Modeling and Robust Attitude Controller Design for a Small Size Helicopter

This paper addresses the design and application controller for a small-size unmanned aerial vehicle (UAV). In this work, the main objective is to study the modeling and attitude controller design for a small size helicopter. Based on a non-simplified helicopter model, a new robust attitude control law, which is combined with a nonlinear control method and a model-free method, is proposed in this paper. Both wind gust and ground effect phenomena conditions are involved in this experiment and the result on a real helicopter platform demonstrates the effectiveness of the proposed control algorithm and robustness of its resultant controller.Comment: 6 page

Automatic Flight Control Systems

The history of flight control is inseparably linked to the history of aviation itself. Since the early days, the concept of automatic flight control systems has evolved from mechanical control systems to highly advanced automatic fly-by-wire flight control systems which can be found nowadays in military jets and civil airliners. Even today, many research efforts are made for the further development of these flight control systems in various aspects. Recent new developments in this field focus on a wealth of different aspects. This book focuses on a selection of key research areas, such as inertial navigation, control of unmanned aircraft and helicopters, trajectory control of an unmanned space re-entry vehicle, aeroservoelastic control, adaptive flight control, and fault tolerant flight control. This book consists of two major sections. The first section focuses on a literature review and some recent theoretical developments in flight control systems. The second section discusses some concepts of adaptive and fault-tolerant flight control systems. Each technique discussed in this book is illustrated by a relevant example

Aeronautical Engineering: A special bibliography with indexes, supplement 62

This bibliography lists 306 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1975

Experimental Investigation of Shrouded Rotor Micro Air Vehicle in Hover and in Edgewise Gusts

Due to the hover capability of rotary wing Micro Air Vehicles (MAVs), it is of interest to improve their aerodynamic performance, and hence hover endurance (or payload capability). In this research, a shrouded rotor conguration is studied and implemented, that has the potential to oer two key operational benets: enhanced system thrust for a given input power, and improved structural rigidity and crashworthiness of an MAV platform. The main challenges involved in realising such a system for a lightweight craft are: design of a lightweight and stiff shroud, and increased sensitivity to external flow disturbances that can affect flight stability. These key aspects are addressed and studied in order to assess the capability of the shrouded rotor as a platform of choice for MAV applications. A fully functional shrouded rotor vehicle (disk loading 60 N/m2) was designed and constructed with key shroud design variables derived from previous studies on micro shrouded rotors. The vehicle weighed about 280 g (244 mm rotor diameter). The shrouded rotor had a 30% increase in power loading in hover compared to an unshrouded rotor. Due to the stiff, lightweight shroud construction, a net payload benefit of 20-30 g was achieved. The different components such as the rotor, stabilizer bar, yaw control vanes and the shroud were systematically studied for system efficiency and overall aerodynamic improvements. Analysis of the data showed that the chosen shroud dimensions was close to optimum for a design payload of 250 g. Risk reduction prototypes were built to sequentially arrive at the nal conguration. In order to prevent periodic oscillations in flight, a hingeless rotor was incorporated in the shroud. The vehicle was successfully flight tested in hover with a proportional-integral-derivative feedback controller. A flybarless rotor was incorporated for efficiency and control moment improvements. Time domain system identification of the attitude dynamics of the flybar and flybarless rotor vehicle was conducted about hover. Controllability metrics were extracted based on controllability gramian treatment for the flybar and flybarless rotor. In edgewise gusts, the shrouded rotor generated up to 3 times greater pitching moment and 80% greater drag than an equivalent unshrouded rotor. In order to improve gust tolerance and control moments, rotor design optimizations were made by varying solidity, collective, operating RPM and planform. A rectangular planform rotor at a collective of 18 deg was seen to offer the highest control moments. The shrouded rotor produced 100% higher control moments due to pressure asymmetry arising from cyclic control of the rotor. It was seen that the control margin of the shrouded rotor increased as the disk loading increased, which is however deleterious in terms of hover performance. This is an important trade-off that needs to be considered. The flight performance of the vehicle in terms of edgewise gust disturbance rejection was tested in a series of bench top and free flight tests. A standard table fan and an open jet wind tunnel setup was used for bench top setup. The shrouded rotor had an edgewise gust tolerance of about 3 m/s while the unshrouded rotor could tolerate edgewise gusts greater than 5 m/s. Free flight tests on the vehicle, using VICON for position feedback control, indicated the capability of the vehicle to recover from gust impulse inputs from a pedestal fan at low gust values (up to 3 m/s)

