No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Active fault tolerant control for a class of linear time-delay systems in finite frequency domain
Abstract
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.
... In the last few decades, it has played a vital role in improving control and research techniques [6][7][8]. It is divided into two major types i.e. active and passive FTC [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The passive FTC uses control algorithm to make the system more robust in case of potential failures. ...
... The time-delay commonly occurs in PEMFCSs due to some communication delays. As the active FTC works on fault estimator model, time-delays and inaccurate fault estimation adversely affects system efficiency [14][15][16][17][18][19][20][21][22]. Speed and accuracy are good performance indicators and play significant role in adaptive observer design. ...
This work develops fault tolerant control (FTC)
design based on robust adaptive fault estimation observer
(RAFEO) for proton exchange membrane fuel cell systems
(PEMFCSs) with time-delays. The robust adaptive fault
estimation algorithm (RAFEA) is used for improving speed
and accuracy of fault estimation. It is proposed using linear
matrix inequality (LMI) technique for increasing system
efficiency. It ensures stability and enhances faulty system
efficiency. An actuator stuck fault is considered in which
faulty input signals are constantly blocked. Time-delay is
considered in deriving both RAFEO and FTC algorithm
which is not incorporated in previous works on PEMFCSs.
Simulation results show efficacies of proposed design
methods in application to cathode pressure model of the
system.
... Therefore, in this paper the nominal controller u 1 (k) is selected as u 1 (k) = K 1x (k), wherex(k) denotes the estimate of the state x(k). On the other hand, in order to have an ideal AFTC system, [16]. However, in practical systems, it is usually impossible to obtain the fault information exactly. ...
... However, based on (10) it is obvious that the design of the observer parameters L and F , and the controller parameter K 1 are independent from each other. Consequently, in most of the existing timetriggered AFTC design methodologies [7], [16], [18]- [20], the AFTC module is implemented in two steps; first, the fault/state estimator is designed and second, the active fault-tolerant controller is designed. Indeed, both estimator and controller modules are designed separately and then their performances are considered together, which is convenient to calculate the design parameters. ...
The problem of event-triggered active fault-tolerant control (E-AFTC) of discrete-time linear systems is addressed in this paper by using an integrated design of event-triggered fault/state estimator with a fault-tolerant controller. An event-triggered observer is proposed which can simultaneously provide an estimate of the system states and faults. Through an event-triggered transmission mechanism it is shown that the amount of data sent to the observer module is significantly reduced. Moreover, an observer-based fault-tolerant controller based on fault and state estimates is obtained. A robust H ∞ formulation of the problem is given that guarantees stability of the resulting closed-loop system, attenuates the effects of external disturbances and compensates the effects of the fault. Linear matrix inequality (LMI) sufficient conditions are derived to simultaneously obtain the observer and controller parameters and the event-triggered condition. Simulation results for an autonomous remotely operated vehicle (ROV) is given to illustrate the effectiveness of the proposed design methodology.
... Over the past three decades, the engineering significance of FTC has been well recognized, and a number of practical systems have adopted the faulttolerant strategy, which creates ample scope for research interests regarding FTC in the system control community (Blanke et al. (2006), Zhang and Jiang (2008), Mahmoud et al. (2003), Yang et al. (2010 and reference therein). Usually, FTC research can be divided into two categories: active fault-tolerant control (AFTC) ( Dong et al. (2012), Kargar et al. (2014), Witczak et al. (2013), Yao et al. (2012), Hu and Xiao (2013) and passive fault-tolerant control (PFTC) (Wang et al. (2006), Wang et al. (2007, Tian et al. (2010), Gao et al. (2011), Liu et al. (2011), Tabatabaeipour et al. (2012). Faults appear within a system in various forms. ...
... Over the past three decades, the engineering significance of FTC has been well recognized, and a number of practical systems have adopted the faulttolerant strategy, which creates ample scope for research interests regarding FTC in the system control community (Blanke et al. (2006), Zhang and Jiang (2008), Mahmoud et al. (2003), Yang et al. (2010and reference therein). Usually, FTC research can be divided into two categories: active fault-tolerant control (AFTC) ( Dong et al. (2012), Kargar et al. (2014), Witczak et al. (2013), Yao et al. (2012, Hu and Xiao (2013)) and passive fault-tolerant control (PFTC) (Wang et al. (2006), Wang et al. (2007, Tian et al. (2010), Gao et al. (2011), Liu et al. (2011), Tabatabaeipour et al. (2012). Faults appear within a system in various forms. ...
