Philippe Goupil

Development of an Active Fault-Tolerant Flight Control Strategy

This paper discusses the design of an active fault-tolerant flight control strategy for improvement of the operational control capability of the aircraft system. The research work draws expertise from actions undertaken within the European Flight Mechanics Action Group [FM-AG(16)] on fault-tolerant control, which develops a collaborative effort in Europe to create new fault-tolerant control technologies that significantly advance the goals of the aviation safety. The methodology is applied to a trimmable horizontal stabilizer runaway fault occurring in a large transport aircraft. The goal is to provide a self-repairing capability to enable the pilot to land the aircraft safely. The fault-tolerant control strategy works in such a way that once the fault is detected by the fault detection and isolation unit, a compensation loop is activated for safe recovery. A key feature of the proposed strategy is that the design of the fault-tolerant control loop is done independently of the nominal autopilot and the nominal flight control system in place. Nonlinear simulation results demonstrate the effectiveness of the proposed fault-tolerant control scheme.

A Nonlinear Observer-Based Strategy for Aircraft Oscillatory Failure Detection: A380 Case Study

Robust and early detection of oscillatory failures in the electrical flight control system of an aircraft is a crucial issue. Oscillatory failures, if not detected and passivated in time, can lead to strong interactions with loads and aeroelasticity and may potentially lead to structural damages. A nonlinear observer-based solution to detect such failures with small amplitude at a very early stage is presented. The stability and convergence proofs are given and experimental results with real A380 flight data are presented.

AIRBUS efforts towards advanced real-time Fault Diagnosis and Fault Tolerant Control

Abstract In this article the industrial goals and objectives of the European Framework 7th project termed “REconfiguration of CONtrol in Flight for Integral Global Upset Recovery (RECONFIGURE)” are presented. Commercial aircraft fault tolerant control (FTC) strategies in the flight control system (FCS) are based on fail-safe flight control law reconfiguration which relies on upstream hardware redundancy-based robust Fault Detection and Diagnosis (FDD). This industrial state-of-practice fits well in the current certification process but it also decreases the easiness of the piloting task as soon as the system level of degradation increases. Thus, the main goal of RECONFIGURE is to research and develop aircraft FDD and FTC technologies that facilitate the automated handling of off-nominal/abnormal events and optimize the aircraft status and flight. The article details the project description of work, from industrial benchmark (fault scenarios and aircraft model) up to industrial verification and validation (V&V) activities, via advanced FDD/FTC research and development. The expected results and perspectives are also presented.

Industrial benchmarking and evaluation of ADDSAFE FDD designs

Abstract In this article the industrial benchmarking and validation process used within a European Framework 7 th project termed “Advanced Fault Diagnosis for Sustainable Flight Guidance and Control (ADDSAFE)” is presented. This process is used with two main goals: (i) benchmark the Fault Detection and Diagnosis (FDD) designs developed within the first phase of the project, (ii) demonstrate the applicability of the proposed FDD techniques in a standardized industrial validation process in order to successfully transfer these techniques to the aeronautics practitioners. The article details the software tools, test-bench facilities, validation process and a summary of the application of the process to the developed ADDSAFE FDD designs.

Model-Based Approaches for Fast and Robust Fault Detection in an Aircraft Control Surface Servo Loop: From Theory to Flight Tests [Applications of Control]

Many innovative solutions have been developed by the aeronautical sector toward achieving the future sustainable aircraft that will be cleaner, quieter, smarter, and more affordable. Weight reduction is one of the most significant contributors to sustainability, as it improves aircraft performance (fuel consumption, noise, range) and consequently decreases its environmental footprint. This article deals with two challenging electrical flight control system (EFCS) failure cases, which may affect structural loading. A simple model-based approach is presented for the robust and rapid detection of such failures. The techniques were tested and validated at the Airbus test facility, and real flight tests have confirmed that a high level of performance and robustness can be obtained.

