Robust Fault-tolerant Control Research Articles

Fault-Tolerant Control for Actuator Faults of Wind Energy Conversion System

The problem of robust fault-tolerant control for actuators of nonlinear systems with uncertain parameters is studied in this paper. Takagi–Sugeno (T-S) fuzzy model is used to describe the wind energy conversion system (WECS). Fuzzy dedicated observer (FDO) and fuzzy proportional integral observer (FPIO) are established to reconstruct the system state and actuator fault, respectively. Fuzzy Robust Scheduling Fault-Tolerant Controller (FRSFTC) is designed by parallel distributed compensation (PDC) method, so as to realize the purpose of active fault tolerance for actuator faults and ensure the robust stability of the system. The stability of the closed-loop system is proved by Taylor series, Lyapunov function, and Linear Matrix Inequalities (LMIs). Finally, the simulation results verify that the proposed method is feasible and effective applied to WECS with doubly fed induction generators (DFIG).

Fault tolerant control of UMV based on sliding mode output feedback

This paper designs the robust fault tolerant controller for unmanned marine vehicle (UMV) systems with thruster faults and external disturbances via sliding mode output feedback. A comprehensive and unified fault model including thruster partial, complete and stuck faults is built for the first time. Based on input matrix full-rank decomposition technique and H∞ technique, a sufficient condition of sliding mode in the form of linear matrix inequality (LMI) is given. Then taking advantage of adaptive mechanism, a nonlinear discontinuous control term and an output feedback controller are aimed to reduce the oscillation amplitudes of the yaw velocity error and the yaw angle. Compared with the existing methods, the general faults including time-varying stuck fault can be dealt with. Eventually, the comparative simulation results have demonstrated the effectiveness and feasibility of the presented strategy in this paper.

Data-driven robust fault tolerant linear quadratic preview control of discrete-time linear systems with completely unknown dynamics

In this paper, we propose a data-driven robust fault tolerant preview control scheme for discrete-time LTI systems with completely unknown dynamics. In general, this work consists of three key design parts. Firstly, the Markov parameters sequence is identified to extract system feature from data. Then, robust linear quadratic preview control policy composed of finite data feedback, integral operation and preview action is designed through establishing data-space characterisation and solving the related convex optimisation problem. Thirdly, an active fault tolerant method composed of fault detection, isolation, estimation and corresponding compensation is further constructed to accommodate fault influence. Note that all these involved designs are performed at Markov parameters sequence level. Thus above integrated preview control scheme can avoid the priori knowledge requirements including system matrices, order, and state variables. The effectiveness of the obtained results is finally verified via a case study of the injection moulding machine.

Fault Tolerant Control of DFIG-Based Wind Energy Conversion System Using Augmented Observer

An augmented sliding mode observer is proposed to solve the actuator fault of an uncertain wind energy conversion system (WECS), which can estimate the system state and reconstruct the actuator faults. Firstly, the mathematical model of the WECS is established, and the non-linear term in the state equation is separated as the uncertain part of the system. Then, the states of the system are augmented, and the actuator fault is considered as part of the augmented state. The augmented sliding mode observer is designed to estimate the system state and actuator fault. A robust fault-tolerant controller is designed to ensure the reliable input of the WECS, maintain the stability of the fault system and maximize the acquisition of wind energy. The numerical simulation results verify the effectiveness of the control strategy.

Distributed Adaptive Control for UAV Formation With Input Saturation and Actuator Fault

The distributed adaptive tracking control schemes are addressed to deal with the formation control problem of multiple unmanned aerial vehicles subject to input saturation, actuator fault, and external disturbance. First, a novel adaptive backstepping control approach associated with a command filter is presented to settle the model uncertainty and input saturation problems. Second, a robust fault-tolerant controller is introduced to tackle the case with external disturbance, actuator fault, and model uncertainty by estimating the upper bounds of the faults and external disturbances. In addition, the proposed controllers enable the asymptotical stability of the closed-loop system in case of undirected interaction graph. Finally, the numerical simulations demonstrate that the proposed approaches are effective for the unmanned aircraft vehicle (UAV) formation system with various constraints.

