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유압 제어계에서 새로운 서보 밸브 선형화 방정식의 제안
김태형(Tae-Hyung Kim),이일영(Ill-Yeong Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.4
In the procedure of the hydraulic control system analysis, a linearized approximate equation described by the first order term of Taylor's series has been widely used. Such a linearized equation is effective just near the operating point. And, as of now, there are no general standards on how to determine the operating point of a servo valve in the process of applying the linearized equation. So, in this study, a new linearized equation for valve characteristics is proposed as a modified form of the existing linearized equation. And, a method for selecting an optimal operating point is proposed for the new linearized equation. The effectiveness of the new linearized equation is confirmed through numerical simulations and experiments for a model hydraulic control system.
지하매설 가스관의 검사를 위한 누설자속탐상 PIG 설계에 관한 연구
박상호,박관수 한국비파괴검사학회 2002 한국비파괴검사학회지 Vol.22 No.2
본 논문에서는 3차원 형태의 결함을 가진 지하매설 가스관에서 누설자속(magnetic flux leakage, MFL) 탐상법을 사용한 결함 검출에 관하여 연구하였다. 영구자석과 요크로 구성된 자기시스템을 유한요소법을 사용하여 해석하고 동작점을 설정하였다. 가스관이 충분히 포화되지 않을 경우에는 측정이 곤란하며, 과대포화된 경우에는 결함에 의한 누설자속의 변화량이 적어서 측정이 곤란하므로 적정한 값을 설정하여야 하므로 자기 시스템의 동작점은 결함이 있을때누설자속 증가율이 최대가 되도록 설정하여야 한다. 본 논문에서는 3차원 비선형 유한요소법을 사용하여, 가스관에 결함이 있는 경우 결함의 크기, 깊이에 따른 결함신호를 예측하여 그 결과 가스관 포화상태의 적절여부, 홀 센서 range 및 resolution의 적정도 등을 연구하였다. 또한 홀 센서의 민감도 향상을 위하여 back-yoke를 사용하여 측정신호를 향상시키는 방법을 제안하였다. This paper describes the magnetic flux leakage(MFL) type non-destructive testing(NDT) system to detect the 3D defects in underground gas pipe. Magnetic systems with permanent magnets and yokes are analyzed by 3D non-lineal finite element method(FEM) with optimum design. In case of under-saturation of gas pipe, sensing signals are too weak to defect. In case of over saturation, the change of the sensing signals are too low to defect the defects sensitivity. So, the operating points of the magnetic system are optimized to increase the change of the MFL signals. The effects of the depth and size of the defects on the sensing signals are analyzed to define the range and resolution of the MFL sensors. To increase the sensor's sensitivity, the back-yoke sensors are introduced and tested.
임채욱(Chae-Wook Lim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.11
Aerodynamic power and torque of wind turbine are highly nonlinear and its operation mode depends on control strategies. Therefore, it is essential to define steady-state curves for the purpose of control and operation of wind turbine system. The steady-state curves of wind turbine can be defined by determining its operating points. In this paper, an algorithm to determine operating points of variable-speed variable-pitch wind turbine is presented on the basis of pitch-to-feather control strategy. And this algorithm is applied to obtain steady-state curves for an 1.5MW wind turbine.
태양광 모듈의 전압 및 전류 파형을 이용한 부정합 진단 기법
안희욱(Ahn Hee-Wook),박기엽(Park Gi-Yob) 한국태양에너지학회 2011 한국태양에너지학회 논문집 Vol.31 No.3
Techniques for mismatch loss minimization to increase the PV system efficiency are under development recently. In this paper, a method to make diagnosis of PV module mismatch is presented, which uses a concept of operating point factor. The method is based on the fact that the ratio of the incremental conductance of a PV module to instantaneous conductance is 1 when the module is operating at its maximum power point. The variations of module voltage and current are taking place by the maximum power point tracker in the power conditioning units of PV system. The effectiveness of the method is verified through an application to a real PV system.
영구자석 비선형 자기특성을 고려한 회전자 타입에 따른 모터 특성 분석
박민로(Min-Ro Park),서갑호(Kap-Ho Seo),황성우(Sung-Woo Hwang),임명섭(Myung-Seop Lim) 한국자기학회 2021 韓國磁氣學會誌 Vol.31 No.3
The permanent magnet is an important component that determines the performance and cost of a synchronous motor. Also, the characteristic of the permanent magnet is a major factor in determining the performance of the electric motor. Therefore, to improve the performance of the permanent magnet synchronous motor and reduce the material cost, the permanent magnets having various characteristics are being developed. However, the magnetic properties of permanent magnets have nonlinearity. Therefore, this paper proposes a method to calculate the operating point of a permanent magnet by considering not only the nonlinear magnetic properties of the electrical steel sheet but also the nonlinear properties of the permanent magnet and analyze the characteristics of the electric motor based on this proposed method. Through this, the characteristics of the permanent magnet synchronous motor are analyzed according to the rotor type and the design direction for each type is suggested.