Modeling of Soft Fiber-Reinforced Bending Actuators

published_or_final_versio

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

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Zur Mechanik vibrationsgetriebener Roboter für terrestrische und aquatische Lokomotion

This thesis discusses the mechanics of mobile robots for terrestrial and aquatic locomotion. Vibration-driven locomotion systems are characterised by an internal periodic excitation, which is transformed to a directed motion due to asymmetric properties of the system. To perform a two-dimensional and controllable locomotion, mechanical properties of robots are investigated dependent on the frequency of the internal excitation. The mechanical description of the robots is done using analytical and numerical methods and supported by experimental studies. The applicability of the results in mobile robots is proved by prototypes.On the basis of mechanical fundamentals, terrestrial and aquatic locomotion principles are discussed and classified. Actuators are reviewed. The purpose is to evaluate the performance as vibration sources for terrestrial and aquatic systems. Piezoelectric bending elements are particular suitable for it. An extensive overview on the state of the art shows the great potential of vibration-driven locomotion systems for miniaturised applications in technics.Systems with bristles can perform unidirectional terrestrial locomotion. Different working principles of bristles are studied based on a rigid body model and experimental investigations. A prototype for the locomotion in tubes is presented. To perform a controllable two-dimensional locomotion with only one actuator, it is needed to overcome the limits of rigid body systems. The applied approach uses the frequency-dependent vibration behaviour of elastic systems, like beams and plates. Models of continuum mechanics and finite element methods are used and supported by experiments. Based on the investigations, a programmable and remote controlled prototype is developed. The locomotion of it can be controlled on different surfaces by a change of the excitation frequency. The velocity of the prototype is up to 100 mm/s and it can support five times its own weight.Concluding, an innovative prototype with a single piezoelectric actuator for a controllable locomotion on flat ground and floating in fluids is developed. The terrestrial and aquatic locomotion behaviour of the robot is investigated. The carrying capacity of it is calculated using a hydrostatic model.Die Mechanik von mobilen Robotern für terrestrische und aquatische Lokomotion ist der Gegenstand der Arbeit. In den untersuchten Systemen wird die periodische Erregung eines inneren Antriebs durch nicht symmetrische Systemeigenschaften in eine gerichtete Fortbewegung gewandelt. Durch die Nutzung des frequenzabhängigen Schwingungsverhaltens von elastischen Systemen, wie Balken oder Platten, werden Systeme realisiert, die durch nur einen Antrieb eine steuerbare zweidimensionale Lokomotion auf festem Untergrund und an der Oberfläche von Flüssigkeiten durchführen können. Der Schwerpunkt der Arbeit liegt auf der mathematisch-mechanischen Beschreibung der Roboter mittels analytischer und numerischer Methoden sowie ihrer experimentellen Untersuchung. Prototypen mobiler Roboter dienen dem funktionellen Nachweis.Auch im Buchhandel erhältlich: Zur Mechanik vibrationsgetriebener Roboter für terrestrische und aquatische Lokomotion / Felix Becker Ilmenau : Univ.-Verl. Ilmenau, 2015. - XIX, 149 S. ISBN 978-3-86360-124-9 URN urn:nbn:de:gbv:ilm1-2015000338 Preis (Druckausgabe): 21,30

International Workshop on MicroFactories (IWMF 2012): 17th-20th June 2012 Tampere Hall Tampere, Finland

This Workshop provides a forum for researchers and practitioners in industry working on the diverse issues of micro and desktop factories, as well as technologies and processes applicable for micro and desktop factories. Micro and desktop factories decrease the need of factory floor space, and reduce energy consumption and improve material and resource utilization thus strongly supporting the new sustainable manufacturing paradigm. They can be seen also as a proper solution to point-of-need manufacturing of customized and personalized products near the point of need

Bioinspired Jumping Locomotion for Miniature Robotics

In nature, many small animals use jumping locomotion to move in rough terrain. Compared to other modes of ground locomotion, jumping allows an animal to overcome obstacles that are relatively large compared to its size. In this thesis we outline the main design challenges that need to be addressed when building miniature jumping robots. We then present three novel robotic jumpers that solve those challenges and outperform existing similar jumping robots by one order of magnitude with regard to jumping height per size and weight. The robots presented in this thesis, called EPFL jumper v1, EPFL jumper v2 and EPFL jumper v3 have a weight between 7g and 14.3g and are able to jump up to 27 times their own size, with onboard energy and control. This high jumping performance is achieved by using the same mechanical design principles as found in jumping insects such as locusts or fleas. Further, we present a theoretical model which allows an evaluation whether the addition of wings could potentially allow a jumping robot to prolong its jumps. The results from the model and the experiments with a winged jumping robot indicate that for miniature robots, adding wings is not worthwhile when moving on ground. However, when jumping from an elevated starting position, adding wings can lead to longer distances traveled compared to jumping without wings. Moreover, it can reduce the kinetic energy on impact which needs to be absorbed by the robot structure. Based on this conclusion, we developed the EPFL jumpglider, the first miniature jumping and gliding robot that has been presented so far. It has a mass of 16.5g and is able to jump from elevated positions, perform steered gliding flight, land safely and locomote on ground with repetitive jumps1. ______________________________ 1See the collection of the accompanying videos at http://lis.epfl.ch/microglider/moviesAll.zi