This paper focuses on the passive fault-tolerant control problem for a class of uncertain nonlinear discrete-time systems subject to multiple intermittent faults. The multiple intermittent faults considered occur on the actual measurement signals in the form of additive faults. To achieve the aim of fault-tolerant control, a dynamic output-feedback controller is designed such that, in the simultaneous presence of parameter uncertainty, a given type of nonlinearity, and multiple additive intermittent sensor faults, the closed-loop system remains stable and guarantees acceptable performance. The linear matrix inequality technique is used to obtain sufficient conditions to derive the controller and ensure that the prescribed H∞ index is satisfied. Finally, the effectiveness of the proposed method is demonstrated though a numerical simulation example.
... Many controllers based on observer have been proposed to control systems with unmeasurable states. Dong et al. [17] proposed an approach based on H-infinity in a generalized internal model control design with an adaptive observer-based fault estimator for active faulttolerant control. The proposed approach uses online fault estimations to guarantee Hinfinity performance and closed-loop system stability. ...
In this paper, a robust fault-tolerant model predictive control (RFTPC) approach is proposed for discrete-time linear systems subject to sensor and actuator faults, disturbances, and input constraints. In this approach, a virtual observer is first considered to improve the observation accuracy as well as reduce fault effects on the system. Then, a real observer is established based on the proposed virtual observer, since the performance of virtual observers is limited due to the presence of unmeasurable information in the system. Based on the estimated information obtained by the observers, a robust fault-tolerant model predictive control is synthesized and used to control discrete-time systems subject to sensor and actuator faults, disturbances, and input constraints. Additionally, an optimized cost function is employed in the RFTPC design to guarantee robust stability as well as the rejection of bounded disturbances for the discrete-time system with sensor and actuator faults. Furthermore, a linear matrix inequality (LMI) approach is used to propose sufficient stability conditions that ensure and guarantee the robust stability of the whole closed-loop system composed of the states and the estimation error of the system dynamics. As a result, the entire control problem is formulated as an LMI problem, and the gains of both observer and robust fault-tolerant model predictive controller are obtained by solving the linear matrix inequalities (LMIs). Finally, the efficiency of the proposed RFTPC controller is tested by simulating a numerical example where the simulation results demonstrate the applicability of the proposed method in dealing with linear systems subject to faults in both actuators and sensors.
... Some other SOF methods can be found in [44,45] and references therein. For the observer-controller approach of linear systems in finite frequency, "two-step" methods for solving the stability conditions of active fault tolerant control are proposed in [46,47]. For discrete-time T-S fuzzy systems, the problem of observer-based H ∞ control in finite frequency domain is investigated in [48]. ...
For the output feedback control problem of continuous‐time T–S fuzzy systems with unknown premise variables, an H∞ observer–controller design method in the low‐frequency domain is proposed. First, an observer–controller structure is given, the unknown premise variables are limited by Lipschitz conditions. Then, the system stability conditions are obtained by the negativeness of eigenvalues' real parts. To achieve better control performance of the system in low frequency, the H∞ index for attenuating the unknown low‐frequency disturbance is guaranteed by generalised Kalman–Yakubovich–Popov lemma. Then, the stability and robustness conditions are converted into linear matrix inequality forms, which can be solved directly by a convex optimisation technique. Finally, several simulation examples carried out to show the effectiveness of the proposed method.
... Fault-tolerant control (FTC) schemes for systems subject to faults have received considerable attention owing to the growing requirement for stable and reliable systems (Gao, Ding, & Cecati, 2015;Jiang, Yang, & Shi, 2010;Stoustrup & Blondel, 2004;Wang, Shi, Zhou, & Gao, 2006;Wang, Zhou, & Gao, 2007). The two types of commonly used FTC techniques are active FTC (AFTC) (Dong, Zhong, & Ding, 2012) and passive FTC (PFTC) (Tao, Shen, Fang, & Wang, 2016). In AFTC techniques, the controller is reconfigured on the basis of information from fault detection and diagnosis (He, Wang, Ji, & Zhou, 2010;Zhong, Ding, & Shi, 2009), whereas PFTC techniques depend on a-priori fault information. ...
