Oscillatory Failure Case Detection Research Articles

An Approach to Oscillatory Failure Case Detection in the Aerospace Industrial Benchmark

This paper proposes an approach to detect the oscillatory failure case (OFC) and reconfigure the flight control law after the OFC detection in the Aerospace Industrial Benchmark. To cope with system nonlinearity, a square root unscented Kalman filter is utilized to generate the residual signal. An estimation of the parameter uncertainty based on the fault-free data is incorporated to reduce the influence of model uncertainty on the residual signal significantly. To evaluate the residual signal, a modified integral absolute error based index is introduced along side a check of the oscillation regularity. Our approach is capable of detecting OFCs with very low amplitudes within at most 3 oscillation periods without producing any false alarm, regardless of load factor command, turbulence level or OFC location, type and frequency. The minimum detectable OFC amplitude is 0.6 mm and 0.9 mA for liquid OFCs located at sensor signal and current input signal, respectively, and 0 mm and 0.9 mA for solid OFCs.

Oscillatory Failure Case detection in flight control systems via wavelets decomposition

A fault detection design is proposed for addressing the Oscillatory Failure Case (OFC) detection problem, introduced in the joint Airbus-Stellenbosch university aerospace industrial-benchmark competition called at the IFAC 2020 World Congress11https://www.ifac2020.org/program/competitions/aerospace-industrial-fault-detection.. The detection scheme is comprised of an output estimator, a wavelet decomposition and an energy-based denoising method, and the residual evaluation unit. The detection problem of wide frequency range OFCs is also addressed. According to the achieved simulation results, the proposed fault detection method is able to satisfy the competition prescriptions in the frequency range [1 10] Hz for those OFC’s having an amplitude greater than 2.3 mm for OFCs at rod position sensor, or 1.4 mA for OFCs at servo input current, regardless of disturbances level, uncertainties and load factor control input. In other cases, faults are detected slightly after the prescribed detection limit, with some interesting exceptions.

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.

From theory to flight tests: Airbus Flight Control System TRL5 achievements

In this article, concrete aerospace industrial achievements corresponding to a level 5 on the Technological Readiness Level (TRL) scale are presented. Starting from basic research levels up to industrial validation, it is shown how it is possible to bridge the gap between advanced methods advocated by the academia and the more and more demanding industrial needs. To illustrate this position, a focus is made on real-time on-board Fault Detection and Diagnosis (FDD) for the upcoming and future innovative Flight Control System (FCS) of civil aircraft. This is exemplified by three concrete cases presenting the research and development process, from theory up to simulator and flight tests: 1) detection of Oscillatory Failure Cases in FCS thanks to a derivative-free variant of an extended Kalman filter; 2) detection of control surface lock-in-place failure (a.k.a. jamming) via recursive parametric modeling; 3) flight parameter Data Fusion with dedicated fuzzy logic.

Second order sliding mode observers for the ADDSAFE actuator benchmark problem

This paper presents the evaluation process and results associated with two different fault detection and diagnosis (FDD) schemes applied to two different aircraft actuator fault benchmark problems. Although the schemes are different and bespoke for the problem being addressed, both are based on the concept of a second order sliding mode. Furthermore both designs are considered as ‘local’ in the sense that a localized actuator model is used together with local sensor measurements. The schemes do not involve the global aircraft equations of motion, and therefore have low order. The first FDD scheme is associated with the detection of oscillatory failure cases (OFC), while the second scheme is aimed at the detection of actuator jams/runaways. For the OFC benchmark problem, the idea is to estimate the OFC using a mathematical model of the actuator in which the rod speed is estimated using an adaptive second order exact differentiator. For the jam/runaway actuator benchmark problem, a more classical sliding mode observer based FDD scheme is considered in which the fault reconstruction is obtained from the equivalent output error injection signals associated with a second order sliding mode structure. The results presented in this paper summarize the design process from tuning, testing and finally industrial evaluation as part of the ADDSAFE project.

New sequential probability ratio test: Validation on A380 flight data

A new residual analysis approach is proposed in order to improve fault detection performance and robustness. The proposed methodology is based on the Wald's sequential test which assumes that residual signal distribution is Gaussian. The new sequential test overcomes this limitation and allows handling a signal with a Laplace distribution. The proposed approach is applied to the detection of oscillatory failure cases on Airbus A380 elevator actuator. The sequential test is assessed on flight data supplied by Airbus. First results are promising as there is already a noticeable improvement over results obtained with the industrial state-of-practice technique implemented on A380.

LPV-model based identification approach of oscillatory failure cases

The reliable early detection of oscillatory failure cases (OFC) for modern fly-by-wire controlled civil aircraft is an important aspect in optimizing the structural design objectives for reducing the environmental footprint of the aircraft. We propose a complete methodology for the design of a model based fault detection and diagnosis (FDD) system, which allows the reliable early detection of OFC characterized by low amplitude oscillations in a given frequency range. The main factors for the achieved enhanced performance are: the accurate modelling of the surface actuator via linear parameter-varying (LPV) models, an improved oscillation detection by employing the recursive discrete Fourier transform, and the integrated tuning of the free parameters of the FDD system using multi-objective optimization techniques.

Sequential probability ratio test using first Laplace distribution for oscillatory fault detection of an hydraulic actuator

AbstractThis paper proposes a sequential test for fault detection in the case of Laplace distribution of residual. This approach is adapted from Wald's sequential test and the paper establishes specific test thresholds for Laplace distributions. The suggested algorithm is applied to the detection of oscillatory failure cases on an Airbus A380 elevator actuator characterized by Laplacian distribution of residual. Moreover the proposed application shows that computing workload resulting from the proposed sequential test is similar to the classical Wald test.

Oscillatory failure case detection in the A380 electrical flight control system by analytical redundancy

This paper focuses on failure detection in the electrical flight control system of Airbus aircraft. Fault tolerance is designed into the system by the use of stringent processes and rules, which are summarized below. Monitoring of the system components is part of this fault-tolerant design. This paper covers the particular case of oscillatory failure monitoring in the electrical flight control system. The main characteristics and consequences of these failures are presented. The detection of oscillatory failures on the A380 is considered, together with the concept of analytical redundancy to detect these failures. A nonlinear actuator model is used to generate a residual on which the failure is detected by oscillation counting. Real application and benefits of the overall method are also presented. The results are highly satisfactory and the overall method is currently implemented on A380 flight control computers.