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김동해,오경택,서용준,김유단,안종민 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11
무인항공기가 조종성을 상실할 경우 유인항공기에 비해 회복이 어려우므로 적절한 회복전략이 필요하다. upset 상황 중에서 진동스핀(Oscillatory Spin)이나 수평스핀(Flat Spin)과 같이 안정적인 평형상태에 빠져들 경우에는 조종면 효과가 급감해 회복이 더욱 어렵다. 본 연구에서는 강화학습을 통한 최적 수평스핀 회복전략을 제시하였다. 제안한 학습 기반 회복전략은 두 가지 단계로 구성된다. 각속도 회복단계에서는 동체 각속도를 최단시간에 줄이기 위한 학습모듈이 작동하며, 각속도가 회복된 후 특이 자세 회복단계에 진입한다. 이 단계에서 외부루프의 학습모듈이 속도 및 자세명령을 만들고, 내부루프의 선형 추종기가 작동해 최단시간에 대칭 수평비행으로 회복한다. 수치시뮬레이션을 수행함으로써 전체 제어시스템에서의 회복절차 타당성을 검증하였다. A recovery procedure is required for UAV (Unmanned Aerial Vehicle) under LOC (Loss of Control) condition. If the UAV is trapped in a stable equilibrium state such as oscillatory spin or flat spin, then the recovery strategy cannot be found easily due to the deficiency of control power. In this study, an optimal recovery controller based on RL (Reinforcement Learning) module is proposed. The controller consists of two parts. First part is ARA (Angular Rate Arrest) where a RL module attenuates an angular rate of the UAV. Second part is UAR (Unusual Attitude Recovery) where the outer-loop RL module generates a reference velocity and pitch angle. A linear tracker follows the reference states in the inner-loop recovering to symmetric level flight. The performance of the proposed control law is demonstrated by six degree-of-freedom simulation.
金東海,金聲俊 中央醫學社 1972 中央醫學 Vol.22 No.5
The clinical observation of 24 cases of the femur neck fracture with internal fixation was performed upon the patients who admitted in orthopedic department of Ewha University-Hospital from January, 1963 to December, 1970. We mainly used nail and side plate for fixation of fracture except SmithPeterson nail used in few cases of high transcervical fractures. We allowed weight bearing only after early union was demonstrated by roentgenograms, and made it a routine schedule that in peritrochanteric fractures, partial weight bearing was started at 8 weeks and full weight bearing at 12 weeks. But started about 4 weeks later than that of the peritrochanteric and trochanteric fractures in the transcervical fractures. The clinical observation was done for one year or more and the results were divided into 4 groups, there were excellent, good, fair and poor. We obtained the following results in few cases of femur neck fracture with internal fixation. 1. The average patient's age was 45.9 years in men and 59.4 years in women. 2. The ratio of men and women was 62.5% :37.5%. 3. The deeper inserted nail, the better result was obtained. 4. The obtained results were relatively good, and non union or avascular necrosis were not developed.
김동해,서용준,오경택,김유단,안종민 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4
무인항공기는 조종성을 상실할 경우 유인항공기에 비해 회복절차를 수행하기 쉽지 않다. 따라서 무인기는 비행영역 보호와 같은 수동적 방법 외에 유인기의 회복절차를 모사해 능동적으로 항공기 upset 상황에 대처할 수 있는 알고리듬이 필요하다. 본 연구는 이러한 upset 상태 회복 제어기 설계에 앞서 항공기의 조종입력에 대한 비행상태 변화를 분기분석(Bifurcation Analysis) 기법을 통해 연구하였다. 나선강하(Spiral Dive)부터 깊은 나선강하(Deep Spiral Dive), 진동스핀(Oscillating Spin) 비행상태까지를 러더입력에 따른 평형점 궤적을 분석함으로써 특성을 관찰하고 천이과정을 밝힌다. 마지막으로 각 비행상태를 대표하는 평형점에서 6 자유도 비선형 시뮬레이션을 수행함으로써 비행거동을 비교 분석하였다. A recovery procedure from LOC(Loss of Control) situation is very hard for UAV(Unmanned Aerial Vehicle). UAV needs not only a passive algorithm such as flight envelope protection but also active one that imitates pilot’s recovery procedure to cope with LOC. Prior to designing the upset recovery controller, in this study, spin conditions with respect to control input are studied via bifurcation analysis. Specifically, by analyzing the flight equilibrium points from spiral dive to oscillating spin along the rudder input, characteristics of each equilibrium state and transition between those flight conditions are identified. Finally, 6DOF nonlinear simulation is carried out at the typical equilibrium points according to each flight conditions to analyze the behavior of aircraft.