This study proposes a fault-tolerant control method for stochastic systems with multiple intermittent faults (IFs) and nonlinear disturbances, and both sensor and actuator faults are considered. The occurrence and disappearance of IFs are governed by Markov chain, and its transition probabilities are partly known. Hence, the faulty system can be described by a Markovian jump system (MJS). In order to ensure that the MJS is stochastically stable and satisfies H∞ performance index, mode-dependent output feedback controllers are modelled using linear matrix inequalities. Numerous sufficient conditions for stochastic stability are obtained on the basis of Lyapunov stability theory. Finally, the effectiveness of the developed method is evaluated on the three-tank system.
... FTC has been well recognized, and a number of practical systems have adopted the fault-tolerant strategy, thus creates ample scope for FTC studies within the system control community [1][2][3][4]. Usually, all reported FTC studies can be divided into two categories: active FTC (AFTC) [5][6][7][8][9][10][11] and passive FTC (PFTC) [12][13][14][15][16][17][18]. To achieve the purpose of AFTC, fault detection and diagnosis, which itself also draws considerable concern in control community [19,20], is necessary to provide real-time fault information to reconfigure the controller. ...
This study focuses on passive fault-tolerant control for a class of uncertain nonlinear discrete-time systems subject to multiple intermittent faults. The considered intermittent faults are assumed to be additive ones in sensors and/or actuators. To achieve fault-tolerant control, a dynamic output-feedback controller is designed such that the closed-loop system remains stable and satisfies acceptable performance, even when there are parameter uncertainties, nonlinearities of specific type, and multiple additive intermittent sensor and/or actuator faults. The linear matrix inequality method is employed to obtain sufficient conditions for achieving fault tolerance and ensuring the prescribed H∞ performance index. Finally, the effectiveness of the proposed method is demonstrated by simulation examples. © 2015 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
... Fault-tolerant control (FTC) is viewed as one of the most effective methods to increase system safety and reliability and has become an attractive topic, which has received considerable attention in the field of the industrial control and engineering research during the last couple of decades [1][2][3]. Depending on how redundancies are being utilized, current FTC can be classified into two categories, namely, passive FTC [4][5][6][7][8] and active FTC [9][10][11][12][13][14][15][16][17]. Passive FTC uses control laws to make the system robust with respect to possible faults, which are considered as a special kind of uncertainties. ...
This study focuses on the design of the robust fault-tolerant control (FTC) system based on adaptive observer for uncertain linear time invariant (LTI) systems. In order to improve robustness, rapidity, and accuracy of traditional fault estimation algorithm, an adaptive fault estimation algorithm (AFEA) using an augmented observer is presented. By utilizing a new fault estimator model, an improved AFEA based on linear matrix inequality (LMI) technique is proposed to increase the performance. Furthermore, an observer-based state feedback fault-tolerant control strategy is designed, which guarantees the stability and performance of the faulty system. Moreover, the adaptive observer and the fault-tolerant controller are designed separately, whose performance can be considered, respectively. Finally, simulation results of an aircraft application are presented to illustrate the effectiveness of the proposed design methods.
... Over the past three decades, to satisfy the growing demands on safety and reliability, the fault-tolerant control system has attracted considerable attention (Zhang & Jiang, 2008), especially in aircraft systems, industrial processes, and other safety-critical systems (Chilin, Liu, Davis, & Christofides, 2012;Gao, Jiang, Qi, & Xu, 2011;Hua, Ding, & Guan, 2012;Hu & Xiao, 2013). From the viewpoint of the control design, the fault-tolerant control design can be classified either as an active method (Dong, Zhong, & Ding, 2012;Guenab, Weber, Theilliol, & Zhang, 2011;Yao, Qin, Wang, & Jiang, 2012) or as a passive one (Tabatabaeipour, Izadi-Zamanabadi, Bak, & Ravn, 2012;Tian, Yue, & Peng, 2010;Wang & Ju, 2013). To achieve the purpose of active fault-tolerant control, fault detection and diagnosis, which itself also draws considerable attention in the control community (He, Wang, Liu, & Zhou, 2013;Hwang, Kim, Kim, & Seah, 2010), is necessary to provide real-time fault information to reconfigure the controller. ...
A passive fault-tolerant control strategy is proposed for systems subject to a novel kind of intermittent fault, which is described by a Bernoulli distributed random variable. Three cases of fault location are considered, namely, sensor fault, actuator fault, and both sensor and actuator faults. The dynamic feedback controllers are designed not only to stabilise the fault-free system, but also to guarantee an acceptable performance of the faulty system. The robust H∞ performance index is used to evaluate the effectiveness of the proposed control scheme. In terms of linear matrix inequality, the sufficient conditions of the existence of controllers are given. An illustrative example indicates the effectiveness of the proposed fault-tolerant control method.
