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신경회로망 기존제어기의 접합기법을 이용한 유도무기 제어
김낙완(Nakwan Kim) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.3
불확실성과 비선형성은 비선형시스템의 제어기 설계에 중요하게 고려할 요소이다. 본 논문에서는 기존 제어기와 신경회로망을 접합하여 불확실성과 비선형성에 대처하는 기법을 소개한다. 이 기법은 기존의 제어기를 사용하기 때문에 신경회로망을 사용하기 위해 역변환 제어기와 같은 새로운 형태의 제어기를 설계할 필요가 없다. 이 기법은 유도무기의 수직 가속도 제어에 적용하여 그 효용성을 제시하였다. The effect of uncertainty and nonlinearity is an important aspect in a control design of a highly nonlinear plant. This paper presents an approach to address uncertainty and nonlinearity by augmenting an existing controller with a neural network based adaptive element. The approach has advantage in the sense that augmentation of neural network does not require to design a new controller architecture like an inversion controller. The approach is illustrated in an application of normal acceleration control for guided munitions.
김낙완(Nakwan Kim),김병수(Byoung-Soo Kim),유창선(Chang Sun Yoo),강영신(Young Sin Kang) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.12
A design of attitude controller for a tiltrotor is presented augmenting L1 adaptive control, neural networks, and feedback linearization. The neural networks compensate for the modeling error caused by the lack of knowledge of tiltrotor dynamics while the L1 adaptive control allows high adaptation gains in adaptation laws thereby, satisfying tracking performance requirement. The efficacy of this control methodology is illustrated in high-fidelity nonlinear simulation of a tiltrotor by flying the tiltrotor in different flight modes from where the L1 adaptive controller with neural networks is originally designed for.
김낙완(Nakwan Kim),유창선(Chang Sun Yoo),강영신(Young Shin Kang) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.6
적응제어신호를 저역필터에 통과시켜 점근적 추종과 과도구간 성능을 동시에 보장하는 £₁ 적응제어 기법과 비선형 시스템을 선형 시불변 형태로 변환하는 피드백 선형화 기법을 결합하여 £₁ 적응제어 기법의 적용가능 범위를 확대하였다. Barbalat의 보조정리를 이용하여 추종오차가 0으로 수렴함을 증명하고 과도구간의 추종오차도 원하는 크기로 감소시킬 수 있음을 보였다. This paper presents an approach to combine £₁ adaptive controller with feedback linearization, which extends the applicability of the £₁ adaptive controller to a wider class of systems. The £₁ adaptive controller guarantees the asymptotic tracking convergence and the transient performance of the tracking error. The feedback linearization transforms a nonlinear plant into a linear time invariant form. The asymptotic tracking convergence is shown by the use of Lyapunov stability analysis and Barbalat’s lemma.
우주현(Joohyun Woo),김낙완(Nakwan Kim) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.3
This paper proposes a potential field-based guidance law for docking a USV (unmanned surface vehicle). In most cases, a USV without side thrusters is an under-actuated system. Thus, there are undockable regions near docking stations where a USV cannot dock to a docking station without causing a collision or backward motion. This paper suggest a guidance law that prevents a USV from enter such a region by decreasing the lateral error to the docking station at the initial stage of the docking process. A Monte-carlo simulation was performed to validate the performance of the proposed method. The proposed method was compared to conventional guidance laws such as pure pursuit guidance and pure/lead pursuit guidance. As a result, the collision angle and lateral distance error of proposed method tended to have lower values compared to conventional methods.
자동화 비행시험기법에 의한 소형 무인헬리콥터의 파라메터 추정
방극희(Keuk-Hee Bang),김낙완(Nakwan Kim),홍창호(Changho Hong),석진영(Jinyoung Suk) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.9
In this paper dynamic modeling parameters were estimated using a frequency domain estimation method. A systematic flight test method was employed using preprogrammed multistep excitation of the swashplate control input. In addition when one axis is excited, the autopilot is engaged in the other axis, thereby obtaining high-quality flight data. A dynamic model was derived for a small scale unmanned helicopter (CNUHELI-020, developed by Chungnam National University) equipped with a Bell-Hiller stabilizer bar. Six degree of freedom equations of motion were derived using the total forces and moments acting on the small scale helicopter. The dynamics of the main rotor is simplified by the first order tip-path plane, and the aerodynamic effects of fuselage, tail rotor, engine, and horizontal/vertical stabilizer were considered. Trim analysis and linearized model were used as a basic model for the parameter estimation. Doublet and multistep inputs are used to excite dynamic motions of the helicopter. The system and input matrices were estimated in the frequency domain using the equation error method in order to match the data of flight test with those of the dynamic modeling. The dynamic modeling and the flight test show similar time responses, which validates the consequence of analytic modeling and the procedures of parameter estimation.