Adaptive Fault-tolerant Control Scheme Research Articles

LSTM-Based Output-Constrained Adaptive Fault-Tolerant Control for Fixed-Wing UAV with High Dynamic Disturbances and Actuator Faults

The unknown disturbances and the changing uncertainties bring difficulties for designing a stable attitude controller for UAV. In this paper, a novel adaptive fault-tolerant attitude control approach is designed based on the long short-term memory (LSTM) network for the fixed-wing UAV subject to the high dynamic disturbances and actuator faults. Firstly, the high dynamic disturbances can be compensated by the adaptive laws. Meanwhile, the actuator faults can be handled by the proposed adaptive fault-tolerant control (AFTC) scheme. Moreover, the LSTM network is introduced to approximate the unknown and time-accumulating nonlinearities. With the introduction of the one-to-one nonlinear mapping (NM), the output constraints in the control system can be guaranteed. Additionally, it can be demonstrated that the boundness of all the signals can be assured. At last, numerical simulation results are provided to illustrate the effectiveness of the proposed method.

Distributed fault-tolerant formation control for multiple unmanned aerial vehicles under actuator fault and intermittent communication interrupt

This article develops a distributed adaptive fault-tolerant formation control scheme for the multiple unmanned aerial vehicles to counteract actuator faults and intermittent communication interrupt, where the issues on control input saturation and mismatched uncertainties are also addressed. The discontinuous communication protocol technique is exploited to achieve the stability of the formation system, if the conditions of dwell time and the rate of communication are satisfied. On the basis of the local information of neighboring unmanned aerial vehicles, a novel distributed adaptive mechanism is designed to estimate the bounds of actuator faults and uncertainties, where the input saturation is explicitly taken into consideration. The stability of the whole formation system under the designed fault-tolerant formation control strategy is analyzed using the Lyapunov approach. Finally, simulation results are presented to illustrate the effectiveness of the proposed scheme.

Fully distributed adaptive fault-tolerant formation control for octorotors subject to multiple actuator faults

In this paper, the fault-tolerant formation control for multiple octorotor unmanned aerial vehicles is investigated. A fully distributed adaptive fault-tolerant formation control scheme is presented to achieve a desired formation flight under multiple uncertainties and actuator faults. The developed controller does not require the global information of the constructed communication network and the knowledge of faults. The robust formation system stability under multiple uncertainties and actuator faults is proven by Lyapunov analysis. Simulation results for octorotor formation flying are provided to demonstrate the effectiveness.

On the synthesis of a sliding-mode-observer-based adaptive fault-tolerant flight control scheme

This paper presents an active Fault-Tolerant Control (FTC) framework to accommodate the actuator faults by using a Fault Estimation (FE) module fitted with an adaptive control law. It focuses on the problem of fault estimation based fault tolerant control for linear uncertain system with mitigation of the reconfiguration transients. In this work, a second-order sliding mode observer is designed to reconstruct the Loss of Effectiveness (LoE) of the actuators. The use of a bumpless strategy to cleverly manage the transient behavior where fault estimation is different from the real one due to an abrupt fault occurrence. Signals provided by the FE module are next used by an augmented fault-tolerant control allocation scheme to accommodate the fault. More precisely, the flight state tracking problem has been addressed with a robust adaptive model-reference Integral Sliding Mode (ISM) control law in a state feedback setting. Next, the problem of stability and performance of the overall FTC scheme with taking into account both FE performance and control law is rigorously considered. At the end, simulation examples on an aircraft from a European program are used to illustrate the effectiveness of the proposed approach.

Iterative Learning Model-Free Control for Networked Systems With Dual-Direction Data Dropouts and Actuator Faults.

In this article, we study the tracking problem for networked nonlinear discrete systems with actuator faults and dual-direction data dropouts. A novel adaptive fault-tolerant iterative learning model-free control strategy is designed. First, by utilizing the method called compact form dynamic linearization, the original nonlinear system model is transformed into an equivalent data-driven model, and the data model contains only one unknown parameter. Both the actuator fault and the system dynamics information are included in this parameter. Then, to model the physical processes of data dropout, a new mathematical relationship is constructed. Furthermore, an adaptive fault-tolerant iterative learning tracking control scheme is developed with only randomly received input/output data. Noting that the high learning rate or convergence rate is required in actual applications, a new varying parameter approach is designed to improve such rate. Finally, it is rigorously proved that the closed loop is stable in the sense of uniform ultimate boundedness, and numerical simulation results are conducted to validate the effectiveness of the designed control strategy.

