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부유식 진자형 파력발전 시스템의 유압회로 설계에 관한 기초적 연구
김현호(H. H. Kim),이일영(I. Y. Lee),신승호(S. H. Shin),최종수(J. S. Choi),천호정(H. J. Cheon),김재환(J. H. Kim) 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.10
The Hydrostatic transmission (HST) converts the reciprocal power into continuous power as the device involved the ocean waver energy converter (OWEC). This paper suggests a simulation model for the hydrostatic transmission (HST). Simulation and experimental results are compared with each other. And the validity of the simulation model is verified. Though the suggested simulation model, basic study is performed for the circuit design of HST.
김현호(H. H. Kim),이일영(I. Y. Lee) 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.10
The purpose of this study is to achieve high-precision and broad-bandwidth reference tracking control for an electric hydrostatic actuator(EHA). For this purpose, firstly, a reference input tracking controller(consisting of a PI-D controller and a feed-forward controller) is designed for the EHA-driven system using the pole placement method and the zero placement method. The feed-forward controller has a tendency to show high gain symptom in frequency response as system"s actuation frequency increases. To suppress the increase of control gain in high frequency range, an input shaping filter(ISF) with the style of a lag compensator is incorporated in the designed control system. To verify the effectiveness of the proposed control system, experiments are performed. The results demonstrate that the application of the proposed control system including the ISF can greatly improve the reference tracking control performance of the EHA-driven system in broad-bandwidth. Also, it is verified that the proposed control system using the ISF is stable with enough margin in broad frequency range.
Mechanical properties of Al₂O₃/CNT/A356 hybrid composite fabricated by infiltration method
H. H. Kim(김현호),C. G. Kang(강충길) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Since the discovery of carbon nanotubes (CNTs), many interesting studies on composites with CNTs have been performed. However, it is extremely difficult to disperse CNTs in metal melts due to their poor wettability and large surface-to-volume ratio. The array of short fibers in a preform could be used to disperse the CNTs in the matrix. The use of hybrid reinforcement is required to solve the dispersion problems. Multi-wall carbon nanotube (MWCNTs)/Al2O3sf preform-based aluminum hybrid composites were studied. A high temperature compression test was performed to evaluate mechanical properties and workability. In addition, dispersion of the carbon fiber was investigated using a hardness test. The compressive strengths of hybrid metal matrix composites (MMCs) increased with increasing Al2O3 fraction. However, the compressive strengths were not necessarily proportional to the CNT fraction. Excessive CNTs adversely affected the material due to agglomeration or poor wettability with the matrix.
김현호(H. H. Kim),허준영(J. H. Huh),이일영(I. Y. Lee) 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.6
Many researchers have studied for improving the control performance of electric hydrostatic actuator(EHA), but studies are limited to improve the characteristics of transient response such as a step response. In this study, ISF-FF-PI-D controller is proposed for the position control of EHA in the high frequency range. First, FF-PI-D control system is designed for compensation of disturbance input and improvement of target tracking performance. In addition, input shaping filter(ISF) is applied to prevent saturation of electric motor using FF-PI-D control system in the high frequency field. As the result, it is confirmed experimentally that target tracking performance of ISF-FF-PI-D control system is better than FF-PI-D control system in the high frequency range.