High order sliding mode observer‐based backstepping fault‐tolerant control for induction motor

AbstractThis paper presents a robust fault tolerant control for an induction motor in presence of inter‐turn short‐circuit fault. The control strategy is based on Backstepping approach and high order sliding mode observer. That ensures a high‐performance control and a good dynamic in presence of inter‐turn short‐circuit fault. The stability of the Backstepping control is proved by Lyapunov theory. A high order sliding mode observer is used for rotor flux estimation. The performances of the fault tolerant control scheme will be examined via numerical simulation and validated through hardware implementation using MATLAB/Simulink with dSpace signal card. The analysis' results show the robustness of the proposed method for the tolerance of the inter‐turn short‐circuit fault.

Robust fault-tolerant saturated control for spacecraft proximity operations with actuator saturation and faults

In this paper, the motion control problem of autonomous spacecraft rendezvous and docking with a tumbling target in the presence of unknown model parameters, external disturbances, actuator saturation and faults is investigated. Firstly, a nonlinear six degree-of-freedom dynamics model is established to describe the relative motion of the chaser spacecraft with respect to the tumbling target. Subsequently, a robust fault-tolerant saturated control strategy with no precise knowledge of model parameters and external disturbances is proposed by combining the sliding mode control technique with an adaptive methodology. Then, within the Lyapunov framework, it is proved that the designed robust fault-tolerant controller can guarantee the relative position and attitude errors converge into small regions containing the origin. Finally, numerical simulations are performed to demonstrate the effectiveness and robustness of the proposed control strategy.

Cascaded Robust Fault-Tolerant Predictive Control for PMSM Drives

This paper presents a cascaded robust fault-tolerant predictive control (CRFTPC) strategy with integral terminal sliding mode observer (IT-SMO) to achieve high performance speed loop and current loop for permanent magnet synchronous motor (PMSM) drives. The modeling of PMSM considers the disturbance caused by parameter perturbation and permanent magnet demagnetization. With this model, we can derive the optimal control law of the proposed scheme, which avoids the tuning work of the weight factor effectively. This new CRFTPC strategy has a cascaded structure, external loop and internal loop, both implemented with robust fault-tolerant predictive control. In addition, a new integral terminal sliding mode observer is designed to estimate the disturbances, and thus the robustness of the proposed method can be increased significantly. Comparative simulations and experimentations verify that the proposed CRFTPC provides fast dynamic response, static-errorless speed, and current tracking, even with the system disturbance.

Robust fault-tolerant control for networked control systems subject to random delays via static-output feedback

This paper focuses on the problem of fault-tolerant controller (FTC) design for uncertain networked control systems (NCSs) with random delays and actuator faults. A new fault model is proposed to represent more class of actuator faults. More precisely, the NCSs with random delays and the possible actuator faults are modeled as a Markovian jump system (MJS) with incomplete transition probabilities (TPs) and then LMI-based sufficient conditions are derived to ensure the stochastic stability of the closed-loop system. The sufficient conditions are constructed to synthesize the mode-dependent static-output feedback (SOF) control laws. Feasibility and reliability of the proposed FTC against actuator faults are indicated through simulation results.

Continuous finite-time extended state observer based fault tolerant control for attitude stabilization

This work investigates the challenging problem of fast robust fault tolerant attitude control for spacecraft to handle external disturbances, actuator failures and misalignments. More specially, a novel nonsingular terminal sliding mode based finite-time extended state observer is first designed to estimate and compensate for the lumped system faults or uncertainties. And the proposed extended state observer is analysed and proved to be stable in the sense of fast finite-time uniformly ultimately bounded stability. Then, utilizing the techniques of super-twisting and terminal sliding mode control synthetically, a novel continuous attitude control algorithm is developed. The finite-time stability of the closed-loop attitude control system is proved by using a continuously-differentiable, homogeneous and strict Lyapunov function. And also the proposed control scheme is continuous with the property of chattering restraining. Finally, some numerical simulation results are shown to verify the effectiveness and superior performances of the spacecraft attitude stabilization control system driven by the proposed fast robust fault tolerant attitude control scheme.

Finite-time consensus of Markov jumping multi-agent systems with time-varying actuator faults and input saturation

This paper gives attention to the issue of finite-time leader-following consensus of nonlinear discrete-time multi-agent systems with Markov jump parameters. A robust fault-tolerant control protocol that takes the effect of time-varying actuator faults and actuator saturation into account is considered for the addressed system. The main purpose of the paper is to design a fault-tolerant controller such that the leader-following consensus of the addressed system is achieved over a prescribed finite-time interval. By using the Lyapunov functional approach, Abel’s lemma and some properties of Kronecker product, a sufficient condition for the existence of fault-tolerant state feedback controller for the addressed system is presented and an explicit parameterization of such a controller is obtained. Eventually, a numerical example along with its simulation results is exploited to reflect the applicability of the proposed design method, wherein the robust performance of controller is exhibited despite the presence of actuator saturation and time-varying actuator faults.

