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.     

Robust sliding-mode observer-based multiple-fault diagnosis scheme

In this study, we simultaneously evaluate the multiple-fault diagnosis problem of a class of Lipschitz nonlinear systems with actuator and sensor faults and unknown input disturbances. A nonsingular system transformation is used to transform the original system into two subsystems for multiple-fault diagnosis: subsystems 1 and 2. At the system level, two robust sliding-mode observers (RSMOs) are proposed. An RSMO is designed for subsystem 1 to detect actuator faults subjected to unknown input disturbances, and another RSMO is designed for subsystem 2 to detect sensor faults subjected to actuator faults. At the component level, a bank of RSMOs is proposed to detect and isolate actuators (sensors) with faults using a dedicated observer scheme. The reachability of RSMOs is comprehensively investigated in the estimation error space. Accordingly, the proposed observer parameters are designed as an optimization problem and solved using the linear matrix inequality (LMI) optimization technique. The effectiveness of the proposed multiple-fault diagnosis scheme was validated through simulations of a modified seventh-order aircraft system.     

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.     

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.     

基于相对输出信息的多智能体系统分布式故障检测

针对一类邻居控制信息未知,且节点只能获得相对输出信息的多智能体系统,研究基于未知输入观测器的分布式故障检测问题,以实现节点对自身及邻居故障的实时检测.首先,通过对节点动力学模型进行分解与变换,构造出基于相对输出信息的故障检测参考模型,并给出未知输入观测器的存在性证明;接着,设计不依赖邻居节点控制信息的未知输入观测器,突破控制信息缺失导致观测器失效的理论难题;最后,借助未知输入观测器设计故障检测算法,并完成算法的分布式实现.仿真结果验证了所提方法的有效性与先进性.     

基于观测器的多智能体系统一致性控制与故障检测

针对一类受到未知干扰的非线性多智能体系统,提出了一种鲁棒一致性控制与故障检测算法.首先,针对每个智能体系统设计了一个未知输入非线性观测器.然后,基于观测器的状态估计信息,设计了鲁棒一致性控制协议.控制协议保证了给定的干扰抑制性能指标.接着,考虑智能体出现故障的情形,采用自适应阈值法,提出了一种分布式故障检测算法.最后,以多个直流电机驱动的单摆系统为例进行了仿真实验,仿真结果表明了一致性控制与故障检测算法的有效性.     

Actuator fault detection and isolation in linear systems

A scheme for the detection and isolation of actuator faults in linear systems is proposed. A bank of unknown input observers is constructed to generate residual signals which will deviate in characteristic ways in the presence of actuator faults. Residual signals are unaffected by the unknown inputs acting on the system and this decreases the false alarm and miss probabilities. The results are illustrated through a simulation study of actuator fault detection and isolation in a pilot plant doubleeffect evaporator.     

Intermittent failure detection of multiple electrical connectors in EWIS

Electrical wiring interconnection system (EWIS) of civil aircraft has been paid more attention in recent years, and intermittent failure detection of electrical connectors in EWIS is a challenging problem. This paper presents a sliding mode observer (SMO) approach for the intermittent failure detection of an aircraft electrical system with multiple connector failures. The mathematical model of the aircraft electrical system which contains multiple connector failures is established for transforming the intermittent failure detection problem into observer-based multiplicative faults isolation and estimation problems. A set of adaptive sliding mode observers are designed to locate the failure connectors preliminarily, the observers can adapt the unknown upper bound of the faults. Furthermore, a fault-reconstruction scheme applying the equivalent output error injection principle is proposed for fault estimation, where the characteristic parameters of connecters are reconstructed to identify the failures. Finally, a numerical example is provided to show the effectiveness of the proposed method.     

Fault‐Tolerant Control Allocation for Overactuated Nonlinear Systems

This paper addresses the problem of fault‐tolerant control allocation for input affine nonlinear systems. The proposed scheme is divided in three main tasks: fault detection and estimation using a nonlinear observer, fault isolation through a bank of unknown input observers with a resetting policy to reduce the effects of nonlinearities and control reconfiguration based on reduced order allocation. Analytical results regarding the isolability and reconfigurability of actuator faults are derived and a simulation example is used to illustrate the the proposed fault tolerant control methodology.