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This paper presents a novel fault tolerance strategy for a class of uncertain high-order fully actuated systems (FASs) with actuator faults. Recently, the FAS approaches have been rapidly developed in different fields. As a control-oriented approach, a great advantage of FAS approaches is the convenient design of controllers for the deterministic nonlinear systems which meet the full-actuation condition. However, the presence of uncertainties and faults brings more challenges. To cope with the fault tolerance issue in FAS framework, a class of uncertain FASs with multiplicative actuator faults is introduced. Based on the Lyapunov stability theory, a fault-tolerant controller is presented to robustly stabilise the considered system. Moreover, for the systems that do not meet the full-actuation condition, previous research has indicated that they may be decomposed into a fully actuated subsystem and an extra autonomous subsystem. Leveraging the theory of input-to-state stability, the proposed fault-tolerant controller is further extended to cope with the stabilisation for such compound systems with nonlinear uncertainties and actuator faults. Both provided controllers can ensure the globally uniformly asymptotically stability of the considered systems and only rely on a few general assumptions. A numerical experiment illustrates the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this article, the adaptive event-triggered fault-tolerant control (FTC) issue of uncertain nonlinear systems suffering from sensor and actuator faults as well as external disturbances is studied. A disturbance observer (DO) is constructed to compensate for external disturbances and approximation errors generated by neural networks (NNs). Then, switching event-triggered control and command filtering techniques are introduced to balance the communication frequency and tracking performance of the controlled systems while avoiding “explosion of complexity” issue caused by iterative derivations of virtual controllers. Furthermore, compensation signals are designed to eliminate filtered errors. Finally, it is proven that the developed FTC scheme can esure that all signals are bounded and free from Zeno phenomenon. Simulation results of a spring damping mechanical system verifies the merits of the designed control algorithm. [ABSTRACT FROM AUTHOR]

This paper is concerned with nonlinear disturbance observer (DO)-based geometric attitude fault-tolerant control (FTC) problem of quadrotor unmanned aerial vehicles (UAVs) subject to system uncertainties, exogenous disturbances, and actuator faults. A disturbance observer-based control (DOBC) framework is devised to tackle the difficulties caused by system uncertainties and external disturbances. The FTC is proposed to cope with the occurrence of actuator faults which can be modelled as a constant loss of effectiveness. The proposed design scheme can provide an effective way to analyse the stability of the closed-loop system, which can ensure the asymptotical convergence of the error. The other method considers actuator failures as part of the lumped disturbance, and the attitude tracking problem of quadrotors concerning the lumped disturbance is solved by the DO-based control method, which can ensure the exponential convergence of the error. The numerical simulations are performed to illustrate the effectiveness of the design techniques. [ABSTRACT FROM AUTHOR]

In this paper, the adaptive finite-time fault-tolerant control (FTC) problem is investigated for uncertain nonlinear strict-feedback systems. The strict-feedback nonlinear system considered in this paper contains unknown nonlinear dynamics and actuator faults (both lock-in-place and loss of effectiveness). In this control process, adaptive laws are used to approximate unknown nonlinear functions. By using the sliding mode control technique and combining it with the adaptive backstepping control design, an adaptive terminal sliding mode FTC scheme is proposed. It is proved that the closed-loop system is finite-time stable and that the system output can track a given reference signal. Simulation results further show the efficacy of the designed control approach. [ABSTRACT FROM AUTHOR]

The fault-tolerant control (FTC) issue for a class of interconnected wave-distributed parameter systems is addressed by using the inclusion principle. Both subsystem faults and coupling faults are considered. First, the original system is expanded into an equivalent decoupled system. The main structure of the expanded system consists of multiple pair-wise subsystems. Second, the pair-wise fault-tolerant controllers are designed to stabilise the pair-wise subsystems, which can compensate for the effects of subsystem faults and major coupling faults. Third, a coordinated fault-tolerant controller with a suitable coordinated compensator for the expanded system is constructed according to the pair-wise fault-tolerant controllers of all subsystems. The coordinated compensator is used to compensate for the effects of other minor interconnections and coupling faults, and the coordinated controller is designed for the expanded system. Furthermore, the fault-tolerant controller is obtained to guarantee asymptotical stability of the faulty interconnected wave system by satisfying the contraction condition. The numerical experiments are presented to illustrate the effectiveness of the FTC method. [ABSTRACT FROM AUTHOR]

This research provides a method that accelerates learning and avoids local minima to improve the policy gradient algorithm’s learning process. Reinforcement learning has the advantage of not requiring a model. Consequently, it can improve control performance, mainly when a model is generally unavailable, such as when an error occurs. The proposed method efficiently and expeditiously investigates the action space. First, it quantifies the resemblance between agents’ and traditional controllers’ actions. Then, the principal reward function is modified to reflect this similarity. This reward-shaping mechanism guides the agent to maximize its return via an attractive force during the gradient ascent. To validate our concept, we establish a satellite attitude control environment with a similarity subsystem. The outcomes demonstrate the effectiveness and robustness of our method. [ABSTRACT FROM AUTHOR]