Composite hierarchical control for Markovian jump systems with multiple disturbances and time-varying fault

We investigate a robust fault-tolerant control problem for continuous-time Markovian jump systems with an actuator fault and multiple disturbances (one is norm-bounded, whereas the other can be modelled by an exogenous system). Our aim is to construct, simultaneously, a model-dependent disturbance observer for modelling the disturbance estimate and a model-dependent fault diagnosis observer for the time-varying fault estimate and then propose a composite hierarchical control scheme by integrating the fault and disturbance estimates using a state feedback control strategy. Application of the [Formula: see text] control methodology ensures stochastic stability of the resulting composite system with fault compensation, disturbance attenuation and rejection performances. On the basis of Lyapunov stability theory, the existence conditions of the disturbance observer, fault diagnosis observer and composite controller are derived from the solution to a convex optimization problem. Finally, a numerical example is given to illustrate the effectiveness of the proposed techniques.

RSimplex

As the complexity of Cyber-Physical Systems (CPS) increases, it becomes increasingly challenging to ensure CPS reliability, especially in the presence of software and/or physical failures. The Simplex architecture is shown to be an efficient tool to address software failures in such systems. When physical failures exist, however, Simplex may not function correctly because physical failures could change system dynamics and the original Simplex design may not work for the new faulty system. To address concurrent software and physical failures, this article presents the RSimplex architecture, which integrates Robust Fault-Tolerant Control (RFTC) techniques into the Simplex architecture. It includes the uncertainty monitor, the High-Performance Controller (HPC), the Robust High-Assurance Controller (RHAC), and the decision logic that triggers the switch of the controllers. Based on the output of the uncertainty monitor, we introduce a monitor-based switching rule in the decision logic in addition to the traditional envelope-based rule. The RHAC is designed based on RFTCs. We show that RSimplex can efficiently handle a class of software and physical failures.

Robust Fault-Tolerant Predictive Current Control for Permanent Magnet Synchronous Motors Considering Demagnetization Fault

In this study, a robust fault-tolerant predictive current control (RFT-PCC) algorithm based on a composite observer is proposed for permanent magnet synchronous motors (PMSMs), which can eliminate the influence of motor parameter perturbation and permanent magnet demagnetization. First, the effects of the parameter perturbation and permanent magnet demagnetization on the current vector are analyzed based on the conventional predictive current control. The composite observer based on the sliding mode observer and the Luenberger observer is then designed to observe the compensation voltage and current prediction value of the next time simultaneously. Finally, an RFT-PCC method is developed. The proposed RFT-PCC is able to effectively enhance robustness against parameter perturbation and permanent magnet demagnetization by adding compensation voltage. The current prediction value of the next time is used to replace the sampled current in RFT-PCC to compensate for the influence of the one-step delay. Comparative simulations and experimentations verify that the proposed RFT-PCC can improve the robustness while maintaining quick dynamic response of the current control loops.

Adaptive Fault-Tolerant Consensus for a Class of Uncertain Nonlinear Second-Order Multi-Agent Systems With Circuit Implementation

In this paper, a robust fault-tolerant consensus control strategy and its circuit implementation method are proposed for a class of nonlinear second-order leader-following multi-agent systems against multiple actuator faults and time-varying state/input-dependent system uncertainties. The faults of partial loss of actuator effectiveness and bias-actuators are considered without knowing eventual faulty information. The uncertainties are supposed to be structured and to satisfy integral quadratic constraints. The nonlinear dynamics of underlying systems are described by linear state-dependent functions based on the differential mean value theorem. By designing adaptive schemes and state-feedback control gains, a novel distributed control strategy is constructed to ensure the asymptotic consensus of agents in the presence of actuator faults, uncertainties, and nonlinear dynamics. The control strategy is further physically implemented based on the circuit theory. The efficiency of the developed control circuits is verified by a multiple coupled nonlinear forced pendulum system based on a circuit simulation software.

