Model-free control algorithms for micro air vehicles with transitioning flight capabilities

Micro air vehicles with transitioning flight capabilities, or simply hybrid micro air vehicles, combine the beneficial features of fixed-wing configurations, in terms of endurance, with vertical take-off and landing capabilities of rotorcrafts to perform five different flight phases during typical missions, such as vertical takeoff, transitioning flight, forward flight, hovering and vertical landing. This promising micro air vehicle class has a wider flight envelope than conventional micro air vehicles, which implies new challenges for both control community and aerodynamic designers. One of the major challenges of hybrid micro air vehicles is the fast variation of aerodynamic forces and moments during the transition flight phase which is difficult to model accurately. To overcome this problem, we propose a flight control architecture that estimates and counteracts in real-time these fast dynamics with an intelligent feedback controller. The proposed flight controller is designed to stabilize the hybrid micro air vehicle attitude as well as its velocity and position during all flight phases. By using model-free control algorithms, the proposed flight control architecture bypasses the need for a precise hybrid micro air vehicle model that is costly and time consuming to obtain. A comprehensive set of flight simulations covering the entire flight envelope of tailsitter micro air vehicles is presented. Finally, real-world flight tests were conducted to compare the model-free control performance to that of the Incremental Nonlinear Dynamic Inversion controller, which has been applied to a variety of aircraft providing effective flight performances

Algorithmes de contrôle sans modèle pour les micro drones de type tail-sitter

Micro Air Vehicle (MAV)s with transitioning flight capabilities, or simply Hybrid Micro Air Vehicle(HMAV)s combine the beneficial features of fixed-wing configurations in terms of endurance,with vertical take-off and landing capabilities of rotorcraft to perform five different flight phasesduring typical missions : vertical takeoff, transitioning flight, forward flight, hovering, and verticallanding. This promising MAV class has a wider flight envelope than conventional MAVs,which implies new challenges for both control community and aerodynamic designers. One ofthe major challenges of HMAVs is the fast variation of aerodynamic forces and moments duringthe transition flight phase, which is difficult to model and control accurately. In this thesis, wefocus on the development of control laws for a specific class of HMAVs, namely tail-sitters.In order to stabilize the HMAV and overcome its modeling problem, we propose a flightcontrol architecture that estimates in realtime its fast nonlinear dynamics with an intelligentfeedback controller. The proposed flight controller is designed to stabilize the HMAV attitude,velocity and position during all flight phases. By using Model-Free Control (MFC) algorithms,the proposed flight control architecture bypasses the need for a precise HMAV model that iscostly and time consuming to obtain. A comprehensive set of flight simulations covering theentire flight envelope of the HMAV is presented, with the respective analysis for each of theflight phases. Furthermore, the control performance and the limitations of the MFC architecture are discussedin order to introduce further applications in real flight experiments. Flight tests clarifyand validate the proposed control methodology in a practical context, thus solving the principalissue of HMAVs; that is, the formulation of accurate HMAV dynamic equations to designcontrol laws. In addition, from simple mathematical algorithms, MFC is easily implemented ona microprocessor without the need for high computational costs, such as time processing andmemory resources. The results obtained provide a straightforward way in which to validatethe methodological principles presented in this thesis, to certify the designed MFC parametersand to establish a conclusion regarding MFC advantages and disadvantages in theoretical andpractical contexts related to aerospace systems.Les micro drones à capacités de vol de transition, ou simplement HMAVs (de l’anglais Hybrid MicroAir Vehicles), regroupent les principales caractéristiques aérodynamiques des configurationsà voilure fixe, en termes d’endurance, avec les capacités de décollage et d’atterrissage verticaldes voilures tournantes afin d’effectuer cinq phases de vol au cours de ses missions, telles quele décollage vertical, le vol de transition, le vol en croisière, le vol stationnaire et l’atterrissagevertical. Cette nouvelle classe de micro drones a un domaine de vol plus large que les microdrones conventionnels, ce qui implique de nouveaux défis pour les automaticiens et les concepteursaérodynamiques. L’un des principaux défis des HMAVs est la variation rapide des forces etdes moments aérodynamiques pendant la phase de vol de transition, qui est difficile à modéliseret à contrôle avec précision. Dans cette thèse, nous nous concentrons sur le développement delois de pilotage pour une classe spécifique des HMAVs, à savoir les tail-sitters.Afin de stabiliser la dynamique des tail-sitters et de surmonter leur problème de modélisation,nous proposons une architecture de contrôle de vol qui estime en temps réel leurs dynamiquesgrâce à un contrôleur à rétroaction intelligent. Le contrôleur de vol proposé est conçu pourstabiliser l’attitude du tail-sitter ainsi que sa vitesse, et sa position pendant toutes ses phasesde vol. En utilisant des algorithmes de la commande sans modèle, l’architecture de contrôle devol proposée contourne le besoin d’un modèle dynamique précis dont l’obtention est coûteuseet longue. Une série complète de simulations de vol couvrant l’ensemble du domaine de vol destail-sitters est présentée et, pour chaque phase de vol, son analyse respective.Avant d’introduire des expériences de vol réel, nous évaluons les performances et les limites del’architecture de commande sans modèle en simulation. Les essais en vol permettent de clarifier etde valider notre méthodologie de contrôle dans un contexte pratique, résolvant ainsi le principalproblème des tail-sitters, à savoir la formulation d’équations dynamiques précises pour concevoirles lois de commande. En outre, à partir d’algorithmes mathématiques simples, la commandesans modèle est facilement implémentée sur microprocesseurs sans nécessiter de coûts de calculélevés, tels que la fréquence de traitement et les ressources de mémoire. Les résultats obtenusfournissent un moyen simple de valider les principes méthodologiques présentés dans cette thèse,de certifier les paramètres obtenus lors de la conception de la commande sans modèle et d’établirune conclusion concernant ses avantages et ses inconvénients dans des contextes théoriques etpratiques liés aux systèmes aérospatiaux

