Sliding Mode Fault-tolerant Control Scheme Research Articles

Neural network-based robust adaptive super-twisting sliding mode fault-tolerant control for a class of tilt tri-rotor UAVs with unmodeled dynamics

Abstract Aiming at alleviating the adverse influence of coupling unmodeled dynamics, actuator faults and external disturbances in the attitude tracking control system of tilt tri-rotor unmanned aerial vehicle (UAVs), a neural network (NN)-based robust adaptive super-twisting sliding mode fault-tolerant control scheme is designed in this paper. Firstly, in order to suppress the unmodeled dynamics coupled with the system states, a dynamic auxiliary signal, exponentially input-to-state practically stability and some special mathematical tools are used. Secondly, benefiting from adaptive control and super-twisting sliding mode control (STSMC), the influence of the unexpected chattering phenomenon of sliding mode control (SMC) and the unknown system parameters can be handled well. Moreover, NNs are employed to estimate and compensate some unknown nonlinear terms decomposed from the system model. Based on a decomposed quadratic Lyapunov function, both the bounded convergence of all signals of the closed-loop system and the stability of the system are proved. Numerical simulations are conducted to demonstrate the effectiveness of the proposed control method for the tilt tri-rotor UAVs.

Finite-time switching-like sliding mode fault-tolerant control for discrete-time cyber-physical systems under DoS attacks and intermittent faults

In this article, the finite-time sliding mode fault-tolerant control problem is addressed for discrete-time cyber-physical systems with intermittent faults and denial-of-service (DoS) attacks. To model the intermittent nature of faults, two sequences of shifted gate functions are employed to depict the fault appearance and disappearance moments. Considering that DoS attacks can prevent transmission of signals, resulting in measurement data losses over the sensor to observer channel, switching-like observer and sliding mode fault-tolerant controller are presented to accommodate both situations with and without attacks. The designed sliding mode fault-tolerant controller can ensure the finite-time reachability of the sliding surface such that it can enter the quasi-sliding mode domain within finite time from any initial state. Moreover, based on the Lyapunov theory, sufficient criteria are derived to guarantee the finite-time boundedness of the closed-loop systems with intermittent faults and DoS attacks in both the reaching and sliding motion phases. Finally, the effectiveness of the proposed sliding mode fault-tolerant control scheme is verified by a numerical example and a practical example.

Anti-disturbance control for HVs system subject to nonlinear actuator characteristics with extended state observer

This paper proposes a radial basis function neural network and the actuator fault extended state observer based fast non-terminal sliding mode fault-tolerant control scheme for hypersonic vehicles (HVs) system. The proposed scheme can cope with actuator faults, actuator saturation, parameter uncertainties, and external disturbances for HVs systems, without relying on redundancy as some passive FTC methods do. Moreover, an anti-windup compensator is designed to mitigate the input saturation effects. Furthermore, the finite-time stability of the attitude angle of the HVs system is proved by Lyapunov's theorem. Numerical simulations validate the effectiveness of the proposed scheme.

Quaternion observer-based sliding mode attitude fault-tolerant control for the Reusable Launch Vehicle during reentry stage

In this paper, the attitude fault tolerant control (FTC) problem for the reusable launch vehicle (RLV) during the reentry stage is addressed, and a novel quaternion observer-based sliding mode attitude FTC scheme is proposed to accommodate the undesirable actuator faults and maintain a good attitude tracking performance. First, the attitude dynamics and kinematics are presented, and control-oriented attitude systems with actuator malfunctions are established based on the unit quaternion, which would avoid the singularity caused by the attitude maneuvering within a wide range in reetry phase. Then, a quaternion observer is proposed to estimate the compound disturbances, including uncertainties and malfunctions information. The norm character of the unit quaternion is retained in the developed observer and the convergence of estimation errors is proved by the coordinate transformation. Employed the estimations, a multivariable integral terminal sliding mode FTC scheme is proposed to guarantee the closed-loop system stability and high-precise attitude tracking even existing aerodynamics uncertainties and actuator faults. Finally, the simulations are developed to validate the effectiveness of the proposed approach.

