Output Feedback Fault-tolerant Control Research Articles

Hybrid Fuzzy Adaptive Fault-Tolerant Control for a Class of Uncertain Nonlinear Systems With Unmeasured States

In this paper, a hybrid adaptive output feedback fault-tolerant control is investigated for a class of uncertain nonlinear systems with unmeasured states. The generalized fuzzy hyperbolic model is used to approximate the unknown nonlinear functions, and the fuzzy state estimator (FSE) is established for estimating the unmeasured states. Based on the backstepping and dynamic surface control technique, a novel adaptive control method is proposed by introducing the prediction errors between FSE and serial–parallel estimation model. It is proved that all the variables of the closed-loop systems are semi-globally uniformly ultimately bounded by Lyapunov approach, and the tracking errors can converge to a small neighborhood. Two simulation examples are used to illustrate the effectiveness of the proposed control method.

Integrated fault estimation and non‐fragile fault‐tolerant control design for uncertain Takagi–Sugeno fuzzy systems with actuator fault and sensor fault

This study proposes an integrated design of robust fault estimation and non-fragile fault-tolerant control for a class of Takagi–Sugeno fuzzy systems subjected to disturbances, actuator fault and sensor fault. A fuzzy adaptive observer is developed to achieve simultaneous estimations of actuator fault and sensor fault, based on which a new non-fragile output feedback fault-tolerant controller is constructed to compensate for the effects of the disturbances and faults. Moreover, the proposed fault-tolerant controller proves non-fragile, since it offers the ability to suppress the control gain perturbations. Simulation results are presented to illustrate the effectiveness of the proposed approach.

Output feedback fault-tolerant control by a set-theoretic description of T–S fuzzy systems

This paper is concerned with the observer-based output feedback fault-tolerant control problem for T–S fuzzy systems. By constructing a set-theoretic description of fuzzy systems, the equivalence class theory in set theory is applied for designing observer and controller for less conservative results. Firstly, we designed the observer to get the information of the actuator faults in the system. Then, we use this information to design the fault-tolerant controller to compensate for the effect of faults and guarantee stability of the system. Finally, a simple nonlinear mass–spring–damper system is presented to illustrate the effectiveness of the proposed approach.

Data-Driven Output-Feedback Fault-Tolerant Compensation Control for Digital PID Control Systems With Unknown Dynamics

For digital proportional–integral–derivative control systems with unknown dynamics, the data-driven output-feedback fault-tolerant control (FTC) problem is studied in this paper. In a framework of active FTC, the issue of online recursive identification of the residual generator, the state observer, and the observability canonical form of the plant under consideration is addressed; the problem of reconfiguration of the data-driven fault-tolerant compensation controller with $L_2$ -gain properties is also dealt with by means of the above-obtained results, the prefilter and the Riccati equation related to $H_{\infty }$ control so as to accommodate faults and ensure tracking performance. The resulting fault-tolerant compensation control scheme is designed based on the closed-loop systems, and therefore has more practical significance than the existing FTC methodologies developed in terms of the open-loop systems. Finally, the effectiveness of the proposed FTC approach is validated by the speed control experiment on a dc motor.

Data-driven output-feedback fault-tolerant L2 control of unknown dynamic systems

This paper studies the data-driven output-feedback fault-tolerant L2-control problem for unknown dynamic systems. In a framework of active fault-tolerant control (FTC), three issues are addressed, including fault detection, controller reconfiguration for optimal guaranteed cost control, and tracking control. According to the data-driven form of observer-based residual generators, the system state is expressed in the form of the measured input–output data. On this basis, a model-free approach to L2 control of unknown linear time-invariant (LTI) discrete-time plants is given. To achieve tracking control, a design method for a pre-filter is also presented. With the aid of the aforementioned results and the input–output data-based time-varying value function approximation structure, a data-driven FTC scheme ensuring L2-gain properties is developed. To illustrate the effectiveness of the proposed methodology, two simulation examples are employed.

