Adaptive backstepping controller design of quadrotor biplane for payload delivery

Performance of the UAVs for a particular application can be enhanced by hybrid design, where take-off, hover, and landing happen like rotary-wing UAVs, and flies like fixed-wing UAVs. A backstepping controller and an adaptive backstepping controller are designed for trajectory tracking and payload delivery in a medical emergency or medical substance delivery like vaccine delivery in the presence of wind gust. Simulation results show that the backstepping controller effectively tracks the trajectory during the entire flight envelope, including take-off, hovering, the transition phase, level flight mode, and landing. A comparison between Backstepping, Integral Terminal Sliding Mode (ITSMC) and Adaptive Backstepping controllers for payload delivery show that the adaptive backstepping controller effectively tracks the altitude and attitude. ITSMC is capable of tracking the desired trajectory for a change in the mass but has sluggish response. The backstepping controller generates a steady-state error in altitude during the mass change in biplane-quadrotor.The publication of this article was funded by Qatar National Library.Scopu

Motion primitives and 3D path planning for fast flight through a forest

This paper presents two families of motion primitives for enabling fast, agile flight through a dense obstacle field. The first family of primitives consists of a time-delay dependent 3D circular path between two points in space and the control inputs required to fly the path. In particular, the control inputs are calculated using algebraic equations which depend on the flight parameters and the location of the waypoint. Moreover, the transition between successive maneuver states, where each state is defined by a unique combination of constant control inputs, is modeled rigorously as an instantaneous switch between the two maneuver states following a time delay which is directly related to the agility of the robotic aircraft. The second family consists of aggressive turn-around (ATA) maneuvers which the robot uses to retreat from impenetrable pockets of obstacles. The ATA maneuver consists of an orchestrated sequence of three sets of constant control inputs. The duration of the first segment is used to optimize the ATA for the spatial constraints imposed by the turning volume. The motion primitives are validated experimentally and implemented in a simulated receding horizon control (RHC)-based motion planner. The paper concludes with inverse-design pointers derived from the primitives

Dual observer based adaptive controller for hybrid drones

A biplane quadrotor (hybrid vehicle) benefits from rotary-wing and fixed-wing structures. We design a dual observer-based autonomous trajectory tracking controller for the biplane quadrotor. Extended state observer (ESO) is designed for the state estimation, and based on this estimation, a Backstepping controller (BSC), Integral Terminal Sliding Mode Controller (ITSMC), and Hybrid Controller (HC) that is a combination of ITSMC + BSC are designed for the trajectory tracking. Further, a Nonlinear disturbance observer (DO) is designed and combined with ESO based controller to estimate external disturbances. In this simulation study, These ESO-based controllers with and without DO are applied for trajectory tracking, and results are evaluated. An ESO-based Adaptive Backstepping Controller (ABSC) and Adaptive Hybrid controller (AHC) with DO are designed, and performance is evaluated to handle the mass change during the flight despite wind gusts. Simulation results reveal the effectiveness of ESO-based HC with DO compared to ESO-based BSC and ITSMC with DO. Furthermore, an ESO-based AHC with DO is more efficient than an ESO-based ABSC with DO.Web of Science71art. no. 4

Conception, modélisation, et commande d'un mini-drone convertible

There is a growing interest to design convertible aerial vehicles that can hover like helicopters and fly forward efficiently like airplanes. This thesis is devoted to the conception, modeling, and control of such a convertible mini-UAV (Unmanned Aerial Vehicle). The main contributions of this work are threefold. Firstly, we design a novel UAV structure by adding to each side of a quadrotor one wing that can rotate around an axis belonging to the propellers' plane. Our prototype has many advantages over existing convertible structures: simple mechanical concept since inspired by a classical quadrotor, flexibility for selecting different components (wings, propellers), flexibility for the control design, etc. Secondly, we provide an energy modeling of this type of convertible UAVs, taking into account their characteristics as compared to full-scale helicopters (large variation of aerodynamic forces, performance degradation at low Reynolds number, etc.). Finally, as for the control design, the degrees of freedom of the wings permit the decoupling between propellers and wings' orientations. This greatly enhances the control flexibility as compared to traditional aircraft. Relying on this feature, several control approaches are proposed. In particular, using a specific geometrical design, we show that an efficient control of our UAV can be obtained without air-velocity measurements. Simulation results confirm the soundness of our control design even in the presence of strong and varying wind. En route to validate the theory, a mechanical prototype of the UAV was constructed in our laboratory and preliminary flight tests were performed.Cette thèse concerne les drones dits "convertibles", qui allient capacité au vol stationnaire et efficacité énergétique en vol de croisière. Les principales contributions de ce travail comportent trois volets. D'abord, nous concevons une nouvelle structure de drone en ajoutant de chaque côté d'un quadrirotor une aile qui peut pivoter autour d'un axe appartenant au plan des hélices. Notre prototype a de nombreux avantages par rapport aux structures convertibles existantes: conception mécanique simple car dérivée d'un quadrirotor classique, flexibilité pour le montage de différents composants (ailes, hélices), etc. Deuxièmement, nous proposons une modélisation énergétique de ce type de drone convertible, en tenant compte de ses caractéristiques par rapport aux hélicoptères avec pilote à bord (grande variation des forces aérodynamiques, dégradation des performances à faible nombre de Reynolds, etc.). Finalement, concernant la conception de la commande, les degrés de liberté des ailes permettent le découplage entre les orientations des hélices et celle des ailes. Cela augmente considérablement les possibilités de contrôle par rapport aux aéronefs traditionnels. S'appuyant sur cette caractéristique, plusieurs approches de contrôle sont proposées. En particulier, en utilisant une conception géométrique spécifique, nous montrons qu'un contrôle efficace peut être obtenu sans mesures de la vitesse air. Les résultats de simulation confortent cette stratégie de contrôle, même en présence de vent fort et variable. Afin de valider la théorie, un prototype mécanique du drone a été construit dans notre laboratoire et des essais en vol préliminaires ont été effectués

