Mathematical modeling and vertical flight control of a tilt-wing UAV

This paper presents a mathematical model and vertical flight control algorithms for a new tilt-wing unmanned aerial vehicle (UAV). The vehicle is capable of vertical take-off and landing (VTOL). Due to its tilt-wing structure, it can also fly horizontally. The mathematical model of the vehicle is obtained using Newton-Euler formulation. A gravity compensated PID controller is designed for altitude control, and three PID controllers are designed for attitude stabilization of the vehicle. Performances of these controllers are found to be quite satisfactory as demonstrated by indoor and outdoor flight experiments

EKF-based parameter identification of multi-rotor unmanned aerial vehiclesmodels

This work presents a method for estimating the model parameters of multi-rotor unmanned aerial vehicles by means of an extended Kalman filter. Different from test-bed based identification methods, the proposed approach estimates all the model parameters of a multi-rotor aerial vehicle, using a single online estimation process that integrates measurements that can be obtained directly from onboard sensors commonly available in this kind of UAV. In order to develop the proposed method, the observability property of the system is investigated by means of a nonlinear observability analysis. First, the dynamic models of three classes of multi-rotor aerial vehicles are presented. Then, in order to carry out the observability analysis, the state vector is augmented by considering the parameters to be identified as state variables with zero dynamics. From the analysis, the sets of measurements from which the model parameters can be estimated are derived. Furthermore, the necessary conditions that must be satisfied in order to obtain the observability results are given. An extensive set of computer simulations is carried out in order to validate the proposed method. According to the simulation results, it is feasible to estimate all the model parameters of a multi-rotor aerial vehicle in a single estimation process by means of an extended Kalman filter that is updated with measurements obtained directly from the onboard sensors. Furthermore, in order to better validate the proposed method, the model parameters of a custom-built quadrotor were estimated from actual flight log data. The experimental results show that the proposed method is suitable to be practically appliedPeer ReviewedPostprint (published version

Validation of Quad Tail-sitter VTOL UAV Model in Fixed Wing Mode

Vertical take-off and landing (VTOL) is a type of unmanned aerial vehicle (UAV) that is growing rapidly because its ability to take off and land anywhere in tight spaces. One type of VTOL UAV, the tail-sitter, has the best efficiency. However, besides the efficiency offered, some challenges must still be overcome, including the complexity of combining the ability to hover like a helicopter and fly horizontally like a fixed-wing aircraft. This research has two contributions: in the form of how the analytical model is generated and the tools used (specifically for the small VTOL quad tail-sitter UAV) and how to utilize off-the-shelf components for UAV empirical modeling. This research focuses on increasing the speed and accuracy of the UAV VTOL control design in fixed-wing mode. The first step is to carry out analysis and simulation. The model is analytically obtained using OpenVSP in longitudinal and lateral modes. The next step is to realize this analytical model for both the aircraft and the controls. The third step is to measure the flight characteristics of the aircraft. Based on the data recorded during flights, an empirical model is made using system identification technique. The final step is to vali-date the analytical model with the empirical model. The results show that the characteristics of the analytical mode fulfill the specified requirements and are close to the empirical model. Thus, it can be concluded that the analytical model can be implemented directly, and consequently, the VTOL UAV design and development process has been shortened

Technology review of flight crucial flight controls

The results of a technology survey in flight crucial flight controls conducted as a data base for planning future research and technology programs are provided. Free world countries were surveyed with primary emphasis on the United States and Western Europe because that is where the most advanced technology resides. The survey includes major contemporary systems on operational aircraft, R&D flight programs, advanced aircraft developments, and major research and technology programs. The survey was not intended to be an in-depth treatment of the technology elements, but rather a study of major trends in systems level technology. The information was collected from open literature, personal communications and a tour of several companies, government organizations and research laboratories in the United States, United Kingdom, France, and the Federal Republic of Germany