무익기형 전기 추진 수직 이착륙기에 대한 다학제 해석 및 시뮬레이션 프레임워크

학위논문(박사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2023. 2. 이관중.A wingless-type electric vertical take-off and landing (eVTOL) is one of the representative aircrafts utilized logistics and delivery, search and rescue, military, agriculture, and inspection of structures. For a small unmanned aerial vehicles of the wingless-type eVTOL, a quadrotor is a representative configuration to operate those missions. For a large size of the wingless-type eVTOL, it is an aircraft for urban air mobility service (UAM) specialized for intracity point-to-point due to its advantages such as efficient hover performance, high gust resistance, and relatively low noisiness. The rotating speed of the multiple rotors in the wingless-type eVTOL has to be changed continuously to achieve stable flight. Moreover, the speed and the loaded torque of the motors also continuously change. Therefore, it is necessary to analyze the rotor thrust and torque with respect to the speed of each rotor as assigned by the controller to predict the flight performance of the wingless-type eVTOL. The electric power required by the motors is also necessary to be predicted based on the torque loaded to the motors to maintain the rotating speed. This study suggests a flight simulation framework based on these multidisciplinary analyses including control, rotor aerodynamics, and electric propulsion system analysis. Using the flight simulation framework, it is possible to predict the flight performance of the wingless-type eVTOL for given operating conditions. The flight simulation framework can predict the overall performance required to resist the winds and the corresponding battery energy of a quadrotor. Flight endurance of an industrial quadrotor was examined under light, moderate, and strong breeze modeled by von Kármán wind turbulence with Beaufort wind force scale. As a result, it is found that the excess battery energy is increased with ground speed, even under the same wind conditions. As the ground speed increases, the airspeed is increased, led to higher frame drag, position error, pitch angle, and required mechanical power, consequently. Moreover, the quadrotor is not operable beyond a certain wind and ground speed since the required rotational speed of rotors exceeds the speed limit of motors. The simulation framework can also predict the overall performance of a wingless eVTOL for UAM service. Because of its multiple rotors, rotor–rotor interference inevitably affects flight performance, mainly depending on inter-rotor distance and rotor rotation directions. In this case, there is an optimal rotation direction of the multiple rotors to be favorable in actual operation. In this study, it was proposed that a concept of rotor rotation direction that achieves the desirable flight performance in actual operation. The concept is called FRRA (Front rotors Retreating side and Rear rotors Advancing side). It was found that FRRA minimizes thrust loss due to rotor-rotor interference in high-speed forward flight. For a generic mission profile of UAM service, the rotation direction set by FRRA reduces the battery energy consumption of 7 % in comparison to the rotation direction of unfavorable rotor-rotor interference in operation.무익기형 전기 추진 수직 이착륙기는 택배 및 운송 서비스, 수색 및 구조, 국방, 농업, 구조물 점검과 같은 분야에서 대표적으로 이용되고 있는 항공기이다. 쿼드로터는 이러한 임무를 수행하기 위한 대표적인 소형 무익기형 전기 추진 수직 이착륙기이다. 대형 무익기형 전기 추진 수직 이착륙기는 효율적인 제자리 비행 성능, 높은 내풍성, 낮은 소음 공해와 같은 특징으로 인해 도심 내 운항 서비스를 위한 항공기로 활용되고 있다. 무익기형 전기 추진 수직 이착륙기의 여러 회전 날개는 안정된 비행을 유지하기 위해, 지속해서 회전 속도를 변화시킨다. 게다가, 모터의 회전 속도와 부하되는 토크 또한 지속적으로 변화한다. 그러므로 무익기형 전기 추진 수직 이착륙기의 비행 성능을 예측하기 위해, 제어기에서 각 회전 날개에 부여된 회전 속도에 따른 추력 및 토크를 해석해야 한다. 그리고 이러한 회전 날개의 회전 속도를 유지하기 위해 모터에 부하 되는 토크를 기반으로, 모터에서 요구되는 전력을 예측해야 한다. 본 논문에서는 제어, 회전 날개 공력, 전기 추진 시스템 해석이 포함된 다학제 해석 기반의 비행 시뮬레이션 프레임워크를 제시한다. 비행 시뮬레이션 프레임워크를 이용하여, 실제 운용 환경에서의 무익기형 전기 추진 수직 이착륙기 비행 성능을 예측할 수 있다. 비행 시뮬레이션 프레임워크를 활용하여 쿼드로터에 대해 외풍을 저항하기 위한 비행 전반적인 성능과 그에 따른 배터리 에너지 소모를 예측하였다. Von Kármán 외풍 난류와 Beaufort 외풍 강도 등급을 활용하여 남실바람, 건들바람, 된바람 환경에 대한 산업용 쿼드로터의 비행시간을 조사하였다. 그 결과, 동일한 외풍 환경일지라도 전진 비행 속도가 증가할수록 배터리 소요 에너지가 증가한다는 것을 밝혔다. 전진 비행 속도의 증가로 인해 쿼드로터에 유입되는 유속이 증가하여, 동체 항력, 위치 오차, 기수 내림 각도, 요구 기계 동력이 증가하였다. 그리고 특정 외풍 속도와 전진 속도 이상에서의 쿼드로터는 요구되는 회전 날개의 회전 속도가 모터의 회전 속도의 한계보다 높으므로 비행할 수 없었다. 또한, 비행 시뮬레이션 프레임워크를 활용하여 도심 운항 서비스용 무익기형 전기 추진 수직 이착륙기의 전반적인 비행 성능을 예측하였다. 여러 회전 날개의 특징으로 인해, 회전 날개 간 거리와 회전 날개의 회전 방향에 따라 회전 날개 간 간섭효과가 필연적으로 비행 성능에 영향을 미친다. 이때, 운용에 유리한 최적의 회전 날개 회전 방향이 존재한다. 본 논문에서 실제 운용에서 바람직한 비행 성능을 발휘하는 회전 날개의 회전 방향에 대한 개념인 FRRA를 제시하였다. FRRA는 전방 로터의 후퇴 측과 후방 로터의 전진 측이 일직선으로 정렬된 상태의 회전 방향이다. FRRA 회전 방향은 고속 전진 비행에서 회전 날개 간 간섭효과로 인한 추력 손실이 최소화된다. 회전 날개 간 간섭효과로 인해 불리한 비행 성능을 가지는 회전 방향 대비 FRRA 회전 방향은 도심 항공 교통 서비스에 대한 일반적인 운용에서 배터리 소모율이 7% 정도 감소하였다.Chapter 1. Introduction 1 1.1 Overview of wingless-type eVTOL 1 1.2 Previous studies about wingless-type eVTOL 6 1.2.1 Multidisciplinary analysis of control, aerodynamic, and EPS 6 1.2.2 External wind of wingless-type eVTOLs for small UAVs 9 1.2.3 Rotor-rotor interference of wingless-type eVTOLs for UAM 10 1.3 Motivation and scope of the dissertation 12 Chapter 2. Simulation Framework 16 2.1 Layout and analysis modules in simulation framework 16 2.1.1 Cascade PID control module 19 2.1.1 Aerodynamic analysis module 24 2.1.2 Electric propulsion system analysis module 30 2.1.3 6-DOF dynamics analysis module 33 2.2 Add-on modules for actual operation 37 2.2.1 Wind turbulence module 37 2.2.2 Rotor-rotor interference module 39 Chapter 3. Validation of Simulation Framework 44 3.1 Static thrust and torque on a single rotor test 44 3.2 Wind resistance test 46 3.3 Rotor-rotor interference of tandem rotors 52 3.4 Rotor-rotor interaction of a quadrotor in CFD 54 3.5 Investigation of rotor-rotor interference with respect to rotation directions in a quadrotor 58 Chapter 4. Flight Performance of Quadrotor under Wind Turbulence 65 4.1 Flight conditions 65 4.2 Wind turbulence conditions 66 4.3 Simulation results 69 Chapter 5. Flight Performance of Wingless-type eVTOL for UAM Service with Respect to the Rotor Rotation Directions 78 5.1 Hypothetical model of a wingless-type eVTOL for UAM service 78 5.2 Rotor rotation directions and aerodynamic performance 83 5.2.1 Hover flight 86 5.2.2 Forward flight at 100 km/h 88 5.2.3 Forward flight in the airspeed of 100 km/h with 30 yaw angle 93 5.3 Surrogate models including the rotor-rotor interaction effect 96 5.4 Simulation results 99 Chapter 6. Conclusion 112 6.1 Summary 112 6.2 Originalities of the dissertation 113 6.3 Future works 116 Appendix 118 References 127 국문 초록 144박