Design and development of a controllable wing loading unmanned aerial system

Vertical takeoff and landing (VTOL) unmanned aerial systems (UAS) offer all the benefits of wing borne flight without the need for conventional takeoff and landing (CTOL) infrastructure. There exists many effective VTOL UAS that utilize battery-powered rotors to provide vertical thrust. The problem with the existing UAS is that the VTOL capability is achieved at the sacrifice of speed, fuel/payload, and operational flexibility. Also, many of these UAS must transition from hover to horizontal flight which is both complex and risky.The current research explores a new type of point launch and landing system that utilizes only liquid fuels, i.e. no electric powered rotors. Instead of exposed rotors, the new configuration has a turbojet engine mounted vertically inside the fuselage to provide vertical thrust. With the turbojet being 'hidden' from the freestream air, it mitigates the drag seen from the other configurations' rotors, allowing a higher top speed. Also, the new configuration bypasses the hover and transition phases of flight.The vertical turbojet effectively changes the weight of the aircraft which allows it to have controllable wing loading (CWL), and therefore variable stall speed. With the jet at full power, the aircraft weighs virtually nothing and can takeoff from the launchpad with almost no airspeed. Likewise, on landing, the aircraft can slow to almost zero airspeed and land with little to no rollout. The CWL configuration has proved it possible to have approximately a 95% reduction in landing distance.This paper describes the study, design, manufacturing, and testing of the point launch and landing CWL configuration. Two commercial off the shelf (COTS) UAVs were retrofitted with a CWL system to test the validity of the idea and the necessary systems.Following the proof of the idea, a composite UAS with a maximum takeoff weight of 50 lb. was designed, manufactured, and flown. It successfully demonstrated both a point launch and point landing while being capable of reaching speeds of up to 100 mph, more than double the top speed of some other VTOL UAS in its weight class

Intelligent Control for Fixed-Wing eVTOL Aircraft

Urban Air Mobility (UAM) holds promise for personal air transportation by deploying "flying cars" over cities. As such, fixed-wing electric vertical take-off and landing (eVTOL) aircraft has gained popularity as they can swiftly traverse cluttered areas, while also efficiently covering longer distances. These modes of operation call for an enhanced level of precision, safety, and intelligence for flight control. The hybrid nature of these aircraft poses a unique challenge that stems from complex aerodynamic interactions between wings, rotors, and the environment. Thus accurate estimation of external forces is indispensable for a high performance flight. However, traditional methods that stitch together different control schemes often fall short during hybrid flight modes. On the other hand, learning-based approaches circumvent modeling complexities, but they often lack theoretical guarantees for stability. In the first part of this thesis, we study the theoretical benefits of these fixed-wing eVTOL aircraft, followed by the derivation of a novel unified control framework. It consists of nonlinear position and attitude controllers using forces and moments as inputs; and control allocation modules that determine desired attitudes and thruster signals. Next, we present a composite adaptation scheme for linear-in-parameter (LiP) dynamics models, which provides accurate realtime estimation for wing and rotor forces based on measurements from a three-dimensional airflow sensor. Then, we introduce a design method to optimize multirotor configuration that ensures a property of robustness against rotor failures. In the second part of the thesis, we use deep neural networks (DNN) to learn part of unmodeled dynamics of the flight vehicles. Spectral normalization that regulates the Lipschitz constants of the neural network is applied for better generalization outside the training domain. The resultant network is utilized in a nonlinear feedback controller with a contraction mapping update, solving the nonaffine-in-control issue that arises. Next, we formulate general methods for designing and training DNN-based dynamics, controller, and observer. The general framework can theoretically handle any nonlinear dynamics with prior knowledge of its structure. Finally, we establish a delay compensation technique that transforms nominal controllers for an undelayed system into a sample-based predictive controller with numerical integration. The proposed method handles both first-order and transport delays in actuators and balances between numerical accuracy and computational efficiency to guarantee stability under strict hardware limitations.</p