Design of Flying Robots for Collision Absorption and Self-Recovery

Flying robots have the unique advantage of being able to move through the air unaffected by the obstacles or precipices below them. This ability quickly becomes a disadvantage, however, as the amount of free space is reduced and the risk of collisions increases. Their sensitivity to any contact with the environment have kept them from venturing beyond large open spaces and obstacle-free skies. Recent efforts have concentrated on improving obstacle detection and avoidance strategies, modeling the environment and intelligent planning to navigate ever tighter spaces while remaining airborne. Though this strategy is yielding impressive and improving results, it is limited by the quality of the information that can be provided by on-board sensors. As evidenced by insects that collide with windows, there will always be situations in which sensors fail and a flying platform will collide with the obstacles around it. It is this fact that inspired the topic of this thesis: enabling flying platforms to survive and recover from contact with their environment through intelligent mechanical design. There are three main challenges tackled in this thesis: robustness to contact, self-recovery and integration into flight systems. Robustness to contact involves the protection of fast-spinning propellers, the stiff inner frame of a flying robot and its embedded sensors from damage through the elastic absorption of collision energy. A method is presented for designing protective structures that transfer the lowest possible amount of force to the platform's frame while simultaneously minimizing weight and thus their effect on flight performance. The method is first used to design a teardrop-shaped spring configuration for absorbing head-on collisions typically experienced by winged platforms. The design is implemented on a flying platform that can survive drops from a height of 2 m. A second design is then presented, this time using springs in a tetrahedral configuration that absorb energy through buckling. When embedded into a hovering platform the tetrahedral protective mechanisms are able to absorb dozens of high-speed collisions while significantly reducing the forces on the platforms frame compared to foam-based protection typically used on other platforms. Surviving a collision is only half of the equation and is only useful if a flying platform can subsequently return to flight without requiring human intervention, a process called self-recovery. The theory behind self-recovery as it applies to many types of flying platforms is first presented, followed by a method for designing and optimizing different types of self-recovery mechanisms. A gravity-based mechanism is implemented on an ultra-light (20.5 g) wing-based platform whose morphology and centre of gravity are optimized to always land on its side after a collision, ready to take off again. Such a mechanism, however, is limited to surfaces that are flat and obstacle-free and requires clear space in front of the platform to return to the air. A second, leg-based self-recovery mechanism is thus designed and integrated into a second hovering platform, allowing it to upright into a vertical takeoff position. The mechanism is successful in returning the platform to the air in a variety of complex environments, including sloped surfaces, corners and surface textures ranging from smooth hardwood to gravel and rocks. In a final chapter collision energy absorption and self-recovery mechanisms are integrated into a single hovering platform, the first example of a flying robot capable of crashing into obstacles, falling to the ground, uprighting and returning to the air, all without human intervention. These abilities are first demonstrated through a contact-based random search behaviour in which the platform explores a small enclosed room in complete darkness. After each collision with a wall the platform falls to the ground, recovers and then continues exploring. In a second experiment the platform is programmed with a basic phototaxis behaviour. Using only four photodiodes that provide a rough idea of the bearing to a source of light the platform is able to consistently cross a 13x2.2mcorridor and traverse a doorway without using any obstacle avoidance, modeling or planning

Factories of the Future

Engineering; Industrial engineering; Production engineerin

Using MapReduce Streaming for Distributed Life Simulation on the Cloud

Distributed software simulations are indispensable in the study of large-scale life models but often require the use of technically complex lower-level distributed computing frameworks, such as MPI. We propose to overcome the complexity challenge by applying the emerging MapReduce (MR) model to distributed life simulations and by running such simulations on the cloud. Technically, we design optimized MR streaming algorithms for discrete and continuous versions of Conway’s life according to a general MR streaming pattern. We chose life because it is simple enough as a testbed for MR’s applicability to a-life simulations and general enough to make our results applicable to various lattice-based a-life models. We implement and empirically evaluate our algorithms’ performance on Amazon’s Elastic MR cloud. Our experiments demonstrate that a single MR optimization technique called strip partitioning can reduce the execution time of continuous life simulations by 64%. To the best of our knowledge, we are the first to propose and evaluate MR streaming algorithms for lattice-based simulations. Our algorithms can serve as prototypes in the development of novel MR simulation algorithms for large-scale lattice-based a-life models.https://digitalcommons.chapman.edu/scs_books/1014/thumbnail.jp

A Novel Soft Biomimetic Microrobot with Two Motion Attitudes

sensor