... This approach needs neither fault detection and identification schemes nor controller reconfiguration, but it has limited fault-tolerant capabilities. On the other hand, AFTC systems (also referred to as self-repairing, reconfigurable or self-designing) react to the system component failures actively so that the stability and acceptable performance of the entire system can be maintained (Blanke et al., 2006;Noura et al., 2009;Dong et al., 2010). Various theoretical approaches have been proposed in the literature to accommodate faults based on linear quadratic, adaptive control, eigenstructure assignment or linear matrix inequality. ...
The objective of fault-tolerant control (FTC) is to minimise the effect of faults on system performance (stability, trajectory tracking, etc.). However, the majority of the existing FTC methods continue to force the system to follow the pre-fault trajectories without considering the reduction in available control resources caused by actuator faults. Forcing the system to follow the same trajectories as before fault occurrence may result in actuator saturation and system's instability. Thus, pre-fault objectives should be redefined in function of the remaining resources to avoid potential saturation. The main contribution of this paper is a flatness-based trajectory planning/re-planning method that can be combined with any active FTC approach. The work considers the case of over-actuated systems where a new idea is proposed to evaluate the severity of faults occurred. In addition, the trajectory planning/re-planning approach is formulated as an optimisation problem based on the analysis of attainable efforts domain in fault-free and fault cases. The proposed approach is applied to two satellite systems in rendezvous mission.
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.
This chapter presents an application of Hi/H∞-optimal FD scheme to LDTV systems with delayed state, focusing on the designing of an evaluation function. The core idea is to directly construct an evaluation function by using a weighted l2-norm of the measurement output, which, simultaneously, achieves an optimal trade-off between the fault sensitivity and the robustness to l2-norm bounded unknown input.
This work describes an integrated fault estimation (FE) and fault tolerant control (FTC) strategy for a class of uncertain Lipschitz systems subject to time-delays in finite frequency domain. First, an FE filter is constructed by modeling the actuator faults and sensor faults as parameter changes. Second, an integral-type sliding mode FTC law based on the FE filter is developed, such that all states of the closed-loop system converge to the origin. By using the reconstructed Lipschitz property, the filter error system and the controlled system are rewritten as an augmented linear parameter varying (LPV) system. In addition, sufficient conditions for the augmented LPV system to have one full frequency and two finite frequency H∞ index bounds are converted to linear matrix inequalities. Finally, two examples are delivered to demonstrate the validity and benefits of the proposed method.
This paper deals with the problem of the optimal fault detection (FD) for linear discrete time-varying (LDTV) systems with delayed state and l
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
-norm bounded unknown input. The novelty lies in the designing of an evaluation function for the robust FD. The basic idea is to directly construct an evaluation function by using a weighted l
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
-norm of the measurement output, which achieves an optimal trade-off between the sensitivity to fault and the robustness to l
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
-norm bounded unknown input. To avoid complex computation, a feasible solution is obtained via the recursive computation by applying the orthogonal projection. It is shown that such an evaluation function provides a unified scheme for both the cases of unknown input being l
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
-norm bounded and jointly normal distribution, while a threshold may be chosen based on a priori knowledge of unknown input. A numerical example is given to demonstrate the effectiveness of the proposed method.
This paper studies a robust constrained model predictive fault-tolerant control (RCMPFTC) problem for a class of industrial processes with uncertainties, interval time-varying delay, unknown disturbances and partial actuator failures, in which the main idea is in the relevant theory of RCMPFTC based on a novel extended state space model description of these industrial processes. This extended model includes the state variables and output tracking error variable of process, which actually regulates the dynamic response of the process state and output tracking error separately. Based on this model, the proposed control law is designed, which not only guarantees the convergence and tracking performance of system but also offers more degrees of freedom for designed controller. To ensure robust stability and reject any unknown bounded disturbances for the uncertain system with admissible failures, the optimized cost function and H ∞ performance index are thus introduced in the RCMPFTC controller design. By using a differential inequality to construct a differential Lyapunov-Krasovskii function candidate without introducing some redundant free-weighting matrices, the novel, less conservative and more simplified delay-range-dependent stable conditions of the RCMPFTC design are further presented in terms of linear matrix inequality (LMI) constraints. By solving these LMIs, the RCMPFTC law is explicitly formulated, possessing the optimized cost and H ∞ performance. Furthermore, the stable condition can also be easily extended from delay-range-dependent to common delay- dependent stability. The comparison results on the liquid level of tank system and multi-input and multi-output glasshouse process show that the proposed control method is effective and feasible for the cases of the constant and random-varying actuator faults.