Data-driven output-feedback fault-tolerant control for unknown dynamic systems with faults changing system dynamics

This paper studies the data-driven output-feedback fault-tolerant control (FTC) problem for unknown dynamic systems with faults changing system dynamics. In a framework of active FTC, two basic issues are addressed: the fault detection employing only the measured input–output information; the controller reconfiguration to achieve optimal output-feedback control in the presence of multiple faults. To detect faults and write the system state via the input–output data, an approach to data-driven design of a residual generator with a full-rank transformation matrix is presented. An output-feedback approximate dynamic programming method is developed to solve the optimal control problem under the condition that the unknown linear time-invariant discrete-time plant has multiple outputs. According to the above results and the proposed input–output data-based value function approximation structure of time-varying plants, a model-free output-feedback FTC scheme considering optimal performance is given. Finally, two numerical examples and a practical example of a DC motor control system are used to demonstrate the effectiveness of the proposed methods.

Output feedback fault-tolerant control for a class of discrete-time fuzzy bilinear systems

This paper studies the fault-tolerant control problem for a class of discrete-time fuzzy bilinear systems with unmeasurable states. A fuzzy detective observer is designed to detect the faults. Based on the fuzzy detective observer, a fuzzy controller is designed by solving a set of linear matrix inequalities (LMIs) to ensure that the closed-loop system without faults is asymptotically stable. For the discrete-time fuzzy bilinear system with faults, a fuzzy adaptive diagnostic observer is designed to estimate the faults by solving a set of LMIs. Then, a fuzzy faulttolerant controller is designed based on the fuzzy diagnostic observer to ensure that the closed-loop system with faults is asymptotically stable. At last, simulation results are presented to verify the effectiveness of the proposed output feedback fault-tolerant control method.

Synthesis of fault-tolerant static output feedback controllers for networked control systems

This paper is concerned with the design of static output feedback control laws for stabilizing a networked control system under possible element failures. Multiple faults can occur on sensors, actuators, or other electrical or mechanical componentes. With considering consecutive packet loss and time-varying network-induced delay, the closed-loop system is modeled as an equivalent time-delay system with several possible modes. By constructing a Lyapunov–Krasovskii function, sufficient conditions for the existence of static output feedback fault-tolerant stabilizing controllers are derived. Moreover, by the simultaneous stabilization approach, it is shown that a static output feedback fault-tolerant controller can be obtained by solving linear matrix inequalities (with equality constraints). Simulation results are presented to validate the theoretical results.

Fuzzy Adaptive Output Feedback Fault-Tolerant Tracking Control of a Class of Uncertain Nonlinear Systems With Nonaffine Nonlinear Faults

This paper studies the fuzzy adaptive output feedback fault-tolerant control (FTC) problem for a class of single-input and single-output uncertain nonlinear systems with time-varying nonaffine nonlinear faults in strict-feedback form. In the design procedure, filtered signals are adopted to circumvent algebraic loop problems on implementing the usual controllers. By using fuzzy logic systems to approximate the unknown nonlinearity effects and changes in model dynamics due to faults, a fuzzy state observer is first presented to estimate the unmeasured states. Based on the online estimating information from the adaptive mechanism, an observer-based dynamic output feedback fault-tolerant controller is designed via the backstepping technique. It is shown that the stability and tracking performances of the closed-loop system can be achieved even in the presence of unknown nonlinear faults. In comparison with the existing approaches, the FTC scheme can handle the nonaffine nonlinear faults effectively. Finally, a simulation example is included to validate the advantages of the proposed approaches.

Reduced-order observer-based fault estimation and fault-tolerant control for a class of discrete Lipschitz nonlinear systems

Summary This paper addresses an issue on reduced-order observer-based robust fault estimation and fault-tolerant control for a class of uncertain nonlinear discrete-time systems. By introducing a nonsingular coordinate transformation, a new nonlinear reduced-order fault estimation observer (RFEO) is proposed with a wide application range in order to achieve an accurate estimation of both states and faults. Next, an improved algorithm is given to obtain the optimal estimation by using a novel iterative linear matrix inequality technique. Furthermore, an RFEO-based output feedback fault-tolerant controller, which is independent of the RFEO, can maintain the stability and performance of the faulty system. Simulation results of an aircraft application show the effectiveness of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.

