Rotational speed control of multirotor UAV's propulsion unit based on fractional-order PI controller

In this paper the synthesis of a rotational speed closed-loop control system based on a fractional-order proportional-integral (FOPI) controller is presented. In particular, it is proposed the use of the SCoMR-FOPI procedure as the controller tuning method for an unmanned aerial vehicle’s propulsion unit. In this framework, both the Hermite-Biehler and Pontryagin theorems are used to predefine a stability region for the controller. Several simulations were conducted in order to try to answer the questions – is the FOPI controller good enough to be an alternative to more complex FOPID controllers? In what circumstances can it be advantageous over the ubiquitous PID? How robust this fractional-order controller is regarding the parametric uncertainty of considered propulsion unit model?info:eu-repo/semantics/publishedVersio

Novel Model-Based Control Mixing Strategy for a Coaxial Push-Pull Multirotor

A Coaxial push-pull multirotor is a Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicle (UAV) having 2n (n ∈ IN*) rotors arranged in n blocks of two coaxial contrarotating rotors. A model-based control allocation algorithm (mixer) for this architecture is proposed. The novelty of the approach lies in the fact that the coaxial aerodynamic interference occurring between the pairs of superimposed rotors is not neglected but rather nonlinear empiric models of the coaxial aerodynamic thrust and torque are used to build the mixer. Real flight experiments were conducted and the new approach showed promising results

Fault Diagnosis and Fault-Tolerant Control of Unmanned Aerial Vehicles

With the increasing demand for unmanned aerial vehicles (UAVs) in both military and civilian applications, critical safety issues need to be specially considered in order to make better and wider use of them. UAVs are usually employed to work in hazardous and complex environments, which may seriously threaten the safety and reliability of UAVs. Therefore, the safety and reliability of UAVs are becoming imperative for development of advanced intelligent control systems. The key challenge now is the lack of fully autonomous and reliable control techniques in face of different operation conditions and sophisticated environments. Further development of unmanned aerial vehicle (UAV) control systems is required to be reliable in the presence of system component faults and to be insensitive to model uncertainties and external environmental disturbances. This thesis research aims to design and develop novel control schemes for UAVs with consideration of all the factors that may threaten their safety and reliability. A novel adaptive sliding mode control (SMC) strategy is proposed to accommodate model uncertainties and actuator faults for an unmanned quadrotor helicopter. Compared with the existing adaptive SMC strategies in the literature, the proposed adaptive scheme can tolerate larger actuator faults without stimulating control chattering due to the use of adaptation parameters in both continuous and discontinuous control parts. Furthermore, a fuzzy logic-based boundary layer and a nonlinear disturbance observer are synthesized to further improve the capability of the designed control scheme for tolerating model uncertainties, actuator faults, and unknown external disturbances while preventing overestimation of the adaptive control parameters and suppressing the control chattering effect. Then, a cost-effective fault estimation scheme with a parallel bank of recurrent neural networks (RNNs) is proposed to accurately estimate actuator fault magnitude and an active fault-tolerant control (FTC) framework is established for a closed-loop quadrotor helicopter system. Finally, a reconfigurable control allocation approach is combined with adaptive SMC to achieve the capability of tolerating complete actuator failures with application to a modified octorotor helicopter. The significance of this proposed control scheme is that the stability of the closed-loop system is theoretically guaranteed in the presence of both single and simultaneous actuator faults

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

Proceedings of the International Micro Air Vehicles Conference and Flight Competition 2017 (IMAV 2017)

The IMAV 2017 conference has been held at ISAE-SUPAERO, Toulouse, France from Sept. 18 to Sept. 21, 2017. More than 250 participants coming from 30 different countries worldwide have presented their latest research activities in the field of drones. 38 papers have been presented during the conference including various topics such as Aerodynamics, Aeroacoustics, Propulsion, Autopilots, Sensors, Communication systems, Mission planning techniques, Artificial Intelligence, Human-machine cooperation as applied to drones

Filling the sensor gap: applying UAS technology to land-use research

Collecting data at ground level typically yields the most detailed information on a subject, however it is limited by the spatial extent that can be covered within a specific timeframe. Remote sensing from an aerial platform increases this spatial extent and the deployment of unmanned aircraft systems (UAS) can provide this ability directly to researchers at an affordable cost and at data resolutions that are very applicable for site specific surveys. Further to this, developments in photogrammetry software allow the creation of orthorectified spectral and structural data that can that can be classified via pixel or object-based analysis methods and applied to a wide variety of different land-use research areas. In this study a sensor package was created consisting of two off the shelf digital cameras, one un-modified and the other modified to be sensitive to near infra-red wavelengths of light. A multi-rotor aerial platform utilising an open source autopilot was assembled to enable data collection and a processing pipeline was devised to transform RAW camera imagery into georeferenced and orthorectified data, using computer vision software following the structure from motion (SfM) approach. This remote sensing tool was applied to a variety of land-use research study sites in central Scotland and Northern England with two main areas focused on. (1) The use of spectral and structural data for the detection of disease within a potato (Solanum tuberosum L.) crop revealed that UAS could be an effective tool for mapping the distribution of diseased plants. (2) Comparisons between aerial data and traditional manual assessments of a trial crop of potatoes revealed that the earliest stages of plant emergence could not be detected but later plant counts, and ground cover estimates correlated well, indicating that UAS could be an effective trials monitoring tool, giving extra structural data and potentially a more representative measure of canopy ground cover compared to traditional manual techniques. This study also showed results from experimental applications investigating the mapping of invasive non-native species and ways of enabling upscaling of greenhouse gas emissions from different land use types. Therefore, this study demonstrates that UAS equipped with basic imaging technology can be of use to a variety of land-use research areas and look set to become an invaluable remote sensing tool, which will improve further with the addition of calibrated multi-spectral sensor payloads, high precision global navigation satellite systems and relaxation in regulations governing their use