In this paper, the adaptive robust H ∞ fault-tolerant control problem for a class of switched nonlinear systems with parameter uncertainty, disturbances and actuator failures is concerned based on event-triggered control strategy. The adaptive laws based on state-dependent switched strategy are designed to eliminate the effects of actuator faults and parameter uncertainties by using the estimations of the unknown upper bounds of uncertain parameters. Then, the robust H ∞ fault-tolerant technique and multiple Lyapunov functions method are used, the designed controller can guarantee that all signals of the switched closed-loop systems are uniformly bounded. Meanwhile, the desired H ∞ performance of the systems is promised. Finally, the simulation results are given to illustrate the effectiveness of the proposed design method. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive fuzzy fault-tolerant control (FTC) scheme is proposed for active seat suspension systems. The addressed system contains electromagnetic actuator faults. In addition, the constraints of the displacements of the car seat, active suspension, and wheel, their vertical vibration speeds and current intensity are included. In the control design, since the systems have dynamic characteristics of complexities and spring non-linearities, the fuzzy logic systems are utilized to approximate the unknown nonlinear dynamics. By the aid of Barrier Lyapunov functions and based on the adaptive backstepping recursive design algorithm, a novel adaptive fuzzy FTC scheme is formulated. When the electromagnetic actuator fails, the developed control scheme can guarantee that all the vertical vibration states are stable. Eventually, the effectiveness of the presented control method is offered to illustrate by a random road surface. [ABSTRACT FROM AUTHOR]

This paper presents a fault-tolerant human-machine shared scheme for collision avoidance considering driver error and actuator fault. A fault-tolerant method of trajectory planning and decision-making is developed for dealing with the actuator fault. We calculate the remainder trajectory tracking capability of the faulted actuator and utilise the motion redundancy in the system to generate feasible fault-tolerant trajectories for collision avoidance. In addition, an assessment criterion of driver error is conducted to supervise the driver's steering response to the potential collision and actuator fault. The shared system dynamically adjusts the driving authority based on the driver error. A model predictive control (MPC) algorithm is employed for tracking the fault-tolerant trajectory. Simulation and hardware-in-the-loop (HIL) experiment results demonstrate the effectiveness of the presented approach, reducing traffic accidents due to driver error and actuator fault. [ABSTRACT FROM AUTHOR]

This paper describes a solution to the problem of fault-tolerant control (FTC) problem for leader-following heterogeneous linear multi-agent systems (MASs) subject to loss of effectiveness and time-varying additive actuator faults. The main goal of the proposed FTC approach is to maintain the behaviour of the heterogeneous MASs in spite of actuator faults and to save on bandwidth required for the MASs communication by using a dynamic event-triggered communication mechanism. Firstly, a fault estimation observer, which deals with linear systems with matched disturbances, is constructed to estimate simultaneously the actuator faults and the followers' states. Then, an FTC with dynamic event-triggered communication is proposed. The latter is based on a dynamic internal reference for each agent and exploits the estimated faults. Thus, it is at first shown that the FTC problem can be indirectly solved through the consensus tracking of the defined internal references. Then, a sufficient condition of consensus tracking for the internal references with a dynamic event-triggered communication is proposed. Finally, a sufficient and necessary condition is derived for the FTC of linear heterogeneous multi-agent systems. The effectiveness of the proposed approach is illustrated with a numerical simulation. [ABSTRACT FROM AUTHOR]

Optimal engine torque management, a fundamental objective, depends predominantly on engine speed tracking performance. It ensures to attain desired speed profile in the presence of uncertainties, disturbances and malfunctions. On the other hand, certain requirements such as emissions control, fuel efficiency and drivability are degraded in case of poor speed tracking. Furthermore, constraints on engine speed tracking performance are even more stringent for hybrid power-train architecture as crankshaft speed and engine torque are the basic variables for coordinated control. Speed tracking is also considered essential for gear shift control of the automatic transmission. In this research work, a framework for fault-tolerant speed tracking of the gasoline engine is proposed using the First Principle-based Engine Model (FPEM). A high-fidelity direct relationship between fuel injection input and engine speed is derived by the transformation of FPEM. Fault is induced in the fuel injection subsystem to generate the torque imbalance. Using the proposed framework, a second-order sliding mode-based control technique is applied to track desired speed profile by mitigating the faults in the fuel injection subsystem. Reference data acquired from the engine test rig is used to demonstrate the offline validity and fault tolerance capabilities of the proposed framework in MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

