꼬리날개 없는 날갯짓 초소형 비행체의 자세조절

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 기계항공공학부, 2020. 8. 김현진.최근 생체모방에 대한 관심이 커지면서 생명체의 구조, 외형, 움직임, 행동을 분석하여 그들의 장점을 로봇에 적용시켜 기존의 로봇이 해결할 수 없거나 특별한 임무를 좀 더 효과, 효율적으로 해결하려는 시도가 늘어나고 있다. 이러한 시도는 무인비행체 개발에도 적용되고 있으며 날갯짓 비행체가 이에 해당된다. 날개짓 비행체는 날개의 반복운동을 통해 발생하는 힘을 통해 비행하는 비행체로 일반적으로 꼬리날개의 유무에 따라 새를 모방한 비행체(미익형 비행체)와 곤충을 모방한 비행체(무미익형 비행체)로 구분할 수 있다. 무미익형 비행체의 경우 제자리 비행을 할 수 있고, 크기가 작고 무게가 가벼워 공기저항도 줄일 수 있으며, 날렵한 비행이 가능하다는 장점이 있지만, 수동 안정성을 확보하기 위한 제어면이 충분하지 않고 추력 생성과 동시에 3축으로의 제어 모멘트를 만들 수 있는 복잡한 매커니즘을 가지고 있다는 특징을 가지고 있다. 본 논문에서는 저자의 미익형 비행체의 연구개발 사례를 토대로 자율 비행을 할 수 있는 무미익형 비행체를 개발하기 위한 요소기술들과 초기 비행체 개발을 목표로 한다. 해당 목표를 달성하기 위해 저자는 시중에서 판매되고 있는 RC장난감을 활용해 30 gram 이하의 무게를 가지고 30cm3 이내의 크기를 가지는 무미익형 날갯짓 비행체를 개발을 진행하였다. 비행체 내부에는 구동기로 DC 모터와 서보모터가 존재하며, DC 모터는 날갯짓을 일으키는 기어 박스를 작동시켜 비행체의 무게를 지탱하기 위한 thrust를 생성하며 roll축 방향으로의 moment 생성에 관여하며, 서보모터는 날갯짓에서 발생하는 좌우 thrust의 방향을 조절하여 pitch 와 yaw 축으로의 모멘트를 생성하는데 사용된다. 비행체 내부에는 아두이노 보드 기반의 마이크로프로세서가 탑재되어 있어 비행체를 제어하기 위한 신호를 생성할 수 있으며 블루투스 통신 모듈을 가지고 있기 때문에 외부와 통신 역시 가능하다. 비행체의 자세를 제어하기 위해서는 구동기의 상호작용으로 인해 발생하는 힘의 물리량을 파악하는 것이 중요하다. 이를 위해 날갯짓 메커니즘에서 발생하는 힘을 측정하는 실험을 수행하였다. 측정실험을 통해 DC모터 입력 대비 thrust 크기, 서보모터 command 입력 대비 moment 크기 등의 관계를 파악하였다. 또한 날갯짓 비행체를 공중에 띄울 수 있는 충분한 크기의 thrust를 발생하는 것을 확인하였으며 자세 제어를 위한 모멘트 생성 역시 가능하다는 것을 확인하였다. 비행체의 자세를 제어하기 위해서는 3축 방향으로의 운동방정식을 유도하는 것이 필요하다. 이를 위해 roll, pitch, yaw 축 방향으로 비행체에서 발생하는 힘과 회전 운동과 관련한 운동방정식을 유도했으며 이를 통해 비행체의 자세를 안정화시킬 수 있도록 하는 PID 제어기 형태의 제어기를 설계하였다. 뿐만 아니라, 비행체의 궤적추종 제어를 위해 내부의 자세 제어기에 비행체의 위치를 토대로 계산되는 추가적인 외부 제어기를 설계하여 이중루프 제어기 형태를 적용시켜 시뮬레이션을 통해 비행체의 자세 제어와 궤적 추종 제어가 이루어짐을 확인하였다. 개발한 비행체와 앞서 설계한 제어기가 사용자의 의도에 맞는 성능을 내는지 확인하기 위해 자이로 실험장치를 제작하여 자세 제어 실험을 수행하였다. 해당 실험장치는 roll, pitch, yaw 축으로 회전이 가능하도록 제작하였으며 실험장치 자체의 무게를 줄이기 위해 MDF 소재를 사용하여 구조물를 만들었다. roll, pitch, yaw 3축이 각각 독립적으로 제어하는 것과 3축을 동시에 제어하는 2가지 상황을 고려하였으며 앞서 설계한 제어기가 해당 실험 장치 내부에서 사용자의 의도에 맞게 제어 성능을 보이는지 확인할 수 있었다. 궤적 추종제어를 위해서는 2가지 비행 상황을 설정하였다. 첫 번째 경우, 천장과 비행체 상단부에 실을 연결하여 2D 평면상에서 비행체가 주워진 궤적에 따라 움직이는지, 두 번째 경우, 비행체 상단부에 헬륨이 주입된 풍선을 연결시켜 3D 공간상에서 주워진 궤적을 따라 추종 비행하는지를 확인할 수 있는 상황이다. 두 가지 상황에서 모두 다양한 형태의 궤적을 비행체가 잘 추종하는지를 확인할 수 있었다. 끝으로, 외부 장치(실, 풍선)를 제거하여 공중에서 비행체가 제자리 비행을 할 수 있는지를 검증하는 실험을 진행하였으며, 15초가량 1m3 공간 내에서 제자리 비행이 이루어지는 것을 확인하였다.Flapping wing micro air vehicles (FWMAVs) that generate thrust and lift by flapping their wings are regarded as promising flight vehicles because of their advantages in terms of similar appearance and maneuverability to natural creatures. Reducing weight and air resistance, insect-inspired tailless FWMAVs are an attractive aerial vehicle rather than bird-inspired FWMAVs. However, they are challenging platforms to achieve autonomous flight because they have insufficient control surfaces to secure passive stability and a complicated wing mechanism for generating three-axis control moments simultaneously. In this thesis, as preliminary autonomous flight research, I present the study of an attitude regulation and trajectory tracking control of a tailless FWMAV developed. For these tasks, I develop my platform, which includes two DC motors for generating thrust to support its weight and servo motors for generating three-axis control moments to regulate its flight attitude. First, I conduct the force and moment measurement experiment to confirm the