FDI System Research Articles

ADVANTAGES OF USING μ-SYNTHESIS FOR FAULT-TOLERANT FLIGHT CONTROL SYSTEM

In the framework of FTFCS, an integration of a controller with an FDI system takes place. The integrated system is supposed to possess the required stability and performance robustness. The synthesis methods differ in handling this requirement. The main theme of this work is to show the advantages of using μ-synthesis over H∞ mixed-sensitivity in designing controllers in the framework of FTFCS with better performance and stability robustness margins. This has been tested for BEll-205 Helicopter using desktop simulations.

ON OBSERVER-BASED FAULT DETECTION AND ISOLATION FOR CONTINUOUS LINEAR DESCRIPTOR SYSTEMS 1

Conditions for existence of observer-based faults detection and isolation systems for continuous linear descriptor systems are presented. These conditions are associated, in a first phase, to the solution of a generalized Sylvester equation and, in a second phase, to the solution of a Sylvester equation under a constraint that describes the faults decoupling of the corresponding estimation error. Two observer structures are used to residual generation and faults reconstruction/isolation, respectively. The proposed results put in evidence some degrees of freedom that can be used for design purposes. Thus, an eigenstructure assignment algorithm to design the FDI system and a illustrative example are presented.

회전익 무인기의 고장진단 및 다중화관리 연구 동향

회전익 무인기의 고장진단 및 다중화관리 연구 동향

A mixed direct/functional redundancy scheme for the FDI on a small commercial aircraft

In this paper we consider the problem of detecting and isolating sensor faults on an aircraft in the presence of external disturbances. A nonlinear observer based approach is proposed which makes use of the complete nonlinear model of the aircraft. This approach exploits the so-called Unknown Input Observer (UIO) theory and guarantees disturbance decoupling with an H∞ performance. A comparison between the application of the classical UIO based FDI scheme and the proposed nonlinear scheme shows the benefits of the approach provided in this paper. Finally we exploit the nonlinear UIO technique to design a mixed hardware/software FDI system to improve the performance of the classical hardware system without the replication of expensive sensors. Some numerical simulations are carried out on the model of the small commercial aircraft under consideration in the project Affordable Digital Fly-By-Wire Flight Control System (ADFCS-II) funded by the European Community.

Fault Detection and Isolation on a System of Heat Exchangers

This study aims at designing a Fault Detection and Isolation system for several interconnected heat exchangers. Since this kind of process is modelled by polynomial equations, this paper shows how the algebra of polynomial rings can mathematically support the FDI system design. The basic principles of FDI extract, from the model, some fault indicators, called residuals, that can be computed from available information. Then, to analytically get these polynomial residuals, we propose a procedure based on the algebraic approach of Elimination Theory. Groebner bases are used to perform the symbolic computation and a structural pre treatment is proposed to handle large systems of equations. Finally these ideas are applied to a system of heat exchangers.

An investigation into the use of the FDI tooth notation system by dental schools in the UK.

This study investigated the use of the FDI tooth notation system in UK dental schools. In addition, the notation system used by dentists referring patients to Manchester Dental Hospital was recorded. A questionnaire was sent to the Deans of all Dental Schools in the UK and letters of referral to Manchester Dental Hospitals Paediatric GA Service were monitored for 1 month. The results showed that only Manchester University Dental School used the FDI system but 6 other schools instructed students in its use. The Palmer system was used by all the other schools for recording clinical information. 136 referral letters were received, only one used the FDI notation, 15 used both FDI and Palmer and the remainder (120) requested extractions using the Palmer notation. The FDI notation system is not used in the majority of UK dental schools. Despite the fact the Dental School in Manchester has been teaching and using the FDI system for over 10 years, it has not been adopted by General Dental Practitioners referring patients into the hospital. The FDI should review the use of their system in other countries, to ascertain whether it has fulfilled its role as an international notation system.

Controller Reconfiguration System Using Parity Equations and Fuzzy Logic

Abstract This paper describes the reconfiguration of a fuzzy controller based on a Fault Detection and Isolation system that uses input-output parity equations as a residual generator. The FDI system uses fuzzy logic in the residual evaluation and in the diagnosis step. An estimation of the size of the fault is made using the value of the residuals and their sensitivity respect the different faults. The result is the failure isolation, with the estimation of its possibility and its size. The accommodation is made using these results and information in the fuzzy rules of the controller. First the FDI system is described and then the method of accommodation is applied to a laboratory plant DC motor that presents sensor and actuator faults.

Design of a Complete FDI System Based on a Performance Index with Application to an Automotive Engine

Assuming residual generators are already available, there are still several choices to be made when a complete FDI system is to be designed. This is a time consuming engineering work so for this purpose, a systematic procedure is proposed. The procedure is phrased as an optimization problem. The goal is to minimize a new probability based performance index, which is derived from measurements on the real process. To increase the robustness of the FDI system, a don't care option is introduced in the residual structure. The procedure is successfully applied to the problem of FDI design for the air intake system of an SI-engine.

On the Application of the Generalised Structured Singular Value to Robust FDI System Design

The generalised structured singular value has proven to be very useful for solving the model validation problem within the robust control framework, This paper considers its application to the design of robust model-based fault diagnosis systems, Three different fields of use are addressed, starting with the determination of model uncertainty, which is of crucial importance for all model-based fault diagnoses, Second, frequency domain model validation is directly used for robust fault detection and isolation, Fault diagnosis for an aircraft actuator is presented as an illustrative application example, Finally, a new idea towards a compact formulation of the FDI optimisation problem, based on the generalised structured singular value, is introduced.

FDI with Adaptive Residual Generation Applied to a DC-Servo

When parity equations are designed ad hoc., the low frequency gain of the fault-to-residual transfer function can become low or even zero which is highly undesirable. As a solution, a systematic design procedure, utilizing the freedom available in residual generator design, is proposed. The method is called residual shaping and guarantees reasonable performance. It is used together with RLS to form an adaptive residual generator, which is important to handle e.g. aging. The RLS algorithm also makes it possible to differentiate between additive and multiplicative faults. The proposed FDI system is evaluated on a DC-servo where the strengths of the system is illustrated.

Improving the observer-based FDI design for efficient fault isolation

A bank of observers is usually needed to detect and isolate faults (FDI) with robust observer-based approaches. In order to improve the real-time property of the FDI system, the total order of the observers should be designed as small as possible. In this paper, two means that contribute to the reduction of the observer orders are studied. First of all, an approach to the design of minimal order robust FDI observers for given fault sensitivity conditions is developed. The minimal observer order is revealed as a function of a minimal row index of a matrix pencil deduced from known system matrices. Then, the possibility and approach of realizing multiple fault sensitivity conditions with a single robust FDI observer is addressed. A sufficient condition is obtained. The decision logic design is also studied in this paper. A sequential decision logic is proposed, which can be applied to time critical situations where running all the FDI observers in real time is not possible. By revisiting an example taken from literature, the advantages of the presented techniques are illustrated.

Fault Detection and Isolation Sytem Design for a Refinery Unit

This paper presents a Fault Detection and Isolation system developped for ELF France. ELF France has been using data reconciliation to settle the global performances of a refinery unit. It was interested by using a supervision system in order to validate the data provided by sensors before using them. The application and its interest are first presented. Then the design of the FDI system is described and illustrated by an example. We focuse on the detection and isolation stages which are rarely treated in the classical approaches. The results are presented in the last part, by giving the global performances obtained with actual plant data.