Adaptive Fault-Tolerant Control and Performance Recovery Against Actuator Failures With Deferred Actuator Replacement

In this article, an adaptive fault-tolerant control (FTC) scheme is proposed for a class of uncertain nonlinear systems with actuator failures, in which a backup actuator is available. Different from existing FTC methods applying dynamic redundant actuators, a situation of deferred actuator replacement is firstly taken into account, i.e., the backup one cannot connect to plant right after failure detection. To recover the tracking error into prescribed performance within a specified time, an error transformation is introduced to render tangent barrier Lyapunov functions valid at the replacement instant, by which reconfigurable controller can be designed for the backup actuator. Simulation results on a flight control system are presented to illustrate the effectiveness of the FTC scheme.

An adaptive fault-tolerant control scheme for a class of fractional-order systems with unknown input dead-zones

An adaptive backstepping fault-tolerant control scheme is presented for a class of fractional-order systems in the presence of unknown input dead-zones. The proposed fault-tolerant control scheme ensures all the closed-loop signals are bounded ultimately. Especially, the tracking error can be made as small as possible by choosing appropriate design parameters. Furthermore, this scheme not only works for fractional-order systems with unknown linear terms but also works for these with unknown nonlinear terms. Finally, several practical examples are simulated to verify the effectiveness of the proposed fault-tolerant control scheme.

Characteristic model–based adaptive fault-tolerant control for four-PMSM synchronization system

In four-motor servo systems, actuator failures influence control performance seriously through huge inertia ratio changes and unknown disturbances. To solve this problem, an adaptive fault-tolerant control scheme based on characteristic modeling and extended state observer is proposed. First, an adaptive sliding mode observer is designed as fault detection part and offers motor information for controller. Second, to simplify complex dynamic model, this servo system is described by a second-order difference equation. This model integrates uncertainties into three time–varying characteristic parameters to reflect system status. Third, a discrete-time extended state observer is applied to restrain system error caused by actuator failure. Then, a fault-tolerant controller is designed based on characteristic model, and its stability is guaranteed in the sense of Lyapunov stability theorem. These four parts make up the adaptive control scheme and its effectiveness in system control, and fault tolerant is evaluated by both simulation and experiment results.

Adaptive Fault-Tolerant Compensation Control for T–S Fuzzy Systems With Mismatched Parameter Uncertainties

This paper is concerned with the adaptive fault-tolerant compensation control problem for a class of Takagi–Sugeno (T–S) fuzzy systems with mismatched parameter uncertainties and actuator faults. A matrix transformation technique is introduced to relax the restriction regarding the input matrices of T–S fuzzy systems considered in the existing results. Moreover, by combining backstepping-like technique and adaptive control method, a new adaptive fault-tolerant control scheme with compensation mechanism is proposed to achieve the desirable control performance. In addition, it is proved that the states of the resulting closed-loop fuzzy system converge to zero asymptotically even in the presence of actuator faults and mismatched parameter uncertainties. Finally, two simulation examples are given to verify the effectiveness of the presented control scheme.

Barrier Lyapunov Functions-Based Adaptive Fault Tolerant Control for Flexible Hypersonic Flight Vehicles With Full State Constraints

One of the key problems for space vehicles is how to deal with the contradiction between the control constraints and the disturbances from multiple resources. This paper focuses on the adaptive full state constrained controller design problem for the flexible air-breathing hypersonic vehicles with multisource uncertainties. In simultaneous presence of the aerodynamical uncertainties, the modeling errors, the external disturbances, and the contingent actuator failures, an adaptive fault-tolerant control scheme is put forward in the context of dynamic surface control. Then, the barrier Lyapunov functions are utilized to guarantee that the constraints on the velocity, the flight path angle, the altitude, and the pitch rate are never violated. In virtue of the bound estimation approach, the multisource disturbances are effectively dealt with. Finally, a number of illustrative examples are provided to demonstrate the effectiveness of the proposed methodology.

