• 제목/요약/키워드: Proximity operations

검색결과 22건 처리시간 0.02초

Integrated System for Autonomous Proximity Operations and Docking

  • Lee, Dae-Ro;Pernicka, Henry
    • International Journal of Aeronautical and Space Sciences
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    • 제12권1호
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    • pp.43-56
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    • 2011
  • An integrated system composed of guidance, navigation and control (GNC) system for autonomous proximity operations and the docking of two spacecraft was developed. The position maneuvers were determined through the integration of the state-dependent Riccati equation formulated from nonlinear relative motion dynamics and relative navigation using rendezvous laser vision (Lidar) and a vision sensor system. In the vision sensor system, a switch between sensors was made along the approach phase in order to provide continuously effective navigation. As an extension of the rendezvous laser vision system, an automated terminal guidance scheme based on the Clohessy-Wiltshire state transition matrix was used to formulate a "V-bar hopping approach" reference trajectory. A proximity operations strategy was then adapted from the approach strategy used with the automated transfer vehicle. The attitude maneuvers, determined from a linear quadratic Gaussian-type control including quaternion based attitude estimation using star trackers or a vision sensor system, provided precise attitude control and robustness under uncertainties in the moments of inertia and external disturbances. These functions were then integrated into an autonomous GNC system that can perform proximity operations and meet all conditions for successful docking. A six-degree of freedom simulation was used to demonstrate the effectiveness of the integrated system.

Optimal Control for Proximity Operations and Docking

  • Lee, Dae-Ro;Pernicka, Henry
    • International Journal of Aeronautical and Space Sciences
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    • 제11권3호
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    • pp.206-220
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    • 2010
  • This paper proposes optimal control techniques for determining translational and rotational maneuvers that facilitate proximity operations and docking. Two candidate controllers that provide translational motion are compared. A state-dependent Riccati equation controller is formulated from nonlinear relative motion dynamics, and a linear quadratic tracking controller is formulated from linearized relative motion. A linear quadratic Gaussian controller using star trackers to provide quaternion measurements is designed for precision attitude maneuvering. The attitude maneuvers are evaluated for different final axis alignment geometries that depend on the approach distance. A six degrees-of-freedom simulation demonstrates that the controllers successfully perform proximity operations that meet the conditions for docking.

OPERATIONS ON SATURATED FUZZY SYNTOPOGENOUS STRUCTURES

  • Chung, Se-Hwa
    • 대한수학회지
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    • 제33권4호
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    • pp.879-889
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    • 1996
  • In order to describe the nearness between fuzzy sets various structures like the fuzzy neighorhood structure ([7])), the Artico-Moresco fuzzy proximity ([2]) and the Lowen fuzzy uniformity ([8]) have been introduced.

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문서관리시스템을 위한 질의처리기 설계 및 구현 (Design and Implementation of a Query Processor for Document Management Systems)

  • 우종원;윤승현;유재수
    • 한국정보처리학회논문지
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    • 제6권6호
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    • pp.1419-1432
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    • 1999
  • 문서관리시스템은 문헌 정보들에 대한 정보 검색 및 관리를 효율적으로 지원하기 위한 시스템이다. 이러한 문서관리시스템은 하나의 테이블만으로 정보들을 관리하기 때문에 기존 데이터 관리 시스템에서 사용되는 조인 연산과 뷰 연산 등 많은 비용이 소요되는 연산을 제공할 필요가 없다. 더불어 문서관리시스템은 기존 데이터베이스관리시스템에서는 제공되지 않았던 새로운 연산이 요구된다. 본 논문은 문서관리시스템에서 자료의 구조 정의, 처리 등을 표현할 수 있는 효과적인 데이터 언어를 정의한다. 특히 문서 검색에 필요한 Ranking 연산, Proximity 연산을 제공하도록 정의하고, 정의된 데이터 언어로 작성된 질의를 효율적으로 처리하기 위한 질의 처리기를 설계하고 구현한다. 구현된 문서관리시스템을 위한 질의처리기는 기존 관계형 데이터베이스 관리 시스템의 질의 처리기를 문서관리시스템의 질의 처리기로 사용할 때 나타나는 성능저하 문제점을 해결할 뿐만 아니라 문서관리시스템에서 필요로 하는 새로운 연산을 제공한다.

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A Study of Consumer Loyalty on Instant Messaging Services

  • Kim, Sun-Tae;Kim, Jong-Woo
    • Management Science and Financial Engineering
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    • 제16권2호
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    • pp.67-80
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    • 2010
  • This study is focused on instant messaging service (IMS) providers' efforts to maintain a steadfast group of consumers who are willing to continuously use one service without switching to another. Various factors, carefully selected to reflect the unique features of instant messaging, were tested to verify their relationship with consumer loyalty. The results suggest that consumer loyalty of IMS users is most significantly affected by trust and perceived reputation a consumer has on the provider of IMS. Network externality, or the size and proximity of relationships formed through an IMS, also proves to have effect on consumer loyalty. Consumer loyalty in IMS users of different age or different internet usage is affected differently by each factor.