비행조건과 돌풍의 영향을 고려한 Blade Element Momentum Theory와 쿼드로터형 무인 비행체의 동역학 결합 해석

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2019. 2. 신상준.New industries such as reconnaissance, surveillance, and courier services are attracting attention as demand and supply of unmanned aerial vehicles increase. Accordingly, many related technologies of unmanned aerial vehicles are being developed. Among them, quadrotor unmanned aerial vehicle (UAV), which is the most famous, is widely used. The vision arrival, and departure algorithm, and many other new technologies have been used to facilitate the use of UAV in urban areas, such as courier transportation or reconnaissance. However, there is a high risk of falling due to crosswinds or shear flows between buildings in urban areas. Therefore, this thesis aims at realistic flight prediction capability by combination between six degree of freedom flight dynamics and precision aerodynamics while considering gust as significant influencing factor. Transformation procedure into the wind frame is conducted to analyze gust. Hover, forward flight, and climb of an individual rotor are analyzed using the blade element momentum theory (BEMT) considering rigid blade flapping. In addition, coupled analysis between 6-degree-of-freedom (DOF) flight and BEMT is attempted. Reliability of the software, XFOIL, is demonstrated by comparison against CFD. Validation for hover, forward flight, and climb condition is attempted using the present BEMT. The experimental environment for the target UAV and verification for hover are performed. In addition, experimental equipment is designed for the wind tunnel test and the experiment will be performed. Through the dynamic characteristics of the HILS system provided by DJI and the parameter estimation, the present 6 degree of freedom simulation that can estimate the gain of the black box type flight controller is constructed.무인비행체의 수요 및 공급이 증가하고 정찰, 감시, 택배등의 새로운 산업이 각광받고 있다. 이에 따라 무인비행체의 관련된 많은 기술들이 개발되는 실정이며 그 중에서도 가장 복잡하지 않은 형태인 쿼드로터 무인기가 많이 사용되고 있다. 이 무인기를 사용하여 도심지에서 택배 운송 혹은 정찰 등에 용이하게 쓰기 위해 카메라를 이용한 비전 알고리즘, 출 도착 알고리즘, 그 외의 많은 신기술들이 사용되고 있으나 도심지의 무인 비행체 운용여건상 건물 사이를 흐르는 측풍 이나 전단류 등에 의하여 추락할 위험성이 높다. 따라서 본 논문에서는 그러한 위험성을 해석하기 위해, 쿼드로터형 무인비행체의 공력 특성을 반영한 6 자유도 해석의 프레임워크를 구축하였다. 돌풍 및 비행 조건들을 고려하기 위해 바람의 좌표계 변환 개념을 제시하였으며, 강체 블레이드 플래핑 운동방정식을 고려한 깃 요소 및 운동량 이론을 이용해 개별 로터의 제자리, 전진, 상승 비행을 해석하였다. 또한 XFOIL을 사용하여 공력 결과를 도출하였고 이를 전산유체역학 해석으로 검증하였다. 개발된 BEMT를 이용하여 제자리, 상승, 전진 비행 조건에 대해 검증을 수행하였다. 또한 목표 기체인 DJI Matrice 100의 블레이드의 삼차원 스캐닝을 수행하여 로터의 제자리 비행 특성을 비교 및 검증하였으며, 추가 풍동실험을 위해 실험장비를 설계하였다. 또한 DJI에서 제공하는 HILS 시스템의 동특성 파악과 파라미터 추정을 통해 블랙박스 형태인 비행 제어기의 게인을 추정 가능한 6 자유도 시뮬레이션을 구축하였다.Chpater 1 Introduction 1 1.1 Background and Motivation 1 1.2 Objectives and Thesis Overview 5 Chpater 2 Theoretical Background 6 2.1 Modified Blade Element Momentum Theory 6 2.1.1 Lift and Drag aerodynamic coefficient table 10 2.1.2 Frame Transformation 14 2.1.3 Aerodynamic Loads Calculation using Blade Element Momentum Theory 20 2.1.4 Blade Element Momentum Theory considering Rigid Blade Flapping 25 2.2 Hybrid Analysis between Blade Element Momentum Theory and Flight Dynamics 29 2.2.1 Quad-rotor Flight Dynamics 29 2.2.2 Coupled Quadrotor Dynamics with Blade Element Momentum Theory 33 2.3 System Identification and Parameter Estimation 35 Chpater 3 Results 41 3.1 XFOIL Verification 41 3.2 Blade Element Momentum Theory verification for hover, climb, and forward flight condition 45 3.3 Coupled Flight Dynamics Simulation Result 59 3.4 Experiment Setting and Result 63 3.4.1 Individual Rotor Thrust Test 63 3.4.2 Hardware Simulation in Loop and Experiment setting for Flight Test 68 Chpater 4 Conclusion and Future Works 78 4.1 Conclusion 78 4.2 Future Works 79 Reference 80 국문초록 84Maste