magnitude and direction of the lift and moment generated from the wing mechanism. From the measurement test, it is confirmed that the wing mechanism generates enough thrust to float the vehicle and control moments for attitude regulation. Through the dynamic equations in the three-axis direction of the vehicle, a controller for maintaining a stable attitude of the vehicle can be designed. To this end, a dynamic equation related to the rotational motion in the roll, pitch, and yaw axes is derived. Based on the derived dynamic equations, we design a proportional-integral-differential controller (PID) type controller to compensate for the attitude of the vehicle. Besides, we use a multi-loop control structure (inner-loop: attitude control, outer-loop: position control) to track various trajectories. Simulation results show that the designed controller is effective in regulating the platforms attitude and tracking a trajectory. To check whether the developed vehicle and the designed controller are operating effectively to regulate its attitude, I design a lightweight gyroscope apparatus using medium-density-fiberboard (MDF) material. The rig is capable of freely rotating in the roll, pitch, and yaw axes. I consider two situations in which each axis is controlled independently, and all axes are controlled simultaneously. In both cases, attitude regulation is properly performed. Two flight situations are considered for the trajectory tracking experiment. In the first case, a string connects between the ceiling and the top of the platform. In the second case, the helium-filled balloon is connected to the top of the vehicle. In both cases, the platform tracks various types of trajectories well in error by less than 10 cm. Finally, an experiment is conducted to check whether the tailless FWMAV could fly autonomously in place by removing external devices (string, balloon), and the tailless FWMAV flies within 1 m^3 space for about 15 seconds1.Introduction 1 1.1 Background & Motivation 1 1.2 Literature review 3 1.3 Thesis contribution 7 1.4 Thesis outline 8 2.Design of tailless FWMAV 13 2.1 Platform appearance 13 2.2 Flight control system 17 2.3 Principle of actuator mechanism 18 3.Force measurement experiment 28 3.1 Measurement setup 28 3.2 Measurement results 30 4.Dynamics & Controller design 37 4.1 Preliminary 37 4.2 Dynamics & Attitude control 39 4.2.1 Roll direction 41 4.2.2 Pitch direction 43 4.2.3 Yaw direction 45 4.2.4 PID control 47 4.3 Trajectory tracking control 48 5.Attitude regulation experiments 50 5.1 Design of gyroscope testbed 50 5.2 Experimental environment 52 5.3 Roll axis free 53 5.3.1 Simulation 54 5.3.2 Experiment 55 5.4 Pitch axis free 56 5.4.1 Simulation 57 5.4.2 Experiment 58 5.5 Yaw axis free 59 5.5.1 Simulation 59 5.5.2 Experiment 60 5.6 All axes free 60 5.6.1 Simulation 60 5.6.2 Experiment 61 5.7 Design of universal joint testbed & Experiment 64 6.Trajectory tracking 68 6.1 Simulation 68 6.2 Preliminary 69 6.3 Experiment: Tied-to-the-ceiling 70 6.4 Experiment: Hung-to-a-balloon 71 6.5 Summary 72 6.6 Hovering flight 73 7.Conclusion 83 A Appendix: Wing gearbox 85 A.1 4-bar linkage structure 85 B Appendix: Disturbance observer (DOB) 87 B.1 DOB controller 87 B.2 Simulation 89 B.2.1 Step input 89 B.2.2 Sinusoid input 91 B.3 Experiment 92 References 95Docto

