Acceptable input sequences for singular 2-D linear systems

Necessary and sufficient conditions for the acceptance of all input sequences on the given rectangle for singular 2-D linear systems are established. A procedure based on elementary row operations for finding the set of acceptable input sequences is given and illustrated by numerical example     

Design of unknown input functional observers for nonlinear systems with application to fault diagnosis

This paper considers the design of low-order unknown input functional observers for robust fault detection and isolation of a class of nonlinear Lipschitz systems subject to unknown inputs. The proposed functional observers can be used to generate residual signals to detect and isolate actuator faults. By using the generalized inverse approach, the effect of the unknown inputs can be decoupled completely from the residual signals. Conditions for the existence and stability of reduced-order unknown input functional observer are derived. A design procedure for the generation of residual signals to detect and isolate actuator faults is presented using the proposed unknown-input observer-based approach. A numerical example is given to illustrate the proposed fault diagnosis scheme in nonlinear systems subject to unknown inputs.     

含未知输入的广义系统的状态与输入估计

研究了含未知输入的广义系统的输入解耦观测器设计问题. 在系统脉冲能控的条件下通过系统输入-状态对的非奇异变换, 把此问题等价地转化为正常状态空间系统的相应问题. 用大家熟知的方法设计正常状态空间系统的观测器, 从而得到广义系统的输入解耦观测器. 然后用广义系统的观测器状态和系统输出的线性组合渐近估计系统的状态与未知输入.     

Perfect observers for singular 2-D Fornasini-Marchesini models

A concept of the perfect observer for singular two-dimensional (2-D) Fornasini-Marchesini models is proposed. Sufficient conditions are established for the existence of the perfect observer. A procedure for design of the perfect observer is also derived and illustrated by a numerical example     

Dissipative design of unknown input observers for systems with sector nonlinearities

In this paper a design method for nonlinear Unknown Input Observers (UIO) for a class of nonlinear systems is proposed. This design is based on a dissipative characterization of the existence conditions for such observers made recently by the authors. The main condition corresponds to an abstract incremental dissipativity property of the plant, which can be made computable by the use of LMI techniques for the considered class of systems. This leads to a constructive design method for nonlinear UIOs. Copyright © 2010 John Wiley & Sons, Ltd.     

H ∞ synthesis of unknown input observers for non-linear Lipschitz systems

The problem of unknown input observer design for non-linear Lipschitz systems is considered. A new dynamic framework which is a generalization of previously used linear unknown input observers is introduced. The additional degrees of freedom offered by this dynamic framework are used to deal with the Lipschitz non-linearity. The necessary and sufficient condition that ensures asymptotic convergence of the new observer is presented, and the equivalence between this condition and an H _∞ optimal control problem which satisfies the standard regularity assumptions in the H _∞ optimization theory is shown. Based on these results, a design procedure that is solvable using commercially available software is presented. A simulation example is given to illustrate the proposed design.     

Multiple sliding mode observers and unknown input estimations for Lipschitz nonlinear systems

Multiple sliding mode observers for state and unknown input estimations of a class of MIMO nonlinear systems are systematically developed in this paper. A new nonlinear transformation is formulated to divide the original system into two interconnected subsystems. The unknown inputs are assumed to be bounded and not necessarily Lipschitz, and do not require any matching condition. Under structural assumptions for the unknown input distribution matrix, the sliding mode terms of the nonlinear observer are designed to track their respective unknown inputs. Also, the unknown inputs can be reconstructed from the multiple sliding mode structurally. The conditions for asymptotic stability of estimation error dynamics are derived. Finally, simulation results are given to demonstrate the effectiveness of the proposed method. Copyright © 2011 John Wiley & Sons, Ltd.     

Design of linear functional observers for linear systems with unknown inputs

This paper presents a reduced-order linear functional state observer for linear systems with unknown inputs. A simple observer construction procedure is provided. A numerical example is given to illustrate the properties of the observer. The example deals with a linear system comprising of 20 states, 2 inputs, 10 outputs and 5 unknown inputs for which a fourth-order observer is designed to estimate two linear functions of the states.     

Adaptive observers for unknown general nonlinear systems

Several neural network (NN) models have been applied successfully for modeling complex nonlinear dynamical systems. However, the stable adaptive state estimation of an unknown general nonlinear system from its input and output measurements is an unresolved problem. This paper addresses the nonlinear adaptive observer design for unknown general nonlinear systems. Only mild assumptions on the system are imposed: output equation is at least C(1) and existence and uniqueness of solution for the state equation. The proposed observer uses linearly parameterized neural networks (LPNNs) whose weights are adaptively adjusted, and Lyapunov theory is used in order to guarantee stability for state estimation and NN weight errors. No strictly positive real (SPR) assumption on the output error equation is required for the construction of the proposed observer.     

