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임종혁(Jonghyuk Lim),정진태(Jintai Chung) 한국소음진동공학회 2018 한국소음진동공학회 논문집 Vol.28 No.1
This paper analyzes the dynamic behavior of a tethered space-tug system. The tethered space-tug system is modelled as two point masses and a string without bending stiffness. The discretized energies for this model are derived by using the absolute nodal coordinate formulation. The equations of motion are obtained by the Lagrange’s equation. For towing the space debris to the Earth, the trust force and time of the tug are calculated through the Hohmann transfer orbit. The dynamic responses of the tethered space-tug system are calculated for the initial attitudes of the tug. The analysis results are analyzed in terms of the thrust motion and free motion. Finally, the possibility of collision of the tug and space debris and the attitude instability of the tethered space-tug system are discussed.
임종혁(Jonghyuk Lim),김민성(Minsung Kim),이규호(Kyuho Lee),박철준(Chuljun Park),정진태(Jintai Chung) 한국소음진동공학회 2015 한국소음진동공학회 논문집 Vol.25 No.5
This paper presents a sorting method of mode vectors and natural frequencies about a rotor-journal bearing system. The rotor is solved by the finite element method, the bearing stiffness and damping coefficient are solved by the finite difference method. At any rotation speed section through the eigenvalue analysis of the system, mode vectors and natural frequencies not sorted are confirmed via the Campbell diagram and the MAC(modal assurance criterion). To sort mode vectors and natural frequencies of the section, a mode sorting method is presented through a method of rearranging the MAC of the mode vectors. Finally, the mode vectors and the natural frequencies are sorted by using the presented method, these are verified through the MAC.
김민성(Minsung Kim),임종혁(Jonghyuk Lim),정진태(Jintai Chung) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.4
In this paper, experiment and dynamics simulations were carried out to identify and reduce the out-of-plane vibration that occurs in a centrifugal fan of an air conditioner installed to a wall. In a wall-installed air conditioner, large space between a case and heat exchanger is often required for the fan to avoid the collision with the case and exchanger. This large space hinders the slim design of the air conditioner even if air conditioner market demands a slim air conditioner. In the present study, in order to determine the cause of the vibration in the centrifugal fan, the out-of-plane vibration and the physical properties were investigated, and the dynamic characteristics of the centrifugal fan were obtained by experiments. Based on these experiments, a dynamic simulation model was established to determine the cause of the out-of-plane vibration of the centrifugal fan. It was found that the main factor of out-of-plane vibration in the centrifugal fan is the axial misalignment between the centrifugal fan and the motor shaft.