Aeronautical engineering: A continuing bibliography with indexes (supplement 269)

This bibliography lists 539 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

DESIGN OF AVIONICS AND CONTROLLERS FOR AUTONOMOUS TAKEOFF, HOVER AND LANDING OF A MINI-TANDEM HELICOPTER

Robotics autonomy is an active research area these days and promises very useful applications. A lot of research has been carried out on Vertical Takeoff and Landing (VTOL) vehicles especially single rotor small scale helicopters. This thesis focuses on a small scale twin rotor helicopter. These helicopters are more useful because of their power efficiency, scalability, long range of center of gravity, shorter blades and most importantly their "all lift" feature. By "all lift" we mean that unlike single rotor helicopters where tail rotor's power is wasted just to cancel the torque of the main rotor both of its rotors are used for generating lift. This makes twin rotors ideal for lifting heavy weights. This thesis considers avionics systems and the controllers development for a twin rotor. It involves electronic component selection and integration, software development, system identification and design of zero rate compensators. The compensators designed are responsible for autonomous take-off, hover and landing of this unmanned aerial vehicle (UAV). Both time and frequency domain system identification approaches were evaluated and a selection was made based on hardware limitations. A systematic approach is developed to demonstrate that a rapid prototyping UAV can be designed from cheap off-the-shelf components that are readily available and functionally compatible. At the end some modifications to existing mechanical structure are proposed for more robust outdoor hovering

Aeronautical engineering: A continuing bibliography with indexes (supplement 271)

This bibliography lists 666 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1991. Subject coverage includes design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics