• Journal of Positioning, Navigation, and Timing
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• 제10권1호
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• pp.35-42
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• 2021

The position accuracy of the stand-alone Regional Navigation Satellite System (RNSS) users is more than tens of meters because of various error sources in satellite navigation signals. This paper focuses on wide-area differential (WAD) positioning technique, which is already applied in Global Navigation Satellite System (GNSS), in order to improve the position accuracy of RNSS users. According to the simulation results in the very narrow ground network in regional area, the horizontal position error of stand-alone RNSS is about RMS 11.6 m, and that of RNSS with WAD technique, named the WAD-RNSS, is about RMS 2.5 m. The accuracy performance has improved by about 78%.

• 반도체디스플레이기술학회지
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• 제21권1호
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• pp.136-141
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• 2022

In this paper, we designed, implemented, and verified the SLAM system that can be used on mobile devices. Mobile SLAM is composed of a stand-alone type that directly performs SLAM operation on a mobile device, and a mapping server type that additionally configures a mapping server based on FastAPI to perform SLAM operation on the server and transmits data for map visualization to a mobile device. The mobile SLAM system proposed in this paper is to mix the two types in order to make SLAM operation and map generation more efficient. The stand-alone type SLAM system was configured as an Android app by porting the OpenVSLAM library to the Unity engine, and the map generation and performance were evaluated on desktop PCs and mobile devices. The mobile SLAM system in this paper is an open source project, so it is expected to help develop AR contents based on SLAM in a mobile environment.

• 한국산업융합학회 논문집
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• 제26권1호
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• pp.27-34
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• 2023

This study conducted a study on a small-capacity PCS using lithium-ion batteries used in personal mobility. Most of the batteries in Personal Mobility only charge with external chargers and are used only as mobile energy sources. However, this paper aims to charge the battery of PM using PV and system power or to use the charged power as a stand-alone power supply. The developed PCS can be operated as a two-channel battery charger/discharger, a battery charger using solar power, and a stand-alone solar inverter depending on the operation method. The validity of the manufactured small-capacity PCS was verified through experiments.

• 전기학회논문지
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• 제64권12호
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• pp.1709-1717
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• 2015

In remote islands PV (Photo Voltaic) panel with BESS (Battery Energy Storage System) supplies electric power to the customers in parallel operation with EG (Engine Generator) to save fuel consumption and to mitigate environmental load. BESS operates in voltage control mode when it supplies power to the load alone, while it operates in current control mode when it supplies power to the load in parallel with EG. This paper proposes a smooth mode change scheme from current control to voltage control of BESS by adding proper initial value to the integral part of voltage control, and a smooth mode change scheme from voltage control to current control by tracking the EG output voltage to the BESS output voltage using PLL (Phase-Locked Loop). The feasibility of proposed schemes was verified through computer simulations with PSCAD/EMTDC, and the feasibility of actual hardware system was verified by experiments with scaled prototype. It was confirmed that the proposed schemes offer a seamless operation in the stand-alone power system in remote islands.

• 한국산업정보학회논문지
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• 제23권1호
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• pp.23-29
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• 2018

독립형 태양광(PV) 시스템은 몽골 유목민 목축업자들에게 가장 중요한 에너지발전 시스템 중 하나이다. 기본적으로 독립형 PV 시스템은 두 개의 DC-DC 컨버터를 사용한다. 이 시스템은 비용이 많이 들고, 사이즈가 커지기 때문에 다른 장소로 이동 할 때 큰 어려움이 있다. 본 논문에서는 배터리의 SOC 제어 와 최대전력추종제어가(MPPT) 결합된 제어 알고리즘을 제안한다. 배터리는 3단계(Bulk, Absorption, Float Charge)로 충 방전된다. 본 논문에서는 Bulk단계에서 MPPT제어 기반으로 충전되는 제어 알고리즘을 제안한다. 제안된 제어 알고리즘을 다양한 날씨 조건에 대해서 적용하였으며, PSIM 소프트웨어를 이용한 시뮬레이션을 통하여 그 효용성을 검증하였다. 본 논문에서 제안한 알고리즘은 몽골 유목민들의 농촌 생활에 필수적인 독립형 태양광 발전 시스템을 설계하는데 유용하게 사용될 것이다.

• Journal of Korean Neurosurgical Society
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• 제59권3호
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• pp.276-281
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• 2016

Objective : Although trunk muscles in the lumbar spine preserve spinal stability and motility, little is known about the relationship between trunk muscles and spinal fusion rate. The aim of the present study is to evaluate the correlation between trunk muscles cross sectional area (MCSA) and fusion rate after posterior lumbar interbody fusion (PLIF) using stand-alone cages. Methods : A total of 89 adult patients with degenerative lumbar disease who were performed PLIF using stand-alone cages at L4-5 were included in this study. The cross-sectional area of the psoas major (PS), erector spinae (ES), and multifidus (MF) muscles were quantitatively evaluated by preoperative lumbar magnetic resonance imaging at the L3-4, L4-5, and L5-S1 segments, and bone union was evaluated by dynamic lumbar X-rays. Results : Of the 89 patients, 68 had bone union and 21 did not. The MCSAs at all segments in both groups were significantly different (p<0.05) for the PS muscle, those at L3-4 and L4-5 segments between groups were significantly different (p=0.048, 0.021) for the ES and MF muscles. In the multivariate analysis, differences in the PS MCSA at the L4-5 and L5-S1 segments remained significant (p=0.048, 0.043 and odds ratio=1.098, 1.169). In comparison analysis between male and female patients, most MCSAs of male patients were larger than female's. Fusion rates of male patients (80.7%) were higher than female's (68.8%), too. Conclusion : For PLIF surgery, PS muscle function appears to be an important factor for bone union and preventing back muscle injury is essential for better fusion rate.

• Journal of Korean Neurosurgical Society
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• 제58권2호
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• pp.119-124
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• 2015

Objective : We compared the clinical and radiographic outcomes of stand-alone polyetheretherketone (PEEK) cage and Zero-Profile anchored spacer (Zero-P) for single level anterior cervical discectomy and fusion (ACDF). Methods : We retrospectively reviewed 121 patients who underwent single level ACDF within 2 years (Jan 2011-Jan 2013) in a single institute. Total 50 patients were included for the analysis who were evaluated more than 2-year follow-up. Twenty-nine patients were allocated to the cage group (m : f=19 : 10) and 21 for Zero-P group (m : f=12 : 9). Clinical (neck disability index, visual analogue scale arm and neck) and radiographic (Cobb angle-segmental and global cervical, disc height, vertebral height) assessments were followed at pre-operative, immediate post-operative, post-3, 6, 12, and 24 month periods. Results : Demographic features and the clinical outcome showed no difference between two groups. The change between final follow-up (24 months) and immediate post-op of Cobb-segmental angle (p=0.027), disc height (p=0.002), vertebral body height (p=0.033) showed statistically better outcome for the Zero-P group than the cage group, respectively. Conclusion : The Zero-Profile anchored spacer has some advantage after cage for maintaining segmental lordosis and lowering subsidence rate after single level anterior cervical discectomy and fusion.

• Journal of Power Electronics
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• 제16권5호
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• pp.1869-1883
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• 2016

In recent years, some converter structures and analyzing methods for the voltage regulation of stand-alone self-excited induction generators (SEIGs) have been introduced. However, all of them are concerned with the three-phase voltage control of three-phase SEIGs or the single-phase voltage control of single-phase SEIGs for the operation of these machines under balanced load conditions. In this paper, each phase voltage is controlled separately through separated converters, which consist of a full-bridge diode rectifier and one-IGBT. For this purpose, the principle of the electronic load controllers supported by fuzzy logic is employed in the two-different proposed converter structures. While changing single phase consumer loads that are independent from each other, the output voltages of the generator are controlled independently by three-number of separated electronic load controllers (SELCs) in two different mode operations. The aim is to obtain a rated power from the SEIG via the switching of the dump loads to be the complement of consumer load variations. The transient and steady state behaviors of the whole system are investigated by simulation studies from the point of getting the design parameters, and experiments are carried out for validation of the results. The results illustrate that the proposed SELC system is capable of coping with independent consumer load variations to keep output voltage at a desired value for each phase. It is also available for unbalanced consumer load conditions. In addition, it is concluded that the proposed converter without a filter capacitor has less harmonics on the currents.

• Korean Chemical Engineering Research
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• 제54권4호
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• pp.470-478
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• 2016

화석연료 사용으로 인한 환경오염과 기후변화는 전 지구적인 환경 문제로 대두되고 있다. 또한 화석연료 고갈 및 경제적 취약성을 극복하기 위하여 태양광, 풍력 등 신재생에너지 자원 기반 에너지공급 시스템 구축이 많은 관심을 받고 있다. 이러한 신재생에너지 시스템은 자원의 낮은 공급안정성을 극복하기 위하여 다양한 자원을 이용한 독립 통합 에너지공급 시스템 설계 및 운전 전략이 필요하다. 따라서 본 연구에서는 PV, Wind turbine, 화석연료 기반 발전 및 저장장치 등으로 구성된 독립 에너지공급 시스템을 설계하였다. 또한 최적화 모델을 이용하여 각 지역별 최적 전력생산 시스템의 구성요소를 규명하고 소요비용을 분석하였다. 제시된 모델 검증을 위하여 한국의 주거, 농업, 상업부문 등 주요 에너지수요 만족을 위한 설계문제를 해결하였다. 그 결과 주거부문의 경우 $0.37~$0.44/kWh, 농업부문의 경우 $0.15~$0.61/kWh, 상업부문의 경우 $0.12~$0.28/kWh의 단위전력 비용을 보였다.

• 융합신호처리학회논문지
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• 제4권1호
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• pp.56-63
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• 2003

본 논문은 실제 무인주행자동차에 적용할 수 있는 비전 기반의 소형 자율이동로봇 개발에 관한 연구를 제시한다. 이전의 자율주행차량은 하드웨어 설계의 복잡성, 실장의 어려움과 많은 계산량으로 인해 PC에 대한 의존도가 높았다. 본 논문에서는 고속에서 정확한 조향 및 빠른 이동을 할 수 있고, 단일 카메라를 사용한 독립형 시스템으로 지능적 인식을 할 수 있는 소형 자율이동로봇을 제안한다. 제안된 시스템은 폭 25~30cm, 총길이 200cm로 만들어진 트랙에서 실험하였다. 실험 로봇은 직선 트랙에서 평균 32.9km/h, 곡률반경 30~40m인 곡선트랙에서 평균 22.3km/h의 속도로 주행할 수 있었다 이 시스템은 실제 무인 자동차를 쉽게 만들기 위해 사용할 수 있는 차선 인식 알고리즘을 적용한 소형 자율이동로봇 시스템에 대한 하나의 모델을 제시할 수 있었다.