학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 8. 안성훈. ; Soft morphing is an emerging technology for applications in various industrial fields, such as wearable devices and biomimetic soft robots, because of its advantages in adaptability to various environmental conditions by mimicking the ‘soft’ motions of nature. Various smart materials-based actuators have been developed to generate active soft morphing in structures, but their limited performance in terms of actuated morphing shapes and actuating speeds have prevented them from being used more widely. This work presents a soft composite actuator capable of achieving flexible and complex motions, using a shape-memory alloy (SMA). The anisotropic material properties of the composite, considered a major defect in composite structures, were accentuated using a scaffold structure, so that the actuator could generate more diverse motions, even in a simple, lightweight structure. The composite characteristics depend on the scaffold structure embedded in the actuator, so actuator motion could be designed according to the scaffold structure. The scaffold structure was easy to fabricate using a three-dimensional (3D) printer. SMA wires were also included to generate a force for actuation ; these components were combined as a composite using a soft polymer. The actuating characteristics of the actuator depended on the type of scaffold: symmetric, anti-symmetric, and asymmetric scaffolds were evaluated, and four different modes of actuation were realized. A design methodology was proposed to permit more diverse and complex motions than the four basic modes of actuation, and was implemented in a turtle mimetic robot as an example application. The motion of a marine turtle flipper was analyzed and simplified into three sections. The required motion for each was matched with an appropriate scaffold design and the three scaffold structures were combined into a single actuator module. This flipper actuator was capable of mimicking two different swimming gaits of the marine turtle with a single actuator, depending on the current pattern applied. The locomotion characteristics of the two swimming gaits were evaluated in terms of efficiency and swimming speed. An actuator design to increase actuating speed and deformation magnitude was also developed, which extended the range of actuating performance for the SMA-bending actuator. Use of a bundle of SMA wires with a small radius instead of a single, thick SMA wire improved the cooling efficiency of the wire and increased the actuating speed, up to 35 Hz. Also, because the natural frequency of the actuator could be controlled by the scaffold structure design, the resonance effect was used actively to increase the actuating deformation. With this, a scaffold design methodology to achieve the required natural frequency of the actuator was developed and confirmed with experimental data. Actuating performance underwater was also evaluated and a model to predict the appropriate actuator length for the best performance was proposed. As an application of the high-speed actuator, a fish mimetic robot capable of 10 Hz fin flapping was developed and its speed was measured. The actuator was also applied to flying wings to mimic the flapping motion of birds or insects by adding a mechanism for passive rotation. ; Chapter 1. Introduction 1 1.1. Overview 1 1.2. Actuator using smart material 2 1.3. Soft bending actuator with smart material 5 1.3.1. Actuating speed and deformation magnitude 5 1.3.2. Actuator design and motion 8 1.4. Manufacturing process for soft actuator 11 1.5. Goal of research 14 Chapter 2. Design of composite actuator 15 2.1. Overview 15 2.2. Categorize actuation modes 15 2.3. Smart Soft Composite structure 16 2.3.1. Component design 16 2.3.2. Actuating mechanism 18 2.2.3. Component fabrication 24 2.4. Performance evaluation 26 2.4.1. Experimental set-up 26 2.4.2. Actuating modes 29 2.4.3. Actuating characteristics of actuator 31 2.4.4. Actuating trajectory 39 2.5. Summary 40 Chapter 3. Complex motion design and application for turtle robot 42 3.1. Overview 42 3.1.1. Bio-mimetic gait change robot 42 3.1.2 Turtle mimetic robot 43 3.2. Complex motion design using SSC structure 44 3.3. Turtle flipper mimetic actuator 46 3.3.1 Turtle locomotion analysis 46 3.3.2. Flipper actuator design 49 3.4. Performance evaluation of flipper actuator 52 3.4.1. Experimental set-up 52 4.4.2. Locomotion gait 55 3.4.3. Thrust of each locomotion gait 58 3.4.4. Swimming efficiency 61 3.5. Turtle robot implementation 65 3.5.1. Turtle robot platform design 65 3.5.2. Turtle robot performance evaluation 67 3.6. Summary 68 Chapter 4. High-speed actuation with large deformation 70 4.1. Overview 70 4.2. Design of high-speed actuator 71 4.3. Actuating characteristics of high-speed actuator 75 4.3.1. Actuator length and actuating frequency 75 4.3.2. Modal analysis of actuator 78 4.4. Long-term actuation 80 4.4.1. Experiment for the heat convection coefficient 80 4.4.2. Prediction model for surface temperature 84 4.4.3. Actuating characteristics in long-term actuation 86 4.5. Scaffold design for tailoring of actuation characteristics 87 4.5.1. Actuator natural frequency design 88 4.5.2. Modeling of Actuation frequency based on filament gap 91 4.5.3. Bend-twist coupled mode design 96 4.6. Actuator deformation control 97 4.7. Payload effect on the actuator performance 100 4.8. Variable actuating speed with stiffness change 102 4.8.1. Design of stiffness control part 102 4.8.2 Stiffness control of SMA 103 4.8.3. Variable actuating speed with stiffness control part 105 4.9. Actuation in water 107 4.9.1. Actuation characteristics in water 107 4.9.2. Effect of number of SMA wires 109 4.10. Application of high-speed actuator 110 4.10.1. Application on the fish mimetic robot 110 4.10.2. Application on the flapping wing actuator 113 4.11. Summary 116 Chapter 5. Conclusion 118 Bibliography 119 초록 141 ; Doctor


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    Title :

    Multi-mode High-speed Actuator using Smart Soft Composite ; 스마트 연성 복합재를 이용한 다중모드 고속 구동기



    Publication date :

    2016-01-01


    Type of media :

    Theses


    Type of material :

    Electronic Resource


    Language :

    English



    Classification :

    DDC:    629



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