A Flight Mechanics-Centric Review of Bird-Scale Flapping Flight

This paper reviews the flight mechanics and control of birds and bird-size aircraft. It is intended to fill a niche in the current survey literature which focuses primarily on the aerodynamics, flight dynamics and control of insect scale flight. We review the flight mechanics from first principles and summarize some recent results on the stability and control of birds and bird-scale aircraft. Birds spend a considerable portion of their flight in the gliding (i.e., non-flapping) phase. Therefore, we also review the stability and control of gliding flight, and particularly those aspects which are derived from the unique control features of birds

Can scalable design of wings for flapping wing micro air vehicle be inspired by natural flyers?

Lift production is constantly a great challenge for flapping wing micro air vehicles (MAVs). Designing a workable wing, therefore, plays an essential role. Dimensional analysis is an effective and valuable tool in studying the biomechanics of flyers. In this paper, geometric similarity study is firstly presented. Then, the pw−AR ratio is defined and employed in wing performance estimation before the lumped parameter is induced and utilized in wing design. Comprehensive scaling laws on relation of wing performances for natural flyers are next investigated and developed via statistical analysis before being utilized to examine the wing design. Through geometric similarity study and statistical analysis, the results show that the aspect ratio and lumped parameter are independent on mass, and the lumped parameter is inversely proportional to the aspect ratio. The lumped parameters and aspect ratio of flapping wing MAVs correspond to the range of wing performances of natural flyers. Also, the wing performances of existing flapping wing MAVs are examined and follow the scaling laws. Last, the manufactured wings of the flapping wing MAVs are summarized. Our results will, therefore, provide a simple but powerful guideline for biologists and engineers who study the morphology of natural flyers and design flapping wing MAVs

