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연태흠(T. H. Yeon),장건희(G. H. Jang),남자현(J. H. Nam) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
This paper analyzes three cantilever-types of piezoelectric actuators of bimorph, unimorph and monomorph in same volume to maximize tip displacement. Tip displacement of each actuator is theoretically derived by using beam theory and numerically verified by FEM. It also investigates the tip displacements of each actuator due to the change of elastic layer. It shows that the piezoelectric actuator of bimorph generates the largest tip displacement among them.
구동방식에 따른 브러시리스 직류 전동기의 기전 연성 특성 해석
장정환(J.H. Chang),장건희(G.H.Jang) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.7(2)
This paper analyzes the electro-mechanical characteristics of the spindle motor in a computer hard disk drive due to the trapezoidal and sinusoidal driving methods. The driving circuit equation is modified by considering the switching action of PWM inverter, and is coupled with the Maxwell equation for the analysis of the magnetic field. Mechanical motion of a rotor is calculated by solving Newton-Euler equation Electro-mechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force<br/>
볼 베어링에 의해 발생하는 HDD 회전축계 NRRO의 온도 상승에 따른 변화
김동균(Kim, D.K.),장건희(Jang, G.H.) 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.9
This research investigates the non-repeatable runout (NRRO) of a HDD spindle system at elevated temperature by analyzing the characteristics of a ball bearing and the natural vibration characteristics of a HDD spindle system due to the effect of elevated temperature. It shows that the elevated temperature results in the increase of the contact angle and the decrease of the deformation of the ball bearing in a HDD spindle system. The variation of bearing frequencies, which are dependent on the cosine function of contact angle, is almost negligible at elevated temperature. However, the decrease of bearing deformation at elevated temperature reduces the stiffness of the ball bearing and the natural frequencies of a HDD spindle system consequently. The latter has a significant effect on the amplitude and the frequency distribution of NRRO at elevated temperature.
역기전력을 활용한 영구자석 전동기의 동적 편심 검출 방법
강경진(K. J. Kang),장건희(G. H. Jang),송정용(J. Y. Song),서보성(B. S. Seo) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
We develop a method to detect the dynamic eccentricity of a permanent magnet (PM) motor by monitoring back electromotive force (BEMF). We derive the mathematical equations of BEMF induced in a tooth and a phase due to dynamic eccentricity of a PM motor. We find that the dynamic eccentricity can be detected by monitoring main harmonic ±1 components of the BEMF induced in a tooth. We also perform the experiment to validate the proposed method by using a PM motor with 8 poles and 12 slots.
조윤제(Y. J. Jo),한미쁨(M. B. Han),조영정(Y. J. Cho),장건희(G. H. Jang) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
This research proposes a reduction method of excessive axial vibration in a wall-mounted drum-type washing machine. Finite element (FE) models of a rotor, a stationary part, and a of the wall-mounted drum-type washing machine were developed to investigate the axial vibration characteristics of the wall-mounted drum-type washing machine due to the excitation of an unbalanced mass and motor. The FE model was verified by experiment. Finally, the reduction method of axial vibration was proposed by utilizing ethylene propylene diene monomer (EPDM) rubber, and it was analyzed evaluated by experiment.
공진을 이용한 스마트 디바이스용 S-morph 피에조액츄에이터 개발
한상헌(S. H. Han),남자현(J. H. Nam),장건희(G. H. Jang) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
We propose a resonant s-morph piezoelectric actuator (RSPA) with high space efficiency and natural frequency within haptic frequency range for applying to smart device vibrators. RSPA consists of base, connector, cantilevers with two layers and weight. S-morph generates smaller displacement than uni-morph, but it has zero bending angle to generate uniform axial motion without tilting and space efficiency. We confirm the natural frequency and static displacement through the finite element analysis. In order to verify the validity of the analysis, we fabricate the RSPA sample and perform the vibration test. We show that the RSPA generate the axial displacement with zero bending angle, and has a natural frequency of 213.1 Hz within haptic frequency range(180 ~ 240 Hz).
3.5인치 HDD용 FDB스핀들 시스템의 훨링, 플라잉과 틸팅 거동에 관한 연구
오승혁(Oh, S.H.),이상훈(Lee, S.H.),장건희(Jang, G.H.) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.1
This research develops an experimental method to measure the motion of a FDB spindle system with a 3.5' disk by using three capacitance probes fixed on the xyz-micrometers, and it shows that a FDB spindle system has the whirling, flying and tilting motion. It also shows that the whirling, flying and tilting motion converge very quickly to the steady state at the same time when the rotor reaches the steady-state speed. However, they are quite large even at the steady state when they are compared with the 10nm flying height of a magnetic head. For the FDB spindle system used in this experiment, the whirl radius and the peak-to-peak variation of flying height and tilting angle at the steady-state speed of 7,200rpm are 0.675m, 30nm and $5.758\times10^{-3^{\circ}}$, respectively, so that the radial motion of the FDB spindle system exceeds a track pitch of a 3.5' HDD with 90,000 TPI.