Fault tolerant control allocation using unknown input observers

This paper focuses on the use of unknown input observers for detection and isolation of actuator and effector faults with control reconfiguration in overactuated systems. The proposed approach consists in tuning the observer parameters in order to make the filters decoupled from faults affecting selected groups of actuators or effectors. The control allocation actively uses input redundancy in order to make relevant faults observable. The case study of an overactuated marine vessel supports theoretical developments.     

A new design approach to unknown input observers

This paper proposes a fundamentally new unknown input observer (UIO) which has, uniquely, r decoupled modes, provides r linearly independent combinations of plant system states, and has zero gain to all p, unknown inputs. The parameter r is adjustable. If the plant system satisfies the conditions of the existing UIO, then r=n=plant system order, and there is no difference between our UIO and the existing regular UIO. However, if the plant system satisfies either of the following two significantly more general conditions: m>p (m is the number of plant output measurements) and at least one stable transmission zero, then 1相似文献   

Robust detection of faulty actuators via unknown input observers

A robust detection scheme for detecting and identifying faulty actuators via unknown input observers is proposed. In this scheme, the uncertainties and some inputs are regarded as unknown inputs. A bank of unknown input observers are thus constructed, each of which is driven by all inputs but one. The residuals of these observers arc used lo construct the detection and identification logic. Simulations based on a non-linear chemical reactor with heat exchanger illustrate the validity of the proposed method. Moreover, a component failure detection scheme via an unknown input observer is also proposed.     

Fault-tolerant sensor reconciliation schemes based on unknown input observers

ABSTRACT

This paper proposes two fault-tolerant sensor reconciliation design methods for over-sensed plants. The aim of the reconciliator is to detect the presence of faults on the existing physical sensors and hide the corrupted measurements in the generation of a virtual output, which one would like to be generated in a reliable way in spite of fault occurrences and hence trustfully usable for control purposes. The sensor faults here considered are limited to variations of both sensor gain and offset values. The proposed approach envisages the use of an unknown input observers coupled with an ‘ad-hoc’ parameters estimator used to estimate online the sensor effectiveness matrix at each time instant. In the paper, two design methodologies are described, based one on the linear parameter varying polytopic formulation and the other on the linear fractional transformation paradigm. All main properties of the considered schemes are investigated and rigorously proved.     

Impulsive functional observers for linear systems

The impulsive functional observer design problem for linear systems is addressed. Piecewise differentiable Lyapunov functions are introduced to analyze the stability of the error dynamics. Sufficient conditions for the existence of the impulsive functional observers that are capable of exponentially estimating any given function of the state vector are derived. Numerical examples are presented to demonstrate the effectiveness of the proposed results.     

基于有限时间未知输入观测器的一类受扰非线性系统故障检测与估计

针对一类非线性系统同时存在执行器故障、传感器故障和扰动的问题,提出一种基于有限时间未知输入观测器的故障检测与估计方法.首先,通过线性非奇异变换将原系统解耦为两个降阶的子系统,其中一个子系统只包含扰动,另一个子系统同时包含扰动和故障;然后,通过一阶低通滤波器获得新的状态并与子系统构成增广系统,实现将原系统的传感器故障转化为增广系统的执行器故障;接着,设计未知输入观测器对增广系统故障进行检测,实现在有限时间内估计出系统的扰动和故障,并通过理论分析验证所设计观测器的有限时间收敛性;最后,基于永磁同步电机(PMSM)转速系统进行仿真研究,仿真结果验证了所提出方法的有效性.     

Full-order impulsive observers for impulsive systems with unknown inputs

This paper studies full-order impulsive observers for impulsive systems with unknown inputs. Two types of full-order impulsive observers are designed respectively. The first type is Luenberger-type impulsive observer (LIO). The second type is for the observed system with eliminable unknown input, where the impulsive observer is allowed to have nonidentical dynamic structure with the observed system. The conditions via the average dwell time technique are derived for the existence of these two types of impulsive observers. It is shown that in the LIO, the observer's state tracks the observed system's state in the sense of input-to-state stability (ISS). Specifically, the observer's state track completely the observed system's state if the unknown input trends to zero. While in the second type of impulsive observer, the observer's state tracks completely the observed system's state regardless of the unknown input trends to zero. Finally, three examples with simulations are presented to demonstrate the effectiveness of the theoretical results.