In order to improve the anti-disturbance ability and reduce the sensitivity to faults for the quadrotor UAV, the robust sliding mode adaptive control strategy based on iterative learning is designed in this paper. Firstly, the dynamic model of the quadrotor UAV is established. Secondly, the iterative learning observer is designed to track the states of the UAV system, and the convergence analysis of the observer is given. Thirdly, for the attitude system of the quadrotor UAV, a robust adaptive sliding mode control strategy based on iterative learning is proposed, and the stability is proved by the Lyapunov theory. Finally, by the simulation for the UAV attitude system, the validity of the iterative learning observer and robust adaptive sliding mode control strategy based on iterative learning is verified. [ABSTRACT FROM AUTHOR]

This study tackles the fault estimation issue for a continuous-time periodic piecewise time-varying systems (PPTVSs) with delays, fault signal and external disturbances. In particular, the PPTVSs are conjured up by segmenting the fundamental period of the periodic system into a finite number of subintervals. Moreover, fault estimator is designed in line with periodic piecewise observer systems to estimate the immeasurable states of the PPTVSs and the fault signal, simultaneously. Subsequently, in accordance with the estimated values of the fault signal and state dynamics, a fault-tolerant controller is devised. Moreover, by utilising Lyapunov stability theory and matrix polynomial lemma, sufficient criteria are procured in context of linear matrix inequalities to affirm the uniform boundedness of the undertaken system and error system. Further, relying on the acquired constraints, the precise configuration of the fault-tolerant control and observer gain matrices are proffered. Eventually, by offering two illustrative examples including mass-spring-damper system, the utility and potential of presented theoretical insights are validated. [ABSTRACT FROM AUTHOR]

An adaptive neural network fault-tolerant control(FTC) scheme is proposed for nonlinear and nonstrict-feedback multi-agent systems (MASs) with directed fixed topology. Firstly, a disturbance observer is designed to estimate the unknown external disturbances in the systems, and realise the dynamic estimation of the disturbances. Secondly, the efficiency factor is estimated online, and then the FTC scheme is designed successfully under the backstepping framework. It is proved that all signals in the closed-loop systems are semi-globally uniformly bounded and the tracking error is controlled in a small range. Finally, an example is given to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a novel prespecified finite-time and overshoot-restrained fault-tolerant tracking control scheme to compensate the intermittent faults in linear uncertain systems. Starting from the system tracking error dynamics model, we design a speed excitation function to improve the response speed of the control. A finite-time performance index function is established in the zero-sum game framework for the fault-free H ∞ optimal control policy. Based on Lyapunov stability theory, a fault compensation oriented fault estimation and diagnosis method is proposed to ensure the uniformly ultimately bounded stability of tracking errors. It is noteworthy that the proposed speeding fault-tolerant control can accelerate the trajectory tracking, narrow the upper bound of tracking errors and restrain the overshoot. Numerical and practical experiments fully illustrate the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

In this paper, aiming at the actuator fault-tolerant trajectory tracking problem of two-wheeled differential-driven mobile robots, a super-twisting fractional-order sliding mode fault-tolerant control method combined with a fault observer is proposed. The method not only ensures the pose tracking of the robot in normal condition but also guarantees the tracking performance while the fault occurs. The proposed method mainly includes: A fractional-order sliding mode surface which improves the transient response is utilized to design the fault-tolerant controller, and the super twisting reaching algorithm is adopted to reduce the chattering; A fault observer is designed to estimate the fault value, ensures system stability and safety through real-time compensation. Finally, the proposed fault-tolerant control method is verified by numerical simulation. The results show that the method proposed in this paper can effectively reduce the impact of actuator fault and ensure trajectory tracking performance. And the advantage of the control strategy over the general sliding mode controller is that compared with the integer-order sliding mode control (IOSMC), the fractional-order sliding mode control (FOSMC) we designed in this paper converges all the error states to zero faster, and the tracking error chattering is smaller. [ABSTRACT FROM AUTHOR]

This paper has studied the adaptive fuzzy fault-tolerant control (FTC) for active suspension systems via the sensor failure compensation method. In the control design, fuzzy logic systems (FLSs) are used to identify the unknown nonlinear dynamics, and the projection technique is utilized to deal with the multiple sensor failures. Combining with the backstepping technique, a novel FTC method has been developed. The proposed control method can guarantee that all the signals in the closed-loop system are all bounded, and the tracking error can converge to the neighbourhood of the origin. Finally, a simulation for the quarter active suspension system is given to verify the effectiveness of the developed control scheme. [ABSTRACT FROM AUTHOR]

This work addresses the design of an active fault-tolerant motion controller for over-actuated road vehicles. Our concept revolves around a control allocation framework, extended with Lyapunov-based stability constraints and costs. Besides the ability to cope with actuator constraints and optimal actuator reconfiguration, the proposed Lyapunov-based control allocation (LCA) allows the graceful degradation of control performance. Theoretical analysis and simulation results demonstrate that, in comparison with classical control allocation, the proposed LCA reduces tracking errors of the motion controller in the aftermath of actuator faults. Experimental tests carried out with the ROboMObil, a robotic electric vehicle prototype with wheel-based steering and traction actuation, demonstrate the effectiveness of the LCA. [ABSTRACT FROM AUTHOR]