Team MAVion entry in the IMAV'17 outdoor challenge – A tail-sitting trajectory-tracking µUAV

International audienceThis paper outlines current research conducted on tilt-body micro air vehicles at ISAE, and how we exploit recent advances to provide a tail-sitting flying-wing entry for the IMAV'17 outdoor challenge capable of performing automatic vertical takeoff , landing, and trajectory-tracking

Système et procédé de contrôle de vol d'un drone convertible à voilure fixe permettant une transition continue stabilisée entre un vol stationnaire vertical et un vol de croisière à l'horizontal

A flight control system is configured to control the flight of a fixed-wing convertible drone (12) having two left and right wings, each supporting a forward propeller and a trailing flap at the rear edge. The control system comprises an attitude regulator (154) of the drone (12) for respectively controlling the roll angles, φ m , pitch angles θ m and yaw angles Ψ m , measured by one or more sensors over reference roll angles φ d, reference pitch angles θ d and reference yaw angles Ψ d . The first attitude controller (154) comprises a first modelless MFC SISO control device (162) at an input-output for regulating and controlling the pitch angle θ m measured over the reference pitch angle θ d by determining a first command δ n for symmetrical deflection of the left and right flaps, applied with the same sign to said left and right flaps.Un système de contrôle de vol est configuré pour contrôler le vol d'un drone convertible à voilure fixe (12), ayant deux ailes gauche et droite supportant chacune une hélice en avant et un volet de déflexion en bordure arrière. Le système de contrôle comporte un régulateur d'attitude (154) du drone (12) pour asservir respectivement les angles de roulis φ m , tangage θ m et lacet Ψ m , mesurés par un ou plusieurs capteurs sur des angles de consigne de roulis φ d, tangage θ d et lacet Ψ d . Le premier régulateur d'attitude (154) comporte un premier dispositif MFC SISO (162) de commande sans modèle à une entrée-une sortie pour réguler et asservir l'angle de tangage θ m mesuré sur l'angle de consigne de tangage θ d en déterminant une première commande δ n de déflection symétrique des volets gauche et droit, appliquée avec le même signe sur lesdits volets gauche et droit

Flight control system and method for a convertible fixed-wing drone providing a stabilized continuous transition between a vertical stationary flight and a horizontal cruise flight: Systeme et procede de controle de vol d'un drone convertible a voilure fixe permettant une transition continue stabilisee entre un vol stationnaire vertical et un vol de croisiere a l'horizontal

A flight control system is configured to control the flight of a convertible fixed-wing drone (12), having two left and right wings, each supporting a propeller in front and a deflection flap at the rear edge. The control system includes an attitude regulator (154) of the drone (12) to respectively control the roll angles ϕm, pitch θ m and yaw Ψm, measured by one or more sensors on setpoint angles ϕd, pitch θ d and lace Ψd. The first attitude regulator (154) comprises a first MFC SISO device (162) for modelless control at one input-one output for regulating and controlling the pitch angle θ m measured on the pitch set angle θ d by determining a first command δn for symmetrical deflection of the left and right flaps, applied with the same sign to said left and right flaps.Un système de contrôle de vol est configuré pour contrôler le vol d'un drone convertible à voilure fixe (12), ayant deux ailes gauche et droite supportant chacune une hélice en avant et un volet de déflexion en bordure arrière. Le système de contrôle comporte un régulateur d'attitude (154) du drone (12) pour asservir respectivement les angles de roulis ϕm, tangage θ m et lacet Ψm, mesurés par un ou plusieurs capteurs sur des angles de consigne de roulis ϕd, tangage θ d et lacet Ψd. Le premier régulateur d'attitude (154) comporte un premier dispositif MFC SISO (162) de commande sans modèle à une entrée-une sortie pour réguler et asservir l'angle de tangage θ m mesuré sur l'angle de consigne de tangage θ d en déterminant une première commande δn de déflection symétrique des volets gauche et droit, appliquée avec le même signe sur lesdits volets gauche et droit