Adaptive fault-tolerant control for hybrid attitude tracking control system with quantized control torque and measurement

In this paper, the problem of fault tolerant control for spacecraft attitude tracking control system in the presence of actuator faults/failures, quantized control torque and measurement, uncertain inertial matrix and external disturbances is taken into account. The dynamical uniform quantizers are developed to quantize the signals of control torque and measurement, which can reduce the data transmission rate. In combination with the CA and FTC technique, a robust adaptive fault tolerant control scheme is proposed to cope with the effects of quantization errors in control torque and measurement, the unknown actuator faults/failures, uncertain inertial matrix and external disturbances. The developed control strategy combined with quantized control torque and measurement can guarantee the stability of overall closed-loop system and achieve satisfactory attitude tracking performance. Finally, simulation results are presented to verify the effectiveness of the proposed methods.

Adaptive fault tolerant control for hypersonic flight vehicle system with state constraints

In this paper, an adaptive fault tolerant control (FTC) scheme based on barrier Lyapunov functions (BLFs) for the hypersonic flight vehicle (HFV) with state constraints is proposed. Complexities of the aerodynamical uncertainties, external disturbances and flexible dynamics are taken into account in the controller design process. The paper deals with the MIMO system properly so that the backstepping technique based on BLFs can be successfully used for the issue of state constraints without neglecting the coupling of HFV system. To aim at the unknown faults of the elevators, an adaptive FTC mechanism is introduced to the BLFs-based controller, which increases the reliability of the system. Finally, simulations are conducted to verify the validity of the designed controller.

Distributed adaptive fault-tolerant close formation flight control of multiple trailing fixed-wing UAVs

This paper considers the reliable control problem for multiple trailing fixed-wing unmanned aerial vehicles (UAVs) against actuator faults and wake vortices. A distributed adaptive fault-tolerant control (FTC) scheme is proposed by using a distributed sliding-mode estimator, dynamic surface control architecture, neural networks, and disturbance observers. The proposed control scheme can make all trailing fixed-wing UAVs converge to the leading UAV with pre-defined time-varying relative positions even when all trailing UAVs encounter the wake vortices generated by the leading UAV and a portion of trailing UAVs is subjected to the actuator faults. It is shown that under the proposed distributed FTC scheme, the tracking errors of all trailing UAVs with respect to their desired positions are bounded. Comparative simulation results are provided to illustrate the effectiveness of the proposed control scheme.

Model‐free adaptive fault‐tolerant control for subway trains with speed and traction/braking force constraints

This study investigates the subway train fault-tolerant control problem for the actuator fault with constraints of speed and traction/braking force. The complex subway train dynamics is first transformed into a compact form dynamic linearization data model with the help of the concept pseudo-partial derivative (PPD) proposed under the framework of model-free adaptive control. By using the approximation of the uncertainty fault with radial basis function neural network (RBFNN), then a model-free adaptive fault-tolerant control (MFAFTC) scheme is designed by only using saturated input/output data of a subway train. The proposed MFAFTC scheme consists of two data driven on-line learning updating algorithms for RBFNN-weights and PPD, and its convergence is strictly proved by rigorous theoretical analysis, and whose correctness and effectiveness are further verified by a numerical simulation.

Adaptive Fault-Tolerant Control of Platoons With Guaranteed Traffic Flow Stability

This paper investigates the fault-tolerant control problem for heterogeneous vehicular platoons where input quantization and dead-zone nonlinearity are also involved. Due to the occurrence of actuator faults, the maximum acceleration changes, which may invalid the traditional quadratic spacing policy. To tackle the dilemma, an improved quadratic spacing policy with the lower bound of fault factor is proposed. Furthermore, the improved quadratic spacing policy removes the assumption of zero initial spacing errors. Based on the new spacing policy, an adaptive fault-tolerant platoon control scheme is developed, by employing radial basis function neural networks (RBFNN) and PID-type sliding mode control method. The given scheme is proved to be capable of guaranteeing individual vehicle stability, string stability and traffic flow stability. The effectiveness of the scheme is verified through comparison simulation studies.

Model free adaptive fault-tolerant tracking control for a class of discrete-time systems

This paper investigates the fault-tolerant tracking control issue for a class of discrete-time systems with sensor fault. A novel model-free adaptive fault-tolerant tracking control scheme is proposed by utilizing the dynamic linearization approach, in which only input/output (I/O) data of controlled plant are required. Moreover, due to the characteristics of simple structure and powerful approximation ability, RBF neural network (RBFNN) is introduced to approximate the fault dynamics after the sensor fault is detected. The approximated fault dynamic is utilized to reconstruct the controller. The major feature of this paper is that the whole fault-tolerant tracking controller structure is derived from the dynamic linearization of the ideal controller, rather than the criterion function. Finally, the proposed model-free adaptive fault-tolerant tracking controller is verified to be effective by numerical simulations.