The consensus control problem of multi-agent systems (MASs) has received an increasing research interest with ever-developing consensus theory. Before it can be widely applied to actual engineering, the consensus theory needs to be improved by addressing some practical problems. One of the key problems is how to ensure the desirable performance of each agent as well as the entire MAS when confronted with faults, which is referred to as the fault-tolerant consensus control (FTCC) issue. In this survey, we review the classic and recent results in the context of FTCC from two aspects, namely, physical security and logical security. In addition, we provide the latest results on FTCC where the physical and logical security are considered simultaneously in a framework. Finally, we outline several potential future research topics on the FTCC issue. [ABSTRACT FROM AUTHOR]

In this paper, the collaborative control of multiple nonlinear Euler-Lagrange systems with actuator faults and stochastic semi-Markov jump networks (SMJNs) is concerned. In order to fulfil high reliability and low consumption, several novel event-triggered fault-tolerant control (ETFTC) algorithms are established to simultaneously eliminate the undesirable faults and save control resources, where only quantised partial-state signal of neighbours is required for the control process. Moreover, some ubiquitous constraints, such as unknown control directions and time-varying communication delays, are also comprehensively considered and effectively excluded so as to further enhance the control reliability. Meanwhile, some sufficient criteria on the algorithm synthesis and stability analysis without involving Zeno behaviour are successfully built with the aid of Lyapunov–Krasovskii functional. Finally, some illustrative simulations are performed to validate the feasibility and effectiveness of the derived ETFTC algorithms. [ABSTRACT FROM AUTHOR]

In this paper, an integrated fault estimation (FE) and fault-tolerant control (FTC) method is proposed for linear parameter varying (LPV) systems using the parameter-dependent Lyapunov function. The observer-based estimation and fault-tolerant control structure causes an uncertainty between systems which is called the bi-directional uncertainty. Additionally, with simultaneous actuator and sensor faults, disturbances, the overall performance of the FTC system decreases. To maintain robust stability of closed-loop systems, an unknown input observer fault estimator approach with both state feedback control and sliding mode control is implemented as a solution by solving H ∞ optimisation using a linear matrix inequality (LMI) formulation. The efficiency of the integrated FE/FTC design is demonstrated using the pitch-axis missile LPV model and simulated to evaluate the merits of the suggested approach. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive dynamic PID sliding surface-based second-order fault-tolerant sliding mode controller for speed control of an electromechanical system is proposed. The paper aims to show how to utilise the robust properties of second-order adaptive dynamic sliding mode control on the problem of structural damage fault. Structural damage fault is apparently studied less than faults of actuator and sensor. Because of this reason, this study focuses on the structural damage fault. In order to solve the chattering which is the main problem of first-order/ traditional SMC, second-order controller is designed. The Lyapunov theorem is used for affirming the design and stability of the closed-loop system. Experimental results show that the control system with the proposed controller is easily implemented. Also, the proposed fault-tolerant controller, concerning parametric uncertainties and disturbances, acquire suitable tracking performance and shows more robustness than the traditional SMC. [ABSTRACT FROM AUTHOR]

In this paper, the event-triggered fixed-time control scheme is developed for a class of stochastic nonlinear systems with prescribed boundary constraints and actuator faults. For the controlled systems with unknown nonlinear functions, the neural networks are employed to reestablish the system model. Based on the event-triggered control technology, an original adaptive fixed-time control strategy with prescribed performance and the fault state is proposed by using the backstepping technique. Under the developed adaptive controller, the tracking error satisfies the predefined boundary functions and all the closed-loop system signals are bounded in probability in a fixed time, and the convergence time is irrelevant to the initial states of the system. The practicability of the designed controller is illustrated by a simulation example. [ABSTRACT FROM AUTHOR]

This paper proposes a fault-tolerant controller for active suspension to improve the bounce and pitch performance of a half-car system. In order to guarantee both the transient and steady-state control objectives, the prescribed performance control (PPC) method is applied to regulate the convergence rate, overshoot and tracking error of the closed-loop (CL) system. The system parametric uncertainties including sprung mass, sprung pitch inertia, suspension stiffness and damping coefficient, and axle distances are considered. The dynamics of three types of frequently encountered actuator faults are elaborated. Unlike most of the existing studies that use the adaptive method or neural network (NN) to estimate the uncertain parameters, this paper proposes a novel approximation-free method to deal with the uncertainties. The stability of the CL system is rigorously proved, and the suspension performance is examined with respect to physical constraints. In the numerical simulation, two kinds of imperfect actuators with hybrid nonlinear characteristic are employed to verify the effectiveness of the proposed controller. Simulation results show that the proposed controller can effectively suppress the bounce and pitch motions for the sprung mass and is robust to system uncertainties and actuator faults. [ABSTRACT FROM AUTHOR]