AIRBUS State of the Art and Practices on FDI and FTC

Abstract This paper deals with industrial practices and strategies for Fault Tolerant Control (FTC) and Fault Detection and Isolation (FDI) in aircraft by focusing mainly on a typical Airbus Electrical Flight Control System (EFCS). This system is a safety-critical one in the sense that catastrophic consequences may result from its failures. It is designed to meet very stringent requirements in terms of safety, availability and reliability that characterized the system dependability. Fault tolerance is designed into the system by the use of stringent processes and rules, which are summarized in the paper. The strategy for monitoring (fault detection) of the system components, as a part of the design for fault tolerance, is also described in this paper. Real application examples and implementation methodology are outlined. Finally, future trends and challenges are presented.

Nonlinear Observer-Based OFC Detection for A380 Aircraft

Abstract In this paper, we address the problem of Oscillatory failure Case (OFC) detection in A380 aircraft. The importance of OFC detection is well known in the literature because of natural mode excitation and the structural loads they can provoke. A novel nonlinear observer-based approach, which has two different gains is proposed in this paper to solve the problem. The main advantage of the proposed residual generator is that, by an adequate selection of observer gains, the residual generator has a kind selective (frequency dependent) attenuation property: disturbances and unmodelled dynamics effects on the residual are reduced while the effect of the fault is slightly amplified in a specific fault frequency range. Further, if the gains are chosen to be zero, the particular case of the technique implemented on A380 Airbus is obtained. A test based on real measurements of an A380 airplane is presented to show the efficiency of the proposed residual over the existing techniques.

Oscillatory Failure Case detection for new generation Airbus aircraft: A model-based challenge

Robust and early detection of Oscillatory Failure Case (OFC) in the Electrical Flight Control System (EFCS) of new generation aircraft (A/C) appears to be a challenging problem. OFC leads to strong interactions with loads and aero-elasticity and consequently must be detected in time. A robust analytical redundancy-based technique implemented in A380 Flight Control Computer (FCC) is used for detecting such unauthorized oscillatory events. The technique has been successfully validated and provides a complete OFC coverage without false alarms in the A380 EFCS. However, for upcoming and future generation A/C, it could be required to detect OFC with less important amplitude. To meet this requirement, it becomes necessary to get more sensitive fault indicating signals. It is shown that the model quality can be significantly improved by reliable estimating of some physical parameters. The fault indicating signals obtained with the proposed methodology are compared to those obtained from A380 FCC during flight tests. The results are quite encouraging and suggest that OFC with less important amplitude could be successfully detected by the new strategy.

Robust and Early Detection of Oscillatory Failure Case for New Generation Airbus Aircraft

This paper addresses the problem of Oscillatory Failure Case (OFC) detection in the Electrical Flight Control System (EFCS) of the Airbus airplanes. The work describes the status of on going research activity undertaken within a collaborative project between Bordeaux University (France) and Airbus. A hydraulic actuator model is presented, which is currently used as the basis for a robust analytical redundancy-based technique implemented in A380 Flight Control Computer (FCC) for detecting unauthorized oscillatory events. The technique has been successfully validated and provides a complete OFC coverage without false alarms in the A380 EFCS. In the context of aircraft overall optimization, for upcoming and future programs, a need has emerged recently to improve the detection performance in case of less important amplitude OFC that may occur in the servo control loops of actuators. To meet this requirement, it becomes necessary to model more efficiently the dynamical behavior of actuators to get more sensitive fault indicating signals. It is shown that the model quality can be significantly improved by reliable estimating of some physical parameters. The fault indicating signals are compared to those obtained from A380 computers during flight tests. The results are quite encouraging and suggest that OFC with less important amplitude could be successfully detected by the new strategy.

A Model-based Solution to Robust and Early Detection of Control Surface Runaways

This paper discusses the design of a model-based fault detection scheme for robust and early detection of runaways in aircraft control surfaces servo-loop. The proposed scheme can be embedded within the structure of in-service monitoring systems as a part of the Flight Control Computer (FCC) software. The final goal is to contribute to improve the performance detection of unanticipated runaway faulty profiles having very different dynamic behaviors, while retaining a perfect robustness. The paper discusses also the tradeoffs between adequacy of the technique and its implementation level, industrial validation process with Engineering support tools, as well as the tuning aspects. The proposed methodology is based on a combined data-driven and system-based approach using a dedicated Kalman filtering. The technique provides an effective method ensuring robustness and good performance (well-defined real-time characteristics and well-defined error rates). Simulation results, using In-flight recorded data sets provided by Airbus, are presented to demonstrate the potential of the developed technique.