• International Journal of Advanced Culture Technology
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• 제8권4호
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• pp.51-57
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• 2020

A propeller-based seesaw system is a system that can represent one of axis of four propeller drones and its stabilization has been replaced by intelligent control system instead of often used control methods such as PID and state space. Today, robots are increasingly use machine learning methods to adapt to their environment and learn to perform the right actions. In this article, we propose a Q-learning-based approach to control the stability of a seesaw system with a propeller. From the experimental results that it is possible to fully learn the balance control of a seesaw system by correctly defining the state of the system, the actions to be performed, and the reward functions. Our proposed method solves the seesaw stabilization.

• Journal of Power Electronics
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• 제17권2호
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• pp.346-357
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• 2017

The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).

• 한국산학기술학회논문지
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• 제13권12호
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• pp.5909-5919
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• 2012

본 연구는 노인여성들을 대상으로 발목관절 전략 집중 훈련이 근력과 균형능력에 어떠한 영향을 미치는지를 알아보고자 하였다. 연구대상자는 65-80세 사이의 여성노인 30명으로 선정하였다. 대조군(n=10)은 아무런 처치를 하지 않았고, 실험군 I(n=10)은 일반적 하지의 운동만 실시하였다. 실험군 II(n=10)는 세라밴드를 이용한 근력운동과 air cushion, unstable board을 이용한 평형운동을 포함한 발목관절 전략 집중 훈련을 실시하였다. 두 실험군은 6주간 주 3회 1시간 훈련을 실시하였다. 6주간 일반적 하지 운동과 발목관절 전략 집중 훈련을 각각 실시한 후 dynamometer, FRT, SEBT를 측정한 결과 대조군과 실험군 I의 변화는 통계학적으로 유의하지 않았지만, 실험군 II의 변화는 유의하게 증가하였다(p<.05). 더불어 노인 낙상 예방 및 치료적 접근에 있어서 발목관절 전략 집중 훈련을 통한 다양한 변인의 추가적인 연구가 필요하다고 생각된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.2058-2074
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• 2017

Dense Heterogeneous Cellular Networks(HCNs) offer a promising approach to meet the target of 1000x increase in aggregate data rates in 5G wireless communication systems. However how to best utilize the available radio resources at densely deployed small cells remains an open problem as those small cells are typically unplanned. In this paper we focus on balancing loads across macro cells and small cells by offloading users to small cells, as well as dynamically switching off underutilized small cells. We propose a joint user association and base station(BS) sleep mangement(UA-BSM) scheme that proactively offloads users to a fraction of the densely deployed small cells. We propose a heuristic algorithm that iteratively solves the user association problem and puts BSs with low loads into sleep. An interference relation matrix(IRM) is constructed to help us identify the candidate BSs that can be put into sleep. User associations are then aggregated to selected small cells that remain active. Simulation results show that our proposed approach achieves load balancing across macro and small cells and reduces the number of active BSs. Numerical results show user signal to interference ratio(SINR) can be improved by small cell sleep control.

• 한국게임학회 논문지
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• 제9권6호
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• pp.3-10
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• 2009

본 논문에서는 게임을 플레이 하는 유저의 성격 특성을 분류하고 각각의 성격이 선호하는 게임플레이에 대해서 연구했다. 또한, 유저의 성격별 선호 게임플레이를 조절함으로써 유저간의 밸런스를 조절할 수 있을지에 대해서 연구 하였다. 연구 결과, 개인의 성격 특성별 선호 게임플레이가 있다는 것을 도출하였다. 이를 바탕으로 게임의 디자인단계에서는 콘텐츠 설계의 기초데이터로서의 활용할 수 있다. 그리고 각 개인유저들의 플레이 유형 및 비율에 따른 콘텐츠를 제공함으로써 유저와 콘텐츠간의 밸런스 조절 방법을 제시하였다. 또한 게임의 서비스와 업데이트 시 기존 유저의 유형별 성격특성을 바탕으로, 업데이트 방향설정에 유용한 자료로서 활용될 수 있으며 유저간의 게임플레이 유형의 밸런스를 맞추는데 있어서 기초 데이터로서의 역할을 수행할 수 있을 것이다.

• 한국정보통신학회논문지
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• 제21권9호
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• pp.1655-1665
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• 2017

최근 많은 클라우드 서비스 제공자, 기업, 연구소 등에서 데이터센터를 활발히 구축하고 있다. 일반적으로 데이터 센터는 부하 분산을 위해 ECMP 데이터 포워딩 기법을 사용하여 트리 토폴로지 형태로 구축된다. 본 논문에서는 트리 토폴로지와 팻트리 토폴로지를 살펴보고, 또한 MLAG와 ECMP 같은 부하 분산 기술을 알아본다. 그리고 데이터 센터내의 호스트에 저장되어 있는 특정 파일을 데이터센터 외부로 효율적으로 송신할 수 있는 스케줄링 알고리즘을 제안한다. 제안된 알고리즘은 팻트리 토폴로지와 오픈플로우 프로토콜을 이용한다. 수치해석을 통해 성능 분석을 수행하며, ECMP의 성능과 비교한다. 이러한 성능 비교를 통해 평균처리율과 파일전송완료시간에 있어서 제안된 알고리즘의 성능이 우수함을 보인다.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1471-1481
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• 2014