A Combined Fault Tolerant and Predictive Control for Network-Based Industrial Processes

This paper investigates the tracking and optimization problems for a class of industrial processes by utilizing output feedback fault-tolerant control (FTC) and predictive compensation strategy. At device layer, the tracking problem for device layer subsystems which subject to random failures and random network-induced delays is investigated. These two different random processes are modeled as Markovian chains. Device layer controllers are designed to guarantee the tracking performance at $H_{\infty}$ disturbance attenuation level. At operation layer, a nonlinear model predictive control (NMPC) strategy is proposed to stabilize the upper operation layer system. Then by considering the effect of radial basis function (RBF) performance index and random packet dropout phenomena, a predictive compensator is designed to guarantee the input-to-state practical stability (ISpS) of the resulting system. In addition, networked flotation processes are considered in the simulation part, and the simulation results further demonstrate the effectiveness of the proposed method.

Robust dynamic output feedback fault-tolerant control for Takagi-Sugeno fuzzy systems with interval time-varying delay via improved delay partitioning approach

Abstract This paper addresses the problem of robust fault-tolerant control design scheme for a class of Takagi-Sugeno fuzzy systems subject to interval time-varying delay and external disturbances. First, by using improved delay partitioning approach, a novel n-steps iterative learning fault estimation observer under H ∞ constraint is constructed to achieve estimation of actuator fault. Then, based on the online estimation information, a fuzzy dynamic output feedback fault-tolerant controller considered interval time delay is designed to compensate for the impact of actuator faults, while guaranteing that the closed-loop system is asymptotically stable with the prescribed H ∞ performance. Moreover, all the obtained less conservative sufficient conditions for the existence of fault estimation observer and fault-tolerant controller are formulated in terms of linear matrix inequalities. Finally, the numerical examples and simulation results are presented to show the effectiveness and merits of the proposed methods.

Disturbance observer based fault estimation and dynamic output feedback fault tolerant control for fuzzy systems with local nonlinear models

This paper addresses the problems of fault estimation (FE) and fault tolerant control (FTC) for fuzzy systems with local nonlinear models, external disturbances, sensor and actuator faults, simultaneously. Disturbance observer (DO) and FE observer are designed, simultaneously. Compared with the existing results, the proposed observer is with a wider application range. Using the estimation information, a novel fuzzy dynamic output feedback fault tolerant controller (DOFFTC) is designed. The controller can be used for the fuzzy systems with unmeasurable local nonlinear models, mismatched input disturbances, and measurement output affecting by sensor faults and disturbances. At last, the simulation shows the effectiveness of the proposed methods.

Adaptive output feedback fault-tolerant control of switched fuzzy systems

This paper investigated the adaptive fault-tolerant control problem for a class of switched Takagi–Sugeno fuzzy systems. The considered switched fuzzy systems contain unmeasured states and actuator failures. In the control design, a switched state observer is designed to estimate the unmeasured states. Under the parallel-distributed compensation (PDC) design scheme and using the online estimation of actuator faults, an adaptive fuzzy fault-tolerant control scheme is proposed, in which a compensation control term is introduced in order to reduce the effect of actuator faults. Utilizing the estimated states and a segmentation of state space, the switching law is constructed. The sufficient conditions for ensuring the asymptotic stability of the switched fuzzy systems are proposed and formulated in the form of linear matrix inequalities (LMIs). By using the single Lyapunov function method, it is proved that the proposed control approach can guarantee the asymptotic stability of the closed-loop system. One practical example and a numerical example are given to illustrate the effectiveness of the proposed control method.

Adaptive output feedback fault-tolerant control design for hypersonic flight vehicles

In this paper, an adaptive output feedback fault-tolerant controller is developed for the longitudinal dynamics of a generic hypersonic flight vehicle in the presence of parameter uncertainties, actuator faults and external disturbances. Firstly, the derivatives of the output are calculated repeatedly so that the relative degree of the system is obtained. Then feedback linearization is used to design the nominal controller. Considering the occurrence of actuator faults, a fault-tolerant controller is developed based on the nominal feedback linearization controller to accommodate the effect of actuator fault, ensure system stability and recover desirable tracking performance. Since some of the states are difficult to measure during actual hypersonic flight, the high-gain observer technique is adopted to achieve output feedback fault-tolerant control. Adaptive laws are designed for updating the controller parameters when both the plant parameters and actuator fault parameters are unknown. Closed-loop stability and output tracking performance are analyzed rigorously. Simulation results verify the effectiveness of the proposed adaptive fault-tolerant control scheme.

