Andrés Marcos

Development of Linear-Parameter-Varying Models for Aircraft

This paper presents a comparative study of three linear-parameter-varying (LPV) modeling approaches and their application to the longitudinal motion of a Boeing 747 series 100/200. The three approaches used to obtain the quasi-LPV models are Jacobian linearization, state transformation, and function substitution. Development of linear parameter varying models are a key step in applying LPV control synthesis. The models are obtained for the up-and-away flight envelope of the Boeing 747-100/200. Comparisons of the three models in terms of their advantages, drawbacks, and modeling difficulty are presented. Open-loop time responses show the three quasi-LPV models matching the behavior of the nonlinear model when in the trim region. Differences between the models are more apparent as the response of the aircraft deviates from the nominal trim conditions. ¯

Reconfigurable LPV control design for Boeing 747-100/200 longitudinal axis

Presents the design of a reconfigurable linear parameter varying (LPV) controller for the Boeing 747-100/200 longitudinal axis in the up-and-away flight regime. The control objectives are to obtain decoupled flight-path angle and velocity command tracking and achieve good disturbance rejection characteristics during normal operation and in the presence of an elevator fault. The LPV controller is synthesized using a quasi-LPV model of the aircraft longitudinal axis based on the Jacobian linearization approach. The controller schedules on three parameters: flight altitude and velocity and a fault identification signal. During normal flight operations, the LPV controller uses the elevators and thrust for flight maneuvers. The stabilizer is used to trim the aircraft. Two elevator fault scenarios are contemplated-lock and float. The proposed control strategy is to use the stabilizer as the alternative longitudinal control surface. Simulation results with elevator faults present show that the reconfigured controller stabilizes the faulted system at the expense of a factor of a designed one-third reduction in the tracking responsiveness of the longitudinal axis and has good disturbance rejection properties.

Linear Parameter Varying Modeling of the Boeing 747-100/200 Longitudinal Motion

This paper presents a Linear Parameter Varying (LPV) modeling approach for the longitudinal motion of a Boeing 747 series 100/200. The three approaches used to obtain the quasi-LPV models are Jacobian Linearisation, State Transformation, and Function Substitution. Linear Parameter Varying models are a key step in applying LPV control synthesis which guarantee a level of stability and robustness for the closed loop. The models are obtained for the Up-and-Away flight envelope of the Boeing 747-100/200. Comparisons of the three models in terms of their advantages, drawbacks and modeling difficulty are presented. Open loop time responses show all the three quasi-LPV models matching the behavior of the nonlinear model when in the trim region. The Function Substitution quasi-LPV model in this particular case is the only valid model for the full flight envelope of interest.

Brief paper: A symbolic matrix decomposition algorithm for reduced order linear fractional transformation modelling

In this paper an algorithm that provides an equivalent, but of reduced order, representation for multivariate polynomial matrices is given. It combines ideas from computational symbolic algebra, polynomial/matrix algebraic manipulations and information logic. The algorithm is applied to the problem of finding minimal linear fractional transformation models. Statistical performance analysis of the algorithm reveals that it consistently outperforms currently available algorithms.

High-performance architecture for design and analysis of robust anti-windup compensators

In this paper a general framework for the design and analysis of robust anti-windup compensators is presented. The proposed framework combines the Weston-Postlethwaite anti-windup scheme with ideas from residual generation and robust high-performance control architectures. 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 clear design trade-off between robust stability and robust performance for the saturated and unsaturated closed-loops

Application of LPV/LFT Modeling and Data-based Validation to a re-entry vehicle

*† ‡ § ** †† ‡‡ In this article an application of LFT/LPV modeling and data-based validation techniques to a re-entry vehicle is shown. This work is part of a European Space Agency project tasked with examining the use of LPV technologies for the control design process of space systems. The application presented serves as an assessment on the technological readiness level of LPV/LFT modeling approaches and data-based validation algorithms, as well as a review of their features, shortcomings and needs. The selected vehicle is the longitudinal nonlinear motion of NASA HL-20 during an approach trajectory from Mach 4.5 down to 1.5.

Piloted assessment of a fault diagnosis algorithm on the ATTAS aircraft

This paper describes the application of a fault diagnosis algorithm in a simulation campaign conducted with the Advanced Technologies Testing Aircraft (ATTAS). To provide a realistic fault scenario suitable for in-flight testing, the effects of actuator rate saturation were considered to be the result of faults acting on the ATTAS. Fault diagnosis algorithms were designed for these faults using H-infinity fault detection and isolation (FDI) filter synthesis tools and online thresholding algorithms. These fault diagnosis algorithms were assessed in an incremental validation campaign by first using the ATTAS high-fidelity nonlinear model, and then the German Aerospace Center (DLR) ATTAS flight simulator. In-flight data from previous flight campaigns investigating methods to alleviate rate saturation effects was used to assess the performance and robustness of the algorithms under real flight conditions.

LPV Modeling, Analysis and Design in Space Systems: Rationale, Objectives and Limitations

Linear parameter varying theory has been in the control community for the last 15 years but its use in space systems has been limited due to the slow transfer of these techniques to the space industry and a lack of reliable commercial software tools. This article summarizes some of the efforts made in Europe to change the situation and serves as an assessment on the advantages, limitations and needs for the use of LPV modeling, analysis and design techniques in space systems. A comparative application between LTI, gain scheduling and LPV control designs for a representative model of a space re-entry vehicle is used in support of the assessment.

Application of H-infinity Fault Detection and Isolation to a Boeing 747-100/200 Aircraft

Fault Detection and Isolation (FDI) methods have been developed over the past thirty years but only in the last several years they have been applied to complex real applications. This paper presents a synthesis of H∞ FDI filters for the longitudinal motion of the Boeing 747-100/200 aircraft. The filters are synthesized to detect and isolate faults in the elevator actuator and pitch rate sensor while attenuating disturbances and noise on the fault signals. They are synthesized for open-loop LTI models of the aircraft. Closed-loop simulations with a highfidelity nonlinear model in the presence of gust and noise are performed to validate the disturbance rejection and robust properties of the H∞ LTI FDI filters.

WORST-CASE ANALYSIS OF FLIGHT CONTROL LAWS FOR RE-ENTRY VEHICLES

Abstract This paper reports results of a joint study between ESA, DEIMOS Space S.L. and the University of Leicester on the robustness analysis of flight control laws for future hypersonic re-entry vehicles. We apply a novel hybridised version of the deterministic global optimisation algorithm, DIviding RECTangles (DIRECT), to perform worst-case analysis of a nonlinear-dynamic inversion (NDI) flight control law for a highly-detailed simulation model of a hypersonic re-entry vehicle. Nonlinear clearance criteria widely used in the European aerospace industry for the clearance of flight control laws for highly manoeuvrable aircraft are developed and applied in the context of the re-entry vehicle flight control problem. The proposed approach is shown to have the potential to improve significantly both the reliability and efficiency of the flight clearance process for future re-entry vehicles.