Robust attitude fault-tolerant control for unmanned autonomous helicopter with flapping dynamics and actuator faults

In this paper, an adaptive robust fault-tolerant control scheme is developed for attitude tracking control of a medium-scale unmanned autonomous helicopter with rotor flapping dynamics, external unknown disturbances and actuator faults. For the convenience of control design, the actuator dynamics with respect to the tail rotor are introduced. The adaptive fault observer and robust item are employed to observe the actuator faults and eliminate the effect of external disturbances, respectively. A backstepping-based robust fault-tolerant control scheme is designed with the aim of obtaining satisfactory tracking performance and closed-loop system stability is proved via Lyapunov analysis, which guarantees the convergence of all closed-loop system signals. Simulation results are given to show the effectiveness of the proposed control method.

An Enhanced Robust Fault Tolerant Control Based on an Adaptive Fuzzy PID-Nonsingular Fast Terminal Sliding Mode Control for Uncertain Nonlinear Systems

This paper develops an enhanced robust fault tolerant control using a novel adaptive fuzzy proportional-integral-derivative-based nonsingular fast terminal sliding mode (AF-PID-NFTSM) control for a class of second-order uncertain nonlinear systems. In this approach, a new type of sliding surface, called proportional-integral-derivative (PID)-nonsingular fast terminal sliding mode (NFTSM) (PID-NFTSM) which combines the benefits of the PID and NFTSM sliding surfaces, is proposed to enhance the robustness and reduce the steady-state error, whilst preserving the great property of the conventional NFTSM controller. A fuzzy approximator is designed to approximate the uncertain system dynamics and an adaptive law is developed to estimate the bound of the approximation error so that the proposed robust controller does not require a need of the prior knowledge of the bound of the uncertainties and faults and the exact system dynamics. The proposed approach is then applied for attitude control of a spacecraft. The simulation results verify the superior performance of the proposed approaches over other existing advanced robust fault tolerant controllers.

Leader-following exponential consensus of input saturated stochastic multi-agent systems with Markov jump parameters

Abstract This paper is concerned with the solvability of leader-following exponential consensus of a stochastic nonlinear multi-agent system in the presence of Markov jump parameters and input saturation by using a fault-tolerant control scheme. Firstly, the interconnection topology that represents the communication between the leader and follower agents is chosen to be undirected and fixed. Secondly, to exhibit real scenario, a time-varying actuator fault model is incorporated in the fault-tolerant control design. Thirdly, by introducing a simple linear transformation, an error system is then formulated. Based on these setups and by employing the tools from algebraic graph theory and Lyapunov–Krasovskii stability theory, a distributed robust fault-tolerant controller is designed for each follower node in terms of linear matrix inequalities such that the closed-loop error system is exponentially stable in the sense of mean-square even in the presence of possible actuator faults. Lastly, a simulation study is presented to illustrate the efficacy of the proposed control design technique.

Fault‐tolerant control of two‐dimensional discrete‐time systems

A robust fault-tolerant controller design for a class of two-dimensional discrete-time systems with mixed actuator faults, stochastic uncertainties and non-linear perturbation in delayed states is proposed in this study. The authors' aim is to investigate the stochastic stabilisation issue with an adequate level of an extended dissipative performance index where the considered system contains failures occurring among the pre-specified subset of actuators with admissible uncertainties. More precisely, the considered stochastic system uncertainties are assumed to follow mutually uncorrelated Bernoulli distributed sequences along with their probability rules. Furthermore, a practical actuator fault model consisting of both linear and non-linear fault terms is proposed. By utilising some inequalities and extended dissipativity theory, the authors develop a robust stochastic stability criterion of the addressed system in the linear matrix inequality framework. Lastly, a simulation example is provided to verify the correctness and significance of the designed fault-tolerant control strategy.

A novel robust attitude control for quadrotor aircraft subject to actuator faults and wind gusts

A novel robust fault tolerant controller is developed for the problem of attitude control of a quadrotor aircraft in the presence of actuator faults and wind gusts in this paper. Firstly, a dynamical system of the quadrotor taking into account aerodynamical effects induced by lateral wind and actuator faults is considered using the Newton-Euler approach. Then, based on active disturbance rejection control U+0028 ADRC U+0029, the fault tolerant controller is proposed to recover faulty system and reject perturbations. The developed controller takes wind gusts, actuator faults and measurement noises as total perturbations which are estimated by improved extended state observer U+0028 ESO U+0029 and compensated by nonlinear feedback control law. So, the developed robust fault tolerant controller can successfully accomplish the tracking of the desired output values. Finally, some simulation studies are given to illustrate the effectiveness of fault recovery of the proposed scheme and also its ability to attenuate external disturbances that are introduced from environmental causes such as wind gusts and measurement noises.