Robust Fault Detection Observer Research Articles

Towards robust fault detection for Takagi–Sugeno nonlinear systems

This paper addresses robust fault detection observer design for a class of discrete-time Takagi–Sugeno nonlinear systems. A novel design method is presented based on finite-frequency H−/H∞ indices and peak-to-peak analysis. The finite-frequency H− and H∞ indices are utilized to characterize fault sensitivity and disturbance robustness, respectively. The peak-to-peak analysis is used to derive a dynamic threshold. An iterative algorithm is further developed to reduce conservatism. Theoretical proof shows that the performance of the proposed method is not worse than some existing works. Simulation results demonstrate the validity and viability of the proposed method.

A comprehensive RFD-FTC-DCA system for hypersonic vehicles with saturation constraints

A comprehensive RFD-FTC-DCA system is proposed for the hypersonic vehicle with saturation constraints to resist the control surface damage, actuator faults, disturbances and parameter perturbation. Firstly, the hypersonic vehicle fault model is established. Secondly, the robust fault detection (RFD) observer is designed to detect the control surface damage and actuator faults accurately under the influences of disturbances and parameter perturbation. Thirdly, the fault-tolerant control (FTC) law is designed to resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously. Finally, a dynamic control allocation (DCA) algorithm is designed to reallocate the FTC law and limit the deflection angle and velocity within saturation constraint. The comparison simulation results are presented to demonstrate that the RFD observer can detect the faults accurately and reduce false alarm rates effectively, the FTC law can resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously, and the tracing errors of attack angle, side-slip angle and roll angle are only , and , respectively, and the DCA algorithm can reallocate the FTC law and limit the deflection angle and velocity within saturation values.

Formula omitted] fault detection observer design for fractional-order singular systems in finite frequency domains

This paper investigates the robust fault detection observer design problem in finite frequency domains for fractional-order singular systems. An H−/H∞ fault detection observer for fractional-order singular systems is designed to meet the system admissibility, disturbance robustness and fault sensitivity indices in finite frequency domains simultaneously. Four theorems and four corollaries about the system admissibility and the performance index H−/H∞ in different frequency ranges are given, and then the sufficient conditions are obtained in terms of linear matrix inequalities. Finally, two numerical examples are given to verify the validity of the presented methods.

Multiple-fault diagnosis for spacecraft attitude control systems using RBFNN-based observers

In this paper, a novel multiple-fault diagnosis (MFD) scheme using radial basis function neural network (RBFNN)-based observers is presented for a spacecraft attitude control system (ACS) in the presence of external disturbances and nonlinear uncertainties. Based on dynamic and kinematic models, robust fault detection observers (FDOs) are designed to detect the simultaneous occurrence of actuator, gyro, and star sensor faults. Then, a series of RBFNN-based fault isolation observers (FIOs) are designed to decouple the faults of different components completely. This complete decoupling will guarantee that the diagnosis result of one component is not affected by the faults of other components; thus, multiple faults can be diagnosed simultaneously. To improve the accuracy of fault detection and reconstruction, disturbance compensation observers (DCOs) based on the RBFNN are also designed to compensate for the external disturbances. It is worth noting that the developed fault diagnosis scheme can be used to detect and isolate small faults. Finally, simulation results are presented to show the effectiveness and feasibility of the proposed method.

Sensor FDD based FTC D esign for Time D elay PEMFC S ystems

An FTC design based on sensor FDD is presented for time-delay PEMFC systems with disturbances and uncertainties. A robust fault detection observer with a fault diagnosis technique is used. The Lyapunov principle derives the adaptive law and estimates sensor fault. A scheme based on FDD adaptive algorithm is derived to obtain fault in the sensor. The PEMFC systems simulations show the utility of the algorithm. Time-delays are considered in deriving both adaptive observer and FTC algorithm which is not incorporated in previous works on PEMFC systems. The simulated results can estimate the fault and validate the FTC design.

Sensor Fault Detection and Fault-Tolerant Control for Buck Converter via Affine Switched Systems

The main purpose of this paper is to study the problem of the sensor fault detection and fault-tolerant control for DC–DC buck converter via affine switched systems. First, the buck converter is model as a switched system model, and a robust fault detection observer with a prescribed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{\infty }$ </tex-math></inline-formula> performance index is designed to produce a residual signal. The residual signal can be used to construct the residual estimation function. Second, fault detection logic is introduced which compares the threshold with the residual estimation function, and the sensor fault detection can be achieved. Third, once the sensor fault is detected, fault-tolerant control can be achieved through the method of system reconfiguration. This method enables the system to achieve asymptotic stability in a new system under the sensor fault. Finally, to show the feasibility of the fault detection and fault-tolerant control, the simulation results of three kinds of sensor faults including open-circuit, gain deviation, and noise abnormity given in this paper.

