• Title/Summary/Keyword: 공간 필터

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An Adaptive Hybrid Filter for WiFi-Based Positioning Systems (와이파이 기반 측위 시스템을 위한 적응형 혼합 필터)

  • Park, Namjoon;Jung, Suk Hoon;Moon, Yoonho;Han, Dongsoo
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.12 no.4
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    • pp.76-86
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    • 2013
  • As the basic Kalman filter is limited to be used for indoor navigation, and particle filters incur serious computational overhead, especially in mobile devices, we propose an adaptive hybrid filter for WiFi-based indoor positioning systems. The hybrid filter utilizes the same prediction framework of the basic Kalman filter, and it adopts the notion of particle filters only using a small number of particles. Restricting the predicts of a moving object to a small number of particles on a way network and substituting a dynamic weighting scheme for Kalman gain are the key features of the filter. The adaptive hybrid filter showed significantly better accuracy than the basic Kalman filter did, and it showed greatly improved performance in processing time and slightly better accuracy compared with a particle filter.

On-line Surface Defect Detection using Spatial Filtering Method (공간필터법을 이용한 온라인 표면결함 계측)

  • Moon, Serng-Bae;Jun, Seung-Hwan
    • Journal of Navigation and Port Research
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    • v.28 no.1
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    • pp.43-49
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    • 2004
  • Defects inspection of commodities are very important with those design and manufacturing process and essential to strengthen the competitiveness of those. If on-line automatic defects detection is performed without damaging to products, the production cost shall be curtailed through the reducing man-power, economical management of Q.C(Quality Control). In this paper, it is suggested three spatial filtering methods which can extract the necessary information in case of defects being on the surface of object like iron plate. In addition, the dependence of filtering characteristics on parameters such as the pitch and width of slits is analyzed and the surface defect detection system is constructed. Several experiments were carried out for determining the adequate spatial filtering method through comparing and analyzing effects of parameters like defect's size and shape, intensity of light, noise of coherent source and slit number.

Range Query Processing using Space and Time Filtering in Fixed Grid Indexing (고정 그리드 인덱싱에서 공간과 시간 필터링을 이용한 범위 질의 처리)

  • Jeon, Se-Gil;Nah, Yun-Mook
    • The KIPS Transactions:PartD
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    • v.11D no.4
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    • pp.835-844
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    • 2004
  • Recently, the location-based service for moving customers is becoming one of the most important service in mobile communication area. For moving object applications, there are lots of update operations and such update loads are concentrated on some particular area unevenly. Range queries, whose range can be window or circular, are the most essential query types in LBS. We need to distinguish completely contained cells from partially contained cells in those range queries. Also, it is necessary to consider temporal dimension to filter out qualifying objects correctly. In this paper, we adopt two-level index structures with fixed grid file structures in the second level, which are designed to minimize update operations. We propose a spatial ceil filtering method using VP filtering and a combined spatio-temporal filtering method using time gone concepts. Some experimental results are shown for various window queries and circular queries with different filtering combinations to show the performance tradeoffs of the proposed methods.

Mitigation of Inter-Symbol Interference in Underwater Acoustic Communication Using Spatial Filter (공간 필터를 이용한 수중음향통신의 인접 심볼 간 간섭 완화)

  • Eom, Min-Jeong;Park, Ji-Sung;Ji, Yoon-Hee;Kim, J.S.
    • The Journal of the Acoustical Society of Korea
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    • v.33 no.1
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    • pp.48-53
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    • 2014
  • The underwater acoustic communication (UAC) is characterized by doubly spread channel. It is included in the time-variant doppler shift and delay-time spreads due to multiple paths. To compensate such distorted signals, various techniques including time-reversal processing, spatial diversity, phase estimator, and equalizer are being applied. In this paper, a spatial filter based on the beamforming is proposed as a method to mitigate such inter-symbol interferences that are generated in time-varying multipath channels. The proposed technique realizes coherent communications by steering the direction of the desired signals and improves the performance of UAC by increasing the signal-to-interference plus noise ratio using the array gain.

A Study of Query Indexing Scheme for RFID Middleware (RFID 미들웨어를 위한 질의 색인 기법에 관한 연구)

  • Park, Jae-Kwan;Hong, Bong-Hee
    • 한국공간정보시스템학회:학술대회논문집
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    • pp.155-160
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    • 2005
  • 최근 이동체 또는 센서 데이터에 대한 연속 질의를 처리하기 위해 다양한 질의 색인 기법들이 연구되고 있다. 그러나 RFID 미들웨어는 이전 연구에서 고려되지 않은 특징이 존재한다. 첫째, 질의 색인에 삽입되는 질의는 Industry, Product, Serial의 세 부분으로 구성되며, 각 값은 범위 값으로 표현될 수 있기 때문에 색인 공간에서 비연속적인 간격의 조각들이 반복해서 나타난다. 둘째, TagID가 가지는 Industry, Product, Serial의 값은 포함관계를 가진다. 즉, 하나의 Industry에 여러 Product가 존재하며, 하나의 Product에 여러 Serial Item이 존재한다. 따라서 이러한 특징을 고려하지 못하는 기존의 질의 색인을 적용하면 다수의 질의 조각을 삽입하게 되어 색인의 성능이 급격히 저하되는 문제점이 있다. 이 논문에서는 RFID 미들웨어의 실시간 필터링 및 컬렉션을 위해서 Tag 스트림에 대한 질의 색인 기법을 제안한다. 이 논문은 ECSpec 필터링 범위의 3단계 계층구조 특징을 고려한 코드 분할(Code Segmented) 도메인을 제시하고 이를 위한 그리드 기반 색인 구조를 제안한다. 또한 ECSpec의 필터링 패턴 특징에 의해 나타나는 질의 조각의 반복 현상을 정의하고 이를 위한 질의 처리 기법을 제시한다.