Adaptive Resilient Secondary Control for Islanded AC Microgrids With Sensor Faults

In this article, we investigate the adaptive resilient secondary voltage and frequency control problem for islanded ac microgrids (MG) in the presence of sensor faults. Sensor faults or data attacks have a great impact on the stability and quality of MG. Existing methods commonly assume that the sensing information from distributed generations (DGs) is healthy or satisfies some ideal conditions. To achieve resilient secondary voltage restoration, a novel adaptive fault tolerant control scheme is proposed. Since the bounds of the time-varying faults are unknown, sufficient conditions are first derived to guarantee the voltage tracking errors to be uniformly ultimately bounded. It is also theoretically shown that the frequency restoration and power sharing can be ensured stable of the overall ac MG system by using the same control scheme. Compared with the existing distributed control methods for secondary control of MG, the considered problem with unknown boundaries sensor faults is more challenging and still not well explored.

Optimal Fault Tolerant Control of Large-Scale Wind Turbines in the Case of the Pitch Actuator Partial Faults

In this paper, an adaptive fault tolerant control strategy is proposed to deal with the three pitch actuator faults in the large-scale wind turbines. Firstly, a simultaneous state and fault estimation was performed through a suitable LMI (linear matrix inequality) based optimal strategy. Hereafter, the new control law is designed using the previously estimated fault information. The actuator efficiency estimator uses as design parameters, respectively, the performance index γ against the wind and the learning rate Ξ. of the fault estimation algorithm. The study shows that the choice of the previous two parameters impacts the response time of the fault estimation and the correlation of the tracking error with the wind. The aim is to choose a small fault estimation response time while keeping a weak correlation between the tracking error and the wind turbulence noise. Finally, a tuning strategy is elaborated to choose the suitable γ and Ξ to match the reconfiguration objective.

A dual adaptive fault-tolerant control for a quadrotor helicopter against actuator faults and model uncertainties without overestimation

This paper presents a dual adaptive fault-tolerant control strategy for a quadrotor helicopter based on adaptive sliding mode control and adaptive boundary layer. Within the proposed adaptive control strategy, both model uncertainties and actuator faults can be compensated without the knowledge of the uncertainty bounds and fault information. By virtue of the proposed adaptive control scheme, the minimum discontinuous control gain is adopted, which significantly reduces the control chattering effect. As compared to the existing adaptive sliding mode control schemes in the literature, larger actuator faults can be tolerated by employing the proposed control scheme while suppressing control chattering. Moreover, boundary layer is used to smoothen control discontinuity and further eliminate control chattering. Nevertheless, the choice of boundary layer thickness is a trade-off between system stability and tracking accuracy. By explicitly considering this fact, an adaptive boundary layer is developed and synthesized with the proposed adaptive control framework to ensure stability and tracking accuracy of the considered system. When the control parameter tends to be overestimated, the thickness of boundary layer can be appropriately adjusted to avoid control parameter overestimation. Simulation and experimental tests of a quadrotor helicopter are both conducted to validate the effectiveness of the proposed control scheme. Its advantages are demonstrated in comparison with a conventional adaptive sliding mode control scheme.

Adaptive fault tolerant attitude control of flexible satellites based on Takagi-Sugeno fuzzy disturbance modeling

This paper investigates the fault tolerance problem of flexible satellites subject to multiple disturbances and actuator faults. An adaptive fault tolerant control (FTC) approach based on disturbance observer is presented for attitude control system (ACS) with actuator faults, elastic modal, modeling error and environmental disturbance torque in this paper. Different from some existing disturbance observer-based control (DOBC) approaches, Takagi-Sugeno (T-S) fuzzy modeling technology is applied to describe the elastic modal. A fuzzy disturbance observer and a fault diagnosis observer are constructed to estimate the elastic modal and actuator fault, respectively. Then, based on fault accommodation and DOBC, a new adaptive FTC strategy is designed to achieve the anti-disturbance performance and improve the system reliability. Finally, the efficiency of the proposed FTC scheme is verified by simulation results.