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Intelligent equipment is an inevitable trend for the high-quality development of the coal industry, With the construction of super high mining height and super long working face in coal mine, scraper conveyor has been developing towards heavy and long distance, and permanent magnet direct drive has gradually replaced “asynchronous motor + reducer” to become the main driving mode of scraper conveyor. However, the traditional dual-drive scraper conveyor has the problems of high shutdown rate, uneven distribution of coal flow and large energy consumption, poor tracking performance, especially the fluctuation of the chain tension under long transport distance causes the surge of the driving motor circuit, which has become the main problem that limits the intelligent development of scraper conveyor in our country. According to the main problems and development needs of scraper conveyor, this paper puts forward a new mode of scraper conveyor with multiple permanent magnet motors in series “drive - drive”, and expounds the research status of key technologies involved in the research field of scraper conveyor with multiple permanent magnet motors in series. Including the scraper conveyor fault diagnosis and state recognition technology, multi-motor series drive “mechanical-electrical” coupling dynamic characteristics, multi-permanent magnet motor synchronous control technology, multi-agent adaptive cooperative control, for the design and development of multi-drive scraper conveyor has certain adaptability and reference. In view of the difficulties faced by the research of multiple permanent magnet motor series drive system of scraper conveyor, the system is divided into four key science and technology: ① new configuration design of multi-drive scraper conveyor; ② nonlinear mechano-electrical coupling dynamics modeling of multi-drive scraper conveyor; ③ chain tension pulsation and active control of multi-drive scraper conveyor; ④ active fault tolerance and adaptive cooperative control of series drive scraper conveyor. From the structural design and optimization, the whole machine operation and maintenance control to achieve scraper conveyor multiple permanent magnet motor series drive system technology research, improve the scraper conveyor intelligent level, promote the level and development of high-end equipment of coal machinery.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the problem of active fault tolerant control (AFTC) is studied for polynomial nonlinear systems subject to asymmetric state constraints and measurement noise. The AFTC scheme is composed of the fault detection and isolation unit and the fault tolerant control unit. By using polynomial filters, the fault detection (FD) module and the fault isolation (FI) module are designed to obtain the accurate estimations of states and faults in the presence of measurement noise. The FD is realized by the residual evaluation approach, while the FI is achieved through the residual matching method. When a fault is detected and isolated, the controller switches from a nominal controller (NC) to a reconfigured controller (RC). To ensure that the asymmetric state constraint is not violated, a universal barrier Lyapunov function is introduced in the design of the NC and the RC. Moreover, the boundedness of tracking errors and estimation errors is analysed. Finally, the effectiveness of the proposed AFTC method is verified by a simulation for a dynamic point-the-bit rotary steerable drilling tool system. [ABSTRACT FROM AUTHOR]

Reliability of proton exchange membrane fuel cells (PEMFCs) is a major issue for large industrialization and commercialization. Indeed, performance can be degraded due to abnormal operating conditions, namely, faults, which lead either to a transient decay of the fuel cell performance or to permanent damage that cannot be recovered. The literature shows that long-time exposure to faults leads to fuel cell degradation. Therefore, it is necessary to use tools that can not only diagnose these faulty conditions, but also modify the fuel cell operations to recover a healthy operating point. For that purpose, one approach is the Active Fault Tolerant Control (AFTC) strategy which is composed of three functions. First, a diagnosis part allows fault detection and identification. Then a decision part, which is an algorithm aiming at finding a new operating point that mitigates the occurring fault. Finally, a control part applies the mitigation strategy established by the decision algorithm. The present work focuses on the decision part. and aims to bring a new contribution to PEMFCs reliability improvement and address water management issues, namely, the cell flooding and membrane drying out with the developed AFTC tool. The strategy is tested and validated on a single PEMFC cell and results are presented, analyzed, and discussed.