Sliding Mode Fault Tolerant Control for a Quadrotor with Varying Load and Actuator Fault

In this paper, an adaptive sliding mode fault-tolerant control scheme based on prescribed performance control and neural networks is developed for an Unmanned Aerial Vehicle (UAV) quadrotor carrying a load to deal with actuator faults. First, a nonsingular fast terminal sliding mode (NFTSM) control strategy is presented. In virtue of the proposed strategy, fast convergence and high robustness can be guaranteed without stimulating chattering. Secondly, to obtain correct fault magnitudes and compensate the failures actively, a radial basis function neural network-based fault estimation scheme is proposed. By combining the proposed fault estimation strategy and the NFTSM controller, an active fault-tolerant control algorithm is established. Then, the uncertainties caused by load variation are explicitly considered and compensated by the presented adaptive laws. Moreover, by synthesizing the proposed sliding mode control and prescribed performance control (PPC), an output error transformation is defined to deal with state constraints and provide better tracking performance. From the Lyapunov stability analysis, the overall system is proven to be uniformly asymptotically stable. Finally, numerical simulation based on a quadrotor helicopter is carried out to validate the effectiveness and superiority of the proposed algorithm.

Decentralized Output Sliding-Mode Fault-Tolerant Control for Heterogeneous Multiagent Systems.

This paper proposes a novel decentralized output sliding-mode fault-tolerant control (FTC) design for heterogeneous multiagent systems (MASs) with matched disturbances, unmatched nonlinear interactions, and actuator faults. The respective iteration and iteration-free algorithms in the sliding-mode FTC scheme are designed with adaptive upper bounding laws to automatically compensate the matched and unmatched components. Then, a continuous fault-tolerant protocol in the observer-based integral sliding-mode design is developed to guarantee the asymptotic stability of MASs and the ultimate boundedness of the estimation errors. Simulation results validate the efficiency of the proposed FTC algorithm.

Backstepping‐based sliding mode fault‐tolerant control for linear interconnected parabolic distributed parameter systems

This study considers the fault-tolerant control (FTC) issue for a class of linear interconnected parabolic distributed parameter systems by utilising the backstepping-based sliding mode control technique. The original interconnected system, which suffers from process/actuator faults and matched disturbances, is converted into a stable target system by using an invertible backstepping transformation. Two types of kernel functions, the distinct diffusivity and the same diffusivity, are obtained. A sliding mode FTC scheme is developed to eliminate the destabilising effects caused by process/actuator faults and matched disturbances. An industrial application example is presented to validate the applicability and the relevance of the developed methodology.

Sliding‐mode fault‐tolerant control using the control allocation scheme

SummaryThis paper is devoted to the design of a novel fault‐tolerant control (FTC) using the combination of a robust sliding‐mode control (SMC) strategy and a control allocation (CA) algorithm, referred to as a CA‐based sliding‐mode FTC (SMFTC). The proposed SMFTC can also be considered a modular‐design control strategy. In this approach, first, a high‐level SMC, designed without detailed knowledge of systems' actuators/effectors, commands a vector of virtual control signals to meet the overall control objectives. Then, a CA algorithm distributes the virtual control efforts among the healthy actuators/effectors using the real‐time information obtained from a fault detection and reconstruction mechanism. As the underlying system is not assumed to have a rank‐deficient input matrix, the control allocator module is visible to the SMC module resulting in an uncertainty. Hence, the virtual control, in this scheme, is designed to be robust against uncertainties emanating from the visibility of the control allocator to the controller and imperfections in the estimated effectiveness gain. The proposed CA‐based SMFTC scheme is a unified FTC, which does not need to reconfigure the control system in the case of actuator fault or failure. Additionally, to cope with actuator saturation limits, a novel redistributed pseudoinverse‐based CA mechanism is proposed. The effectiveness of the proposed schemes is discussed with a numerical example.