This paper investigates an adaptive cooperative fault-tolerant supervisory control problem for nonlinear strict-feedback leader-following systems with unknown control coefficients and actuator faults under the fixed directed graph. Radial basis function neural networks are used to approximate system uncertainties. The Nussbaum gain technique is introduced to address unknown signs of control gains. Then, based on the dynamic surface control method, a distributed adaptive fault-tolerant control scheme is presented to compensate for the actuator faults of followers. For neural networks approximation theory, the unknown smooth function can only be approximated on a compact set due to the approximation errors. By theoretic analysis, the supervisory-based adaptive controllers are proposed to guarantee that system state signals can converge to compact sets and the leader-following systems can achieve the practical output consensus. Finally, the simulation results are provided to show the validity of the proposed consensus scheme. [ABSTRACT FROM AUTHOR]

The paper concerns the digital twin design and fault-tolerant control of a production system. The real laboratory system under consideration consists of two subsystems: an assembly part and an automated guided vehicle transportation one. The proposed approach focuses, simultaneously, on both concurrency and synchronization problems as they are inevitable in such a kind of modern systems. The research contribution deals with the development of an analytical description of both an assembly system and a multiple automated guided vehicles transportation layer along with algorithms that are able to determine an optimum sequence of starting individual operations. Subsequently, diagnostics and fault-tolerant control schemes are elaborated and applied to the two-layer system being investigated. The core advantage of the proposed approach is that it can compensate or eliminate the impact of some faults, e.g. delays occurring in the assembly unit or reduced velocities of transportation means. This makes it possible to keep the desired schedule as far as possible. The paper concludes with a series of illustrative use cases and comparisons which exhibit the performance of the novel approach in both cases, i.e. faulty and fault-free. [ABSTRACT FROM AUTHOR]

In this article, a novel constrained fault-tolerant control (FTC) scheme is proposed to solve the attitude tracking control problem of the hypersonic vehicle (HSV) subject to multiple constraints, actuator faults, and disturbances. The reentry model of HSV with state constraints and the fault model of aerodynamic surface considering surface deflection constraints are constructed firstly. The adaptive robust unscented Kalman filter (ARUKF)-based estimation algorithm is designed, which can quickly estimate state variables, stuck faults, partial loss of effectiveness (PLOE) faults, and disturbances at the same time. By utilising the improved model predictive static programming (MPSP) technique, the complexity of processing multiple constraints and the computation are significantly reduced. Moreover, the closed-loop control system stability of HSV is analysed and the simulation results under two fault cases are given to demonstrate the effectiveness of the presented FTC scheme. [ABSTRACT FROM AUTHOR]

A new kind of kinematic underwater vehicle modelling, which uses the screw theory and the Davis method, is proposed. This latter one makes possible to treat the direct and inverse kinematic in the same way, using virtual kinematic chains. By a specific way, the kinematic model allows simplifying the Jacobian matrix, since it is not restricted to the base frame. A transformation from Euler angles to Octonions avoids possible singularities. In addition, a new linear quadratic regulator control that uses the design of variables gains based on low-pass filter and l ∞ norm. Global stability of the State-Dependent Riccati Equation is performed by using Lyapunov analysis with La'Salle's Principle. The allocation of faults in this strategy by using virtual fuzzy thrusters is addressed, which minimises the fault impact expressed as an abrupt discontinuity in the thruster system, as observed in the simulation results. [ABSTRACT FROM AUTHOR]

The problem of fault-tolerant control for the time-invariant system subject to actuator faults and multiple disturbances is focused. The multiple disturbances are composed of two kinds: one is a norm-bounded vector; the other described by an exogenous system is viewed as a harmonic signal with known amplitude and unknown frequency and phase. An improved disturbance observer is designed to obtain the modelled disturbance with partially known information. Based on this, two novel fault-tolerant control algorithms are put forward to the analysis and compensate two different types of actuator faults (one is norm-bounded, and the other is with an unknown boundary). The effectiveness and robustness of control schemes can be exhibited through some numerical simulations with different cases. [ABSTRACT FROM AUTHOR]

This article proposes a design framework for an event-triggered active fault-tolerant control system. The considered control system is modelled with an injected actuator fault into the plant system, and it includes: (i) two event detectors to determine when information is to be sampled or updated, (ii) a fault diagnosis observer to provide the fault and state information, and (iii) a fault-tolerant controller to compensate the fault. The proposed design framework allows for the separation of the designs of the fault diagnosis observer and the fault-tolerant controller, to mitigate the coupling effect caused by the event-triggered mechanisms and avoid the computations of a higher order system. Also, a design procedure is presented to deliver the computation of the design variables to reduce the information transfer, in both centralised and decentralised cases. Finally, a batch reactor benchmark system is adopted to demonstrate the applicability and superiority of the proposed design framework. [ABSTRACT FROM AUTHOR]

