Conceptual design and control of twin-propeller tail-sitter mini-UAV: Conceptual study of V-TS mini-UAV

This paper describes progress made on the design and analysis of a twin-propeller tail-sitter mini-UAV (named V-TS). Since the V-TS mini-UAV is a combination of airplanes and copters, high energy efficiency during the forward flight and VTOL capability in the hover flight are achieved. However, this configuration also brings new challenges and difficulties, especially in the case of control. Free software which was used in the design process is presented and described. AVIGLE Demonstrator is analyzed in SU2 to verify correct settings of the aerodynamic analysis. Furthermore, 3D model of the V-TS mini-UAV with the Y-tail configuration and its basic geometrical parameters are shown. The results prove that it is aerodynamically efficient for our purpose. In addition, probably all control modes, transitional flight phases, and difficulties which appear in the control of the twin-propeller tail-sitter mini-UAV are defined and solutions are proposed. The transitional flight phases are determined as a combination of the control modes and sub-modes. © 2019, Deutsches Zentrum für Luft- und Raumfahrt e.V

Sizing Tool for Quadrotor Biplane Tailsitter UAS

The Quadrotor-Biplane-Tailsitter (QBT) configuration is the basis for a mechanically simplistic rotorcraft capable of both long-range, high-speed cruise as well as hovering flight. This work presents the development and validation of a set of preliminary design tools built specifically for this aircraft to enable its further development, including: a QBT weight model, preliminary sizing framework, and vehicle analysis tools. The preliminary sizing tool presented here shows the advantage afforded by QBT designs in missions with aggressive cruise requirements, such as offshore wind turbine inspections, wherein transition from a quadcopter configuration to a QBT allows for a 5:1 trade of battery weight for wing weight. A 3D, unsteady panel method utilizing a nonlinear implementation of the Kutta-Joukowsky condition is also presented as a means of computing aerodynamic interference effects and, through the implementation of rotor, body, and wing geometry generators, is prepared for coupling with a comprehensive rotor analysis package

Aerodynamic detailed design of an Unmanned Aerial Vehicle with VTOL capabilities

ALF/ENGAER 139424-L Vasco Luís Martins Ferreira Coelho. Examination Committee: Chairperson: BGEN/EngEl 119923-E Rui Fernando da Costa Ferreira; Supervisor: MAJ/EngAer 131603-G Joao Vítor Aguiar Vieira Caetano, Dr. Frederico José Prata Rente Reis Afonso; Member of the Committee: Prof. Dr. Afzal SulemanEsta tese está integrada num projeto de desenvolvimento de um veículo aéreo não tripulado capaz de efetuar descolagem e aterragem vertical, e tendo hidrogénio como principal fonte de energia utilizando para tal uma célula de combustível. A dissertação foca-se nas fases de desenvolvimento preliminar e detalhada no que diz respeito a estudos aerodinâmicos e desempenho em voo. A fase preliminar abrange a conceção da asa e da cauda, recorrendo ao software XFLR5, em conjunto com uma estimativa da resistência aerodinâmica total da aeronave, recorrendo a expressões semi-empíricas. Para a análise detalhada, foi utilizado o software de mecânica de fluidos computacional Fluent. A escolha do modelo de turbulência SST, em conjunto com o modelo de transição y_Re0 , é validada pelas simulação 2D do perfil SG6042, apresentando resultados consistentes com os dados experimentais. A polar aerodinâmica da asa é obtida através da simulações 3D da mesma para vários ângulos de ataque. Por forma a melhorar as propriedades aerodinâmicas da asa, foi aplicada torção à ponta da asa, movendo a região inicial da perda da ponta da asa para a raiz. O impacto do sistema de propulsão vertical na resistência aerodinâmica em voo cruzeiro é avaliado através da realização de testes em túnel de vento e simulações em Fluent. Simulações de toda a aeronave concluem que, dependendo do alinhamento dos rotores, a resistência aerodinâmica da aeronave varia entre 16.32 e 19.22 N para voo cruzeiro, resultando num tempo total de voo entre 3H05 e 3H25.This thesis is part of a project to design an unmanned aerial vehicle capable of performing vertical take-off and landing, and having hydrogen as its main energy source by using a fuel cell. The present dissertation is focused on the preliminary and detailed design phases regarding aerodynamics and flight performance studies. The preliminary phase encompasses the wing and tail design, with the aid of XFLR5, together with an estimate of the total aircraft drag by resorting to semi-empirical expressions. A longitudinal static stability analysis is conducted, and the unmanned aerial vehicle characteristics are presented after the preliminary phase of the project. For the detailed analysis, Fluent was chosen as the computational fluid dynamics software to be used. 2D simulation over the SG6042 wing airfoil validated the choice of the SST turbulence model, coupled with the y_ Re0 transition model, as the results were consistent with experimental data. The drag polar of the wing is obtained by simulating the 3D wing at various angles of attack. To enhance the wing aerodynamic properties, twist was given to the wingtip, moving the stall region from the wingtip to the root. The impact of the vertical propulsion system on the drag at cruise is assessed by performing wind tunnel tests and simulations on Fluent. Simulations of the entire aircraft conclude that, depending on the stopping position of the rotors, the drag of the aircraft varies between 16.32 and 19.22 N for cruise, which results in a total flight time between 3H05 and 3H25.N/