Reliability of proton exchange membrane fuel cells (PEMFCs) is a major issue for large industrialization and commercialization. Indeed, performance can be degraded due to abnormal operating conditions, namely, faults, which lead either to a transient decay of the fuel cell performance or to permanent damage that cannot be recovered. The literature shows that long-time exposure to faults leads to fuel cell degradation. Therefore, it is necessary to use tools that can not only diagnose these faulty conditions, but also modify the fuel cell operations to recover a healthy operating point. For that purpose, one approach is the Active Fault Tolerant Control (AFTC) strategy which is composed of three functions. First, a diagnosis part allows fault detection and identification. Then a decision part, which is an algorithm aiming at finding a new operating point that mitigates the occurring fault. Finally, a control part applies the mitigation strategy established by the decision algorithm. The present work focuses on the decision part. and aims to bring a new contribution to PEMFCs reliability improvement and address water management issues, namely, the cell flooding and membrane drying out with the developed AFTC tool. The strategy is tested and validated on a single PEMFC cell and results are presented, analyzed, and discussed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Flight Control System (FCS) is considered as the brain of an aerial vehicle. It is a mechanism through which pilot's commands are transferred to the actuators of the aircraft control surfaces. In order to ensure safety and increase reliability of aerial vehicles, development of fault tolerant FCSs has been the focus of research community for past few decades. Fault tolerant ability enables an aircraft to maintain satisfactory performance even in the state of a fault. Fault Tolerant Control Systems (FTCS) are categorized as passive and active control systems. Passive FTCS are designed to mitigate the effects of certain known faults. These faults can be related to sensor failure, actuator failure, or system component failure. On the other hand, active FTCS contain a controller reconfiguration mechanism, whereby, they can adjust the controller input online to mitigate the effects of the faults. In this way, they can accommodate complicated and versatile faults as compared to their passive counterparts. This paper presents a review of significant research during last decade in active fault tolerant control with applications to FCSs. A review of state-of-the-art works in this domain has also been presented. Upon review, these state-of-the-art research interests have been categorized into respective categories. Furthermore, research works have been cataloged based on their technology readiness levels. Based on these reviews, future research directions have also been highlighted. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation on active fault tolerant control (AFTC) for discrete-time switched systems subject to disturbances and known switching signals. The proposed approach employs interval observers in a two-step implementation strategy. Firstly, a fault detection and isolation (FDI) module based on interval observers is introduced to estimate actuator faults affecting the switched system. In order to enhance the accuracy of this module, an L ∞ criterion is utilized. Secondly, a feedback control law is designed to compensate the impact of actuator faults. The controller parameters are determined by solving linear matrix inequalities (LMI). The effectiveness of the proposed AFTC scheme is demonstrated through extensive analysis and simulation studies. [ABSTRACT FROM AUTHOR]

In this article, we present an active fault tolerant control scheme based on fault detection and isolation (FDI) for a class of uncertain systems subject to sensor faults. The FDI unit consists of a fault detection (FD) module and a fault isolation (FI) module, to determine when and where the sensor fault happens. It is noted that the FD module is based on a proposed adaptive interval observer where adaptive parameters instead of conservative uncertainty bounds are used, as a result, the sensitivity to faults is improved. When the FD module detects a fault, a compensation controller (CC) and an FI module are activated. The CC is designed to maintain some level of performance assuming all sensors are faulty. After the FI module determines the location of the fault, a reconfigured controller is activated to give improved performance with reduced conservatism. Importantly, the unmeasurable states and faulty output are approximated as a linear combination of their upper and lower bounds, and linear parameter are determined by adaptive laws. Finally, a simulation example is utilized to verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper focuses on speed and current sensor Faults Detection and Isolation (FDI) in an Induction Motor (IM) drive. The effect of sensors faults on the IM vector control is presented, then, new detection and isolation approaches are suggested. Speed sensor faults are detected when an error between only two points from speed data exceeds a certain threshold. An algorithm based on RMS currents is developed to detect and isolate any faulty current sensor. This requires three current sensors, each per phase. Besides, open circuit faults of inverter power switches are taken into account too. To ensure continuous functionality of the drive, we conceived an Active Fault Tolerant Controller (AFTC) with smoother reconfiguration feature. Simulations in Matlab/Simulink are carried out to show the efficiency of the suggested schemes.