Simplified Dynamic Models for Modern Flying Vehicles

This dissertation contributes to the definition of minimum–complexity approaches that allows for representing realistic effects typical of modern fixed- and rotary-wing configurations, limiting as much as possible increase in order and overall complexity of the dynamic model of the class of aerial vehicles considered. In particular, the thesis deals with (1) the development of a novel low–order mathematical model for including structural deformation effects in the analysis of response to control inputs of flexible aircraft; (2) the derivation of a simplified models for unsteady aerodynamic effects, with an application to helicopter main rotor; (3) modeling and assessment of the maneuvering potential for a novel quadrotor configuration with tilting rotors. A mixed Newtonian–Lagrangian approach is proposed for the derivation of flexible aircraft equations of motion, where Lagrange equations are used for flexible degrees of freedom, discretized by means of Gal¨erkin method, whereas the evolution of transport degrees of freedom (position and attitude variables) is obtained by means of Newton second law and generalized Euler equation. A strong link with conventional rigid aircraft equations of motion is maintained, that allows highlighting those terms less relevant for aircraft response. When negligible, these terms are removed and a minimum complexity flexible aircraft model is derived, suitable for real–time simulation and control law synthesis. Similarly, unsteady aerodynamic effects over a rotating blade are modeled by means of an available approach, namely the ONERA dynamic stall model. Some reasonable simplifying assumptions based on the comparison of simulation results with a quasi–static aerodynamic model are then derived and a minimum complexity, 6 degree–of–freedom helicopter model is proposed which takes into account the issues related to retreating blade stall. Finally, an existing inverse simulation algorithm is applied for the first time to the determination of the control laws for tracking desired maneuvers by means of an unconventional quad-rotor configuration featuring four tilting rotors. This novel configuration allow access to an extended maneuver envelope and ad hoc instruments are needed for assessing its maneuvering potential. For all the considered problems, the approaches developed are demonstrated by means of numerical results, applied to a particular class of modern fixed- or rotary-wing aircraft, but the possibility of extending the results to different classes of vehicles is also highlighted

The Phoenix Drone: An Open-Source Dual-Rotor Tail-Sitter Platform for Research and Education

In this paper, we introduce the Phoenix drone: the first completely open-source tail-sitter micro aerial vehicle (MAV) platform. The vehicle has a highly versatile, dual-rotor design and is engineered to be low-cost and easily extensible/modifiable. Our open-source release includes all of the design documents, software resources, and simulation tools needed to build and fly a high-performance tail-sitter for research and educational purposes. The drone has been developed for precision flight with a high degree of control authority. Our design methodology included extensive testing and characterization of the aerodynamic properties of the vehicle. The platform incorporates many off-the-shelf components and 3D-printed parts, in order to keep the cost down. Nonetheless, the paper includes results from flight trials which demonstrate that the vehicle is capable of very stable hovering and accurate trajectory tracking. Our hope is that the open-source Phoenix reference design will be useful to both researchers and educators. In particular, the details in this paper and the available open-source materials should enable learners to gain an understanding of aerodynamics, flight control, state estimation, software design, and simulation, while experimenting with a unique aerial robot.Comment: In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA'19), Montreal, Canada, May 20-24, 201

Unified incremental nonlinear controller for the transition control of a hybrid dual-axis tilting rotor quad-plane

Overactuated Tilt Rotor Unmanned Aerial Vehicles are renowned for exceptional wind resistance and a broad operational range, which poses complex control challenges due to non-affine dynamics. Traditional solutions employ multi-state switched logic controllers for transitions. Our study introduces a novel unified incremental nonlinear controller for overactuated dual-axis tilting rotor quad-planes, seamlessly managing pitch, roll, and physical actuator commands. The control allocation problem is addressed using a SQP iterative optimization algorithm, well-suited for nonlinear actuator effectiveness in thrust vectoring vehicles. The controller design integrates desired roll and pitch angle inputs. These desired attitude angles are autonomously managed by the controller and then conveyed to the vehicle during slow airspeed phases, when the vehicle maintains its 6 DOF. We incorporate an AoA protection logic to prevent wing stall and a yaw rate reference model for coordinated turns. Flight tests confirm the controller's effectiveness in transitioning from hovering to forward flight, achieving desired vertical and lateral accelerations, and reverting to hovering