Modeling, Simulation and Control of Very Flexible Unmanned Aerial Vehicle

This dissertation presents research on modeling, simulation and control of very flexible aircraft. This work includes theoretical and numerical developments, as well as experimental validations. On the theoretical front, new kinematic equations for modeling sensors are derived. This formulation uses geometrically nonlinear strain-based finite elements developed as part of University of Michigan Nonlinear Aeroelastic Simulation Toolbox (UM/NAST). Numerical linearizations of both the flexible vehicle and the sensor measurements are developed, allowing a linear time invariant model to be extracted for control analysis and design. Two different algorithms to perform sensor fusion from different sensor sources to extract elastic deformation are investigated. Nonlinear least square method uses geometry and nonlinear beam strain-displacement kinematics to reconstruct the wing shape. Detailed information such as material properties or loading conditions are not required. The second method is the Kalman filter, implemented in a multi-rate form. This method requires a dynamical system representation to be available. However, it is more robust to noise corruption in sensor measurements. In order to control maneuver loads, Model Predictive Control is applied to maneuver load alleviation of a representative very flexible aircraft (X-HALE). Numerical studies are performed in UM/NAST for pitch up and roll maneuvers. Both control and state constraints are successfully enforced, while reference commands are still being tracked. MPC execution is also timed and current implementation is capable of almost real-time operation. On the experimental front, two aeroelastic testbed vehicles (ATV-6B and RRV-6B) are instrumented with sensors. On ATV-6B, an extensive set of sensors measuring structural, flight dynamic, and aerodynamic information are integrated on-board. A novel stereo-vision measurement system mounted on the body center looking towards the wing tip measures wing deformation. High brightness LEDs are used as target markers for easy detection and to allow each view to be captured with fast camera shutter speed. Experimental benchmarks are conducted to verify the accuracy of this methodology. RRV-6B flight test results are presented. System identification is applied to the experimental data to generate a SISO description of the flexible aircraft. System identification results indicate that the UM/NAST X-HALE model requires some tuning to match observed dynamics. However, the general trends predicted by the numerical model are in agreement with flight test results. Finally, using this identified plant, a stability augmentation autopilot is designed and flight tested. This augmentation autopilot utilizes a cascaded two-loop proportional integral control design, with the inner loop regulating angular rates and outer loop regulating attitude. Each of the three axes is assumed to be decoupled and designed using SISO methodology. This stabilization system demonstrates significant improvements in the RRV-6B handling qualities. This dissertation ends with a summary of the results and conclusions, and its main contribution to the field. Suggestions for future work are also presented.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144019/1/pziyang_1.pd

Flight control of hybrid drones towards enabling parcel relay manoeuvres

This work addresses the modeling and controlling process of a hybrid UAV, aimed for parcel relay maneuvers. Hybrid UAVs bring big advantages with the capability of flying in two flight modes, rotary and fixed wing. But with them comes added complexity both in modeling and controlling. This work is based on a popular airframe, a tilt tri-rotor UAV, containing all the specific system dynamics such vehicle category provides. The model is then validated by designing two separate controllers for both flight modes, capable of trajectory tracking in eachmode,makinguseofacustomhybridcontrolallocationtechniquethatdifferentiates the control in three parts: vertical, horizontal, and transitional flight modes. Finally, a hybrid controller is proposed, using a finite state machine capable of handling logical events, with the aim to provide control logic to perform autonomous mid flight transitions. All the designs system are simulated using a mathematical framework and a power-full simulation tool.Este trabalho aborda o processo de modelação e controlo de um veículo aéreo não tripulado híbrido com o objetivo de proporcionar manobras de transição de carga. Drones híbridos trazem grandes vantagem com a sua capacidade de voar em dois modos de voo, de asa rotativa e asa fixa. Por outro lado, estas vantagens adicionam complexidade ao sistema dificultando o processo de modulação e controlo. Nestetrabalhoestápresenteummodelodeumdronetrirotortendodoisrotoresmovíveis. Este contém todas as dinâmicas especificas que um sistema deesta categoria de UAV obriga. O modelo é posteriormente validado com dois controladores separados em modo de voo, capazes de proporcionar medidas de seguimento de trajetória em cada modo, usando uma técnica de alocação de controlo personalizada que diferencia o controlo em três partes: vertical, horizontal e de transição. Por fim, é proposto um controlador híbrido contento uma máquina de estados capaz de tratar de eventos lógicos, de modo a proporcionar transições de modo de voo autónomas em pleno voo. Todos os sistemas propostos são devidamente simulados usando ferramentas matemáticas e também poderosos sistemas de simulação