In this article, we propose an active fault tolerant control (FTC) scheme to achieve trajectory tracking for unmanned underwater vehicle (UUV) subject to sensor faults and multiple uncertainties (including external disturbances and modeling errors). To make matters more challenging, it is assumed that the velocities (linear and angular) are unavailable. The proposed active FTC scheme includes a fault detection and isolation (FDI) unit and an FTC unit. The FDI is performed by an adaptive interval observer whose parameters are determined automatically by adaptive laws, relaxing the requirement on the bound of uncertainty. The FDI mechanism is if an output error exceeds its upper and lower bound estimates, then an alarm implying the corresponding sensor has a fault will be triggered. If the sensor is healthy, then the nominal controller is still adopted; otherwise, an FTC unit (where the real output of the faulty sensor is estimated as a linear representation of its upper and lower bounds) will be constructed to ensure the acceptable tracking performance of the faulty system. Finally, a simulation example is used to prove the efficacy of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents an attitude active fault tolerant control for a satellite simulated model. The proposed fault tolerant controller consists of two main parts: a nominal controller, designed assuming that the system is healthy, and a fault diagnosis module which aims at detecting, isolating and estimating the fault affecting the system. The fault diagnosis module is designed by using the non-linear geometric approach tool which allows to obtain detection residuals and estimation filter decoupled from the aerodynamic disturbance representing the main uncertainty in low Earth orbits. The simulation results show the advantages, in terms of attitude tracking accuracy, obtainable when implementing the proposed method. [ABSTRACT FROM AUTHOR]

Summary: The main aim of this paper is to design an active fault tolerant controller for switched positive linear systems. A theorem is proved for fault and state estimation of switched positive linear systems in terms of matrix inequality by considering average dwell‐time approach. By utilizing the theorem results, not only a fast and exact estimation of fault and state is obtained but also the positivity of state estimation is ensured. The feasibility problem is solved by formulating it into a special sequential optimization problem subject to LMI constraints. Based on the fault estimation information, an observer‐based fault tolerant control guaranties the stability and positivity of the closed‐loop system. Finally, a practical example including a data communication network is presented to illustrate the efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive state-of-the-art review of Fault Tolerant Control Systems (FTCS) is presented with the latest advances and applications. The overall aim of an FTCS is to accommodate faults in the system components during operation and maintain stability with little or acceptable degradation in the performance levels. Such systems are of great importance for safety and mission-critical applications where human lives are involved and service continuity is of extreme importance. In this paper, various types of faults in the sensors and actuators have been described. Types and classifications of Fault Tolerant Control (FTC) including active, passive and hybrid approaches with the latest design techniques are presented. Finally, a review of the stability and reliability analysis of FTCS is presented with research gaps. The contribution of the study is to benefit new and existing researchers in FTCS domain with the latest trends and applications for future research directions. [ABSTRACT FROM AUTHOR]

