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김휘재(Wheejae Kim),박노철(No-Cheol Park) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Haptic feedback technology, which has been widely applied to interactive touch surfaces recently, provides more information to users through tactile effects on the touch surface. In order to provide desired tactile effects to users through a touch screen, rendering an accurate and uniform vibration pattern at all touch positions of surface is a very important issue. The method using the frequency response function between the actuator excitation and the vibration response of the surface can obtain actuator driving signals for uniform vibrotactile rendering. Because this method uses different actuator driving signals for each touch position, each vibrotactile rendering radiates different acoustic sound from the surface. In this study, the sound radiation generated during vibrotactile rendering at each touch position was analyzed. In addition, the effect of the actuator configuration on sound radiation was analyzed.
충격 하중의 주파수 특성을 고려한 안테나 구조물의 모드 기반 구조 경량화
김휘재(Wheejae Kim),박영진(Youngjin Park),김대근(Daekeun Kim),임선빈(Seonbin Lim),이종학(Jong-Hak Lee),신동준(Dong-Jun Shin),박경락(Gyeong-Rak Park),김희준(Hee-Joon Kim),김태석(Tae-Suk Kim),박노철(No-Cheol Park) 한국소음진동공학회 2023 한국소음진동공학회 논문집 Vol.33 No.6
The antenna structure of the close-in weapon systems, which is integrated into the machine gun, needs to be lightweight to reduce the load on the gun’s driving. Additionally, the antenna structure must ensure structural integrity against shock loads to guarantee survivability in various naval combat environments. Although topology optimization is commonly used for lightweight design, it requires transient response analysis, which is significantly costly. In this study, we propose a modal-based structural optimization method that ensures structural integrity for lightweight design by considering the frequency characteristics of shock loads and the dynamic characteristics of the structure. The optimization problem was defined using constraints to avoid the natural frequencies of the structure from the frequency range of the shock loads, and objective function that reducing mass of the structure. To verify the optimization method, modal and transient response analyses of the lightweight model obtained were performed, and the structural integrity of the antenna structure was evaluated.
Dynamic analysis of multilayer ceramic capacitor for vibration reduction of printed circuit board
김동준,Wheejae Kim,김완진 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4
Owing to their high permittivity and volumetric efficiency, the demand for multilayer ceramic capacitors (MLCCs) has increased rapidly in recent times. Because of the electromechanical characteristics of BaTiO 3 , MLCC vibrates, resulting in printed circuit boards (PCBs) generating acoustic noise. To construct an accurate finite element model of an MLCC, piezoelectric and electrostrictive coefficients were extracted and verified through experiments. The top cover layer thickness and bandwidth were chosen as design parameters to reduce the vibration of PCB. The simulation results indicate that the bandwidth and top cover layer thickness are highly related to the vibration in the top direction and the rotational moment generated from the head surface, respectively. Based on the analysis results, a novel MLCC was suggested and it exhibited reduced vibrational characteristics of PCB about 75 % compared with that of commercial MLCCs.
유준선,임선빈,Wheejae Kim,김동욱,Dongju Yoon,박노철 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3
Vehicle vibrations cause the physical and mental fatigue, thereby degrading the riding comfort. The vehicle accelerator pedal constantly generates vibrations while driving and is in direct contact with the driver. However, relevant studies on the vibration effects of the accelerator pedal have not been sufficiently conducted. This paper presents a method to evaluate the level of vibrotactile sensation perceived by drivers due to the vehicle accelerator pedal vibration and be able to predict riding comfort. Equivalent comfort contours for foot-transmitted vibrations are derived based on the sensitivity of the foot sole measured through vibrotactile sensation tests. With the equivalent comfort contours, weighting filters for three types of vehicles—conventional gasoline, hybrid, and electric—are generated. Then, weighted vibrations representing the vibrotactile sensation level perceived by drivers from the vehicle accelerator pedal are produced by applying the weighting filters to measured vibration data from the accelerator pedal of each vehicle type.