This paper presents the new power dissipation model of individual switching device in a high-level modular multilevel converter (MMC), which can be mostly used in voltage sourced converter (VSC) based high-voltage direct current (HVDC) system and flexible AC transmission system (FACTS). Also, the voltage balancing method based on sorting algorithm is newly proposed to advance the MMC functionalities by effectively adjusting switching variations of the sub-module (SM). The proposed power dissipation model does not fully calculate the average power dissipation for numerous switching devices in an arm module. Instead, it estimates the power dissipation of every switching element based on the inherent operational principle of SM in MMC. In other words, the power dissipation is computed in every single switching event by using the polynomial curve fitting model with minimum computational efforts and high accuracy, which are required to manage the large number of SMs. After estimating the value of power dissipation, the thermal condition of every switching element is considered in the case of external disturbance. Then, the arm modeling for high-level MMC and its control scheme is implemented with the electromagnetic transient simulation program. Finally, the case study for applying to the MMC based HVDC system is carried out to select the appropriate insulated-gate bipolar transistor (IGBT) module in a steady-state, as well as to estimate the proper thermal condition of every switching element in a transient state.

• 디지털융복합연구
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• 제15권12호
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• pp.323-331
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• 2017

본 논문에서는 사물인터넷을 증착 순서 공정에 적용하여 증착 공정을 진행하는 과정의 제어에 온도제어기, 압력제어기, 가스제어기, 입출력 제어기 등 네 가지 종류를 대체하여 개선된 순서제어에 따른 부하균등을 해석하였다. 먼저 증착 설비에서 사물인터넷의 적용 전과 후의 시퀀스 절차를 통해 각각의 기능을 갖는 온도제어기, 압력제어기, 가스제어기, 입출력 제어기로 제어에 필요한 데이터를 전송받아서 개선된 시퀀스 순서대로 실행을 비교하여 순서과정을 제안하였다. 또한, 증착 공정에서 사물인터넷의 도입 전과 후를 비교하면서 증착 공정의 시퀀스 다이어그램을 작성하여 증착과정의 센싱 영역에 대한 부하 균등을 수행하였다. 이를 위해 각 센서입출력을 랜덤 프로세스와 버스트 프로세스 도착으로 모델링하고 CPU 부하와 메모리 부하를 수행한 결과를 도출하였다. 결과적으로 증착설비의 증착 공정에 장비제어기에서 수행하던 일부 기능을 사물인터넷에서 수행함으로써 장비제어기의 부하 균등 조절로 부하를 감소시키고 순서제어의 감소로 신뢰성은 높아지는 결과를 확인하였다. 본 논문을 통해 확인한 바와 같이, 사물인터넷을 증착 공정에 적용하면 설비의 확장 시에도 장비제어기의 부하를 최소화 함으로써 설비의 안정성을 향상시킬 수 있을 것을 것으로 기대된다.

• 한국통신학회논문지
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• 제22권4호
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• pp.618-636
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• 1997

DQDB(Distributed Queue Dual Bus) protocol, the IEEE 802.6 standard protocol for metropolitan area networks, does not fully take advantage of the capabilities of dual bus architecture. Although fairness in bandwidth distribution among nodes is improved when using so called the bandwidth balancing mechanism, the protocol requires a considerable amount of time to adjust to changes in the network load. Additionally, the bandwidth balancing mechanism leaves a portion of the available bandwidth unused. In a high-speed backbone network, each node may act as a bridge/ router which connects several LANs as well as hosts. However, Because the existence of high speed LANs becomes commonplace, the congestionmay occur on a node because of the limitation on access rate to the backbone network and on available buffer spaces. to release the congestion, it is desirable to install some congestion control algorithm in the node. In this paper, we propose an efficient congestion control mechanism and fair and waster-free MAC protocol for dual bus network. In this protocol, all the buffers in the network can be shared in such a way that the transmission rate of each node can be set proportional to its load. In other words, a heavily loaded node obtains a larger bandwidth to send the sements so tht the congestion can be avoided while the uncongested nodes slow down their transmission rate and store the incoming segments into thier buffers. this implies that the buffers on the network can be shared dynamically. Simulation results show that the proposed probotol significantly reduces the segment queueing delay of a heavily loaded node and segment loss rate when compared with original DQDB. And it enables an attractive high throughput in the backbone network. Because in the proposed protocol, each node does not send a requet by the segment but send a request one time in the meaning of having segments, the frequency of sending requests is very low in the proposed protocol. so the proposed protocol signigificantly reduces the segment queuing dely. and In the proposed protocol, each node uses bandwidth in proportion to its load. so In case of limitation of available buffer spaces, the proposed protocol reduces segment loss rate of a heavily loaded node. Bandwidth balancing DQDB requires the wastage of bandwidth to be fair bandwidth allocation. But the proposed DQDB MAC protocol enables fair bandwidth without wasting bandwidth by using bandwidth one after another among active nodes.

• 설비공학논문집
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• 제20권3호
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• pp.175-180
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• 2008

Flow quantity to supply to a coil in floor heating system is important to achieve comfortable indoor air condition in the winter season. The hot water header is used to distribute the water into the coil. Experimental study has been performed using the water header that have 5 branches consisted of flow control valves and automatic shut-off valves. Each branch line connected it with X-L pipe. Experimental tests accomplished it to investigate the flow distribution characteristics of the hot water header. Experimental results show that the selection of the pump head and differential pressure are very important to save running energy of the system, and high differential pressure needs more friction loss in the case of suitable differential pressure for balancing of the header.