Abstract Wind turbines are developed to generate electrical energy with more efficiency and reliability. Modern fault detection, diagnosis, and accommodation structures are crucial to realize required level of reliability and efficiency for wind turbines. In this paper, a novel active fault tolerant controller is addressed to control rotor speed and power of a wind turbine in the presence of actuator faults and uncertainties. The proposed controller is a sliding mode controller with an integral surface and an adaptive gain which is known as adaptive output feedback sliding mode controller. An output feedback and a full-order compensator are utilized to shape the integral sliding surface and control law. The full-order compensator is proposed for fault and disturbance attenuation. The control law parameters adjustment and closed-loop system stability are satisfied using linear matrix inequality technique and Lyapunov stability theorem, respectively. Efficiency of the suggested controller is tested on a 5-MW wind turbine benchmark model in an extreme wind speed profile. In this regard, performance of the proposed strategy is compared with proportional-integral-derivative and disturbance accommodation control techniques. Simulation results show desirable performance and robustness behaviour for the adaptive output feedback integral sliding mode controller under the healthy and faulty actuator. Highlights • Wind turbines are developed to generate electrical energy with much efficiency and reliability. • An adaptive output feedback integral sliding mode controller is developed for pitch angle control. • Less rotor speed, generator speed and generated power fluctuations have been achieved using AOFSMC. • The AOFSMC shows less fatigue on the components such as gearbox, generator and etc. • The AOFSMC keeps the rotor speed and generated power quality in the post-fault phase. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell systems are promising technologies for the integration of renewable energy. They pave the way for further emission-reduction and energy autonomy initiatives. However, widespread commercialization still faces several challenges to extend their durability, improve their reliability while reducing their cost. Control strategies included information about the state of heath are among promising levers to tackle these challenges. In this context, an active fault tolerant control strategy based on three modules is introduced. Firstly, a fault diagnosis tool identify the system state of health and detect abnormal conditions. Then, a decision process based on diagnosis results, manages to find a fault strategy mitigation. Finally, a set of controllers, or a re-configurable controller, are used to apply the decision strategy. This third module has to be suited to the real-time specifications of the system. In this context, neural networks-based controllers with adaptive learning appear to be especially appropriate methods for system state of health consideration. For this reason, this paper aims to bring a literature review for adaptive neural-based control applied on proton exchange membrane fuel cell systems. Based on this overview of recent works available, propositions are made to fill the resource gaps about fuel cell control and give some answers to the aforementioned issues. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of active fault-tolerant coordination control (AFTCC) for proton exchange membrane fuel cells (PEMFCs), which are complex nonlinear systems with multiple inputs and outputs. Conventional fault-tolerant control methods cannot properly coordinate multiple operating variables and prevent constraint violations in PEMFCs. Our proposed AFTCC method seeks to stabilize the output performance of four operating variables and avoid PEMFC operating constraint violations during failure scenarios. Our method is supported by a curriculum-based multiagent deep meta-deterministic policy gradient (CMA-DMDPG) algorithm, which integrates meta-reinforcement learning, multiagent reinforcement learning and curriculum learning to achieve multitask collaboration of multiple agents, thereby enhancing PEMFC robustness. The algorithm consists of a meta-learner and a base learner. The base learner regards the hydrogen controller, oxygen controller, pump controller and radiator controller as four independent agents and thus achieves a cooperative control policy. The meta-learner detects PEMFC faults and selects an appropriate cooperative control policy. The performance of AFTCC under various stochastic and fault conditions is evaluated using a 75 kW PEMFC model. The results showed that the performance of AFTCC surpassed 11 other fault-tolerant control methods in terms of output voltage, oxygen excess ratio, and stack temperature, and avoided constraint violations. • An AFTCC method is proposed to realize active fault-tolerant control of the PEMFC. • A CMA-DMDPG algorithm is proposed to realize multi-task collaboration of controllers. • The AFTCC improved PEMFC control performance and prevent constraint violation. [ABSTRACT FROM AUTHOR]

We focused in this work on a fault tolerant control of a non linear hybrid system class based on diagnosis method (determine and locate the defects and their types) and on the faults reconfiguration method. In literature we can found many important research activities over the fault-tolerant control of non linear systems and linear Hybrid systems. But it dosen´t exist too many for the non linear hybrid system. The main idea in this paper is to consider a new approach to improve the reconfiguration performance of the non linear hybrid system by using hammerstein method which is designed to works only for linear systems. This method compensated the effect of the faults and guarantees the closed-loop system stable. The proposed method is simulated with a hydraulic system of two tanks with 4 modes. [ABSTRACT FROM AUTHOR]

This paper presents a finite frequency-based active fault tolerant control approach for the compensation of unknown failures in linear time-delay plants. An integration of fault detection filter based on observer technology and H∞ controller in residual feedback form is considered in the active fault tolerant control system. Different from the traditional schemes, exact fault estimation is not necessary in the proposed active fault tolerant control. To achieve the desired system performance when a fault occurs, the residual is directly embedded in the control loop as a feedback term to compensate the influence of fault. By employing the Generalized Kalman--Yakubovich--Popov lemma, we derive the sufficient conditions of the existence of such an active fault tolerant control plant, and iterative algorithms are applied to obtain the solutions to the fault detection filter and controller parameter matrices. Finally, simulation results are proposed to demonstrate the effectiveness of the developed scheme. [ABSTRACT FROM AUTHOR]