In this paper, we will investigate the problem of finite frequency memory fixed-order output feedback controller design for Takagi-Sugeno (T-S) fuzzy affine systems. It is assumed that the disturbances reside in a finite frequency range, i.e., the low, middle, or high frequency range. The objective is to design a memory piecewise affine (PWA) controller by using past output measurements to guarantee the asymptotic stability of the resulting closed-loop system with a prescribed finite frequency ℋ
<sub xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub>
performance. Via the system state-input augmentation, a novel descriptor system approach is proposed to facilitate the controller design. All the design conditions are formulated in the form of linear matrix inequalities. It is also proven that the ℋ
<sub xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub>
performance can be improved with the memory control strategy. Finally, simulation studies are presented to show the effectiveness of the proposed design method.
In this paper, the problem of adaptive fault-tolerant tracking control for a class of uncertain nonlinear systems in the presence of input quantisation and unknown control direction is considered. By choosing a class of particular Nussbaum functions, an adaptive fault-tolerant control scheme is designed to compensate actuator faults and input quantisation while the control direction is unknown. Compared with the existing results, the proposed controller can directly compensate for the nonlinear term caused by actuator faults and the nonlinear decomposition on the quantiser without estimating its bound. Furthermore, via Barhalant's Lemma, it is proven that all the signals of the closed-loop system are globally uniformly bounded and the tracking error converges into a prescribed accuracy in prior. Finally, an illustrative example is used for verifying effectiveness of the proposed approach.
This paper addresses an issue on reduced-order observer-based robust fault estimation and fault-tolerant control for a class of uncertain nonlinear discrete-time systems. By introducing a nonsingular coordinate transformation, a new nonlinear reduced-order fault estimation observer (RFEO) is proposed with a wide application range in order to achieve an accurate estimation of both states and faults. Next, an improved algorithm is given to obtain the optimal estimation by using a novel iterative linear matrix inequality technique. Furthermore, an RFEO-based output feedback fault-tolerant controller, which is independent of the RFEO, can maintain the stability and performance of the faulty system. Simulation results of an aircraft application show the effectiveness of the proposed method. Copyright
A new fault-tolerant control scheme is proposed for a nonlinear collaborative system that contains two robot subsystems. When fault occurs in one subsystem, the fault-free subsystem is used to compensate the fault influence of the faulty one on the whole collaborative system. When the faulty subsystem could not repair itself or the repair process needs a long time, the controller of the fault-free subsystem is reconfigured using the fault diagnosis information and other measured information, leading to the fault tolerant control of the robot collaborative system. Simulations of fault tolerant control for the robot collaborative system show the effectiveness of the proposed method.
A new fault tolerant control method is proposed for a sequential continuous system which includes two subsystems. The fault of either of the two subsystems can be diagnosed using the adaptive observer method. The controller reconfiguration can be carried out by the other faultless subsystem using the fault estimation information and other measured information, leading to the fault tolerant control of the sequential continuous system. If the fault in the subsystem can not be repaired or there is long time delay when the fault is compensated, traditional fault tolerant control methods of the complex systems can not be used. Fault tolerant control scope is extended by the proposed method. Computer simulation results illustrate the validity of the method.
For the chattering problem in the traditional sliding mode observer-based fault estimation, a second order sliding mode observer based on the Super-twisting algorithm was proposed. In order to avoid the cumbersome process of proving the stability of the Super-twisting algorithm, a Lyapunov function was adopted. An active fault tolerant control law was designed based on the fault estimation. Finally, simulation show the effectiveness of the proposed approach.
This paper investigates the problem of fault detection for linear discrete time-varying systems with delayed state by using Hi/H∞ and/or Hi/H∞ optimization. A residual generator, which is the so-called Hi/H∞ fault detection filter (FDF), is designed by finding filter gain matrices and a post-filter. By utilizing projection and innovation re-organization technique, an optimal Hi/H∞ -FDF can be given in terms of recursions. Moreover, the obtained evaluation function is a unified solution and, in order to detect the presence of a fault, the selection of a threshold is dependent on the characteristics of unknown input and a prescribed false alarm rate. A numerical example is used to demonstrate the effectiveness of the proposed method.
