Font Size: a A A

Study On Schemes Of Fault Detection And Diagnosis & Fault Tolerant Control

Posted on:2005-04-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:D J WangFull Text:PDF
GTID:1118360152956695Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
Modern control systems trend to be more scaled and more complicated with development of science and technology and requirements of practical application. It will result in seriously damage to operators or machines in presence of faults in such systems. Strong reliability and security mean that the safety of operators and more profits can be guaranteed. Fault tolerant control (FTC) schemes compensate influence of faults automatically in presence of faults such that stability can be guaranteed and dynamic performance can be recovered as possible in the post-fault systems, and the systems run stable. Hence, FTC schemes provide new ways to improve the reliability and security of complex systems. Fault Detection and Diagnosis (FDD) technology is one of main technologies to support FTC, which has been developed for many years as one branch of control theory. The task of FDD is to describe characteristic of faults first, and to detect and isolate faults occurring in systems, subsequently. For better fault tolerance, efficient FDD scheme are necessary to provide more information on faults to implement FTC task.It is necessary that redundancy exist in systems for fault tolerance. Namely, There exists the actuation redundancy for actuator fault tolerance, exists measurement redundancy for sensor fault tolerant. The task of FTC systems design is how to such redundancy. Generally speaking, depending on how redundancy is being utilized, fault tolerant control systems can be categorized into passive and active types. In passive fault tolerant control, potential system component faults are known a priori and are all taken into consideration in the control system design stage. In contrast, active fault tolerant control systems rely on an adaptive algorithm to tracking faults or a Fault Detection and Isolation (FDI) scheme to detect the occurrence of faults in the system to obtain information on the faults, such as the source and seriousness of the faults. Based on the FDI information, a fault accommodation scheme can then be designed to maintain a certain degree of control performance of the post-fault system. Generally, passive and active fault tolerant control systems depend on system models-quantitative, qualitative or quasi- quantitative. Model based FTC schemes attract much interest to this day. In present, non-model-based FTC methods are also becoming hot, in which intelligent schemes are used for fault tolerance of non-linear systems. The non-model based FTC schemes are not interfered in this thesis.Actuators are subject to be in presence of faults for consisting operation. Fault tolerance for actuators should be considered more carefully. Originally, FTC is used in aerospace field, such as reliable flights control, etc. And gradually, its application is enlarged into other fields, for example, industry process control, which is significant. In early days, the faulty actuators are thrown off ignoring their remaining actuation and only healthy actuators are used for fault tolerance, which is not always brain way. Because it will reduce design freedoms and system driving power ignoring the remaining actuation in faulty actuators. And if possible, the remaining actuations should be used for fault tolerance via actuation reconfiguration.In this thesis, the designs of FDD and FTC scheme are presented with consideration of linear systems. And some researches hot are investigated carefully. This thesis is organized as follows, in which the main research works are included. 1. A tutorial of FDD and FTC schemes is presented. And some research interest is pointed out. Furthermore, some foundations in FTC systems, such as fault models, redundancy, control task, etc, are described.2. Taking the condition numbers of systems as robustness index, robust eigenstrucure assignment algorithm is utilized for passive FTC system design. Sufficient conditions, of which the robustness for system parameter perturbations is optimized, are derived. And the corresponding controller design is presented. And using the proposed method,...
Keywords/Search Tags:Fault tolerant control, Fault detection and diagnosis, Effectiveness factor, Control reconfiguration, Actuation reconfiguration, Adaptive reconfigurable control, Interconnected system
PDF Full Text Request
Related items