Summary: This work deals with the problem of a model reference tracking based on the design of an active fault tolerant control for linear parameter‐varying systems affected by actuator faults and unknown inputs. Linear parameter‐varying systems are described by a polytopic representation with measurable gain scheduling functions. The main contribution is to design an active fault tolerant controller whose control law is described by an adaptive proportional integral structure. This one requires 3 types of online information, which are reference outputs, measured real outputs, and the fault estimation provided by a model reference, sensors, and an adaptive polytopic observer, respectively. These types of information are used to reconfigure the designed controller, which is able to compensate the fault effects and to make the closed‐loop system able to track reference outputs in spite of the presence of actuator faults and disturbances. The controller and the observer gains are obtained by solving a set of linear matrices inequalities. Performances of the proposed method are compared to another previous method to underline the relevant results. [ABSTRACT FROM AUTHOR]

This paper focuses on speed and current sensor Faults Detection and Isolation (FDI) in an Induction Motor (IM) drive. The effect of sensors faults on the IM vector control is presented, then, new detection and isolation approaches are suggested. Speed sensor faults are detected when an error between only two points from speed data exceeds a certain threshold. An algorithm based on RMS currents is developed to detect and isolate any faulty current sensor. This requires three current sensors, each per phase. Besides, open circuit faults of inverter power switches are taken into account too. To ensure continuous functionality of the drive, we conceived an Active Fault Tolerant Controller (AFTC) with smoother reconfiguration feature. Simulations in Matlab/Simulink are carried out to show the efficiency of the suggested schemes. [ABSTRACT FROM AUTHOR]

This study investigates the active fault tolerant control (FTC) problem for the attitude system of a rigid satellite, which is affected by parameter uncertainty, unknown exogenous disturbance and actuator time‐varying faults. The upper bounds of the actuator time‐varying fault and the generalised perturbation are unknown. A novel adaptive non‐linear fault estimation observer is designed in order to obtain the estimated value of unknown time‐varying faults. Then, an active fault tolerant attitude control approach is proposed under the framework of both backstepping control and adaptive control theory. Consequently, the Lyapunov theory is used to prove the robust asymptotic stability for the closed‐loop attitude system of a faulty satellite under the proposed FTC scheme. Finally, simulation results on an in‐orbit rigid satellite are provided to show the good fault tolerant performance, which validate the effectiveness and feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

Reference Governor is an important component of Active Fault Tolerant Control. One of the main reasons for using Reference Governor is to adjust/modify the reference trajectories to maintain the stability of the post-fault system, especially when a series of actuator faults occur and the faulty system can not retain the pre-fault performance. Fault estimation error and delay are important properties of Fault Detection and Diagnosis and have destructive effects on the performance of the Active Fault Tolerant Control. It is shown that, if the fault estimation provided by the Fault Detection and Diagnosis (initial “fault estimation”) is assumed to be precise (an ideal assumption), the controller may not show an acceptable performance. Then, it is shown that, if the worst “fault estimation” is considered, it will be possible to reduce the effects of fault estimation error and delay and to preserve the performance of the controller. To reduce the effects of this conservative assumption (worst “fault estimation”), a quadratic cost function is defined and optimized. One of the advantages of this method is that it gives the designer an option to select a less sophisticated Fault Detection and Diagnosis for the mission. The angular velocity stabilization of a spacecraft subjected to multiple actuator faults is considered as a case study.

Reference Governor is an important component of Active Fault Tolerant Control. One of the main reasons for using Reference Governor is to adjust/modify the reference trajectories to maintain the stability of the post-fault system, especially when a series of actuator faults occur and the faulty system can not retain the pre-fault performance. Fault estimation error and delay are important properties of Fault Detection and Diagnosis and have destructive effects on the performance of the Active Fault Tolerant Control. It is shown that, if the fault estimation provided by the Fault Detection and Diagnosis (initial "fault estimation") is assumed to be precise (an ideal assumption), the controller may not show an acceptable performance. Then, it is shown that, if the worst "fault estimation" is considered, it will be possible to reduce the effects of fault estimation error and delay and to preserve the performance of the controller. To reduce the effects of this conservative assumption (worst "fault estimation"), a quadratic cost function is defined and optimized. One of the advantages of this method is that it gives the designer an option to select a less sophisticated Fault Detection and Diagnosis for the mission. The angular velocity stabilization of a spacecraft subjected to multiple actuator faults is considered as a case study. [ABSTRACT FROM AUTHOR]