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Implementation of Transaural filter method for sound localization (공간 음상정위를 위한 Transaural 필터 구현기법)

  • Cheung Wan-Sup;Lee Jeung-Hoon;Bhang Seungbeum;Kim Soonhyob
    • Proceedings of the Acoustical Society of Korea Conference
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    • pp.207-212
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    • 1999
  • 본 논문에서는 공간에 위치한 음원으로부터 양 귀에 들리는 음향을 좌우 대칭형 스피커를 이용하여 재현하는 기술에 대한 문제점, 즉 좌우 스피커와 양 귀의 음압전달 특성에 수반되는 Cross-talk 제거와 음향학적 모델 선정에 대한 문제점들을 우선 소개한다. 이러한 문제점을 해결할 수 있는 Transaural 필터의 모델 제시와 본 모델의 음향학적 특성을 고찰한다. 본 연구에서는 인간 청각 기관의 공간 인지량적 인자인 ILB(interaural Level Difference)와 ITD(Tnteraural Time Difference)의 개념을 이용한 새로운 Cross-talk 제거 방법과 그리고 청각기관의 "Masking" 특성을 이용한 Transaural 필터의 진폭 보상 방법을 새로이 제안한다. 끝으로 제안된 기법은 음색 왜곡과 음질 저하를 최소화할 수 있는 장점 뿐 아니라 현장 음향 기사들이 직접 음향제작에 적용할 수 있는 장점 또한 제공한다.

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The Realization of State-Space Digital Filters with Minimum Output Error Variance by Weighted Function (가중함수에 의한 최소 출력오차 분산을 갖는 상태공간 디지틀 필터 실현)

  • 김정화;정찬수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.17 no.9
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    • pp.909-917
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    • 1992
  • This paper proposes the realization of state-space digital filters with minimum output error variance. The algorithm is transforms of controllability and observability gramian in linear time invariant systems by weighted function and can improve performance of the digital filters by reducing the put error variance for state space coeffient variation. A numerical example shows that algorithm structure has much lower output error variance than that of other four structures(canonical, parallel, statistical sensitivity, balanced).

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The Unscented Kalman Filter Based Backward Filters for the Precise INS/GPS System (정밀 INS/GPS시스템을 위한 언센티드 칼만 필터 기반의 역방향 필터연구)

  • Kwon, Jay-Hyoun;Lee, Jong-Ki;Lee, Ji-Sun
    • Journal of the Korean Association of Geographic Information Studies
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    • v.13 no.2
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    • pp.157-167
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    • 2010
  • Unscented Kalman filter based backward filter is derived and the positions from extended Kalman filter, unscented Kalman filter, and extended Kalman smoother are compared and analyzed through a simulation test. Considering the poor GPS signal reception, the simulation is performed under the assumption of only the start and end points of the trajectory, composed of 4 curves and 5 straight sections in the area of $40m{\times}40m $, are known. The test shows that the smoothers generate much better positioning results of 8~9m improvement compared to those from the forward filters. For the comparison between the smoothers, the analysis is performed separately for the curves and straight segments. In both cases, the unscented Kalman smoother generates better positioning error; 10cm and 23cm improved positioning results in straight segment and curves, respectively.

Quadratic Kalman Filter Object Tracking with Moving Pictures (영상 기반의 이차 칼만 필터를 이용한 객체 추적)

  • Park, Sun-Bae;Yoo, Do-Sik
    • Journal of Advanced Navigation Technology
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    • v.20 no.1
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    • pp.53-58
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    • 2016
  • In this paper, we propose a novel quadratic Kalman filter based object tracking algorithm using moving pictures. Quadratic Kalman filter, which is introduced recently, has not yet been applied to the problem of 3-dimensional (3-D) object tracking. Since the mapping of a position in 2-D moving pictures into a 3-D world involves non-linear transformation, appropriate algorithm must be chosen for object tracking. In this situation, the quadratic Kalman filter can achieve better accuracy than extended Kalman filter. Under the same conditions, we compare extended Kalman filter, unscented Kalman filter and sequential importance resampling particle filter together with the proposed scheme. In conculsion, the proposed scheme decreases the divergence rate by half compared with the scheme based on extended Kalman filter and improves the accuracy by about 1% in comparison with the one based on unscented Kalman filter.

Design and Implementation of Optimal Adaptive Generalized Stack Filter for Image Restoration Using Neural Networks (신경회로망을 이용한 영상복원용 적응형 일반스택 최적화 필터의 설계 및 구현)

  • Moon, Byoung-Jin;Kim, Kwang-Hee;Lee, Bae-Ho
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.36S no.7
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    • pp.81-89
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    • 1999
  • Image obtained by incomplete communication always include noise, blur and distortion, etc. In this paper, we propose and apply the new spatial filter algorithm, called an optimal adaptive generalized stack filter(AGSF), which optimizes adaptive generalized stack filter(AGSF) using neural network weight learning algorithm of back-propagation learning algorithm for improving noise removal and edge preservation rate. AGSF divides into two parts: generalized stack filter(GSF) and adaptive multistage median filter(AMMF), GSF improves the ability of stack filter algorithm and AMMF proposes the improved algorithm for reserving the sharp edge. Applied to neural network theory, the proposed algorithm improves the performance of the AGSF using two weight learning algorithms, such as the least mean absolute(LAM) and least mean square (LMS) algorithms. Simulation results of the proposed filter algorithm are presented and discussed.

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