Jérôme Cieslak

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.

Output tracking of systems subjected to perturbations and a class of actuator faults based on HOSM observation and identification

This paper deals with the output tracking problem of a MIMO system subjected to a class of actuator faults and unmatched perturbations. The proposed methodology is based on high order sliding mode observation and identification techniques. A dynamic sliding surface is proposed using a backstepping-like design strategy in order to counteract the effects of the unmatched perturbations. Whereas a continuous sliding mode control is designed to steer the states toward the sliding surface. The identified value of the fault is injected to alleviate the control gain while accomplishing fault accommodation. As a consequence, the chattering is attenuated. A simulation example for a 3-DOF helicopter highlights the efficiency of the present method.

Actuator fault detection in aircraft systems: Oscillatory Failure Case study

This paper is devoted to the detection of Oscillatory Failure Case (OFC) in the Electrical Flight Control System (EFCS). Such failures lead to a strong interaction between loads and aeroelasticity and must be quickly detected and passivated. This paper proposes a hybrid monitoring scheme for robust and early detection of such unauthorized oscillatory events. The proposed technique has been developed within ADDSAFE project (a collaborative project supported by the European Seventh Framework Program: Advanced Fault Diagnosis for Sustainable Flight Guidance and Control, http://addsafe.deimos-space.com). A robust finite-time differentiator is used to estimate derivatives in a noisy environment. Fault reconstruction is next achieved by solving on-line a nonlinear equation using a gradient descent method. Finally, fault detection and confirmation stage is based on the decision making rules currently used for in-service Airbus A380 airplane. Robustness and performance of the proposed fault detection scheme are tested using a high fidelity benchmark and intensive Monte Carlo simulations for several flight scenarios as specified within ADDSAFE project.

Fault detection and isolation for redundant aircraft sensors

A method for failure detection and isolation for redundant aircraft sensors is presented. The outputs of the concerned sensors are involved in the computation of flight law controls, and the objective is to eliminate any perturbation before propagation in the control loop when selecting a unique flight parameter among a set (generally 3) of redundant measurements. The particular case of an oscillatory failure is investigated. The proposed method allows an accurate fault detection and isolation of erroneous sensor and computes a consolidated parameter based on the fusion of data from remaining valid sensors. The benefits of the presented method are to enhance the data fusion process with FDI techniques which improves the performance of the fusion when only few sources (less than three) are valid.

Design of a non-homogeneous differentiator for actuator oscillatory failure case reconstruction in noisy environment

This work addresses the problem of oscillatory failure case detection in the electrical flight control system of a generic commercial airplane. A non-homogeneous differentiator is first used to provide accurate derivatives in noisy environment and fast convergence time. In this study case, fault detection is addressed in the unknown input estimation issue for fault reconstruction with the same evaluation techniques currently employed in Airbus A380 airplanes. Based on the non-homogeneous differentiator theory, an algorithm for differentiator tuning is provided to manage a trade-off between the accuracy of fault reconstruction and the convergence time that is compliant with specified detection time requirements. Performance and robustness of the developed monitoring strategy are assessed using a high-fidelity Airbus benchmark and a parametric test campaign for the flight scenarios defined in the EU-FP7 ADDSAFE project.

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.

Adaptive second-order sliding mode observer for quadrotor attitude estimation

The problem studied in this paper is that of quadrotor attitude estimation using an adaptive second-order sliding mode (SM) observer. The gains are dynamically adapted to the sliding motion to ensure the convergence of observer error to the sliding manifold in the finite time. Position measurements of quadrotor are used in this adaptive SM observer to provide the pitch and roll angle estimates that are robust to the accelerometer and/or gyroscope faults. In addition, the observer is extended for the case where position measurements are corrupted by bias and noise. Simulation results illustrate the benefits of the proposed techniques compared to kalman and complementary filter.

Design of Fault Tolerant Control Systems: a Flight Simulator Experiment

Abstract This paper discusses a method for developing fault tolerant flight control systems. The ultimate goal is to increase aircraft safety and autonomy. The research work draws expertise from actions undertaken within European Flight Mechanics Action Group (FM-AG(16)) on Fault Tolerant Control (FTC), which develops a collaborative effort in Europe to create new FTC technologies that significantly advance the goals of the aviation safety. The methodology is developed within the H∞ setting and is applied to a Trimmable Horizontal Stabilizer (THS) runaway fault. Fault compensability properties are discussed and in order to show the efficiency of the proposed method, a flight test campaign which was carried out within the FM-AG(16) project is presented. A key feature of the proposed strategy is that the design of the fault tolerant control loop is done without removing the validated and certified nominal flight control system (FCS).

Coupling-Characterization-Based Robust Attitude Control Scheme for Hypersonic Vehicles

The issue of couplings makes the attitude control design for hypersonic vehicles (HSVs) challenging. This paper focuses on the characterization of coupling and its application in the control system synthesis. A novel coupling characterization index is introduced via the Lyapunov stability theory to indicate whether a coupling harms or benefits the system. The control scheme is designed to eliminate the detrimental couplings while keeping the beneficial couplings. The novelty of this paper is that the system couplings are explicitly utilized in the controller design leading to better dynamic performance. The robustness of the proposed controller is enhanced by using a disturbance observer. The effectiveness of the proposed scheme is validated by simulations in the HSV attitude system.

Supervisory fault tolerant control via common lyapunov function approach

The problem of active fault tolerant control (FTC) design with reconfiguration mechanism for linear systems with external disturbances is addressed. The solution is based on the supervisory control approach. Starting from the well known in FTC literature conditions for independent design of fault detection, isolation and fault compensation systems we propose new set of united conditions and the computational procedure providing mutual performance of the system. The efficiency of the approach is demonstrated on a flight system benchmark example.