• 제어로봇시스템학회논문지
• /
• 제18권3호
• /
• pp.243-250
• /
• 2012

This paper proposes a 3D map-building algorithm using one LRF (Laser Range Finder) while a mobile robot is navigating on the slanted surface. There are several researches on 3D map buildings using the LRF. However most of them are performing the map building only on the flat surface. While a mobile robot is moving on the slanted surface, the view angle of LRF is dynamically changing, which makes it very difficult to build the 3D map using encoder data. To cope with this dynamic change of the view angle in build 3D map, IMU and balance filters are fused to correct the unstable encoder data in this research. Through the real navigation experiments, it is verified that the fusion of multiple sensors are properly performed to correct the slope angle of the slanted surface. The effectiveness of the balance filter are also checked through the hill climbing navigations.

• Journal of Power Electronics
• /
• 제16권5호
• /
• pp.1928-1938
• /
• 2016

The three-phase four-wire shunt active power filter (APF) is an effective method to solve the harmonic problem in three-phase four-wire power systems. In addition, it has two possible topologies, a four-leg inverter and a three-leg inverter with a split-capacitor. There are some studies investigating DC-link voltage control in three-phase four-wire APFs. However, when compared to the four-leg inverter topology, maintaining the balance between the DC-link upper and lower capacitor voltages becomes a unique problem in the three-leg inverter with a split-capacitor topology, and previous studies seldom pay attention to this fact. In this paper, the influence of the balance between the two DC-link voltages on the compensation performance, and the influence of the voltage balance controller on the compensation performance, are analyzed. To achieve the balance between the two DC-link capacitor voltages, and to avoid the adverse effect the voltage balance controller has on the APF compensation performance, a new DC-link voltage balance control strategy for the three-phase four-wire split-capacitor APF is proposed. Representative simulation and experimental results are presented to verify the analysis and the proposed DC-link voltage balance control strategy.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권7호
• /
• pp.3245-3271
• /
• 2016

To obtain well-dehazed images at the receiver while sustaining low bit rates in the transmission pipeline, this paper investigates the effects of image dehazing methods using dehazing contrast-enhancement filters on image compression for surveillance systems. At first, this paper proposes a novel image dehazing method by using a new method of calculating the transmission function—namely, the direct denoising method. Next, we deduce the dehazing effects of the direct denoising method and image dehazing method based on dark channel prior (DCP) on image compression in terms of ringing artifacts and blocking artifacts. It can be concluded that the direct denoising method performs better than the DCP method for decompressed (reconstructed) images. We also improve the direct denoising method to obtain more desirable dehazed images with higher contrast, using the saliency map as the guidance image to modify the transmission function. Finally, we adjust the parameters of dehazing contrast-enhancement filters to obtain a corresponding composite peak signal-to-noise ratio (CPSNR) and blind image quality assessment (BIQA) of the decompressed images. Experimental results show that different filters have different effects on image compression. Moreover, our proposed dehazing method can strike a balance between image dehazing and image compression.

• Journal of Power Electronics
• /
• 제11권6호
• /
• pp.914-921
• /
• 2011

Commencing with incandescent light bulbs, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and their response to problems caused by harmonics. The prevalent difficulties with harmonics are voltage and current waveform distortions. In addition, Electronic equipment like computers, battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies generate perilous amounts of harmonics. Issues related to harmonics are of a greater concern to engineers and building designers because they do more than just distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality is becoming more and more serious with each passing day. As a result, active power filters (APFs) have gained a lot of attention due to their excellent harmonic compensation. However, the performance of the active filters seems to have contradictions with different control techniques. The main objective of this paper is to analyze shunt active filters with fuzzy and pi controllers. To carry out this analysis, active and reactive current methods ($i_d-i_q$) are considered. Extensive simulations were carried out. The simulations were performed under balance, unbalanced and non sinusoidal conditions. The results validate the dynamic behavior of fuzzy logic controllers over PI controllers.

• 감성과학
• /
• 제20권4호
• /
• pp.135-142
• /
• 2017

In the present study, we investigated the physiological effects of smartphone use at night when the display luminance and white balance were differently manipulated. Two levels of luminance and two types of white balance were combined to form four types of displays. Subjects were instructed to use smartphones between 23:00 to 01:00 twice a week for two weeks, and for each trial, subjects were given one of the four display types. Melatonin concentration in the saliva, body temperature and heart rate were measured before and after each experiment. The experimental result showed that the low luminance display supported melatonin secretion and thermoregulation compared to the high luminance display. With regard to the white balance, higher melatonin level was observed when using the display that filtered blue light. The low luminance display together with yellowish tint best supported restful sleep at night in terms of every physiological response. This study collectively demonstrates that bright and blue light emitted from smartphone displays adversely affect melatonin secretion, body temperature, and heart rate, and therefore, suggests the use of a display with low luminance or a display that filters blue light for a restful sleep at night.