Reducing the burden of the remaining actuators through decreasing the performance gracefully is an important field in active fault tolerant control. According to the literature, two important points have been identified in the works considering graceful performance degradation: 1) using single-objective optimization, 2) assuming an engineering insight into the performance of the faulty system. This paper has two contributions: First, it is shown that in some cases, single-objective optimization may not be able to provide a satisfactory solution for the problem. Second, a new systematic and general method is proposed to remove the need for the engineering insight. The proposed method is based on multi-objective optimization. Attitude tracking of a faulty spacecraft is considered as a case study. Simulation results show the advantages of the proposed methodology. [ABSTRACT FROM AUTHOR]

This paper studies the problem of fault estimation (FE) and the active fault tolerant control (FTC) for Takagi–Sugeno (T-S) fuzzy systems with interval time-varying delay and norm-bounded external disturbance. Based on the fast adaptive fault estimation (FAFE) algorithm, our attention focuses on designing an adaptive observer-based controller to guarantee the filtering error system to be asymptotically stable and satisfy theH∞performance index. By constructing a new Lyapunov–Krasovskii functional including the information of the lower and upper delay bounds, the sufficient delay-dependent conditions have been established to guarantee the existence of adaptive observer-based controller in terms of linear matrix inequalities (LMIs). Compared with the constant delay and time-varying delay, the interval time-varying delay is the less conservative form. Furthermore, we make full use of the information of the delay and no terms are ignored when the stability of the system is analysed. In addition, the results for the systems with time-varying structured uncertainties are established. The results of the active FTC are showed in terms of LMIs. Finally, two examples are given to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a novel active fault tolerance framework for uncertain high-order fully-actuated systems (HOFASs). Starting from the uncertain faulty HOFAS model with nonlinear measurement, the advantages of this description are revealed via Lie Derivatives. A HOFAS adaptive observer and controller integration is established and further a closed-loop HOFAS dynamic data modeling structure is derived. This structure uncovers the dynamic characteristics including fault features, and naturally yields a fault detectability condition. Based on the fault information from the dynamic data model, an active fault tolerant control strategy for HOFASs is proposed, which enriches HOFAS control theory. The uniformly bounded stability of the HOFAS model is proved theoretically and illustrated experimentally. [ABSTRACT FROM AUTHOR]

In this paper, an active fault tolerant control (FTC) approach based on transient performance index is proposed for the attitude control systems of unmanned aerial vehicle (UAV) with actuator fault. The nonlinear attitude control system model for UAV with actuator faults is given, which represents the dynamic characteristics of UAV. A fault diagnosis component is used for fault detection and estimation. According to the fault estimation information obtained during the fault diagnosis, the fault tolerant control scheme is developed by adopting the adaptive dynamic surface control technique, which guarantees the asymptotic output tracking and ultimate uniform boundedness of the closed-loop attitude control systems of UAV in actuator faulty case. Further, a prescribed transient performance of the FTC attitude control systems is considered which characterizes the convergence rate and maximum overshoot of the attitude tracking error. Finally, simulation results are shown that the attitude control system states remain bounded and the output tracking errors converge to a neighborhood of zero. [ABSTRACT FROM AUTHOR]

