Adaptive Output Feedback Fault-tolerant Control Research Articles

Adaptive output feedback fault-tolerant control for a class of nonlinear systems based on a sensor fusion mechanism

This paper investigates an output feedback adaptive fault-tolerant tracking control for a class of nonlinear systems with system nonlinearities, sensor failures and external disturbances, in which sensor redundancy is employed to enhance measurement reliability. A sensor fusion mechanism, together with a novel history-based weighted average algorithm is first designed to fuse all sensor outputs. Then, an adaptive controller based on the sensor fusion output, a dynamic gain and a state observer is constructed to handle all the uncertainties caused by system nonlinearities, external disturbances, sensor failures and fusion mechanism. It is shown that by using the proposed scheme, the closed-loop system is stable, the sensor fusion mechanism can eliminate the effects of faulty sensors, and the real tracking error can be driven into a small compact set mainly affected by the fusion error. Experimental results are accomplished to validate the proposed scheme.

Fuzzy Adaptive Output Feedback Fault-Tolerant Control for Nonlinear Switched Large-Scale Systems With Sensor Faults

To handle the decentralized fuzzy adaptive outputfeedback fault-tolerant control problem for nonlinear switched large-scale systems with sensor faults and unknown control gains, a decentralized fault-tolerant control (FTC) strategy is proposed. As only the actual outputs are measurable when the sensor faults occur, a novel state observer is designed to estimate unmeasured states and address unknown control gains simultaneously. The unknown nonlinear functions are approximated by fuzzy logic systems. Based on the backstepping technique and the average dwell time method, decentralized FTC controllers are designed. It is proven that all states of the closed-loop system are semiglobal uniformly ultimately bounded and the tracking errors can converge to a small neighborhood of zero. A simulation example is presented to show the effectiveness of the developed strategy.

L1 adaptive output-feedback fault-tolerant control for uncertain nonlinear systems subject to unmodeled actuator dynamics and faults

This paper develops a L1 adaptive output-feedback fault-tolerant controller for uncertain nonlinear systems in the presence of unmodeled actuator dynamics and actuator faults. The proposed controller consists of the output predictor, adaptive laws, and the control law. The output predictor is a dynamic system expressed as a linear system with adaptive parameters which mean the matched uncertainties and the unmatched uncertainties. Piecewise-constant adaptive laws are designed to update the adaptive parameters so that the estimation error is driven to zero at each integration time step. The control law with low-pass filters is introduced to compensate for the performance degradation because of system uncertainties, unmodeled actuator dynamics and faults, and to guarantee the uniform boundedness of the input and output signals of the system. Two simulation examples verify the effectiveness of the proposed controller.

Output to state description-based convergent fault tolerant control for linear systems with actuator faults

This paper focuses on the output to state description-based convergent fault tolerant control (FTC) for a class of linear time invariant (LTI) systems. An output to state description theorem is proposed, by which, an adaptive output feedback FTC with a function equation constraint is designed for the LTI system in consideration. A controller reconfiguration algorithm is proposed to solve the constraint and construct an approximate controller that can compensate effectively the fault effect on systems. Furthermore, in certain conditions, the output feedback control gains can be determined by the state feedback control gains. A linear longitudinal dynamics of an aircraft and a linearised dynamic model of a vertical takeoff and landing (VTOL) aircraft in the vertical plane are applied to illustrate the effectiveness and merits of the proposed method.

Distributed adaptive output-feedback fault tolerant control for nonlinear systems with sensor faults

Distributed adaptive output-feedback fault tolerant control for nonlinear systems with sensor faults

Sampled observer-based adaptive output feedback fault-tolerant control for a class of strict-feedback nonlinear systems

This paper studies the sampled outputs-based adaptive fault-tolerant control problem for a class of strict-feedback uncertain nonlinear systems, where the nonlinear functions are allowed to include the unmeasured system states. Within the framework, a sampled output observer is introduced to jointly estimate the system states and parameters. By combining the estimated states and the supervisory switching strategy, an adaptive fault-tolerant controller is designed to achieve the desirable tracking performance. By using Lyapunov stability theory, it is proved that all the signals of the closed-loop systems are bounded and the tracking error converges to an adjustable neighbourhood of the origin eventually both in the fault free and faulty cases. Especially, if the outputs are available all the time, the proposed output feedback fault-tolerant control method can ensure the tracking error satisfy the prescribed performance bounds regardless of the faults. Finally, two examples are used to illustrate the effectiveness of the proposed method.

Fault-Estimation-Based Output-Feedback Adaptive FTC for Uncertain Nonlinear Systems With Actuator Faults

This paper investigates the adaptive output-feedback fault-tolerant control (FTC) problem for a class of uncertain nonlinear pure-feedback systems subject to actuator faults. To address the challenges incurred by the actuator faults and unmeasured state, a novel fault compensation observer-based adaptive controller is designed by estimating fault parameters online. By combining the backstepping design framework with prescribed performance and command filters techniques, it is proved that the proposed FTC scheme guarantees that all the signals in the closed-loop system are bounded and that the tracking error remains within the predefined bounds even if actuator faults occur. Compared with the existing output-feedback FTC design methods, the compensation state observer removes the restriction that the fault parameters are known or the uncontrollability caused by input saturation. The simulation and experimental results verify the effectiveness of the proposed method.

Observer-Based Adaptive Output-Feedback Fault-Tolerant Control of a Class of Complex Dynamical Networks

This paper is concerned with the observer-based adaptive output-feedback fault-tolerant control (FTC) problem for a class of complex dynamical networks (CDNs) with actuator faults. First, to address the coupling terms involved in the node dynamics, algebraic graph theory is used to design a new distributed state observer. Then, an observer-based adaptive output feedback FTC scheme is given to achieve the desired synchronization performance. Furthermore, via the Lyapunov analysis approach, it is proved that both the state estimation errors and the synchronization errors are all bounded for the faulty cases, while the asymptotical convergence is ensured for the fault-free case. In addition, it is shown that the proposed FTC scheme is valid for CDN with both time-invariant and time-variant graphs. Finally, a simulation example is given to illustrate the effectiveness of the theoretical results.

Neural network-based adaptive output feedback fault-tolerant control for nonlinear systems with prescribed performance

In this paper, an adaptive fault-tolerant control (FTC) approach is proposed for nonlinear systems involving input saturation and unknown control directions. In the framework of dynamic output feedback FTC, neural networks (NNs) are used to approximate the unknown nonlinear functions, and then a novel adaptive controller is further designed by combining the Nussbaum function property. Unlike some existing works incorporating an auxiliary state variable, the asymmetric actuator saturation is handled by the Nussbaum function in this approach. Furthermore, it is proven that all signals in the closed-loop system are bounded and the output tracking error satisfies the prescribed performance condition through using the barrier Lyapunov function method. Finally, simulation examples are presented to illustrate the effectiveness of the proposed control method.

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.

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.

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.