signal transfer of the closed‐loop system is under a networked communication scheme and therefore is subject to time delay, packet loss, and/or packet out of order. Four new theorems are proved to cover the conditions for the robust mean square stability of the systems under study in terms of LMIs, and a decoupling method for the filter design is developed. Two examples, one of them is based on a model of an inverted pendulum, are provided to demonstrate the design method. Copyright © 2011 John Wiley & Sons, Ltd.

Fuzzy control with estimated variable sampling period for non-linear networked control systems: 2-DOF helicopter as case study

This paper presents a fuzzy controller for class of non-linear networked control systems; the varying time delays and packet loss are taken as a variable sampling period of the system. The variable sampling period is estimated using a time stamped and probability density function. A fuzzy model smoothly switches to estimate the system state; the antecedent input is the estimated sampling period and the consequent part is formed by linear models discretized with specific sampling periods. The fuzzy controller generates a control input using the estimated states to ensure system stability for a wide range of sampling periods. A two-degree-of-freedom helicopter is used to show the applicability and effectiveness of the controller with robustness to traffic.

Fault detection for nonlinear networked systems with random packet dropout and probabilistic interval delay

SUMMARYIn this paper, the fault detection (FD) problem of nonlinear networked control systems (NCSs) is investigated. A nonlinear stochastic systems model is proposed to account for the NCSs with network‐induced random packet dropout and non‐uniformly distributed time‐varying delay in both from sensor to controller and from controller to actuator. On the basis of the new model, by employing FD filter as residual generator, the addressed FD problem is converted into auxiliary nonlinear H ∞ filtering problem. Then, with the help of Lyapunov functional approach, a sufficient condition for the desired FD filter is constructed in terms of certain linear matrix inequalities, which depends on not only nonlinear level but also delay interval occurrence rate and successful joint packet transmission rate. Especially, a trade‐off phenomenon among maximum allowable delay bound, nonlinear level, and successful joint packet transmission rate is found, which typically resulted from the limited bandwidth of the communication networks. The effectiveness of the proposed methods is demonstrated by simulation examples. Copyright © 2011 John Wiley & Sons, Ltd.

State estimation and stabilization for nonlinear networked control systems with limited capacity channel

This paper investigates the control problem for nonlinear networked control systems with global Lipschitz nonlinearities subject to output quantization and data packet dropout. The system states are unavailable and the outputs are quantized in a logarithmic form before transmitted through network. In the communication channel, two types of packet losses are considered simultaneously: (i) packet losses from sensor to controller and (ii) packet losses from controller to actuator, which are modeled as two independent Bernoulli distributed white sequences, respectively. Based on the proposed model, an observer-based controller is designed to exponentially stabilize the networked system in the sense of mean square, and sufficient conditions for the existence of the controller are established. Finally, a numerical example is presented to illustrate the effectiveness and applicability of the proposed technique.