Starting with the baseline controller design, this paper proposes an integrated approach of active fault tolerant control based on proportional derivative extended state observer (PDESO) for linear parameter varying descriptor systems. The PDESO can simultaneously provide the estimates of the system states, sensor faults, and actuator faults. The L2 robust performance of the closed-loop system to bounded exogenous disturbance and bounded uncertainty is achieved by a two-step design procedure adapted from the traditional observer-based controller design. Furthermore, an LMI pole-placement region and the L2 robustness performance are combined into a multiobjective formulation by suitably combing the appropriate LMI descriptions. A parameter-varying system example is given to illustrate the design procedure and the validity of the proposed integrated design approach. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The paper proposes an observer based active fault tolerant control (AFTC) approach to a non-linear large rotor wind turbine benchmark model. A sensor fault hiding and actuator fault compensation strategy is adopted in the design. The adapted observer based AFTC system retains the well-accepted industrial controller as the baseline controller, while an extended state observer (ESO) is designed to provide estimates of system states and fault signals within a linear parameter varying (LPV) descriptor system context using linear matrix inequality (LMI). In the design, pole-placement is used as a time-domain performance specification while H ∞ optimization is used to improve the closed-loop system robustness to exogenous disturbances or modelling uncertainty. Simulation results show that the proposed scheme can easily be viewed as an extension of currently used control technology, with the AFTC proving clear “added value” as a fault tolerant system, to enhance the sustainability of the wind turbine in the offshore environment. [ABSTRACT FROM AUTHOR]

This paper deals with the design of an Active Fault Tolerant Control (AFTC) approach for polytopic uncertain Linear Parameter-Varying (LPV) systems subject to uncertainties and actuator faults. First, a fault estimation method is developed by integrating robust observer design with zonotopic techniques. The proposed observer is developed using L ∞ norm to attenuate the effects of the uncertainties and to improve the accuracy of the estimation. Then, an AFTC strategy is used to compensate actuator fault effect and maintain system stability. Finally, the effectiveness of the proposed method is demonstrated by a case study on a 4.8MW wind turbine benchmark system. [ABSTRACT FROM AUTHOR]

This work shows how to use a differential geometry tool to design a novel nonlinear active fault tolerant flight control system for aircraft. The proposed control scheme consists of two main subsystems: a controller, which is designed for the nominal plant, and a fault detection and diagnosis module, which provides fault estimation. A further feedback loop exploits the fault estimation to accommodate faults affecting the system. The estimate convergence and the stability of the active fault tolerant flight controller are theoretically proved. Finally, high fidelity simulations show the effectiveness of the scheme. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents new results regarding the development of a supervision scheme for a nonlinear satellite model. The main issue concerns the handling of frequency faults affecting the reaction wheels of a spacecraft attitude control system, that is, how to detect and isolate faults, how to determine the different frequencies characterising these faults through spectral analysis and lastly, how to prevent propagation into failures with potential mission abortion as a consequence. Thus, this work investigates the design of a scheme for fault detection, isolation and control reconfiguration applied to the reaction wheels of a spacecraft attitude control, based on the satellite model. This scheme is classifiable as active fault tolerant control. As the study focuses on a general satellite nonlinear model, where aerodynamic and gravitational disturbances, as well as measurement errors, are present, the robustness of the suggested strategy is achieved by exploiting an explicit disturbance decoupling method via a nonlinear geometric approach. To achieve accurate fault diagnosis, aerodynamic disturbance decoupling represents the key point because the aerodynamic model is often uncertain. Moreover, an improvement of the nonlinear geometric approach is presented, to realise both aerodynamic and manoeuvre decoupled fault diagnosis. To the best authors' knowledge, this is the first works presenting a methodology for frequency fault diagnosis, which is based on the nonlinear geometric approach for fault and disturbance decoupling. The obtained results demonstrate that the proposed methodology can achieve better performances with respect to traditional fault detection and isolation schemes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to active sensor fault tolerant tracking control (FTTC) for offshore wind turbine (OWT) described via Takagi–Sugeno (T–S) multiple models. The FTTC strategy is designed in such way that aims to maintain nominal wind turbine controller without any change in both fault and fault-free cases. This is achieved by inserting T–S proportional state estimators augmented with proportional and integral feedback (PPI) fault estimators to be capable to estimate different generators and rotor speed sensors fault for compensation purposes. Due to the dependency of the FTTC strategy on the fault estimation the designed observer has the capability to estimate a wide range of time varying fault signals. Moreover, the robustness of the observer against the difference between the anemometer wind speed measurement and the immeasurable effective wind speed signal has been taken into account. The corrected measurements fed to a T–S fuzzy dynamic output feedback controller (TSDOFC) designed to track the desired trajectory. The stability proof with H ∞ performance and D-stability constraints is formulated as a Linear Matrix Inequality (LMI) problem. The strategy is illustrated using a non-linear benchmark system model of a wind turbine offered within a competition led by the companies Mathworks and KK-Electronic. [ABSTRACT FROM AUTHOR]