This paper develops a fault compensation scheme for a class of Euler–Bernoulli beam-ODE cascade systems to deal with certain boundary input faults, using a model transform-based backstepping control design. A model transformation is introduced to convert the Euler–Bernoulli beam-ODE cascade system to a Schrödinger-ODE cascade system. The FTC law is designed to compensate boundary input faults for the Schrödinger-ODE cascade system by constructing a normal intermediate system and a new exponentially stable target system. The purposes of the two-step backstepping are to bring in a state feedback and to improve the system performance. The performance of the target system, intermediate system, and Schrödinger-ODE cascade system is analysed in the Riesz basis frame. The stability analysis of the original Euler–Bernoulli beam-ODE cascade system is further provided. Simulation results illustrate the effectiveness of the proposed fault compensation scheme. [ABSTRACT FROM AUTHOR]

In this article, an adaptive fuzzy fault-tolerant control problem is investigated for a class of fractional order non-strict feedback nonlinear systems with actuator faults, where the unknown nonlinear functions are approximated by fuzzy logic systems. Within the framework of the backstepping technique we proposed a novel backstepping controller to avoid the algebraic loop problem via the property of fuzzy basis functions. Meanwhile, a compensation term in the form of smoothing functions of conventional control law is utilised to compensate for the effects caused by actuator faults where the number of them is allowed to be infinite. Finally, the fractional Lyapunov stability theory demonstrates that the tracking performance and boundedness of the close-loop systems are achieved in finite time. The simulation results are carried out to validate the effectiveness of the design scheme. [ABSTRACT FROM AUTHOR]

Most existing robust adaptive control designs for robotic systems only address the issue of modelling uncertainties and external disturbances. In this paper, we present a control method exhibits several salient features, such as robustness against modelling uncertainties, adaptation to unknown system parameters, tolerance to actuation failures, and obedience to motion constraints. It also ensures prescribed performance bounded (PPB) for any initial conditions, removing the shortcoming of the current PPB method. The proposed control scheme consists of two units: supervisory control and prescribed performance bounded (PPB) control. The role of the former is to drive the tracking error from any initial condition within the domain of interest to a residual set, so that the PPB control can be activated to ensure pre-given performance specifications. A soft connector is introduced to maintain continuous control action during the switching. Theoretical analysis and simulation verification confirm the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper considers the fault-tolerant control (FTC) problem for switched systems described by linear hyperbolic partial differential equations with the process and boundary faults. The effect of faults is compensated by designing the desirable boundary control gain. Both the accumulative and dissipative characteristics of faults are considered, respectively. Several Lyapunov-based FTC schemes that depend on the system parameters and boundary conditions are proposed which guarantee the exponential stability of the non-switched hyperbolic systems. The new result is further extended to the switched linear hyperbolic systems where the boundary control gain of each mode and the switching law are designed comprehensively. It shows that the FTC goal can be achieved even if only some faulty modes are stabilizable. An air traffic flow example is taken to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

In this study, a novel integrated fault estimation (FE) and fault-tolerant control (FTC) design approach is developed for a system with time-varying delays and additive fault based on a dynamic event-triggered communication mechanism. The traditional static event-triggered mechanism is modified by adding an internal dynamic variable to increase the inter-event interval and decrease the amount of data transmission. Then, a dynamical observer is designed to estimate both the system state and the unknown fault signal simultaneously. A fault estimation-based FTC approach is then given to remove the effects generated by unknown actuator faults, which guarantees that the faulty closed-loop systems are asymptotical stable with a disturbance attenuation level γ. By theory analysis, the Zeno phenomenon is excluded in this study. Finally, a real aircraft engine example is provided to illustrate the feasibility of the proposed integrated FE and FTC method. [ABSTRACT FROM AUTHOR]

In order to take into account both the system performance and economical utilisation of network resources, under the discrete event-triggered communication scheme, the problems of the robust L 1 fault-tolerant control for a class of uncertain networked control systems with actuator fault constraint are investigated. In consideration with the imperfect networked environment with transmission delay and quantisation, a model of the error dependent networked closed-loop fault system is established. By constructing an appropriate delay-dependent Lyapunov–Krasovskii functional, the sufficient condition for the existence of robust L 1 fault-tolerant controller is obtained for an error dependent networked closed-loop fault system, and a co-design method for gaining the discrete event-triggered parameter and L 1 fault-tolerant controller is proposed in terms of linear matrix inequalities. Notice that the structure of Lyapunov–Krasovskii functional which considers the piecewise-linear sawtooth structure characteristic of transmission delay, a less conservative result is obtained. Finally, simulation examples are provided to illustrate the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes an interval sliding mode observer (ISMO)-based sliding mode actuator fault accommodation (FA) framework for non-minimum phase linear-parameter-varying (LPV) systems involving online control allocation (CA) problem. Firstly, a specifically designed coordinate transformation is introduced to deal with the non-minimum phase issue. Then, an ISMO is proposed to estimate the set of admissible values for the states of the faulty LPV systems, which combines the interval observer technique and the sliding mode observer technique. A fault-tolerant control (FTC) law with an online CA scheme is subsequently designed by stabilising the ISMO instead of the original faulty LPV system. Finally, a simulation for an inverter used in China Railway High-speed (CRH) is presented to illustrate the effectiveness of the proposed framework. [ABSTRACT FROM AUTHOR]