This paper is concerned with statistical χ2 testing based fault detection (FD) for a class of linear discrete time-varying (LDTV) stochastic systems with delayed state. Different from the traditional residual based FD, we propose to construct the evaluation function by directly using measurement observations. Then an equivalent solution can be given in terms of Riccati recursion by utilizing projection and innovation analysis technique. Moreover, the fault free case evaluation function is with central χ2 distribution and the heavy computational burden is reduced. Furthermore, strategies of χ2 statistic testing on evaluation function are also discussed. Finally, a numerical example is given to illustrate the proposed method.
This paper deals with the problem of observer-based fault estimation for a class of linear systems with multi time-delay. The key of this paper is the introduction of a generalized coordinate transform, such that in the new coordinates, all the time-delay terms are injected by the system's input and output. Based on the new obtained system expression, the design of fault estimator is formulated in the framework of Hoc, filtering by incorporating the prior knowledge of fault into the design procedure, and the dynamics of the estimation error is converted into a general linear time invariant form with generalized unknown input time-delay terms. Based on the bounded real lemma, the observer gain matrix is obtained in terms of linear matrix inequality. A numerical example is given to illustrate the effectiveness of the proposed approach.
This paper deals with the fault detection (FD) problem in the finite frequency domain for linear time-invariant discrete-time systems with bounded disturbances. A fault detection observer is designed by employing two performance indesxes which are used to increase the fault sensitivity in finite frequency domain and attenuate the effects of disturbances in full frequency domain. With the aid of the generalized Kalman–Yakubovich–Popov (GKYP) Lemma, the design methods are presented in terms of solutions to a set of linear matrix inequalities (LMIs). Numerical examples are given to illustrate the effectiveness of the proposed method.
In this paper, a method of fault estimation and fault tolerant control for networked control system (NCS) with transfer delay and process noise is presented. First, the networked control system is modeled as a multiple-input-multiple-output (MIMO) discrete-time system with transfer delays, process noise, and model uncertainties. Under this model and under some conditions, a fault estimation method is proposed to estimate the system faults. On the basis of the information on fault estimation and the sliding mode control theory, a fault tolerant controller is designed to recover the system performance. Finally, simulation results are used to verify the efficiency of the method.
A linear matrix inequality (LMI) based filter design approach for
fixed-order robust fault detection and isolation (FDI) is examined. The
proposed filter design provides necessary and sufficient conditions for
the existence of a solution to the detection and isolation of faults
using an H<sub>∞</sub> formulation. These conditions are expressed
in terms of LMIs with matrix rank constraints, and a parameterization of
all admissible filters is provided, which corresponds to a feasible
solution. A convex LMI problem is obtained for the full-order FDI filter
design. Finally, the proposed methods are demonstrated using a
structural system simulation example, which include faulty actuators,
sensors and external disturbances
For systems with both state and input time delays, a novel state and sensor fault observer is proposed in this paper to estimate system states and sensor faults simultaneously. In this design, a descriptor system approach and a linear matrix inequality technique are adopted, where the considered sensor fault may be in any form, even unbounded. Unbounded sensor faults will make the system fail unavoidably; it is indispensable to derive a reliable control scheme against sensor failures. Using the estimated state and sensor fault, a reliable observer-based controller is proposed, which makes the system work well no matter whether sensor faults occur or not. The present approaches are next extended to the case for systems with multiple time delays. Finally, a simulation example of the network of three cascaded reactors is used to illustrate the design procedure and demonstrate the efficiency of the present techniques.
In this brief, a methodology for detection and accommodation of actuator faults for a class of multi-input-multi-output (MIMO) stochastic systems is presented. First, a new real-time fault estimation module that estimates the actuator effectiveness is developed. The actuator fault diagnosis is based on the estimation of the state vector. Under some conditions, the stochastic system is transformed into two separate subsystems. One of them is not affected by actuator faults, so a reduced order Kalman filter can be used to estimate its states. The other, whose states are measurable, is affected by the faults. Then, the output of the nominal controller is reconfigured to compensate for the loss of actuator effectiveness in the system. Simulation results of a helicopter in vertical plane is presented to demonstrate the performance of the proposed fault-tolerant control scheme.