Integration of Polyimide Flexible PCB Wings in Northeastern Aerobat

The principal aim of this Master's thesis is to propel the optimization of the membrane wing structure of the Northeastern Aerobat through origami techniques and enhancing its capacity for secure hovering within confined spaces. Bio-inspired drones offer distinctive capabilities that pave the way for innovative applications, encompassing wildlife monitoring, precision agriculture, search and rescue operations, as well as the augmentation of residential safety. The evolved noise-reduction mechanisms of birds and insects prove advantageous for drones utilized in tasks like surveillance and wildlife observation, ensuring operation devoid of disturbances. Traditional flying drones equipped with rotary or fixed wings encounter notable constraints when navigating narrow pathways. While rotary and fixed-wing systems are conventionally harnessed for surveillance and reconnaissance, the integration of onboard sensor suites within micro aerial vehicles (MAVs) has garnered interest in vigilantly monitoring hazardous scenarios in residential settings. Notwithstanding the agility and commendable fault tolerance exhibited by systems such as quadrotors in demanding conditions, their inflexible body structures impede collision tolerance, necessitating operational spaces free of collisions. Recent years have witnessed an upsurge in integrating soft and pliable materials into the design of such systems; however, the pursuit of aerodynamic efficiency curtails the utilization of excessively flexible materials for rotor blades or propellers. This thesis introduces a design that integrates polyimide flexible PCBs into the wings of the Aerobat and employs guard design incorporating feedback-driven stabilizers, enabling stable hovering flights within Northeastern's Robotics-Inspired Study and Experimentation (RISE) cage.Comment: 42 pages,20 figure

유격을 고려한 무미익 초소형 날갯짓 비행체 통합 설계: 기하분석 및 수치 해석을 통한 접근

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 협동과정 우주시스템 전공, 2021. 2. 신상준.Unlike birds, an insect type tailless flapping wing does not possess tail wings. Therefore, insect type flapping wing may be fabricated in small size and of decreased weight. Because of the taillessness, however, stable flight of an insect type flapping wing depends only on main wings. Thus, a number of researches were conducted regarding its control mechanisms. In this thesis, the trailing edge control, one of the methods developed to produce control moments, is adopted. Such method requires additional shafts that connect the root of the main wing and control mechanism, and the shafts are rotated to deform the wing shape. In this manner, asymmetric aerodynamic forces are produced. The control mechanism uses micro actuators for compact design. However, small size of the micro actuator gearbox causes relatively large backlash and the resulting free play of the main wings that generates undesirable aerodynamic forces. Under such circumstance, design improvement of the control mechanism is conducted to minimize the effects of the free play. First, geometry analysis is performed to investigate the factors that cause the free play. Control mechanism design for the minimized free play is obtained. Then, three-dimensional computer aided design (CAD) of modified configuration is drawn, and kinematic simulations are conducted by RecurDyn to determine the prevention of interference. Finally, the feasibility of modified design is examined by the numerical simulation. The main wings are modeled by the displacement-based geometrically exact beam model combined with cross-sectional analysis. To mimic the free play appropriately, the spring elements are attached to the joints. At the same time, two-dimensional unsteady aerodynamic model is used for aerodynamic forces. Consequently, the reasonable control moments are gathered in terms of the maneuverability.곤충 모방형 날갯짓 비행체는 꼬리날개가 없기 때문에 새 모방형 날갯짓 비행체와 비교하여 가볍고 작게 설계될 수 있다. 그러나, 곤충 모방형 날갯짓 비행체는 꼬리날개가 없다는 특징으로 인하여, 오직 두 날개만을 이용하여 조종력을 발생시킨다. 따라서, 이에 대한 많은 연구가 수행되었고 개발된 여러 자세 제어 방법 중 본 학위 논문에선 날개 끝단 비틀림을 이용한 자세 제어 장치를 다룬다. 해당 방법은 주날개의 뿌리 부분을 자세 제어 장치와 연결하고 이를 회전시켜 날개 끝단에 변형을 발생시킨다. 자세 제어 장치에는 경량화를 위하여 가볍고 작은 장비들이 사용된다. 그러나, 자세 제어 장치 제작에 사용되는 초소형 구동기는 작은 크기로 인하여 내부 기어에 백래시를 갖고 있다. 따라서, 이는 주날개의 불필요한 유격을 발생시킬 수 있다. 이러한 유격은 주날개의 진동으로 이어져, 불필요한 비대칭적 공력을 발생시킬 수 있다. 이러한 상황 때문에 유격이 최소화된 자세 제어 장치 설계를 수행하였다. 첫째로, 기하학적 해석을 통하여 유격에 영향을 주는 요인을 파악하였다. 이를 통하여 유격을 최소화한 설계를 도출하였으며, 3차원 computer aided design (CAD) 형상과 RecurDyn을 이용하여 동역학적 해석을 수행하였다. 이를 통하여 자세 제어 장치의 구동 중 발생하는 간섭을 확인하였다. 최종적으로, 수치적 시뮬레이션을 이용하여 개선된 자세 제어 장치의 타당성을 확인하였다. 이때, 주날개는 변위 기반 기하학적 정밀 보로 모델링 되었으며, 2차원 단면 해석 결과를 사용하여 해석을 수행하였고 공력 모델은 2차원 비정상 모델을 사용하였다. 또한, 유격을 모사하기 위하여 스프링 요소를 관절에 삽입하여 해석을 수행하였다. 결과적으로, 본 연구에서 설계한 자세 제어 장치가 유효한 조종력을 발생시키는 것을 확인하였다.Abstract i Contents iii List of Tables vi List of Figures vii List of Symbols x Preface xi Chpater 1 Introduction 1 1.1 Background 1 1.2 Previous Researches 3 1.2.1 Review of Control Mechanism Design Regarding the Insect-Type Flapping Wing 3 1.2.2 Review of Numerical Simulation Studies Regarding the Insect-type Flapping Wing 6 1.3 Research Objectives and Thesis Outline 8 Chpater 2 Control Mechanism Design with Free play 9 2.1 Overview of Control Mechanism Design with Free play 9 2.2 Control Mechanism: Trailing Edge Control 11 2.3 Components of the Control Mechanism 14 2.4 Control Mechanism Design with Minimize free play effect 17 Chpater 3 Numerical Simulations of FWMAV 25 3.1 Overview of Numerical Simulation based on Flexible Multibody Dynamics 25 3.2 Simulation Setup 26 3.2.1 Simulation Methodology 31 3.2.2 Aerodynamics 34 3.3 Numerical Simulation 37 Chpater 4 Conclusions 47 4.1 Contirbutions 47 4.2 Future Works 48 Acknowledgments 50 References 50 국문초록 55Maste

