Andres Marcos

Fault reconstruction using a LPV sliding mode observer for a class of LPV systems

Abstract This paper proposes a new sliding mode observer for fault reconstruction, applicable for a class of linear parameter varying (LPV) systems. Observer schemes for actuator and sensor fault reconstruction are presented. For the actuator fault reconstruction scheme, a virtual system comprising the system matrix and a fixed input distribution matrix is used for the design of the observer. The fixed input distribution matrix is instrumental in simplifying the synthesis procedure to create the observer gains to ensure a stable closed-loop reduced order sliding motion. The ‘output error injection signals’ from the observer are used as the basis for reconstructing the fault signals. For the sensor fault observer design, augmenting the LPV system with a filtered version of the faulty measurements allows the sensor fault reconstruction problem to be posed as an actuator fault reconstruction scenario. Simulation tests based on a high-fidelity nonlinear model of a transport aircraft have been used to demonstrate the proposed actuator and sensor FDI schemes. The simulation results show their efficacy.

Linear parameter-varying detection filter design for a boeing 747-100/200 aircraft

We present a fault detection and isolation (FDI) filter design using a linear parameter-varying (LPV) model of the longitudinal dynamics of a Boeing 747 series 100/200. The LPV FDI filter design is based on an extension of the fundamental problem of residual generation concepts elaborated for linear, time-invariant systems. Typically, the FDI filters are designed for open-loop models, and applied in closed loop. An application is shown of an LPV FDI filter for actuator failure detection and isolation in the closed-loop longitudinal LPV system to the full nonlinear Boeing 747 aircraft simulation, which represents the “true” system.

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.

An Architecture for Design and Analysis of High-Performance Robust Antiwindup Compensators

In this note, a general framework for the design and analysis of high-performance robust antiwindup (AW) compensators is presented. The proposed framework combines the Weston-Postlethwaite AW scheme with ideas from residual generation and from robust control architectures based on high-performance nominal controllers. It is shown that the framework is well connected to the Youla controller parameterization and to fault tolerant/detection schemes. Furthermore, the proposed framework provides a transparent analysis of the interactions between the different design parameters which allows for a clearer design tradeoff between robust stability and robust performance for the saturated and unsaturated closed loops.

FDI for a Mars orbiting satellite based on a sliding mode observer scheme

In this paper the design of sliding mode observers for gyro and thruster fault detection and isolation in the Mars Express satellite is presented. The results are part of a project with the goal of examining the potential applicability of the sliding mode observer technique to on-board satellite deployment. A Monte Carlo campaign has been performed to assess the performance and robustness of the sliding mode FDI observers for the rigid satellite model with variations in initial conditions and parametric uncertainty. The results indicate that the observers provide good potential to isolate gyro and thruster faults. No effort were made at this stage to implement a threshold logic, but preliminary implementations are promising.

Gain-Scheduled FDI for a Re-entry Vehicle

This paper presents the design of a gain scheduled fault detection and isolation (FDI) filter for the Hopper reusable launch vehicle (RLV). The fault scenario is that of faults in the vehicles rudder actuator and sideslip sensor during a focused 90 second period of the re- entry. Both of the considered faults strongly affect the lateral response of the vehicle, making simultaneous FDI difficult. A dynamically stable model of the Hopper RLV is considered and FDI filter design is performed on linearised models of the vehicle trimmed about the re- entry trajectory. H-infinity theory is employed for the FDI filter synthesis, with a set of LTI FDI filters designed at the trim points and then scheduled to form the gain scheduled FDI filter. The effectiveness of the LTI point-design filters and the gain-scheduled filter are determined by simulation using a tightly gain-scheduled model of the linearised vehicles open-loop response that captures the strongly parameter varying vehicle behaviour as it tracks the re-entry trajectory. The advantages of using gain-scheduled FDI filters for FDI on RLVs are highlighted via the simulations.

Atmospheric re-entry NDI control design for the hopper RLV concept

Abstract In this paper an NDI control design for the automated atmospheric re-entry of the Hopper reusable-launch vehicle (RLV) concept is presented. The NDI design is characterized by i) an inversion step where the trim and flight surfaces deflections are independently calculated and ii) by avoiding the standard linearization of the known aerodynamic database. The resulting control design is validated through time simulations using a high-fidelity model of the Hopper RLV in the face of parametric and aerodynamic database uncertainties, sensor noise and realistic atmospheric environment.

ROBUSTIFICATION OF STATIC AND LOW ORDER ANTI-WINDUP DESIGNS

Abstract In this paper an approach for improving the robustness of static and low order anti-windup compensators is introduced. These types of anti-windup compensators are typically designed to recover performance in the face of windup but can result in loss of performance (including stability) for the closed loop in the face of uncertainty. The proposed approach improves the anti-windup design by incorporating an additional robustifying compensator which is active when uncertainty is present in the system. An appealing practical feature of the scheme is that, for the static anti-windup case at least, the number of additional states is kept to a minimum.

Development of an Integrated LPV/LFT Framework: Modeling and Data-Based Validation Tool

In this paper, the development of a software tool for linear parameter varying (LPV)/linear fractional transformation (LFT) modeling and data-based validation techniques is described. This tool represents a step towards industrialization of these techniques, which although still suffering from a certain theoretical complexity are increasingly shown to help deal effectively with important real world applications. The tool is a key component for the development of an integrated LPV/LFT framework for control modeling, analysis, and design which is also a necessity for successful transfer of LPV/LFT techniques to industry. The focus of this paper is on describing the development of the integrated modeling/validation software and examining the applicability problems associated with these techniques. The technical readiness of the tool is exemplified through the development of validated LFT models used for LPV control design and analysis of a nonlinear longitudinal model of the NASA HL-20 re-entry vehicle.