This paper is concerned with the active fault tolerant control problem for reconfigurable manipulator actuator based on local joint information. It is considered that the entire reconfigurable manipulator system consists of a couple of independent joint modules as subsystems, which are controlled using unified radial basis function neural network adaptive algorithm using local joint information when actuators are fault free. For the subsystem in actuator fault situation, fault detection is achieved through comparing the user defined threshold to the residual between actual velocity value and nonlinear velocity observation value. The unknown input state observer is exploited for fault identification. Based on the information aforementioned, a compensation term is added to the proposed control algorithm for switching to realize active fault tolerant control when subsystem in fault. The advantages of the presented scheme are that unlike the complex control structure in centralized control, this scheme possesses simple control structure, as well as could isolate and tolerant the fault in subsystem. Furthermore, it can be easily applied to different configurations without any parameters modification. It means that the local fault could not affect the joint in normal situation. In order to demonstrate the effectiveness of the proposed method, two different 2-DOF reconfigurable manipulators are employed for simulation. [ABSTRACT FROM AUTHOR]

This paper proposes an active Fault Tolerant Control (FTC) scheme for polytopic uncertain Linear Parameter-Varying (LPV) systems subject to uncertainties and actuator faults. First, a fault estimation interval observer is designed to estimate the system state and the actuator fault. A novel approach is developed using the L ∞ norm to attenuate the effects of the uncertainties and to improve the accuracy of the proposed observer. Then, based on the fault estimation information, the FTC strategy is designed using a linear state feedback control law and H ∞ technique to compensate actuator faults and maintain system performance and stability, even under faulty conditions. Finally, the effectiveness of the proposed method is demonstrated by its application to a vehicle lateral dynamic nonlinear model. • Fault Tolerant Control using interval state estimation and robust stabilization. • Set-membership framework for the design of Linear Parameter Varying systems. • Fault estimation observer design for descriptor system. • L ∞ norm-based design method to attenuate the effect of fault and uncertainties and to improve the estimation performance. [ABSTRACT FROM AUTHOR]

The goal of this paper is to describe a novel fault tolerant tracking control (FTTC) strategy based on robust fault estimation and compensation of simultaneous actuator and sensor faults. Within the framework of fault tolerant control (FTC) the challenge is to develop an FTTC design strategy for nonlinear systems to tolerate simultaneous actuator and sensor faults that have bounded first time derivatives. The main contribution of this paper is the proposal of a new architecture based on a combination of actuator and sensor Takagi-Sugeno (T-S) proportional state estimators augmented with proportional and integral feedback (PPI) fault estimators together with a T-S dynamic output feedback control (TSDOFC) capable of time-varying reference tracking. Within this architecture the design freedom for each of the T-S estimators and the control system are available separately with an important consequence on robust L2 norm fault estimation and robust L2 norm closed-loop tracking performance. The FTTC strategy is illustrated using a nonlinear inverted pendulum example with time-varying tracking of a moving linear position reference. [ABSTRACT FROM AUTHOR]

This article deals with the problem of active fault tolerant control (AFTC) for a class of linear time-delay systems in a finite frequency domain. A new ℋ∞ controller in generalised internal model control architecture with an observer-based fault estimator is proposed for the AFTC system. Based on online fault estimation and accommodation, the closed-loop system stability and ℋ∞ performance for both fault free and faulty cases are guaranteed. With the aid of the generalised Kalman–Yakubovich–Popov lemma for time-delay systems, sufficient conditions on the existence of such an AFTC system ensuring simultaneous finite frequency estimation and control performance are derived. The calculation procedure of the parameter matrices of the fault estimator and ℋ∞ controller is also proposed. Finally, a numerical example is given to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]