Full-order Unknown Input Observer Research Articles

Asymptotical Consensus of MIMO Linear Multiagent Systems With a Nonautonomous Leader and Directed Switching Topology: A Continuous Approach

In this paper, we investigate the asymptotical consensus tracking problems for multiple-input-multiple-output (MIMO) linear multi-agent systems (MASs) with directed switching topology and a non-autonomous leader subject to nonzero unknown inputs. First, we design a full order unknown input observer (UIO) based on relative outputs to estimate the relative full states. Based on this UIO, we design a continuous consensus controller by introducing a decay function which remains positive into the term that is used to eliminate the effects of leader's nonzero inputs. And by using the multiple Lyapunov functions (MLFs) method, we prove that asymptotical consensus can be achieved if the average dwell time (ADT) is greater than a positive threshold. Second, we design a continuous consensus controller based on a reduced order UIO that can significantly simplify calculations. Finally, we give two examples about multiple unmanned aerial vehicles (UAVs) to verify the theoretical results. Compared with existing works, the continuous controllers here can not only achieve zero error consensus tracking, but also are chattering free.

Observer-Based Consensus Protocol for Directed Switching Networks With a Leader of Nonzero Inputs.

We aim to address the consensus tracking problem for multiple-input-multiple-output (MIMO) linear networked systems under directed switching topologies, where the leader is subject to some nonzero but norm bounded inputs. First, based on the relative outputs, a full-order unknown input observer (UIO) is designed for each agent to track the full states' error among neighboring agents. With the aid of such an observer, a discontinuous feedback protocol is subtly designed. And it is proven that consensus tracking can be achieved in the closed-loop networked system if the average dwell time (ADT) for switching among different interaction graph candidates is larger than a given positive threshold. By using the boundary layer technique, a continuous feedback protocol is skillfully designed and employed. It is shown that the consensus error converges into a bounded set under the designed continuous protocol. Second, as part of the full states' error can be constructed via the agents' outputs, a reduced-order UIO is thus designed based on which discontinuous and continuous feedback protocols are, respectively, proposed. By using the stability theory of the switched systems, it is proven that the consensus error converges asymptotically to 0 under the designed discontinuous protocol, and converges into a bounded set under the designed continuous protocol. Finally, the obtained theoretical results are validated through simulations.

Multiple fault-based FDI and reconfiguration for aircraft engine sensors

PurposeCondition monitoring and health management of an aircraft engine is of importance due to engine’s critical position in aircraft. Missions require uninterrupted and safer conditions during the flight or taxi operations. Hence, the deviations, abnormal situations or failures have to be under control. This paper aims to propose a cascade connected approach for an aircraft engine fault tolerant control.Design/methodology/approachThe cascade connected structure includes a full-order unknown input observer for fault detection and eliminating the unknown disturbance effect on system, a generalized observer scheme for fault isolation and a Boolean logic mechanism for decision-making in reconfiguration process, respectively. This combination is simulated on a linear turbojet engine model in case of unknown input disturbance and under various sensor failure scenarios.FindingsThe simulation results show that the suggested fault detection isolation reconfiguration (FDIR) approach works effectively for multiple sensor failures with various amplitudes.Originality/valueDifferent from other studies, the proposed model is sensitive to unknown input disturbance and failures that have unknown amplitudes. One another notable feature of suggested FDIR approach is adaptability of structure against multiple sensor failures. Here, it is assumed that only a single fault is to be detected and isolated at a time. The simulation results show that the proposed structure can be suggested for linear models especially for physical redundancy-based real-time applications easily, quickly and effectively.

A new strategy for integration of fault estimation within fault-tolerant control

The problem of active fault tolerant control (FTC) of dynamical systems involves the process of fault detection and isolation/fault estimation (FDI/FE) used to either make a decision as to when and how to change the control, based on FDI or to compensate the fault in the control system via FE. The combination of the decision-making/estimation and control gives rise to a bi-directional uncertainty in which the modelling and fault uncertainties and disturbances all affect the quality and robustness of the FTC system. This leads to the FTC requirement for an integrated design of the FDI/FE and control system reconfiguration. This paper focuses on the FTC approach using FE and fault compensation within the control system in which the design is achieved by integrating together the FE and FTC controller modules. The FE is based on a modified reduced-/full-order unknown input observer and the FTC system is constructed by sliding mode control using state/output feedback. The integrated design is converted into an observer-based robust control problem solved via H∞ optimization with a single-step LMI formulation. The performance effectiveness of the proposed integrated design approach is illustrated through studying the control of an uncertain model of a DC motor.

An Optimal Unknown Input Observer Based Fault Diagnosis Method

摘要: 针对含有未知输入干扰和噪音的不确定动态系统,使用全阶未知输入观测器(Unknown input observer, UIO)来消除干扰项,实现状态估计, 结合Kalman滤波器算法来求解状态反馈矩阵,以使得输出残差信号的协方差最小,从而增强系统对噪声的鲁棒性,实现了 一种基于最优未知输入观测器的残差产生器.采用极大似然比(Generalized likelihood ratio, GLR)的方法对残差信号进行评估,通过设定的阈值来提高诊断率. 最后以风力发电机组传动系统出现加性传感器故障和乘性传感器故障为例, 进行了残差信号的仿真,仿真结果说明了该方法的有效性. 关键词: 故障诊断 / 未知输入观测器 / Kalman滤波器 / 极大似然比

RESIDUAL GENERATOR DESIGN FOR LINEAR NEUTRAL DELAY SYSTEMS

A novel residual generator design for fault diagnosis is proposed for linear neutral delay system with one time-varying delay in the state and output, and one constant delay in the state's derivative. Disturbance and fault are represented as structured unknown inputs in the state equation. The resulting residual generator is in the form of a full-order unknown input observer (UIO) that is exponential stable delay-dependently whose existence and stability conditions are presented. A systematic design method is also provided, which is illustrated by a numerical example.

Unknown input observers designed by eigenstructure assignment

A simple and direct method for full-order unknown input observer design is proposed. The procedure is straightforward and no further complex conditions are needed, provided that the solutions exist. The solutions for the observer matrices and for the eigenvectors are represented in parametric forms. Owing to the parametric forms of the solutions, more properties of the observer such as robustness, eigenvalue sensitivity and minimum gain can be considered. The existence condition of the observer is also established.

Unknown Input Observers Designed by Eigenstructure Assignment

A simple and direct method for full-order unknown input observer design is proposed. The procedure is straightforward and no further complex conditions are needed, provided that the solutions exist. The solutions for the observer matrices and for the eigenvectors are represented in parametric forms. Owing to the parametric forms of the solutions, more properties of the observer such as robustness, eigenvalue sensitivity and minimum gain can be considered. The existence condition of the observer is also established.

Design of unknown input observers and robust fault detection filters

Fault detection filters are a special class of observers that can generate directional residuals for the purpose of fault isolation. This paper proposes a new approach to design robust (in the disturbance de-coupling sense) fault detection filters which ensure that the residual vector, generated by this filter, has both robust and directional properties. This is done by combining the unknown input observer and fault detection filter principles. The paper proposes a new full-order unknown input observer, and gives necessary and sufficient conditions for its existence. After the disturbance de-coupling conditions are satisfied, the remaining design freedom can be used to make the residual have the directional property, based on the fault detection filter principle. A nonlinear jet engine system is used to illustrate the robust fault isolation approach presented. It is shown that linearization errors can be approximately treated as unknown disturbances and be de-coupled in the design of a robust fault detect...