Extended state observer‐based sliding mode fault‐tolerant control for unmanned autonomous helicopter with wind gusts

This study proposes a sliding mode fault-tolerant control (FTC) scheme for the medium-scale unmanned autonomous helicopter with rotor flapping dynamics in the presence of wind gusts and actuator faults using extended state observer technique. The radial basis function neural networks are employed to tackle the unknown non-linear interaction functions and adaptive neural network extended state observers are constructed to estimate the unknown wind gusts. Meanwhile, the adaptive fault observers are developed to estimate the fault parameters in position, attitude and flapping motion subsystems. With the aim of obtaining satisfactory trajectory tracking performance, a robust adaptive sliding mode FTC scheme is presented based on the backstepping sliding mode control technique and the closed-loop system stability is rigorously proved via Lyapunov analysis. Simulation results are carried out to validate the effectiveness of the proposed control method.

Adaptive sliding mode fault-tolerant control for hypersonic vehicle based on radial basis function neural networks

In this article, an adaptive sliding mode fault-tolerant control scheme is proposed to address the problem of robust and fast attitude tracking for a hypersonic vehicle in the presence of unknown e...

Nearly optimal sliding mode fault-tolerant control for affine nonlinear systems with state constraints

In this paper, the problem of fault-tolerant control for a class of affine nonlinear systems subject to state constraints is investigated. Firstly, the nearly optimal controller design for the constrained nominal system is considered. By introducing proper slack variables, the nonlinear optimal control problem with state constraints is transformed into an unconstrained one for an augmented nonlinear system. Then, an adaptive weight update algorithm based on neural network (NN) is given to solve the Hamilton–Jacobi–Bellman (HJB) equation, which can generate an approximated optimal control policy for the augmented system. In order to achieve the fault-tolerant control objective, an NN observer with novel adaptive laws is constructed to identify the actuator faults. An integral sliding mode fault-tolerant control scheme is employed to guarantee the stability of the constrained faulty system, which is designed using the fault estimations and the obtained nominal nearly optimal control policy. Finally, simulations are presented to illustrate the effectiveness of the proposed method.

Integral-Type Sliding Mode Fault-Tolerant Control for Attitude Stabilization of Spacecraft

Two fault-tolerant control (FTC) schemes for spacecraft attitude stabilization with external disturbances are proposed in this brief. The approach is based on integral-type sliding mode control strategy to compensate for actuator faults without controller reconfiguration. First, a basic integral-type sliding mode FTC scheme is designed so that sliding manifold can be maintained from the very beginning. Once the system enters the sliding mode, the dynamics of the closed-loop system with actuator fault is identical to that of the nominal healthy system. Second, the integral-type sliding mode fault-tolerant controller is incorporated with adaptive technique to accommodate actuator faults so that the required boundary information can be relaxed. The effectiveness of the proposed schemes against actuator faults is demonstrated in simulation.

Adaptive Sliding Mode Fault-Tolerant Control of the Uncertain Stewart Platform Based on Offline Multibody Dynamics

In this paper, we propose a novel adaptive sliding mode fault-tolerant control scheme based on offline multibody dynamics for the uncertain Stewart platform under loss of actuator effectiveness. The asymptotic stability is analyzed by Lyapunov method in the presence of friction, unmodeled dynamics, environmental disturbances, and even the unpredictable actuator faults. To cope with the nonlinear coupling and various properties of freedom directions, the offline nominal multibody dynamics are employed to design the initial upper bound of uncertainties and to realize the dynamic compensation, which achieves high online computational efficiency and significantly improves the characteristics of the six degree-of-freedom (DOF) directions. We also introduce a novel adaptive updating law to adjust the control torque based on the real-time position tracking errors, which alleviates the chattering phenomenon of the sliding mode controller. Finally, the fault-free and faulty conditions are analyzed to corroborate the advantages of the proposed control scheme in comparison with the nominal sliding mode control scheme.