미국 CDI사의 건축물 발파해체 기법 (On the explosive demolition technology of construction building CDI, USA)

  • 장병하
    • 화약ㆍ발파
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    • 제13권4호
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    • pp.73-81
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    • 1995
  • Explosives demolition mothod is allowed for more efficient time-saving and safer demolitioni operations as compared to conventional / mechanical demolition methods. CDI has to minimize the effects of noise, dust and various demolition hazards to the public areas, and residences that are located adjacent to the project site. CDI's explosives demolition work on the Nam san Foreigner's Apartment Complex and chosun trading Co's factory are backed by over 45 years of explosives experience in the demolition of over 6,000 structures worldwide, many of these structures are similar to the Nam san Foreigner's Apt. and Chosun trading's factory in construction and proximity to sensitive adjacent exposures. Recoginized worldwide as the founder of the leader in explosives demolitioni technology, CDI always will applied "State-of-the-Art" explosives techniques to safely and successfully achieve the desired demolition results on these project. CDI has never injured, much less caused any fatality, to either a worker on one of our sites or to a third party during the implosion of high-rise structure.

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Minimizing the Average Distance of Separated Points on the Plane in the L1-Distance

  • Kim, Jae-Hoon
    • Journal of information and communication convergence engineering
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    • 제10권1호
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    • pp.1-4
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    • 2012
  • Given separated points divided by a line, called a wall, in a plane, we aim to make a gate in the wall to connect the separated points to each other. In this setting, the problem is to find a location for the gate that minimizes the average distance between the points. The problem is a variant of the well-known facility location problem, which is extensively studied in the fields of operations research, location theory, theoretical computer science, and so on. In this paper, we consider the $L^1$-distance of the points in the plane. The points are projected onto the wall and so the problem is transformed to a proximity problem of points on a line. Then it is shown that the transformed problem is related to the weighted median problem of points on the line. Therefore, we obtain an O(n log n)-time algorithm to solve our problem.

무인자동운전 경전철시스템 고가교량의 비상운전 중 안전성평가 (Safety Evaluation of Elevated Guideway during Abnormal Operation on LRT of Driverless Automatic Driving System)

  • 손은진;김민수;임영수;임종필
    • 한국철도학회논문집
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    • 제9권1호
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    • pp.29-35
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    • 2006
  • Trains in LRT(Light Railway Transit) system usually have shorter car length than metro's because of their smaller passensers demand. Therefore it is very likely that the load condition of LRT system in abnormal operation, in case of which trains are in close proximity by system broke or train rescue works, could be worse rather than in normal operation, in spite of rare probability of abnormal operation. In this study, the target reliability indexes of several abnormal operations are estimated in accordance with the occurrence probabilities of each abnormal operation case and the reliability index of normal operation presented by the specification. From the indexes, load factors for the abnormal operation cases are estimated and the safety evaluation is performed for Yong-in LRT project.

Value Object를 이용한 EJB 엔티티빈의 성능에 관한 연구 (A Study of the Performance on EJB Entity Bean with Value Object)

  • 최은희;이남용
    • 한국정보과학회:학술대회논문집
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    • 한국정보과학회 2001년도 가을 학술발표논문집 Vol.28 No.2 (1)
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    • pp.403-405
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    • 2001
  • In an EJB 1.1 specification, every method call made to the Enterprise Java Bean, is potentially remote call. Such remote invocations use the network layer regardless of the proximity of the client to the bean, creating a network overhead. Especially. because entity bean is more notable performance fail by remote call than session bean, frequency of use on Session Bean in work-site operations is much more than Entity Bean. We focus on how to improve the performance on the entity bean with Value Object, which is one of J2EE patterns suggested by Sun Microsystems. We presents related design-issues fur performance testing, the testing results compared with original entity bean and our findings.

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Work load analysis for determination of the reduction gear ratio for a 78 kW all wheel drive electric tractor design

  • Kim, Wan-Soo;Baek, Seung-Yun;Kim, Taek-Jin;Kim, Yeon-Soo;Park, Seong-Un;Choi, Chang-Hyun;Hong, Soon-Jung;Kim, Yong-Joo
    • 농업과학연구
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    • 제46권3호
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    • pp.613-627
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    • 2019
  • The purpose of this study was to design a powertrain for a 78 kW AWD (all wheel drive) electric tractor by analyzing the combination of various reduction gear ratios on a commercial motor using data from actual agricultural work and driving conditions. A load measurement system was constructed to collect data using wheel torque meters, proximity sensors, and a data acquisition system. Field experiments for measuring load data were performed for two environmental driving conditions (on asphalt and soil) and four agricultural operations (plow tillage, rotary tillage, loader operation, and baler operation). The attached implements and gear stages were selected through farmer surveys. The range of the reduction ratio was determined by selecting the minimum reduction ratio needed to satisfy the torque condition required for agricultural operations and the maximum reduction gear ratio to satisfy the maximum travel speed. The minimum reduction gear ratio selected was 57 in consideration of the working load condition and the maximum reduction gear ratio selected was 62 considering the maximum running speed. In the range of the reduction gear ratio 57 - 62, the selected motor satisfied all working torque conditions. As a result, the combination of the selected motor and reduction gear ratio was applicable for satisfying the loads required during agricultural operation and driving operation.