형상기억합금의 복원력 및 복원량은 열 하중 및 기계적 하중으로 인한 마르텐사이트 상에서 오스테나이트 상으로의 상 변이에 의한 상변형률 발생에 기인한다. 복원력 및 복원량은 초기 형상 및 하중 부여 방식에 따라 차이가 발생하는데 적절 한 설계 전략없이 상변형률에만 의지한 경우 큰 복원력은 발생할 수 있어도 큰 복원량을 기대하기는 어렵다. 이는 형상기 억합금의 큰 복원력과 작은 복원량 간의 비대칭성에 기인하며 형상기억합금의 효율적인 이용에 걸림돌이 된다. 본 연구에 서는 형상기억합금의 상변이로 발생하는 복원량을 극대화하는 방안으로 형상기억합금 선이 이중으로 감겨있는 이중 나선 구조 형상기억합금 스프링을 제안한다. 그리고 열 하중에 의해 발생하는 복원량을 예측하고 단일 나선 구조 형상기억합금 스프링과 비교 분석하여 이중 나선 구조 형상기억합금 스프링이 단일 나선 구조 형상기억합금 스프링보다 성능 비대칭성 을 보다 완화시킬 뿐만 아니라 복원력 대비보다 큰 복원량을 가짐을 보였다.

Dynamic plastic deformation behavior of copper particles occurred during the cold spray processing was numerically analyzed using the finite element method. The study was to investigate the impact as well as the heat transfer phenomena, happened due to collision of the copper particle of in diameter with various initial velocities of into the copper matrix. Effective strain, temperature and their distribution were investigated for adiabatic strain and the accompanying adiabatic shear localization at the particle/substrate interface.

Legged locomotion has high mobility on irregular surfaces by touching the ground at discrete points. Inspired by the creature’s legged locomotion, legged robots have been developed to explore unstructured environments. In this paper, we propose a modular crawler that can easily adjust the number of legs for adapting the environment that the robot should move. One module has a pair of legs, so the number of legs can be adjusted by changing the number of modules. All legs are driven by a single driving motor for simple and compact design, so the driving axle of each module is connected by the universal joint. Universal joints between modules enable the body flexion for steering or overcoming higher obstacles. A prototype of crawler with three modules is built and the driving performance and the effect of module lifting on the ability to overcome obstacles are demonstrated by the experiments.

Inspired by small insects, which perform rapid and stable locomotion based on body softness and tripod gait, various milli-scale six-legged crawling robots were developed to move rapidly in harsh environment. In particular, cockroach’s leg compliance was resembled to enhance the locomotion performance of the crawling robots. In this paper, we investigated the effects of changing leg compliance for the locomotion performance of the small light weight legged crawling robot under various payload condition. First, we developed robust milli-scale six-leg crawling robot which actuated by one motor and fabricated in SCM method with light and soft material. Using this robot platform, we measured the running velocity of the robot depending on the leg stiffness and payload. In result, there was optimal range of the leg stiffness enhancing the locomotion ability at each payload condition in the experiment. It suggests that the performance of the crawling robot can be improved by adjusting stiffness of the legs in given payload condition.

Recently, soft robots using soft materials are presented. Thanks to soft materials, soft robots have flexible, highly-stretchable or adaptable features. However, due to the flexibility of soft material, it is hard for soft robots to control accurately or perform high force. To deal with these limitations, variable stiffness technology, which enables the stiffness control of structure, has been developed. In this research, a dual-stiffness structure that is actuated by the assembly of two flexible structures are presented. Each flexible structure consists of flexible film part and rigid parts placed at regular intervals. The flexibility of film between rigid parts allows each structure to move softly. On the other hand, by combining two structures rigid part of each part constrain the degrees of freedom of the other side part. And this causes the stiffness of whole structure to be increased. This paper will cover concepts, design, analysis and experiments of this structure.

Previous shape sensors including bend sensors and optic fiber based sensors are widely used in various applications including goniometer and surgical robots. But theses sensors have large nonlinearity, limited in the range of sensing curvature, and sometimes are expensive. This study suggests a new concept of bend sensor using cable-conduit which consists of the outer sheath and the inner wire. The outer sheath is made of helical coil whose length of the central line changes as the sheath bends. This length change of the central line can be measured with the length change of the inner cable. The modeling and the experimental results show that the output signal of the proposed sensor is linearly related with the bend angle of the sheath with root mean square error of 5.3% of 450° sensing range. Also the polynomial calibration of the sensor can decrease the root mean square error to 2.1% of the full sensing range.

Fish generates thrust with a compliant fin which is known to increase the efficiency. In this paper, the performance of a robotic dolphin, the velocity and the stability, was improved using an optimal compliant caudal fin under certain oscillating frequency. Optimal compliance of the caudal fin exists that maximizes the thrust at a certain oscillating frequency. Four different compliant fins were used to find the optimal compliance of the caudal fin at a certain frequency using the half-pi phase delay condition. The swimming results show that the optimal compliant fin increases the velocity of the robotic fish. The compliance of the caudal fin was also shown to improve the stability of the robotic fish. A reactive motion at the head of the robotic dolphin causes fluctuation of the caudal fin. This phenomenon increases with the oscillating frequency. However, compliant fin reduced this fluctuation and increased the stability.

In nature, many small insects are using jumping as a survival strategy. Among them, fleas jump in a unique method. They use an elastomer, 'Resilin’, an extensor muscle and a trigger muscle. By contracting the extensor muscle, the elastic energy, that makes a flea to jump, is stored in the resilin. After storing energy, the trigger muscle begins contracting and pulling the extensor muscle. When the extensor muscle crosses the rotational joint, direction of torque generated from the extensor muscle reverses, ‘torque reversal mechanism’. Simultaneously, the elastic energy stored in the resilin releases rapidly and is converted into the kinetic energy. It makes a flea to jump 150 times its body length. In this paper, miniaturized jumping robot using flea-inspired catapult mechanism is presented. This mechanism is based on the 4-bar linkage and the reversal joint and is actuated by Shape Memory Alloy (SMA) coiled springs describing the flea’s muscle. The robot prototype is fabricated by SCM process using glass fiber prepregs and a sheet of polyimide film. The prototype is 20mm link length, 34mm width and 2.0g weight and can jump 103cm.

본 연구는 교사의 수업 전문성 향상을 위해 시행중인 교원능력개발평가의 평가지표를 좋은 수업의 조건이라는 관점에서 기존의 선행연구와 평가지표를 비교 분석하여 논의하였다. 교원능력개발평가가 교사의 수업 개선에 기여하는 측면이 있음은 분명하나 전문적 수업개선 평가라 할 수 있는 동료교원 평가의 경우 첫째, 수업 개선의 구체적인 정보를 제공하지 못하고 있으며, 둘째, 지식 전달의 관점에 초점을 맞추고 있고, 셋째, 수업의 바탕이 되는 학습조직과 학급분위기에 대한 고려가 없으며, 넷째, 활동의 적절성보다는 활동 여부에 초점이 있고, 다섯째, 평가가 형식적으로 이루어진다는 문제점을 가지고 있다. 따라서 교원능력개발평가가 본래의 목적에 충실할 수 있도록 수업관찰시간을 확대하여 필요한 정보를 해당 교사에게 제공하고, 수업 분위기의 중요성에도 관심을 확대하여야 하며, 마지막으로 확산적 사고, 구성적 지식을 촉진하는 수업으로 개선되어야 할 것이다.