Chemical Process Disturbance Compensation as a Fault Tolerant Control Problem

In general, the control of chemical processes that involve unknown disturbances presents interesting challenges. Research issues have been focused on detailed modelling of the involved phenomena in order to use e.g. robust on-line disturbance compensation procedures or attempting to cancel out the disturbance effect in the feedback control of the chemical system. However, the chemical modelling problem can remain a very difficult challenge due to the unknown or partially-known dynamics occurring in the process under investigation. Therefore, this article proposes a new approach to the disturbance compensation, which is recasted into the theory of robust fault estimation. The disturbances acting in the system can be thus viewed as faults with time-varying characteristics to be estimated and compensated within an output feedback fault-tolerant control scheme. In this way, the limitations arising from the use of model-based approaches are obviated. The unknown input estimation problem is hence embedded inside a control system with required stability and performance robustness. This can be a significant advantage over model-based unknown input compensation methods, in which the detailed modelling of the disturbance term can be essential, and for which robustness with respect to its characteristics is difficult to achieve using purely nonlinear modelling strategies.

Fault Tolerant Controller Design for T–S Fuzzy Systems With Time-Varying Delay and Actuator Faults: A K-Step Fault-Estimation Approach

This paper is concerned with the problem of robust fault estimation and fault-tolerant control for a class of Takagi–Sugeno (T–S) fuzzy systems with time-varying state delay and actuator faults. Based on the ( $k-1$ )th fault estimation information, a novel $k$ -step fault-estimation observer is proposed to construct the $k$ th fault error dynamics. The obtained fault estimates via $k$ -step fault-estimation can practically better depict the size and shape of the faults. Then, based on the information of online $k$ -step fault-estimation, a dynamic output feedback fault tolerant controller is designed to compensate the fault effects on the closed-loop fuzzy system. Furthermore, some less conservative delay dependent sufficient conditions for the existence of fault estimation observers and fault tolerant controllers are given in terms of solution to a set of linear matrix inequalities. Finally, simulation results of two numerical examples are presented to show the effectiveness and merits of the proposed methods.

Dynamic output feedback fault tolerant controller design for discrete-time switched systems with actuator fault

This paper investigates the problem of dynamic output feedback fault tolerant controller design for discrete-time switched systems with actuator fault. By using reduced-order observer method and switched Lyapunov function technique, a fault estimation algorithm is achieved for the discrete-time switched system with actuator fault. Then based on the obtained online fault estimation information, a switched dynamic output feedback fault tolerant controller is employed to compensate for the effect of faults by stabilizing the closed-loop systems. Finally, an example is proposed to illustrate the obtained results.

Observer-based fuzzy adaptive control of nonlinear systems with actuator faults and unmodeled dynamics

In this paper, an adaptive fuzzy output feedback fault-tolerant control scheme is developed for a class of nonlinear systems with actuator faults, unmodeled dynamics and without assuming the states being available for control design. Fuzzy logic systems are employed to approximate unknown nonlinear functions, and a fuzzy state observer is established to estimate the unmeasured states. By combining adaptive backstepping technique with changing supplying function technique and the nonlinear fault-tolerant control theory, a novel adaptive fuzzy fault-tolerant output feedback control approach is developed. It is proved that proposed control approach guarantees that all the variables of the closed-loop system are bounded. The simulation results are provided to illustrate the effectiveness of the proposed control approach. Compared with the existing results, the main contributions of this paper are as follows: (1) the proposed control method removes the restrictive assumption that all the states of the controlled system be measured directly; and (2) the proposed control method cannot only compensate for the actuator faults, but also solve the problem of the unmodeled dynamics.

Fault-Tolerant Control for LPV Systems Based on Fault Compensator

This paper proposes a fault-tolerant control (FTC) scheme for polytopic linear parameter varying (LPV) systems. We first propose a fault compensator whose structure is simple, but effective against actuator faults. Then, in order to show its basic idea, we consider a state feedback FTC scheme based on the fault compensator. Next, the FTC algorithm is extended to output feedback FTC scheme. The FTC scheme for LPV systems involves a fault compensator based on the estimated fault and a robust observer based on linear matrix inequality (LMI). The proposed FTC method is applicable for a variety of systems and guarantees the robust stability of the system in the event of actuator faults. Numerical examples are given to demonstrate its effectiveness.