Investigation of a tilt-wing proof of concept for a high-speed VTOL jet UAV using thrust vectoring for balance

Success of Special operations forces (SOF) missions depends on a high level of situational awareness within sensitive areas of interest, especially when arriving in volatile, sensitive environments. Oftentimes intelligence, surveillance, and reconnaissance (ISR) UAS platforms expand situational awareness for small, clandestine teams for Special Operations; however, there is a demonstrable need for a high-speed, long-range platform capable of point launches and landings to improve outcomes of rapid response missions. This thesis intends to provide the fundamental mechanics of one solution to that platform centered on the premise of a conventional jet UAV being modified into a tilt-wing V/STOL UAV using its existing features.The proof of concept being explored emulates modifying a fast, conventional UAV configuration. That concept possessed a tubular carbon spar that was used as a point of rotation. Motor pods were attached to the wing for the lift system and only used during takeoffs and landings, after which, the propellers were folded away to reduce drag in cruise. Additionally, a thrust vectoring unit was added to the central propulsion system for balance under stall-speeds. The final configuration culminated into a novel tilt-wing VTOL system with the potential to add minimal weight and drag increases to the base configuration. This configuration was then scrutinized for its fundamental challenges to evaluate its effectiveness.Through the research and development of the proof of concept, several milestones were met. Solidworks Flow Simulation (SWFS) was validated for unsteady propeller analyses. Using lessons learned from this validation effort, the tilt-wing concept was found to have the best net lift characteristics over the tilt-rotor after verifying the effects of download experienced in tilt-rotors in SWFS. In fact, the tilt-rotor expressed a net loss in lift of 25% whereas the tilt-wing saw negligible losses. This fully rationalized the tilt-wing as a viable system for the mission profile. After construction and preliminary testing of a prototype, a CG condition was discovered for balancing novel VTOL concepts using separated propulsion systems. This discovery was key in demonstrating the tilt-wing proof of concept where it was shown to execute point launches and landings as intended through simulated testing where the runway footprint of the prototype model was reduced significantly

Flight Testing Small UAVs for Aerodynamic Parameter Estimation

A flight data acquisition system was developed to aid unmanned vehicle designers in verifying the vehicle\u27s design performance. The system is reconfigurable and allows the designer to choose the correct combination of complexity, risk, and cost for a given flight test. The designer can also reconfigure the system to meet packaging and integration requirements. System functionality, repeatbility, and accuracy was validated by collecting data during multiple flights of a radio-controlled aircraft. Future work includes sensor fusion, thrust prediction methods, stability and control derivative estimation, and growing Cal Poly\u27s small-scale component aerodynamic database

System-of-Systems Considerations in the Notional Development of a Metropolitan Aerial Transportation System

There are substantial future challenges related to sustaining and improving efficient, cost-effective, and environmentally friendly transportation options for urban regions. Over the past several decades there has been a worldwide trend towards increasing urbanization of society. Accompanying this urbanization are increasing surface transportation infrastructure costs and, despite public infrastructure investments, increasing surface transportation "gridlock." In addition to this global urbanization trend, there has been a substantial increase in concern regarding energy sustainability, fossil fuel emissions, and the potential implications of global climate change. A recently completed study investigated the feasibility of an aviation solution for future urban transportation (refs. 1, 2). Such an aerial transportation system could ideally address some of the above noted concerns related to urbanization, transportation gridlock, and fossil fuel emissions (ref. 3). A metro/regional aerial transportation system could also provide enhanced transportation flexibility to accommodate extraordinary events such as surface (rail/road) transportation network disruptions and emergency/disaster relief responses