Adaptive technique‐based distributed fault estimation observer design for multi‐agent systems with directed graphs

This paper focuses the development of an adaptive observer-based distributed fault estimation observer (DFEO) for multi-agent nonlinear time-delay systems under a directed communication topology. The process involves constructing a fault estimation observer for each agent based on their relative output estimation errors. An adaptive DFEO design is proposed for multi-agent systems with a directed communication topology. Furthermore, investigating the effect of faulty agents on the criteria of fault detection on healthy agents. The proposed design is represented with Linear Matrix Inequalities (LMIs) to establish a systematic design procedure. The study also includes simulation results to demonstrate the effectiveness of the proposed design techniques.

In this study, a new distributed fault estimation observer (DFEO) design method is proposed based on unknown input observer (UIO) for interconnected systems with external disturbances. The coupling terms among interconnected subsystems are utilised to construct DFEO. At the same time, according to the characteristics of UIO, external interference is completely decoupled to improve the robustness of fault estimation. Furthermore, the authors propose a multi‐constraint design with robust and regional pole configurations to analyse and design gain matrices of DFEO, which can be calculated using linear matrix inequalities. Furthermore, asymptotic estimation of sensor faults is discussed with the help of DFEO. Finally, a simulation of the interconnected system is provided to illustrate the effectiveness of the proposed technique.

SummaryThis paper focuses on the fault estimation observer design problem in the finite‐frequency domain for a class of Lipschitz nonlinear multiagent systems subject to system components or actuator fault. First, the relative output estimation error is defined based on the directed communication topology of multiagent systems, and an observer error system is obtained by connecting adaptive fault estimation observer and the state equation of the original system. Then, sufficient conditions for the existence of the fault estimation observer are obtained by using a generalized Kalman‐Yakubovich‐Popov lemma and properties of the matrix trace, which guarantee that the observer error system satisfies robustness performance in the finite‐frequency domain. Meanwhile, the pole assignment method is used to configure the poles of the observer error system in a certain area. Finally, the simulation results are presented to illustrate the effectiveness of the proposed method.

In this paper, a new distributed fault estimation observer with adjustable parameters is designed for a class of nonlinear interconnected systems. The presented fault estimator consists of proportional and integral terms to improve the accuracy of fault estimation. The observer gain matrices of the proposed fault estimation scheme for the underlying systems are calculated based on robust L2-L2 and L2-L∞ performance. The proposed method achieves a lower performance level in the aspect of quantitative analysis compared with existing fault estimation approaches. A simulation example is provided to demonstrate the effectiveness of the new design method.

In this paper, a distributed fault estimation observer based on intermediate estimator method is studied, which eliminates the constraints of observer matching conditions on fault estimation. First, the relative output estimation errors of MASs and intermediate estimator system are established based on communication topology. Second, we constructed a new Lyapunov function containing both original system state and intermediate estimation variables, the sufficient conditions for the stability of the global dynamic error system are obtained, and the gain matrix of the distributed fault estimation observer is calculated. At the end of this paper, the effectiveness and feasibility of the developed method are illustrated in two cases: the system satisfies and not satisfy the observer matching condition.

SummaryThis paper proposes a framework of fault estimation observer design in finite‐frequency domain for discrete‐time systems. First, under the multiconstrained idea, a full‐order fault estimation observer in finite‐frequency domain is designed to achieve fault estimation by using the generalized Kalman–Yakubovich–Popov lemma to reduce conservatism generated by the entire frequency domain. Then, a reduced‐order fault estimation observer is constructed, which results in a new fault estimator to realize fault estimation using current output information. Furthermore, by introducing slack variables, improved results on full‐order fault estimation observer and reduced‐order fault estimation observer design with finite‐frequency specifications are obtained such that different Lyapunov matrices can be separately designed for each constraint. Simulation results are presented to illustrate the advantages of the theoretic results obtained. Copyright © 2014 John Wiley & Sons, Ltd.

Distributed finite-time fault estimation and fault-tolerant control for cyber-physical systems with matched uncertainties

In this paper, we propose the pseudo multi-hop distributed consensus algorithm under directed communication topologies. The property and convergence rate of the pseudo multi-hop distributed consensus algorithm under directed communication topologies are analyzed, and the convergence conditions for the pseudo multi-hop distributed consensus algorithm is given. In particular, the convergence rate is determined by the spectral radius of the matrix depend on the communication topology. Finally, simulation results are provided to verify these analytical results.

