• Title/Summary/Keyword: Pointing Performance

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AN ADAPTED METHOD FOR REDUCING CHANGE DETECTION ERRORS DUE TO POINTING DIRECTION SHIFTS OF A SATELLITE SENSOR

  • Jeong, Jong-Hyeok;Takagi, Masataka
    • Proceedings of the KSRS Conference
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    • 2005.10a
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    • pp.126-129
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    • 2005
  • Change detections is carried out under the assumption that pixel boundaries of geometrically corrected time series satellite images cover the same location. However that assumption can be wrong when shifts in the pointing direction of a satellite sensor occurs. Currently, although the influence of misregistration on landcover change detection has been investigated, there has been little research on the influence of pointing direction shifts of a satellite sensor. In this study, a simple method for reducing the effects of pointing direction shifts of a satellite sensor is proposed: the classification of two ASTER images was carried out using the linear spectral mixture analysis, the two classification results were resampled into a geometrically fixed grid, and then the change detection of the two ASTER images was carried out by comparing the resampled classification results of the two images. The proposed method showed high performance in discriminating between changed areas and unchanged areas by removing the pointing direction shifts of a satellite sensor.

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Target Pointing Guidance Design Using Time-to-Go Estimator (Time-to-Go 추정기를 이용한 목표점 지향 유도 법칙 설계)

  • Whang, lck-Ho
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.1
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    • pp.60-66
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    • 2002
  • In this paper, a new target pointing guidance algorithm is proposed by combining the optimal target pointing solution and a simple time-to-Go estimator. Also investigated are some properties of the guidance algorithm which include a relation to conventional PNG, convergence region and convergence trajectories of error states according to the time-to-go estimator gain. Some guidelines for designing the pointing guidance law are commented based on the convergence properties. A design example in the case of large initial heading errors is presented and its performance is investigated by simulation.

A Study on Improvement of Aiming Ability using Disturbance Measurement in the Ground Military Vehicle (지상무기체계에서의 외란측정을 이용한 정밀 지향성 향상 연구)

  • Yoo, Jin-Ho;Park, Byung-Hun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.10 no.2
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    • pp.12-20
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    • 2007
  • The aiming ability is a key to improve the accuracy performance of the gun pointing system in the ground military vehicle. This paper describes the new detection method of chatter vibration using disturbance acceleration in the pointing structure. In order to analysis the vibration trends of the pointing system occurred while the vehicle driving, acceleration data obtained from vehicle was processed by using data processing algorithm with moving average and Hilbert transform. The specific mode constants of acceleration were obtained from various disturbances. Vehicle velocity, road condition and property of pointing structure were considered as factors which make the change of vibration trend in vehicle dynamics. Finally, back propagation neural networks have been applied to the pattern recognition of the classification of vibration signal in various driving conditions. Results of signal processing were compared with other condition result and analysed.

Gyrocompass Correction and Pointing Accuracy Improvement of the Ship-Borne Mobile Down Range Antenna for Launcher Telemetry (우주발사체 텔레메트리용 해상 이동형 다운레인지 안테나의 자이로컴퍼스 보정과 포인팅 정확도 향상)

  • Lee, Sun-Ik;Yeom, Kyung-Whan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.5
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    • pp.532-541
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    • 2014
  • The ship-borne mobile down range telemetry antenna system having 4.6 m reflector antenna and 3-axis mounting structure at S-band requires the precise pointing accuracy at sea for the launch mission. Using the LEO satellites tracking, a method to determine and verify the antenna pointing and tracking performance, and to find the pointing bias which dominantly contributes to the pointing inaccuracy, is presented. Based upon the tests conducted on the Jeju sea and Pacific sea, the pointing bias is determined and its origin is also identified as the drift of the heading angle of the gyrocompass. The applied systematic correction taking into account the pointing bias, and the achieved improvement of the pointing accuracy are shown. Thanks to the correction, it is presented that this antenna tracked the launcher(KSLV-I) stably within the required pointing accuracy in the following KSLV-I third launch.

Human performance evaluation of the three-dimensional input devices in virtual environment system (가상현실 시스템에서의 3차원 입력장치의 인간성능 평가)

  • Park, Jae-Hui;Park, Gyeong-Su
    • Journal of the Ergonomics Society of Korea
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    • v.19 no.1
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    • pp.49-61
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    • 2000
  • An experiment was designed to evaluate Fitts' law for the three-dimensional virtual pointing task and to compare the three input devices; Spaceball, Spacemouse, and 3D-Mouse. The result showed that Fitts law fitted poorly for the three-dimensional pointing tasks with relatively low coefficients of determinant. Three reasons, high degree-of-freedom, dynamic egocentric viewpoint change, and clutching problem were discussed to explain the poor fitness of Fitts' law. In terms of device comparison, the 3D-Mouse was superior to the other input devices. Also, the stereoscopic display significantly increased the performance. The results of this study can be used for the design of virtual control tasks and the selection of suitable input devices.

