Anne-Lise Gehin

From control to supervision

Abstract This paper is concerned with the terminology and fundamental problems of FTC and supervision. Based on the idea that at any level, engineers are concerned with the control (or at least the mastering) of a (healthy or faulty) system, successive extensions of the Standard Control Problem (SCP) are proposed in order to provide a clear definition of Fault tolerance and Supervision problems.

Structural Analysis of System Reconfigurability

Abstract We present a graphic approach to the analysis of system reconfigurability. The system is described by its structural graph. We define the set of causal matchings, and associate a causal graph with a causal matching. Structural system properties such as observability and controllability are shown to be exhibited through the analysis of the causal graph. The system reconfigurability is a consequence of its conditional controllability with respect to some failure events.

Signed Bond Graph for multiple faults diagnosis

Different approaches have been developed to perform diagnosis and supervision on continuous systems. On the one hand, Consistency-Based Diagnosis (CBD) as a qualitative approach has proved its convenience to diagnose multiple faults. However, it faces some problems regarding robustness in decision step and difficulties to obtain an accurate qualitative model. On the other hand, the quantitative approaches based Fault Detection and Isolation (FDI) enable to generate a set of fault indicators called residuals in order to carry out on-line diagnosis. The performances of such methods depend mainly on the behavioural model accuracy and their implementation is sometimes difficult to realise, especially when the possibility of multiple faults is taken into account. To overcome the drawbacks of such methods and to fully exploit their strengths, we give a formal description of a graphical model called Signed Bond Graph (SBG). This formalism exploits its qualitative and quantitative structural properties enabling the generation of multiple behaviour predictions (i.e. possible conflicts). Furthermore, since the SBG is constructed from the Bond Graph (BG) model, the use of this latter as a quantitative method for residuals generation allows to compare the results emanating from the qualitative reasoning based SBG in order to eliminate the possible conflicts which are inconsistent or not physically possible even though they sound logical from a qualitative point of view. The proposed approach is illustrated by a real application to a traction system of an intelligent and autonomous vehicle performed within the European project InTraDE. The result shows its good applicability and efficiency.

Functional and Behavior Models for the Supervision of an Intelligent and Autonomous System

The graphical approaches often have different backgrounds and view a system or an algebraic model from different perspectives in order to facilitate the communication and the understanding. These graphical approaches satisfy the modeling needs and give a clear and easily understandable overview of the behavioral and functional models and make easier to see what the process is, which vulnerabilities and asset that are involved and how the system works. The main goal of this paper is to develop and implement a methodology which combines the functional analysis and the bond graph (BG) tool for intelligent and autonomous systems. As a result, a supervisory interface is obtained, given under a finite automaton, displaying to the operators the possibilities the system has to achieve or not, its objectives. Each operating mode, corresponding to a vertex of the automaton, is associated with a set of services from a functional point-of-view and is defined accurately by a behavioral BG model. Furthermore, the service availability (associated to the BG elements) and the conditions for switching from one mode to another one are analyzed by fault detection and isolation algorithms generated on the basis of the structural and causal properties of the BG tool. Moreover, when a fault is not completely isolable some results can nevertheless be expressed in terms of available or unavailable services.

A formal framework of reconfigurable control based on model checking

This paper proposes a formal framework for reconfigurable control, based on model checking. This framework first generates a flexible model (i.e., an execution structure) according to the diagnosis, then defines a temporal specification language to deal with the problems due to infinite execution cycles and non-determinism, and finally provides the algorithms that will automatically verify whether the updated model satisfies the desired specification.

Fault Detection and Isolation and Mode Management in Smart Actuators

Abstract This paper presents the generic functional architecture of a smart actuator. It mainly addresses the decomposition level relative to Fault Diagnosis and Isolation and details the mode management module.

An extended qualitative multi-faults diagnosis from first principles I: Theory and modelling

This paper is part I of a two part effort that is intended to present a framework of multi-faults diagnosis. Reiter [14] has proposed a consistency-based approach for multi-faults diagnosis. We extend his theory to deal with the dynamic and continuous systems and offer a necessary assumption and a formal demonstration. Multi-faults diagnosis is a partially observable problem because there is usually not enough information about faults. So the STRIPS, a classic technique of automated planning, is chosen to build the system model. It provides the reasoning ability for the multi-faults diagnosis when diagnosis is formalized as reasoning from effects to causes with causal knowledge.

An extended qualitative multi-faults diagnosis from first principles II: Algorithm and case study

This paper continues to present the framework of multi-faults diagnosis from the preceding paper. There are two main contributions in this part. One is aimed at developing a new diagnostic process for continuous and dynamic system and its corresponding consistency-checking module. This diagnostic process and its consistency-checking module are all based on the models defined by STRIPS actions. The other is that the fault models are introduced into the consistency-checking module for preventing the impossible diagnoses. Moreover, the STRIPS can qualitatively define the fault models without requiring detail and precise knowledge about faulty components.

Model Aggregation for Reconfigurable Control Based on Generic Component Model

In this paper, we propose an approach based on generic component model to realize the model aggregation for reconfigurable control. This is a component-oriented method. Two elementary notions, the service and the operating mode, are introduced to construct a hierarchical system and to assure the coherences between specification and realization at each level and between levels. The consideration of aggregated, complex components leads to extend this description to the possibilities of reconfiguration

Faulty resources management in automation systems

An automation system provides services to users. For this, hardware resources are required and data are processed. Fault detection and isolation algorithms allow to detect faulty resources and nonsignificant data. The results of these algorithms are used by the operators and by the automation system in order to increase its robustness and its operational safety. The robustness is obtained by the implementation of several versions of the procedures which perform a given service and the operational safety is obtained by the structuration of the set of services into coherent subsets.