This paper is devoted to a containment control problem with time-delay for second-order nonlinear multi-agent systems subject to external disturbances under a directed communication topology. First of all, a distributed delay-coupled protocol is proposed based on relative states among the neighboring agents. Then, sufficient conditions in terms of linear matrix inequality(LMI) are derived to make the followers asymptotically converge to the convex hull spanned by the leaders while satisfying desired H ∞ performance. It is proved that the time-delay protocol is sensitive to time delays. Finally, numerical simulations are provided to show the effectiveness of our theoretical results.

In this paper, consensus analysis and design are investigated for discrete-time multi-agent systems (MASs) with consecutive packet losses in communication links of directed communication topology. It is assumed that at each transmitted instant, the packet loss is stochastic and described by Bernoulli distribution, but during a given time window, the data could be successfully transmitted to the agent from each of its neighbors. First, we utilize the incidence matrix of a directed spanning tree of the communication topology to construct a linear transformation matrix so that the consensus problem is equivalently transformed into a mean square asymptotic stability problem of a reduced-order system. Second, by using Lyapunov–Krasovskii functional approach, we derive some sufficient conditions of consensus criterion in terms of linear matrix inequalities (LMIs). These conditions express the relationship among the control gain matrix, packet loss rate, and the number of consecutive packet losses. Based on the conditions, gain matrix in the consensus protocol is designed to guarantee the MAS with stochastic packet losses to achieve mean square asymptotic consensus. Moreover, for the special case of undirected communication topology, by using the matrix decomposition method, the variables of LMIs are transformed into the low-order conditions independent of the network size. Finally, some numerical examples are given to show the effectiveness of the proposed method.

In this study, the problem of fault estimation observer design with finite-time convergence specification for continuous-time dynamic systems subject to external disturbances. First, the unknown input observer is constructed to achieve accurate estimation of the occurred fault and to guarantee robustness against the disturbance. Then a pole placement-based fault estimation observer is constructed using time-delay design such that the fault estimation error converges to zero in finite time. Unlike conventional literatures, the proposed fault estimator with finite-time convergence specification does not contain discontinuous sign function. Finally, simulation results of an aircraft application are presented to illustrate the finite-time convergence of the proposed fault estimation observer.

In this paper, the fault-estimation problem for discrete-time systems is considered. A multiconstrained reduced-order fault estimation observer (RFEO) design is proposed to handle the case of abrupt and time-varying faults, and a comparison with full-order fault estimation observer is discussed in detail. Then, by introducing a slack matrix, a new multiconstrained RFEO result is obtained to reduce conservatism generated by the conventional method. Further, the present authors investigate robust RFEO design to cope with external disturbances. Simulation results of an aircraft example illustrate their contributions.

This paper studies the problem of robust fault estimation (FE) observer design for discrete-time Takagi-Sugeno (T-S) fuzzy systems via piecewise Lyapunov functions. Both the full-order FE observer (FFEO) and the reduced-order FE observer (RFEO) are presented. The objective of this paper is to establish a novel framework of the FE observer with less conservatism. First, under the multiconstrained design, an FFEO is proposed to achieve FE for discrete-time T-S fuzzy models. Then, using a specific coordinate transformation, an RFEO is constructed, which results in a new fault estimator to realize FE using current output information. Furthermore, by the piecewise Lyapunov function approach, less conservative results on both FFEO and RFEO are derived by introducing slack variables. Simulation results are presented to illustrate the advantages of the theoretic results that are obtained in this paper.

This paper addresses the event-triggered consensus tracking for general linear multi-agent systems with nonlinear uncertainty dynamics under directed communication topology. The proposed event-triggered consensus strategy relaxes the assumptions in existing works that the control gain and local inputs must be continuous. With the consensus tracking condition being satisfied, the cooperative control law with bounded parameter is developed based on the intermittent samples. It shows that if the sampling condition, in terms of LMIs, is satisfied, the resulting closed-loop general linear multi-agent uncertain systems will achieve the consensus. Simulation results are provided to verify the proposed approach.

This paper studies the adaptive fuzzy bounded control problem for leader-follower multiagent systems, where each follower is modeled by the uncertain nonlinear strict-feedback system. Combining the fuzzy approximation with the dynamic surface control, an adaptive fuzzy control scheme is developed to guarantee the output consensus of all agents under directed communication topologies. Different from the existing results, the bounds of the control inputs are known as a priori, and they can be determined by the feedback control gains. To realize smooth and fast learning, a predictor is introduced to estimate each error surface, and the corresponding predictor error is employed to learn the optimal fuzzy parameter vector. It is proved that the developed adaptive fuzzy control scheme guarantees the uniformly ultimate boundedness of the closed-loop systems, and the tracking error converges to a small neighborhood of the origin. The simulation results and comparisons are provided to show the validity of the control strategy presented in this paper.