This paper presents the design of a self‐scheduled fault‐tolerant controller for the lateral/directional motion of MuPAL‐ research aircraft using a polynomial‐scheduled structured H control. The controller is designed to be tolerant against loss‐of‐efficiency faults in the aileron and rudder, but based on industrial best practices it is scheduled with respect to an overall fault level instead of with respect to the individual faults. The performance and robustness of the resulting controller is verified first using frequency and time domain analysis, and subsequently it is validated in the Aircraft‐In‐the‐Loop configuration of MuPAL‐, where the real aircraft is operated in research Fly‐By‐Wire mode by the pilot on‐ground while coupled to an emulation computer that simulates the aircraft flying motion. The results show good behavior of the controlled aircraft across the defined fault scenarios.

This article presents the design, verification, and validation of a fault tolerant linear parameter varying controller for JAXA’s MuPAL-α aircraft. The design focuses on the synthesis of a lateral/directional LPV controller robust to velocity changes and actuator uncertainty, and with the scheduling variable chosen to make it fault tolerant to aileron and/or rudder loss-of-efficiency faults. The verification activities include linear, frequency and time, analyses as well as time-domain simulations –the latter with the LPV controller as it will be implemented in the aircraft. The validation is performed in the so-called Aircraft-In-the-Loop, which is best described as a type of aircraft Iron-Bird test-bench where the full aircraft is connected in the hangar to an external computer that allows to introduce exogenous effects (such as wind/gust) while using pilot, or also computer user-defined, commands. The verification and validation results show very good robustness and fault tolerance characteristics of the LPV controller for a wide set of fault conditions and speeds. The article discusses in detail the design and implementation issues for such type of controllers.

In view of the increase in the number of Unmanned Aerial Vehicles (UAVs) in the commercial and private sectors, it is imperative to make sure that such systems are safe, and thus resilient to faults and failures. This paper considers the numerical design and practical implementation of a linear parameter-varying (LPV) sliding mode observer for Fault Detection and Diagnosis (FDD) of a quadrotor minidrone. Starting from a nonlinear model of the minidrone, an LPV model is extracted for design, and the observer synthesis procedure, using Linear Matrix Inequalities (LMI), is detailed. Simulations of the observer FDD show good performance. The observer is then implemented on a Parrot(R) Rolling Spider minidrone and a series of flight tests is performed to assess the FDD capabilities in real time using its on-board processing power. The flight tests confirm the performance obtained in simulation, and show that the sliding mode observer is able to provide reliable fault reconstruction for quadrotor minidrone systems.

The paper details the research and corresponding implementation and testing steps of the FLEXOP demonstrator aircraft.Within the EU funded project an unmanned demonstrator aircraft is built to validate the mathematical modelling, flight control design and implementation side of active flutter mitigation.In order to validate the different methods and tools developed in this project, a flight test campaign is planned, in which the design and manufacturing of stiff wings (-0), are compared with very flexible wings (-1) with active flutter control, to see the overall benefit vs. risk of such technology.The mathematical models of the aircraft are first developed using FEM and CFD tools, what are later reduced by model order reduction techniques.The high-fidelity models are updated using Ground Vibration Test results.Manufacturing tolerances and variations in aircraft parameters are captured by systematic modelling of parametric and dynamic uncertainties.Both the simulation environment and the control design framework use different modelling fidelity, what are described within the paper.Reduced models are developed using two distinctive methods, respecting the control design needs: top-down balanced LPV reduction and bottom-up structure preserving methods.Based on the reduced order models various control design techniques have been elaborated by the consortium partners.In particular DLR developed and implemented a modal control method using H2 optimal blends for inputs and outputs.University of Bristol developed structured H-infinity optimal control methods, while SZTAKI proposed a worst-case gain optimal method structured controller synthesis method handling parametric and complex uncertainties.After the brief introduction of hardware-in-the-loop test setup and the description of mission scenarios the implementation issues of the baseline and flutter controllers are discussed.DLR and SZTAKI flutter controllers are evaluated in a hybrid software-/ hardware-in-the-loop test setup as at this stage of development the latter can not tolerate the estimated delay of the hardware system but their comparison is advantageous before future developments.Recommendations on active flutter mitigation methods are given based on the experience of synthesis and implementation of these controllers.Flight test results will follow these experiments, once the flight testing of the flutter wing commences.

Flutter is an aeroelastic phenomenon affecting flexible structures in a fluid flow and may lead to unstable oscillations and to critical structural damage. This paper concerns the design of a contr...