This paper reports the development and application of an interval max-plus fault-tolerant control to a seat assembly system. Such systems will undergo a profound change because novel seats for autonomous driving contain expanded safety systems and are more voluminous and heavy. Automated guided vehicles are a promising means of transportation in these systems, but they require dedicated and advanced control systems. This rises new challenges because such an assembly system can dispose both shared resources and redundant elements. This paper presents a fault-tolerant control framework, which allows dealing with systems containing shared resources as well as redundancies. It also overcomes the problem of uncertainties and constraints, which are inevitable in industrial reality. [ABSTRACT FROM AUTHOR]

Production-line sensors are essential for synchronisation and execution of the correct workflow in a manufacturing process. Usually, sensor faults lead to serious delays, or even the complete termination of the manufacturing process, to carry out maintenance. Thus, sensor faults compromise the reliability of the manufacturing system and disturb the production schedule. This study proposes a multiple-sensor fault detection and isolation scheme for manufacturing series production lines. The proposed scheme adopts a global-redundancy method, using a digital camera and an ad-hoc video processing algorithm to detect and isolate faulty sensors. The main objective of this research is to preserve continuity of the production workflow and solve the problem of production delays and interruptions. Moreover, the scheme provides the possibility of online and post-process system maintenance. Further, the collected information on sensor false alarm rates can be used for a reliability analysis of the production line. The proposed scheme was tested using a laboratory production line model. The results show that the proposed scheme achieves the established objectives and improves the reliability of the manufacturing process. [ABSTRACT FROM AUTHOR]

This paper addresses the fault-tolerant control issue for a class of flexible air-breathing hypersonic vehicles. Firstly, a longitudinal dynamic model with process faults is established, which contains an ordinary differential equation (ODE) for rigid body, an Euler–Bernoulli beam equation for flexible modes, and a new boundary connection between them; Secondly, a novel fault-tolerant control scheme is proposed to accommodate process faults and suppress vibrations, which relies on the direct Lyapunov method and the bilinear matrix inequalities (BMIs) technique; Thirdly, in order to compute the gain matrices of the fault-tolerant control law, a two-step algorithm is provided to solve the BMI feasibility problem in terms of linear matrix inequality optimisation technique. Finally, the simulation results are provided to illustrate the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

This paper reviews some main results and process concerning with fault diagnosis and accommodation with flight control applications. The fault detection and diagnosis including the quantitative and qualitative methods and the fault-tolerant control including passive and active schemes are introduced, respectively. The control designs and developments of the fault diagnosis and accommodation for continuous-time systems and discrete-time systems, the fault diagnosis and fault-tolerant control for switched systems and interconnected systems as well as the applied flight control research including hypersonic vehicle, spacecraft and helicopter systems are summarised. [ABSTRACT FROM AUTHOR]

In this paper, an integrated framework for fault diagnosis and control is designed based on residual decoupling technology, which has fully considered the balance between the robustness of control system and the sensitivity of fault diagnosis system. To this end, the decoupling technology is first used for separation of fault and disturbance. Then, robust controller and fault-tolerant controller are designed for rejecting the system disturbance and guaranteeing the system performance, respectively. Finally, the application to three-tank system is given to demonstrate the performance and effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper proposes a fault diagnosis and fault-tolerant control method for a system with a fast time-varying delay and time-varying parameters. A fault observer is designed to estimate faults, and an improved fast adaptive fault estimation (FAFE) algorithm is developed to reduce the relevant constraints in the general form of this algorithm. With newly introduced relaxation matrices, this study estimates faults in a system exhibiting a fast time-varying delay. Based on the estimated faults, an output feedback controller is designed to accommodate the faults. The fault-tolerant control is realized using the introduced relaxation matrices. An algorithm is derived to solve for the observer and controller. Finally, the theory and method are validated using a real example of a helicopter system. [ABSTRACT FROM AUTHOR]

In this paper, a robust adaptive fault tolerant controller guaranteeing with time-varying performance bounds is designed for a class of time delay uncertain nonlinear systems subject to actuator failures and external disturbance. The influence of time delay on the system is mitigated and the system performance can be guaranteed by introducing a positive nonlinear control gain function and the generalised restricted potential function. A new method with more design degrees of freedom is developed to ensure the norm of the system state within a-priori, user-defined time varying performance bounds. Using the online estimation information provided by adaptive mechanism, a robust adaptive fault-tolerant control method guaranteeing time varying performance bounds is proposed. It is shown that all the signals of the resulting closed-loop system are bounded and the system state less than a-priori, user-defined performance bounds. Finally, simulation results are given to demonstrate the efficacy of the proposed fault-tolerant control method. [ABSTRACT FROM AUTHOR]