Hybrid Active-Passive Robust Fault-Tolerant Control of Event-Triggered Nonlinear NCS

In this paper, the authors aimed to analyze uncertain nonlinear networked control systems (NCS) under discrete event-triggered communication scheme (DETCS), in which an integrated design methodology between robust fault detection observer and active fault-tolerant controller is proposed. Moreover, the problem of hybrid active–passive robust fault-tolerant control, which integrated passive fault-tolerant control, fault detection, and controller reconstruction, is researched. In consideration of the impact of uncertainties and network-induced delay on system performance, a new class of uncertain nonlinear NCS fault model is established based on T-S fuzzy model. By employing Lyapunov stability theory,H∞control theory, and linear matrix inequality method, the fault detection observer and hybrid fault-tolerant controller are both appropriately designed. In addition, the sufficient condition that guaranteed the asymptotically robust stability of nonlinear NCS against any actuator failures is deduced. Finally, a numerical simulation is provided to show the effectiveness of the proposed methods.

Fault detection and accommodation of saturated actuators for underactuated surface vessels in the presence of nonlinear uncertainties

This paper investigates a fault detection and accommodation (FDA) problem of saturated actuators for trajectory tracking of underactuated surface vessels (USVs) in the presence of nonlinear uncertainties. A robust fault detection observer and a time-varying detection criterion are presented to detect the actuator faults distinguished from uncertainties in nonlinear dynamics and external disturbances. Then, we develop an adaptive fault accommodation scheme using the dynamic surface design to compensate the detected faults. For the fault accommodation control, the auxiliary variables and their dynamics are derived to consider the saturation problem of actuators with the nonholonomic property of USVs and to analyze the stability of the sway dynamics clearly. To ensure that tracking errors are globally uniformly ultimately bounded, the projection algorithm is employed for the design of the bounded virtual and actual control laws. The effectiveness of the proposed FDA system is demonstrated by simulation results.

PI robust fault detection observer for a class of uncertain switched systems using LMIs

This paper addresses a method for robust fault detection and estimation by minimizing the disturbance and uncertainties to residual sensitivity. It consists in the design of proportional integral observer while minimizing the well known H∞ norm for worst case uncertainties and disturbance attenuation, and combining a transient response specification. This multi-objective problem is formulated as linear matrix inequalities (LMI) feasibility problem in which a cost function is minimized subject to LMI constraints. This approach is employed to generate a set of robust observers for uncertain switched systems.

Robust fault detection observer design under fault sensitivity constraints

In this paper, a reduced-order robust fault detection observer (FDO) for continuous linear time-invariant systems with unknown inputs is designed by combining the algebraic unknown input decoupling principle with linear matrix inequalities (LMIs)-based optimization of fault sensitivity constraints. Algebraic unknown input decoupling is incorporated into the design of fault detection observers, thereby leading to a reduced-order robust FDO that is decoupled from unknown inputs. The gain matrix of the reduced-order robust FDO is determined from the optimal solution that maximizes the LMIs, which are based on the H_ index performance and the additional pole placement in a specified LMI region. This ensures that the designed robust FDO provides the optimal fault sensitivity on the residual. The efficiency of the proposed approach is evaluated through simulation studies and compared with the pole placement design and the mixed H_/H∞ observer given in the work of [9].

Robust Unknown Input Observer Design for Linear Uncertain Time Delay Systems with Application to Fault Detection

AbstractIn this paper, a novel approach is proposed to design a robust fault detection observer for uncertain linear time delay systems. The system is composed of both norm‐bounded uncertainties and exogenous signals (noise, disturbance, and fault) which are considered to be unknown. The main contribution of this paper is to present unknown input observer (UIO)‐based fault detection system which shows the maximum sensitivity to fault signals and the minimum sensitivity to other signals. Since the system contains uncertainty terms, an H∞ model‐matching approach is used in design procedure. The reference residual signal generator system is designed so that the fault signal has maximum sensitivity while the exogenous signals have minimum sensitivity on the residual signal. Then, the fault detection system is designed by minimizing the estimation error between the reference residual signal and the UIO residual signal in the sense of H∞ norm. A sufficient condition for the existence of such a filter is exploited in terms of certain linear matrix inequalities (LMIs). Application of the proposed method in a numerical example and an engineering process are simulated to demonstrate the effectiveness of the proposed algorithm. Simulation results show the validity of the proposed approach to detect the occurrence of faults in the presence of modeling errors, disturbances, and noise.

Formula omitted] fault detection filter design for discrete-time Takagi–Sugeno fuzzy system

In this note, a robust fault detection observer is designed for a T–S (Takagi–Sugeno) fuzzy model with sensor faults and unknown bounded disturbances. The method applies the technique of descriptor systems by considering sensor faults as an auxiliary state variable. The idea is to formulate the robust fault detection observer design as an H−/H∞ problem. Based on nonquadratic Lyapunov functions, a solution of the considered problem is then given via a Linear Matrix Inequality (LMI) formulation. An example is proposed to illustrate the design conditions.