Design optimization and wind tunnel investigation of a flapping system based on the flapping wing trajectories of a beetle's hindwings

To design a flapping-wing micro air vehicle (FWMAV), the hovering flight action of a beetle species (Protaetia brevitarsis) was captured, and various parameters, such as the hindwing flapping frequency, flapping amplitude, angle of attack, rotation angle, and stroke plane angle, were obtained. The wing tip trajectories of the hindwings were recorded and analyzed, and the flapping kinematics were assessed. Based on the wing tip trajectory functions, bioinspired wings and a linkage mechanism flapping system were designed. The critical parameters for the aerodynamic characteristics were investigated and optimized by means of wind tunnel tests, and the artificial flapping system with the best wing parameters was compared with the natural beetle. This work provides insight into how natural flyers execute flight by experimentally duplicating beetle hindwing kinematics and paves the way for the future development of beetle-mimicking FWMAVs

Modelling and simulation of a novel bioinspired flapping-wing rotary MAV

© The AuthosAchieving high lift efficiency represents a major research focus in the Micro Air Vehicle (MAV) domain due to stringent size and payload constraints. The Cranfield research team presents a novel semi-biomimetic design called the Flapping Wing Rotor (FWR) to address this challenge. This innovative concept combines a bioinspired flapping wing mechanism with passive rotor rotation, leveraging unsteady aerodynamic principles analogous to insect flight. The research aims to highlight a promising biomimetic flapping-rotor MAV enabled through advanced modeling to unlock the benefits of bio-inspired unsteady aerodynamics. To demonstrate this approach, a 60g proof-of-concept prototype was developed alongside a digital twin methodology for modeling, simulation, and control. A mathematical model has been formulated to analyze FWR's lift generation performance and enable flight control system design for stabilization and controllability. This work concentrates on enhancing the physical modeling process. The model is refined by tuning two key aerodynamic coefficients to account for nonlinearities from unsteady aerodynamics, flexible structures, and low Reynolds number flow inherent in MAV flight. This improved model achieves superior lift prediction accuracy versus real flight test data. Ongoing efforts focus on optimizing control torque, load distribution, and stability to further augment FWR's flight capabilities