Full model-free control architecture for hybrid UAVs

International audienceThis paper discusses the development of a control architecture for hybrid Unmanned Aerial Vehicles (UAVs) based on model-free control (MFC) algorithms. Hybrid UAVs combine the beneficial features of fixed-wing UAVs with Vertical Take-Off and Landing (VTOL) capabilities to perform five different flight phases during typical missions, such as vertical takeoff, transitioning flight, forward flight, hovering and vertical landing. Based on model-free control principles, a novel control architecture that handles the hybrid UAV dynamics at any flight phase is presented. This unified controller allows autonomous flights without discontinuities of switching for the entire flight envelope with position tracking, velocity control and attitude stabilization. Simulation results show that the proposed control architecture provides an effective control performance for the entire flight envelope and excellent disturbance rejections during the critical flight phases, such as transitioning and hovering flights in windy conditions

Fixed-wing UAV with transitioning flight capabilities : Model-Based or Model-Free Control approach? A preliminary study

Transitioning vehicles experience three different flight phases during typical missions. The hovering and forward flight phases have been researched widely, however the transition phase in between is more challenging and has been the subject of less research. One of the control approaches to handle the transition phase relies on model-based methods which require sophisticated wind-tunnel characterization. Accurate modeling of force and moments of a partially stalled wing and control surfaces is highly challenging and time consuming. In addition, these models usually require several flight measurements (such as angle of attack and low airspeed) that are difficult to obtain. As an alternative, some control approaches manage the transition phase without the need for sophisticated models. One example of such an approach is the Model Free Control (MFC). This paper compares the results obtained from both MFC and Linear Quadratic Regulator (LQR) applied to fixed-wing UAV with transitioning flight capability during hovering, transition and forward flight modes. Both of the controllers are designed for a transitioning vehicle called MAVion. The simulation results demonstrated that MFC increases the stability of the aircraft, especially in disturbed flight conditions

Towards a unified model-free control architecture for tailsitter micro air vehicles: Flight simulation analysis and experimental flights

Best Paper Award American Institute of Aeronautics and Astronautics (AIAA) 2020International audienceHybrid Micro Air Vehicles (MAVs) combine the beneficial features of rotorcraft with fixed-wing configurations providing a complete flight envelope that includes vertical take-off, hover, transitioning flights, forward flight and vertical landing. Tailsitter MAVs belong to a particular class of hybrid MAVs and its peculiar issue is related to the transitioning flight phase where, for high incidence angles, fast changing of aerodynamic forces and moments are observed which are difficult to model and control accurately. To overcome this issue, we proposed a control architecture with model-free control (MFC) algorithms that has been able to stabilize the hybrid MAV's attitude, velocity, and position without any modeling process. The proposed control architecture consisted basically two steps~: 1) The attitude control, to ensure the hybrid MAV's attitude tracking and stability within the entire flight envelope; 2) The guidance system responsible to control both velocity and position. We validated the MFC architecture according to a comprehensive set of flight simulations and experimental flight tests. Experimental flight tests shown an effective and promising control strategy solving the principal issue of hybrid MAVs that was the formulation of accurate hybrid MAV's dynamic equations to design control laws. The obtained results have provided a straightforward way to validate the methodological principles presented in this article as well as to certify the designed MFC parameters, and to establish a conclusion regarding MFC benefits in both theoretical and practical contexts

Fixed-wind UAV with transitioning flight capabilities: Model-Based or Model-Free Control approach? A preliminary study

International audienceTransitioning vehicles experience three different flight phases during typical missions. The hovering and forward flight phases have been researched widely, however the transition phase in between is more challenging and has been the subject of less research. One of the control approaches to handle the transition phase relies on model-based methods which require sophisticated wind-tunnel characterization. Accurate modeling of force and moments of a partially stalled wing and control surfaces is highly challenging and time consuming. In addition, these models usually require several flight measurements (such as angle of attack and low airspeed) that are difficult to obtain. As an alternative, some control approaches manage the transition phase without the need for sophisticated models. One example of such an approach is the Model Free Control (MFC). This paper compares the results obtained from both MFC and Linear Quadratic Regulator (LQR) applied to fixed-wing UAV with transitioning flight capability during hovering, transition and forward flight modes. Both of the controllers are designed for a transitioning vehicle called "MAVion." The simulation results demonstrated that MFC increases the stability of the aircraft, especially in disturbed flight conditions