In this paper, design and development of fault-tolerant control (FTC) is investigated for linear systems subject to loss of effectiveness and time-varying additive actuator faults as well as an external disturbance using the fault-hiding approach. The main aim of this approach is to keep the nominal controller and to design a virtual actuator that is inserted between the faulty plant and the nominal controller in order to hide actuator faults and disturbances from the nominal controller, and consequently the performance of the system before and after the occurrence of actuator faults is kept to be the same. The proposed adaptive virtual actuator does not require a separated fault detection, isolation and identification (FDII) unit and both state and output feedback cases are considered. An illustrative example is given to demonstrate the effectiveness of the proposed adaptive virtual actuator in both cases. [ABSTRACT FROM AUTHOR]

In this paper, we describe how vehicle systems and the vehicle motion control are affected by automated driving on public roads. We describe the redundancy needed for a road vehicle to meet certain safety goals. The concept of system safety as well as system solutions to fault tolerant actuation of steering and braking and the associated fault tolerant power supply is described. Notably restriction of the operational domain in case of reduced capability of the driving automation system is discussed. Further we consider path tracking, state estimation of vehicle motion control required for automated driving as well as an example of a minimum risk manoeuver and redundant steering by means of differential braking. The steering by differential braking could offer heterogeneous or dissimilar redundancy that complements the redundancy of described fault tolerant steering systems for driving automation equipped vehicles. Finally, the important topic of verification of driving automation systems is addressed. [ABSTRACT FROM AUTHOR]

In the fault-tolerant control theory based on model following control, the desired signal of the control system is the output of a reference system. This paper is concerned with the design of the preview controller for a class of fault systems. A composite vector is introduced by including error vector, fault system state vector and reference system state vector. Then, we derived an augmented system from the known system equation, in which the reference input has equal status with the desired signal in the traditional preview control theory. Therefore, we can use the known theory to design the preview controller for the augmented system, then the preview controller of the original fault system can be obtained by the integration method. This paper strictly discusses the connection between stabilisation and detectability of the augmented system and the corresponding characteristics of the original system. Finally, by applying this theory to a real steam generator water level control system, it is found that the actions of the reference input preview and the fault signal preview can effectively eliminate the effect of the fault signal on the water level of the steam generator. The simulation shows the effectiveness of the controller designed. [ABSTRACT FROM AUTHOR]

In this paper, we present a fault-tolerant control scheme for linear parameter-varying systems that utilises multiple sensor switching to compensate for sensor faults. The closed-loop scheme consists of an estimator-based feedback tracking controller and sensor-estimate switching strategy which allows for the reintegration of previously faulty sensors. The switching mechanism tracks the transitions from faulty to healthy behaviour by means of set separation and pre-computed transition times. The sensor-estimate pairings are then reconfigured based on available healthy sensors. Under the proposed scheme, preservation of closed-loop system boundedness is guaranteed for a wide range of sensor fault situations. An example is presented to illustrate the performance of the fault-tolerant control strategy. [ABSTRACT FROM AUTHOR]

The tracking control problem for high-speed trains (HSTs) with the running resistance, the additional resistance and unknown actuator faults is investigated. First, based on the linearisation principle HSTs are modelled as the linear system with the unmatched time-varying uncertainty resulting from the interactive force among the connected carriages. Then, during the procedure of controller design, the adaptive control is applied to compensating for the unknown actuator faults. Meanwhile, control is used for rejecting and attenuating the effects of the norm-bounded disturbance. In order to obtain good tracking performances, two novel adaptive active fault-tolerant controllers are proposed. The stability of the closed-loop system via two control schemes is proved by the Lyapunov theory and linear matrix inequation. The effectiveness of the presented control scheme is validated by simulation results. [ABSTRACT FROM AUTHOR]

In this paper, the problem of distributed containment fault-tolerant control for a class of nonlinear multi-agent systems in strict-feedback form is studied. The considered nonlinear multi-agent systems are subject to unknown nonlinear functions and actuator faults with loss of effectiveness and lock-in-place. By resorting to the universal approximation capability of fuzzy logical systems, the command filtered backstepping technique and nonlinear fault-tolerant control theory, distributed controllers are designed recursively. From the Lyapunov stability theory, it is proved that all signals of the resulting closed-loop systems are cooperatively semi-globally uniformly ultimately bounded and the containment errors converge to a small neighbourhood of origin by properly tuning the design parameters. Finally, a numerical example is provided to show the effectiveness of the proposed control method. [ABSTRACT FROM AUTHOR]