• 전자공학회논문지S
• /
• 제35S권10호
• /
• pp.175-185
• /
• 1998

본 논문에서는 Adams에 의해 제안된 제한된 최소 자승 오차 기준에 의한 FIR 필터 설계 방법을 기초로 하여 저역 통과 필터 외의 다른 여러 가지 필터를 설계할 수 있는 방법론을 제시하였다. 이 방법에 의한 설계는 기존의 자승 오차 최소화 방법과 최대 오차 최소화 방법의 혼합된 형태로써 오차 기준으로 자승 오차와 최대 오차 두 가지를 동시에 고려하게 되며, 최고 이득, 전이 대역폭, 자승 오차 세가지가 모두 만족될 때만 그 해 즉, 임펄스 응답을 찾을 수 있게 된다. 이때 최적화 과정에서는 다중 교환 알고리즘을 이용하였다. 본 논문은 위의 두 중요 오차 기준의 상호 보완을 통하여 다중 대역 통과 필터, 미분기 및 Hilbert 변환기등의 최적 설계에 적용할 수 있는 방법에 대해 고찰하였으며, 그 결과 제한된 최소 자승 오차 기준에 의한 설계 방법이 단순한 저역 통과 필터 뿐만이 아니라 여러 가지 다양한 FIR 필터 설계에 있어서도 그 우수함을 증명할 수 있었다.

• 한국통신학회논문지
• /
• 제24권6A호
• /
• pp.913-919
• /
• 1999

ADSL POTS splitter를 설계하기 위한 체계적인 합성 과정을 제안하였다. 이들은 single-ended 인덕터, 균형 인덕터, 그리고 균형 밀결합 변압기 형태의 저역-통과 여파기로 구성된다. 이 3개의 저역-통과 여파기를 시뮬레이션한 결과, 주파수 특성이 일치함을 보여준다. ADSL 시스템에 적용하기 위해, 상업용 균형 밀결합 변압기를 이용하여 POTS splitter를 설계하였다. 그것을 실험한 결과, ADSL 시스템에서 POTS splitter가 0.2 kHz에서 3.4kHz까지의 주파수 범위에서(또는 음성 대역 주파수에서) $\pm$0.5dB보다 작은 리플 데시벨과 0.6 kHz에서 3.2kHz까지의 주파수 범위에서 130 $\mu\textrm{s}$보다 작은 지연 왜곡을 가진다는 것을 알았다.

• Korean Chemical Engineering Research
• /
• 제53권4호
• /
• pp.489-495
• /
• 2015

대기오염물질처리를 위한 생물살수여과법에서 물질전달현상을 이해하기 위한 선행 실험결과를 기초로 각각의 운전조건에서 기체/액체(살수액), 기체/고체(미생물)와 액체/고체에서의 model을 이용하여 물질전달계수를 평가하였다. 생물살수여과법에서 기/액에서는 정상상태물질수지, 그리고 액/고와 기/고에서는 동적물질수지를 이용하여 물질전달 model을 확립하고 그 결과를 고찰하였다. 물질전달 model은 여과탑을 일정크기 구획하여, 각 구획에서 동적 물질수지식을 수치해석 전산코드를 이용해 계산하였다. 동적물질수지식을 이용하여 계산된 결과는 실험결과와 비교하여 생물살수여과법에서 기/액, 기/고, 액/고 각상간의 물질전달계수($K_La$)를 산정하였다. 본 연구에서는 대기오염제어를 위한 생물살수여과법에서 물질전달계수를 결정하기 위한 실험방법개발과 model을 이용하여 물질전달현상을 고찰하였다.

• 한국자동차공학회논문집
• /
• 제20권1호
• /
• pp.147-154
• /
• 2012

The number of vehicles applied diesel engine are rapidly rising for fuel economy. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced emission regulation. The Diesel Particulate Filter (DPF) system is considered as the most efficiency method to reduce particulate matter (PM) by car makers but also in retrofit market. In recently, various kinds of partial flow DPF are widely used for proper filtration performance and reducing of pressure drop but it is difficult to define the characteristics of these filters because the filtration mechanism is obscure according to the status of these systems. In this paper we investigated the characteristics of cell open type DPF according to the status of filter especially, PM loading. The PM loading mass in the p-DPF are predicted from increase of differential pressure of DPF and the trend of filtration efficiency so that we can measure filtration efficiency and Balance Point Temperature (BPT) of this p-DPF according to PM loading.

• 한국세라믹학회지
• /
• 제45권7호
• /
• pp.423-429
• /
• 2008

Ceramic Fiber separator is the promising material for thermal battery system because it reduces the production cost and offers the potential to a new application compared to a pellet type electrolyte. The molten salt electrolytes for thermal battery were prepared by the impregnation of the commercial glass filters such as GF-A, C and F (Whatman, USA) with two types of molten-lithium salts, LiCl-KCl and LiK-LiBr-LiF. The wetting properties were evaluated by wetting balance test and wetting angle measurement. The wetting behaviors were strongly affected by the composition of the molten salts and the pore structure of the glass separators. The optimum wetting conditions for maximum loading and effective retention of the molten electrolyte were also studied.