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Fanglai Zhu,Wei Zhang,Jiancheng Zhang,Shenghui Guo 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.1
In this paper, we investigate the state estimation, unknown input and measurement noise reconstructionproblems and the feedback controller design issues for a linear discrete-time system with both unknown inputsand measurement noises. First, an augmented system is constructed and the state vector of the augmented systemconsists of the original system state and the measurement noise, and the preconditions between the original systemand the augmented system is discussed in detail. Second, for the augmented system, a reduced-order observeris designed so that the original system state estimates and the measurement noise reconstruction can be obtained. Third, in order to get the asymptotical unknown input reconstruction, an interval observer for part of the measurableoutput is proposed and an unknown input reconstruction method based on the interval observer is developed. Finally,an observer-based state feedback and unknown input controller is designed and the closed-loop system stability isanalyzed. We point out that the closed-loop system satisfies the so-called separation property. At last, two simulationexamples are given to verify the effectiveness of the proposed methods.
Fanglai Zhu,Yu Shan,Yuyan Tang 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.9
In this paper, we discuss actuator fault and sensor fault detection and isolation (FDI) problems for a classof switched nonlinear systems with external disturbances. First, an augmented descriptor system is constructedwhere the augmented state vector consists of the original states, the actuator faults and sensor faults. Secondly, aspecific transformation, which transforms the descriptor system into a general system, is made and the relationshipbetween the preconditions relative to these two kinds of systems are discussed in detail. Thirdly, based on theequivalent general switching system, a sliding mode observer which is robust to external disturbances and sensitiveto both actuator and sensor faults is designed. Furthermore, based on the proposed fault detection method, a faultisolation method which can isolate the actuator faults from sensor faults is developed by using multiple observerdesign techniques. Finally, a numerical example is given to illustrate the effectiveness of these methods.
Fault Detection and Reconstruction for Discrete Nonlinear Systems via Takagi-Sugeno Fuzzy Models
Shenghui Guo,Fanglai Zhu,Wei Zhang,Stanisław H. Zak,Jian Zhang 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.6
Observer-based actuator fault detection and sensor fault reconstruction for a class of discrete-time nonlinear systems with actuator and sensor faults are investigated in this paper. A descriptor Takagi-Sugeno (T-S) fuzzy model is employed to construct observer-based systems for the purpose of fault detection and sensor fault reconstruction. Two methods for observer design are proposed. In the first method, the observer gains are computed off-line. In the second method, the observer gains are computed on-line at each iteration. The observer designs are formulated using linear matrix inequalities. Sufficient conditions for the existence of the observer-based fault detection and sensor fault reconstruction systems are provided. Comparative simulation study to illustrate the validity of the proposed methods is performed.
Unknown Input Observer Design for Takagi-Sugeno Fuzzy Stochastic System
Shenghui Guo,Fanglai Zhu,Liyun Xu 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.4
This paper deals with the unknown input observer design for Takagi-Sugeno (T-S) fuzzy models subjected to measurement noise and stochastic noise. The method applies the singular system theory by considering the measurement noise as an augmented system state, and then an unknown input observer based on the techniques of singular systems is developed to estimate both the system states and measurement noise simultaneously. Under a necessary assumption, the error dynamic system of the observer is free from the unknown inputs. And the observer gain matrix is determined by means of minimum covariance matrix of state residual. Two simulation examples are given to illustrate the correctness and effectiveness of the proposed method.
Output Control of MIMO System with Unmatched Disturbance based on High-order Unknown Input Observer
Jiancheng Zhang,Fanglai Zhu 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.2
In this paper, the output control for a general MIMO linear system subjected to unmatched disturbance isconsidered. A smooth backstepping control law is developed under the assumption that the state and disturbance aswell as its derivatives are known firstly. Then in order to estimate the required information, a high-order unknowninput observer (HOUIO) is developed, and it is proven that based on the estimation by such the HOUIO, the designedcontroller can compensate all the disturbances from output channels and asymptotically drive the output to zero. Comparing with the traditional sliding mode control laws, the control law we design does not contain any switchingfunction, so it can effectively reduce the chattering. Finally, simulation results are given to show the effectivenessof our methods.
Junqi Yang,Fanglai Zhu,Xin Wang,Xuhui Bu 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.5
This paper deals with the issues of sensor fault estimation, actuator fault detection and isolation for a class of uncertain nonlinear systems. By taking the sensor fault vector as a part of an extended state vector, the original system with sensor faults, actuator faults and unknown inputs is transformed into an augmented singular system which is just with actuator faults and unknown inputs. For the constructed singular system, a robust sliding-mode observer is developed to simultaneously estimate the states and sensor faults of original system, and the observer gain matrices are computed in terms of linear matrix inequalities by solving an optimization problem. Then an actuator fault detector is designed to detect actuator faults when ones occur, and multiple observers used as actuator fault isolators are proposed to identify which actuator is with fault. Finally, a simulation example is given to illustrate the effectiveness of the proposed methods.
Sliding-mode Observers for Nonlinear Systems with Unknown Inputs and Measurement Noise
Junqi Yang,Fanglai Zhu,Wei Zhang 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.5
This paper deals with the design of observers for Lipschitz nonlinear systems with not only unknown inputs but also measurement noise when the observer matching condition is not satisfied. First, an augmented vector is introduced to construct an augmented system, and an auxiliary output vector is constructed such that the observer matching condition is satisfied and then a high-gain sliding mode observer is considered to get the exact estimates of both the auxiliary outputs and their derivatives in a finite time. Second, for nonlinear system with both unknown inputs and measurement noise, an adaptive robust sliding mode observer is developed to asymptotically estimate the system’s states, and then an unknown input and measurement noise reconstruction method is proposed. Finally, a numerical simulation example is given to illustrate the effectiveness of the proposed methods.
Jian Zhang,Xiaohang Li,Fanglai Zhu 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.3
In this paper, we consider problems of state estimation, unknown input, and measurement noise reconstructionfor a class of Lipschitz nonlinear systems. By extending the measurement noise as an auxiliary statevector, the original system is transformed into an augmented descriptor system. Then an adaptive H∞ observeris developed for estimating the states, unknown input and measurement noise simultaneously. Further, sufficientconditions of the existence of the adaptive H∞ observer are given in the form of linear matrix inequality, which canbe solved easily via some efficient mathematic tools. Finally, two simulation examples are given to illustrate theeffectiveness of the proposed method.
Jiancheng Zhang,Jun Li,Fanglai Zhu,Xiaohang Li 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6
This paper develops a new unknown input observer (UIO) design method for a class of discrete-timelinear descriptor systems when the observer matching condition is not satisfied. By equivalent transformations, thestate and unknown input observations of the descriptor system are changed to the UIO design problem for a generallinear dynamic system firstly. Then based on some further discussion on the concept of the system left invertibility,a new auxiliary output vector is constructed which allows us to remove the unknown inputs from the dynamicequation, and thereby a Luenberger-type observer can be constructed. One of the advantages of the present methodis that it can work only under the single strongly detectable condition. Finally, a simulation example is given toverify the effectiveness and show the superiorities of our methods.