This note investigates process fault accommodation in a class of nonlinear continuous-time systems. A new fault estimation module, based on an adaptive estimator, is first proposed. The fault tolerant controller is constructed to compensate for the effect of the faults by stabilizing the closed-loop system. A flexible joint robotic example is given to illustrate the efficiency of the proposed approach
This paper deals with the problem of active fault tolerant control for a class of linear time-delay systems. A new H∞ controller in generalized internal model architecture and an adaptive observer-based fault estimator are proposed for the active fault tolerant control system. On the basis of online fault estimation and accommodation, the closed-loop system stability and H∞ performance for both fault free and faulty cases are guaranteed. Delay-dependent sufficient conditions on the existence of such an active fault tolerant control system and solutions to the controller and fault estimator parameter matrices are derived in terms of linear matrix inequalities. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method.
Based on a nonlinear state predictor (NSP) and a strong tracking filter (STF), a sensor fault tolerant generic model control (FTGMC) approach for a class of nonlinear time-delay processes is proposed. First, the NSP is introduced, and it is used to extend the conventional generic model control (GMC) to nonlinear processes with large input time-delay. Then the STF is adopted to estimate process states and sensor bias, the estimated sensor bias is used to drive a fault detection logic. When a sensor fault is detected, the estimated process states by the STF will be used to construct the process output to form a soft sensor, which is then used by the NSP (instead of the real outputs) to provide state predictors. These procedures constitute an active fault tolerant control scheme. Finally, simulation results of a three-tank-system demonstrate the effectiveness of the proposed approach.
This paper studies the robust fault detection problem using the standard H∞ filtering formulation. With this formulation, the minimization of the disturbance effect on the residual is formulated as a standard H∞ filtering problem and the design is solved using an algebraic Riccati equation. To facilitate the enhancement of the residual sensitivity to the fault, the difference between the residual and the fault (or filtered fault) is minimized against the disturbance and the fault. The residual generated in this way is a faithful replicate of the fault and the reliable detection can be achieved. The paper also incorporates the modelling error into the robust residual design using the standard H∞ filtering formulation.
This paper is concerned with the reliable design problem for linear systems. A more practical model of sensor and actuator failures than outage is considered. Procedures for designing reliable controllers are presented for the case of sensor failures and actuator failures that can be modeled by a scaling factor and a disturbance. The resulting control systems are reliable in that they provide guaranteed asymptotic stability and H∞ performance when all control components (sensors and actuators) are operational as well as when some control components experience failures. A numerical example is also given to illustrate the design procedures and their effectiveness.
Chemical process plant safety, production specifications, environmental regulations, operational constraints, and plant economics are some of the main reasons driving an upward interest in research and development of more robust methods for process monitoring and control. Principal component analysis (PCA) has long been used in fault detection by extracting relevant information from multivariate chemical data. The recent success of wavelets and multi-scale methods in chemical process monitoring and control has catalyzed an interest in the investigation of wavelets based methods for fault detection. In the present work, multi-scale principal component analysis (MSPCA) is used for fault detection and diagnosis. MSPCA simultaneously extracts both, cross correlation across the sensors (PCA approach) and auto-correlation within a sensor (wavelet approach). Using wavelets, the individual sensor signals are decomposed into approximations and details at different scales. Contributions from each scale are collected in separate matrices, and a PCA model is then constructed to extract correlation at each scale. The multi-scale nature of MSPCA formulation makes it suitable to work with process data that are typically non-stationary and represent the cumulative effect of many underlying process phenomena, each operating at a different scale. The proposed MSPCA approach is able to outperform the conventional PCA based approach in detecting and identifying real process faults in an industrial process, and yields minimum false alarms. Additionally, the advantage of MSPCA, over the traditional PCA approach for sensor validation, is also demonstrated on an industrial boiler data set.
This article considers the problem of control synthesis via state feedback for linear time-delay systems with design specifications in finite frequency ranges. First, a finite frequency performance analysis condition for time-delay systems is presented. Then, a resulting state feedback control synthesis condition is given in terms of solutions to a set of linear matrix inequalities (LMIs). Finally, the design procedure and the effectiveness of the proposed method are illustrated via a numerical design example.