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Performance Improvement of the Tank Gun-Pointing System Stabilized Drive (전차포 표적지향 시스템의 안정화ㆍ구동성능 향상연구)

  • 이대옥;김학성;안태영
    • Journal of the Korea Institute of Military Science and Technology
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    • v.1 no.1
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    • pp.65-81
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    • 1998
  • Objective technology development has been carried out aiming performance improvement of the stabilized gun-pointing system for Type-4 tank. The full nonlinear simulation programs with gun bending modes and nonlinearities were developed to estimate, analyze and design the driving and stabilization system, and validated through the comparisons between simulations and test results of the existing Type-1 tank. The prototype is designed, fabricated, tested and evaluated on the test range as well as in the laboratory and followed by development and operational tests. The performance test results on stationary and on-the-move conditions are turned out to be superior to those of the advanced tanks developed in foreign countries.

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The design of a fuzzy logic controller for the pointing loop of the spin-stabilized platform (자전 안정화 플랫트폼 위치제어용 퍼지 논리 제어기 설계)

  • 유인억;이상정
    • 제어로봇시스템학회:학술대회논문집
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    • 1992.10a
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    • pp.112-116
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    • 1992
  • In this paper, a fuzzy logic controller(FLC) is designed for the pointing loop of the spin-stabilized platform. For the fuzzy inference, a fuzzy accelerator board using the Togai InfraLogic software and digital fuzzy processor(DFP110FC) is designed, and a validation of an algorithm for fuzzy logic control is also presented. The pointing loop of the spin-stabilized platform using FLC has better performance of step responses than a proportional controller in case of same loop hain through the software simulation and the experiment of implemented hardware.

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Performance estimation model of the three-dimensional pointing tasks in virtual environment systems (가상환경에서의 3차원 포인팅작업 성능평가 모형)

  • 박재희;박경수
    • Proceedings of the ESK Conference
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    • 1996.04a
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    • pp.253-258
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    • 1996
  • Virtual reality environment system is expected to be used as a new user interface tool oweing to its high immersiveness and high interactivity. To use VR interface effectively, we should identify the characteristics of the three-dimensional control tasks as if we did in two-dimensional graphic user interface environments. As a first step, we validated Fitts'law for the three-dimensional pointing tasks with the two input devices, Spaceball and Spacemouse. Different from the two-dimensional control tasks, VR pointing tasks needed inclusion of a new variable, size of the moving object, to Fitts'law. The modified

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Performance Investigation of Semi-Active Control Logic to Minimize a Pointing Performance Degradation of On-Board Payload by Chattering Effects (Chattering에 의한 위성 탑재체 지향성능저하 최소화를 위한 반능동제어기법 성능분석)

  • Oh, Hyun-Ung;Choi, Young-Jun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.9
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    • pp.882-889
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    • 2010
  • Semi-active vibration control is one of the attractive control methods for space application due to its robustness as passive damping system and much higher damping performance than passive system. However, a chattering induced by the sudden variation of damping force at the time of On-Off switching of semi-active control device degrades pointing performance of the on-board payload. In this paper, to enhance the pointing performance of the on-board payload, we proposed a semi-active vibration isolation with a strategy for attenuating chattering effect. Numerical simulation results using simplified analysis model indicated that the proposed semi-active control strategy produced much better isolation performance than the conventional Bang-Bang control semi-active control laws derived from skyhook and LQ theories.

Nonlinear Control of High Precision Pointing Stabilization Systems with Heavy Loads (대부하 정밀 표적지향 안정화 시스템의 비선형 제어기법 연구)

  • 이대옥;강태하;김학성;박광웅
    • Journal of the Korea Institute of Military Science and Technology
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    • v.4 no.2
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    • pp.157-178
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    • 2001
  • In this paper, the nonlinear control of high precision pointing stabilization system using feedback-linearization design methodology based on system parameter identification is discussed. Modern nonlinear servomechanism theory is adapted to cope with the hard nonlinearities inherent in the turret system. The mathematical models of electrical turret driving system to develop a high performance control algorithm are derived, and the parameter estimation algorithm identifying the unknown system parameters such as vicious and coulomb frictions, stiffness and inertia is developed. Through computer simulation and experiments, it is shown that pointing and tracking accuracy and stabilization against the wideband stochastic disturbance induced by vehicle running on the bump course are improved. Therefore, it is considered the proposed nonlinear control technique is effective in counteracting the nonlinearities and disturbances.

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