Multi‐objective H − ∕ H ∞ fault detection observer design for Takagi–Sugeno fuzzy systems with unmeasurable premise variables: descriptor approach

SUMMARYThis paper investigates the problem of robust fault detection observer design for nonlinear Takagi–Sugeno models with unmeasurable premise variables subject to sensor faults and unknown bounded disturbance. The main idea is to synthesize a robust fault detection observer by means of a mixed H − ∕ H ∞ performance index. The considered observer is used to estimate jointly states and faults. Using the technique of descriptor system representation, we proposed a new less‐conservative approach in term of a linear matrix inequality (LMI) by considering the sensor fault as an auxiliary state variable. A solution of the problem is obtained by using an iterative LMI procedure. Copyright © 2012 John Wiley &amp; Sons, Ltd.

LMI approach to mixed H_/H ∞ fault detection observer design

To investigate the robust fault detection (RFD) observer design for linear uncertain systems, the H t_ index and H ∞ norm are used to describe this observer design as optimization problems. Conditions for the existence of such a fault detection observer are given in terms of matrix inequalities. The solution is obtained by new iterative linear matrix inequality (ILMI) algorithms. The RFD observer design over finite frequency range in which D f does not have full column rank for a system is also considered. Numerical example demonstrates that the designed fault detection observer has high sensitivity to the fault and strong robustness to the unknown input.

An LMI Approach to Mixed &lt;i&gt;H_/H&lt;/i&gt;&lt;sub&gt;∞&lt;/sub&gt; Robust Fault Detection Observer Design

This paper investigates the problem of the robust fault detection (RFD) observer design for linear uncertain systems with the aid of the H_ index and the H∞ norm, which are used to describe the problem of this observer design as optimization problems. Conditions for the existence of such a fault detection observer are given in terms of matrix inequalities. RFD problem with structured uncertainties in the system matrices is also considered. The solution is obtained by an iterative linear matrix inequality (ILMI) algorithm. Numerical example is employed to demonstrate the effectiveness of the proposed methods.

Robust Fault Detection for Nonlinear Systems with Distributed Delays

This paper focuses on the problem of robust fault detection for a class of nonlinear time-delay systems. The system under study involves distributed time delay, unknown inputs and nonlinear fault distribution functions which is dependent on the inputs, outputs and states of the system. By applying Lyapunov stability theory and free-weighting matrix methods, a novel delay-dependent sufficient condition, which is in terms of linear matrix inequality (LMI) and ensures existence of the desired robust fault detection observer for the nonlinear systems, is proposed. When the LMI is feasible, an explicit expression of a desired observer gain is given. Based on the observer technique, desired approach to robust fault detection is presented

Design of robust fault detection observer for Takagi-Sugeno models using the descriptor approach

This paper deals with the design of a robust fault detection observer for a Takagi-Sugeno (T- S) fuzzy model affected by sensor and actuator faults and unknown bounded disturbances simulta- neously. An observer based on the technique of descriptor systems is studied. Indeed, by considering faults as auxiliary state variables, both states and faults are estimated simultaneously. In order to guar- antee the best robustness to disturbances and sensitivity to faults, the developed observer combine the H-/H∞ performances. Then, based on Lyapunov method, asymptotic stability conditions are given to design the observer parameters. In order to get convenient and reliable faults estimator in computations, an iterative linear matrix inequality (LMI) algorithm is developed. This algorithm, solved easily using existing numerical tools, allows to minimize influences of disturbances and maximize the ones of faults. Finally, a numerical example is proposed to illustrate the effectiveness of the result.

Robust fault detection observer design for linear uncertain systems

This article addresses the fault detection observer design issue for linear time invariant (LTI) systems with additive or multiplicative uncertainties, which are also subject to unknown disturbances. The observer design is investigated under the ℋ∞/ℋ− index framework using the generalised KYP lemma in the finite-frequency domain. Sufficient conditions for the existence of such a fault detection observer are given in terms of linear matrix inequalities (LMIs). The threshold design issue is discussed and a method for estimating the worst undetectable fault size is proposed. The effectiveness of the proposed algorithms is illustrated by numerical simulation examples.

Design of Robust Fault Detection Observers for Discrete-time Linear Switched Systems

AbstractThis work addresses the design of a robust hybrid observer for discrete-time switched linear systems subject to unknown inputs and modeling errors. The observer herein proposed is synthesized, for the case when the active mode is unknown and in the purpose of robust fault detection. We'll show that a suitable trade-off between the robustness to unknown inputs and sensitivity to faults can be obtained through a H∞ performance index. The latter is optimized using an iterative LMI solution procedure. The efficiency of the proposed approach is illustrated by a numerical example.

Robust Fault Detection Observer and Fault Estimation Filter Design for LTI Systems Based on GKYP Lemma

This paper addresses the robust fault detection observer and fault estimation filter design issues for linear time invariant (LTI) systems with parameter uncertainties in a polytope and the systems are subject to unknown inputs as well. The observer and filter design are investigated in the H∞/H– index framework in the finite frequency interval by using the generalized KYP lemma. The threshold design and the worst undetectable fault size estimation are discussed. A numerical example is given to illustrate the effectiveness of the derived algorithms.