This paper concerns the incremental L2-gain stability of piecewise-affine (PWA) systems. We propose sufficient conditions derived from dissipativity theory to compute an upper bound on the incremental L2-gain. This is achieved by constructing piecewise-polynomial storage functions through the use of sum of squares (SOS) relaxations. The constraints are expressed as linear matrix inequalities (LMIs), which can be solved numerically in an efficient way. The proposed conditions are verified to be less conservative than previous results found in the literature by means of a numerical example.

In this article a comparison of two controllers for the active suppression of flutter of a flexible remotely-piloted aerial vehicle is presented. The H∞ technique is used for both, but the first relies on the standard (non-structured) approach and the second on the structured synthesis. High-fidelity models derived from finite element modeling are used to verify the performance of the obtained controllers. Reduced-order models are used for the control synthesis, which are obtained from applying a combination of balanced and modal reduction techniques on the high-fidelity models. The results show that both controllers are similar in performance and robustness, and both are capable of suppressing flutter and extending the flight envelope well beyond the open-loop flutter speed.

Flutter is an aeroelastic phenomenon affecting flexible structures in a fluid flow, and which may lead to unstable oscillations and to critical structural damage. This article concerns the design of a controller to provide active flutter suppression (AFS) on an unmanned flexiblewing demonstrator, currently under construction. The aircraft models used in the control design are obtained using a combination of balanced and modal reduction techniques from a high-fidelity nonlinear aeroservoelastic model, and include information about actuator and sensor dynamics as well as the phase loss introduced by the flight control computer. The controller is synthesized by posing and solving a weighted ∞-norm optimization problem with the goal to provide damping for the flutter modes and extend the flight envelope above the open-loop flutter speed. The article concludes with a thorough analysis and verification of the performance achieved by the closed-loop system, including simulations with the highfidelity nonlinear model of the actual maneuvers that will be performed by the unmanned demonstrator during future flight tests.

This article presents the design and validation of a fault-tolerant Y* flight controller for the Japanese Aerospace Exploration Agency's (JAXA) Multi-Purpose Aviation Laboratory- $\alpha$ (MuPAL- $\alpha$ ) aircraft. A structured $\mathbf{H}_{\infty}$ controller is synthesized by using non-smooth optimization to address performance and robustness constraints (specifically, uncertain actuator delays and varying airspeed) as well as loss-of-efficiency faults of a specific range with reduced online numerical complexity. The performance of the closed-loop system is validated through hardware-in-the-Ioop (HIL) simulations using the actual MuPAL- $\alpha$ aircraft, and they show that an improved fault tolerant capability is achieved when compared to Y* design robust only against the actuator delays.

Lur'e-type nonlinear systems are virtually ubiquitous in applied control theory, which explains the great interest they have attracted throughout the years. The purpose of this paper is to propose conditions to assess incremental asymptotic stability of Lur'e systems that are less conservative than those obtained with the incremental circle criterion. The method is based on the approximation of the nonlinearity by a piecewise-affine function. The Lur'e system can then be rewritten as a so-called piecewise-affine Lur'e system, for which sufficient conditions for asymptotic incremental stability are provided. These conditions are expressed as linear matrix inequalities (LMIs) allowing the construction of a continuous piecewise-quadratic incremental Lyapunov function, which can be efficiently solved numerically. The results are illustrated with numerical examples.

This paper is concerned with incremental stability properties of nonlinear systems. We propose conditions to compute an upper bound on the incremental L2-gain and to assess incremental asymptotic stability of piecewise-affine (PWA) systems. The conditions are derived from dissipativity analysis, and are based on the construction of piecewise-quadratic functions via linear matrix inequalities (LMI) that can be efficiently solved numerically. The developments are shown to be less conservative than previous results, and are illustrated with numerical examples. In the last part of this paper, we study the connection between incremental L2-gain stability and incremental asymptotic stability. It is shown that, with appropriate observability and reachability assumptions on the input-output operator, incremental L2-gain implies incremental asymptotic stability. Finally, it is shown that the converse implication follows provided some regularity conditions on the state space representation are met.

In this paper we are interested in the incremental stability of piecewise-affine (PWA) systems. We present conditions to compute an upper bound on the incremental ℒ2-gain based on dissipativity analysis. These conditions are expressed as linear matrix inequalities (LMI) allowing the construction of a continuous piecewise quadratic storage function. It is also shown that these conditions imply incremental asymptotic stability of the system. The result is illustrated with numerical examples.