In this paper, a new formulation of fault detection and estimation algorithm has been presented for a class of known nonlinear dynamic systems with a linear output structure. Under certain assumptions on the nonlinear dynamics of the system and its model uncertainty, an adaptive observer-based approach is established so as to construct several effective residual signals that can be used to perform the required fault detection and estimation. A parameter dependent Lyapunov function is used to formulate a set of adaptive tuning rules for the time-varying parameters involved in both the adaptive observer and the fault estimation error. It has been shown that the algorithms can be applied to estimate both constants and slow-drifting faults with convergent residual signals. A simple simulation example is included to illustrate the use of the proposed methods and encouraging results have been obtained. Copyright © 2004 John Wiley & Sons, Ltd.
This paper studies the fault estimations problem for linear time-invariant systems with polytopic uncertainties. Both discrete-time and continuous-time cases are considered, and the recently developed Generalized Kalman-Yakubovich-Popov (GKYP) Lemma is exploited to formulate the fault estimation filter design problem in finite frequency domain. The filter is designed to make the error between residual and fault as small as possible despite of the disturbance effects and model uncertainties. Design methods are presented in terms of solutions to a set of Linear Matrix Inequalities (LMIs). Numerical examples are given to illustrate the effectiveness of the proposed methods.
This paper studies the problem of fault estimation and accommodation for a class of nonlinear time-varying delay systems using adaptive fault diagnosis observer (AFDO). A novel fast adaptive fault estimation algorithm that does not need the derivative of the output vector is proposed to enhance the performance of fault estimation. Meanwhile, a delay-dependent criteria is obtained based on free weighting matrix method with the purpose of reducing the conservatism of the AFDO design. On the basis of fault estimation, an observer-based fault-tolerant controller is designed to guarantee the stability of the closed-loop system. In terms of matrix inequality, we derive sufficient conditions for the existence of the adaptive observer and fault-tolerant controller. Simulation results are presented to illustrate the efficiency of the proposed method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
This article addresses fault detection, estimation, and compensation problem in a class of disturbance driven time delay nonlinear systems. The proposed approach relies on an iterative learning observer (ILO) for fault detection, estimation, and compensation. When there are no faults in the system.. the ILO supplies accurate disturbance estimation to the control system where the effect of disturbances on estimation error dynamics is attenuated. At the same time, the proposed ILO can detect sudden changes in the nonlinear system due to faults. As a result upon the detection of a fault, the same ILO is used to excite an adaptive control law in order to offset the effect of faults on the system. Further, the proposed ILO-based adaptive fault compensation strategy can handle multiple faults. The overall fault detection and compensation strategy proposed in the paper is finally demonstrated in simulation on an automotive engine example to illustrate the effectiveness of this approach. Copyright (c) 2005 John Wiley & Sons, Ltd.
This paper deals with fault-tolerant master-slave synchronization for Lur'e systems using time-delay feedback control. Taking a general nature of fault in the master system into account, a new synchronization scheme, namely, fault-tolerant master-slave synchronization, is proposed, by which the master-slave synchronization can be achieved no matter if the fault occurs or not. By making use of an observer-based fault estimator and a modified time-delay feedback controller, the fault-tolerant master-slave synchronization is formulated so as to discuss the global asymptotic stability of the error system and the bound of energy gain from fault to state and fault estimation error vectors. Some new delay-dependent criteria are derived to analyze the synchronization error system, and based on the analysis results, a sufficient condition on the existence of such a master-slave synchronization scheme and a solution to the controller and fault-estimator gain matrices are obtained in terms of linear matrix inequalities. Finally, a Chua's circuit is used to illustrate the effectiveness of the proposed method.
This article deals with the problem of adaptive fault-tolerant control against unknown actuator faults for a class of nonlinear time delay systems with disturbance. The actuator faults are types of loss of effectiveness. The aim is to find an adaptive fault tolerant controller, such that the system is not only stabilized, but also the state vectors of normal and fault cases with disturbance track that of the normal case without disturbance, which has the designed performance. A new delay-dependent adaptive law is proposed to design the adaptive reconfigurable controller, which is excited to offset the effect of faults and disturbance automatically. Numerical and simulation results are provided to demonstrate the effectiveness of the proposed controller.
We propose a new feedback controller architecture. The
distinguished feature of our new controller architecture is that it
shows structurally how the controller design for performance and
robustness may be done separately which has the potential to overcome
the conflict between performance and robustness in the traditional
feedback framework. The controller architecture includes two parts: one
part for performance and the other part for robustness. The controller
architecture works in such a way that the feedback control system can be
solely controlled by the performance controller when there is no model
uncertainties and external disturbances and the robustification
controller can only be active when there are model uncertainties or
external disturbances