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하이브리드 메모리 큐브 (HMC) 시스템의 고속 직렬 링크 (SerDes)를 위한 모델링 및 성능 분석
전동익,정기석,Jeon, Dong-Ik,Chung, Ki-Seok 대한임베디드공학회 2017 대한임베디드공학회논문지 Vol.12 No.4
Various 3D-stacked DRAMs have been proposed to overcome the memory wall problem. Hybrid Memory Cube (HMC) is a true 3D-stacked DRAM with stacked DRAM layers on top of a logic layer. The logic die is mainly used to implement a memory controller for HMC, and it is connected through a high speed serial link called SerDes with a host that is either a processor or another HMC. In HMC, the serial link is crucial for both performance and power consumption. Therefore, it is important that the link is configured properly so that the required performance should be satisfied while the power consumption is minimized. In this paper, we propose a HMC system model included the high speed serial link to estimate performance accurately. Since the link modeling strictly follows the link flow control mechanism defined in the HMC spec, the actual HMC performance can be estimated accurately with respect to each link configuration. Various simulations are conducted in order to deduce the correlation between the HMC performance and the link configuration with regard to memory utilization. It is confirmed that there is a strong correlation between the achievable maximum performance of HMC and the link configuration in terms of both bandwidth and latency. Therefore, it is possible to find the best link configuration when the required HMC performance is known in advance, and finding the best configuration will lead to significant power saving while the performance requirement is satisfied.
전동익,오화석,이상철,변상균,박종승,강민영,이승우,Cheon, Dong-Ik,Oh, Hwa-Suk,Lee, Sangchul,Byun, Sang-Kyun,Park, Jong-Seung,Kang, Min-Young,Rhee, Seung-Woo 항공우주시스템공학회 2007 항공우주시스템공학회지 Vol.1 No.4
Labyrinth seal is most common way to protect the bearings installed in Reaction wheel. In spite of wide applications, no such research was found about the sealing utility of the Labyrinth seal in the condition of vacuum and high temperature. In this research, we tried to verify the utility of Labyrinth seal. Numerical analysis had been executed to predict the benefit of the Labyrinth seal and also experiments were performed to verify the utilization. Two Bearings were installed at the vacuum chamber, one was assembled with Labyrinth seal and the other was stand alone. After executing the vacuum test, it was found to be the stand alone bearing had lost more weight than the one that was assembled with the labyrinth seal. In this result, it is verified that the Labyrinth seal has useful function to preserve the lubricant that affects to the life-cycle of the Bearing.
Low Power and High Performance Level-up Shifters for Mobile Devices with Multi-VDD
전동익,한광수,정기석 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.5
Reducing power consumption in a processor using multiple supply voltages is commonly adopted in mobile embedded systems. Level shifters are crucial components in such systems to interface two modules operating with different supply voltage levels. In this paper, we propose two low power and high performance level-up shifters called dual step level-up shifter (DSLS) and stacked dual step level-up shifter (SDSLS). DSLS has a dual step buffer structure to improve the speed and the circuit size over conventional level-up shifters as well as power consumption by avoiding contention. SDSLS is proposed to improve DSLS further for low power consumption by utilizing transistor stacking. By selectively using these two level-up shifters according to the difference between high and low supply voltages, delay is reduced by up to 79.0% and power consumption is reduced by up to 50.2%.
모멘텀 휠의 내부 진공 유지를 위한 커넥터 밀봉방법 개발
전동익,공성철,오화석,이승우,Cheon, Dong-Ik,Gong, Sung-Chul,Oh, Hwa-Suk,Lee, Seung-Wu 항공우주시스템공학회 2008 항공우주시스템공학회지 Vol.2 No.4
In general, we utilize momentum wheel to control spacecraft. It needs vacuum test to analyze the effect of space environments. The conventional vacuum connector which is composed of steel has problems for test with built in momentum wheel because of weight, thermal expansion, etc. We suggest possibility to manufacture the vacuum connector using aluminum mount, epoxy and industrial D-Sub considering cost, weight. We verify the performance through vacuum test.
Reaction Wheel Disturbance Reduction Method Using Disturbance Measurement Table
전동익,장은정,오화석 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.4
Momentum changing actuators like reaction wheels and control moment gyros are generally used for spacecraft attitude control. This type of actuators produces force and torque disturbances. These disturbances must be reduced since they degrade the quality of spacecraft attitude control. Major disturbances are mainly due to static and dynamic imbalances. This paper gives attention to the reduction of the static and dynamic imbalance. Force/torque measurement system is used to measure the disturbance of the test reaction wheel. An identification method for the location and magnitude of the imbalance is suggested, and the corrections of the imbalance are performed using balancing method. Through balancing, the static and dynamic imbalance is remarkably reduced