• Title/Summary/Keyword: Aerospace applications

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SATELLITE OPERATION DESIGN FOR ASSESSING MTF PERFORMANCE OF EARTH OBSERVATION SATELLITE USING STELLAR SOURCES (별을 이용한 지구 관측 위성의 MTF 성능 분석을 위한 위성 운영 설계)

  • Kim, Hee-Seob;Chung, Dae-Won;Choi, Hae-Jin
    • Journal of Astronomy and Space Sciences
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    • v.24 no.4
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    • pp.379-388
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    • 2007
  • Modulation Transfer Function (MTF) of satellite image is an important performance index in satellite image applications. Therefore MTF performance is assessed using satellite image for the ground target during LEOP phase after launch. But the MTF performance assessment using the ground target can be affected by imaging conditions such as cloud and weather. In this paper system requirements and satellite operation for assessing MTF performance of satellite image using stellar sources are proposed. Satellite capability in collecting stellar sources using the satellite which is designed for earth observation and satellite image usefulness for assessing MTF performances were analyzed. The proposed approach will be useful to assess MTF performance of earth observation satellite in lower earth orbit.

Long Range and High Axial Load Capacity Nanopositioner Using Single Piezoelectric Actuator and Translating Supports

  • Juluri, Bala Krishna;Lin, Wu;Lim, Lennie E N
    • International Journal of Precision Engineering and Manufacturing
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    • v.8 no.4
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    • pp.3-9
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    • 2007
  • Existing long range piezoelectric motors with friction based transmission mechanisms are limited by the axial load capacity. To overcome this problem, a new linear piezoelectric motor using one piezoelectric actuator combined with a novel stepping mechanism is reported in this paper. To obtain both long range and fine accuracy, dual positioning control strategy consisting of coarse positioning and fine positioning is used. Coarse positioning is used for long travel range by accumulating motion steps obtained by piezoelectric actuator. This is followed by fine positioning where required accuracy is obtained by fine motion displacement of piezoelectric actuator. This prototype is able to provide resolution of 20 nanometers and withstand a maximum axial load of 300N. At maximum load condition, the positioner can move forward to a travel distance of 5mm at a maximum speed of 0.4 mm/sec. This design of nanopositioner can be used in applications for ultra precision positioning and grinding operations where high axial force capacity is required.

Multibody models with flexible components for inflatable space structures

  • Petrolo, Marco;Governale, Giorgio;Catelani, Daniele;Carrera, Erasmo
    • Advances in aircraft and spacecraft science
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    • v.5 no.6
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    • pp.653-669
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    • 2018
  • This work has the objective to analyze multibody mechanisms of inflatable structures for manned space applications. The focus is on the evaluation of the main characteristics of MaxFlex, a new module of MSC Adams including the effect of nonlinear flexible bodies. MaxFlex integrates the nonlinear Finite Element Analysis (FEA) of Nastran-SOL400-and the Adams multibody capabilities in one unique solver, providing an improvement concerning the concept and technology based on the co-simulation among solvers. MaxFlex converts the equations of motion of the nonlinear FEA into phase-space form and discretizes them according to the multibody system integrator framework. The numerical results deal with an inflatable manned space module having rigid components and a flexible coating made of Kevlar. This paper is a preliminary assessment of the computational capabilities of the software and does not provide realistic guidelines for the actual design of the structure. The analysis leads to some recommendations related to the main issues to consider in a nonlinear simulation including both rigid and flexible components. The results underline the importance of realistic deployment times and applied forces. Also, a proper structural modeling is necessary, but can lead to excessive computational overheads.

A Process of the Technical Performance Management for A Space Launch Vehicle R&D Project (우주발사체 개발사업을 위한 기술성능관리 프로세스)

  • Yoo, Il Sang;Cho, Dong Hyun;Kim, Keun Taek
    • Journal of the Korean Society of Systems Engineering
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    • v.10 no.2
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    • pp.71-79
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    • 2014
  • To enhance success probability of a system development project, its overall risk level should be minimized through systematically managing schedules, costs, and technical performances. However, Attempts to manage technical performance compared to numerous efforts to control costs and schedules in such projects are deficient. Particularly, a space launch vehicle, a large complex system, development project is much less likely to meet its technical performance objectives due to its technological difficulty, along with schedule delay and cost overrun. The technical performance management (TPM) is a method for tracking and managing technical progress in order to achieve technical performance targets within schedule and budget. In this paper, we investigate applications of the TPM in several space launch vehicle development projects. Then we propose and validate the TPM process to achieve a successful mission in such projects.

Non-linear Adaptive Attitude Controller Design of Quadrotor UAV (쿼드로터 무인기 비선형 적응 자세제어기 설계)

  • Choi, In-Ho;Park, Mu-Hyuk;Kim, Hyun-Gi
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.6
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    • pp.2421-2427
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    • 2012
  • This paper is discussed the design on non-linear adaptive attitude controller for quadrotor UAV. Quadrotor UAV featured to have four rotor, required the special controller to compensate for the model parameter uncertainties as the unstable nonlinear system. In this research, we designed the adaptive controller to compensate for the payload changes even though it is changed with industrial applications. Especially, based on the mathematical model of UAV, non-linear adaptive controller is suggested and the stability is verified using the Lyapunov function and finally proved its performance and effectiveness of update laws with various payload by simulation.

Dilution of Precision (DOP) Based Landmark Exclusion Method for Evaluating Integrity Risk of LiDAR-based Navigation Systems

  • Choi, Pil Hun;Lee, Jinsil;Lee, Jiyun
    • Journal of Positioning, Navigation, and Timing
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    • v.9 no.3
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    • pp.285-292
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    • 2020
  • This paper introduces a new computational efficient Dilution of Precision (DOP)-based landmark exclusion method while ensuring the safety of the LiDAR-based navigation system that uses an innovation-based Nearest-Neighbor (NN) Data Association (DA) process. The NN DA process finds a correct landmark association hypothesis among all potential landmark permutations using Kalman filter innovation vectors. This makes the computational load increases exponentially as the number of landmarks increases. In this paper, we thus exclude landmarks by introducing DOP that quantifies the geometric distribution of landmarks as a way to minimize the loss of integrity performance that can occur by reducing landmarks. The number of landmarks to be excluded is set as the maximum number that can satisfy the integrity risk requirement. For the verification of the method, we developed a simulator that can analyze integrity risk according to the landmark number and its geometric distribution. Based on the simulation, we analyzed the relationship between DOP and integrity risk of the DA process by excluding each landmark. The results showed a tendency to minimize the loss of integrity performance when excluding landmarks with poor DOP. The developed method opens the possibility of assuring the safety risk of the Lidar-based navigation system in real-time applications by reducing a substantial amount of computational load.

Study on Satellite Vibration Control Using Adaptive Algorithm

  • Oh, Choong-Seok;Oh, Se-Boung;Bang, Hyo-Choong
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.2120-2125
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    • 2005
  • The principal idea of vibration isolation is to filter out the response of the system over the corner frequency. The isolation objectives are to transmit the attitude control torque within the bandwidth of the attitude control system and to filter all the high frequency components coming from vibration equipment above the bandwidth. However, when a reaction wheels or control momentum gyros control spacecraft attitude, vibration inevitably occurs and degrades the performance of sensitive devices. Therefore, vibration should be controlled or isolated for missions such as Earth observing, broadcasting and telecommunication between antenna and ground stations. For space applications, technicians designing controller have to consider a periodic vibration and disturbance to ensure system performance and robustness completing various missions. In general, past research isolating vibration commonly used 6 degree order freedom isolators such as Stewart and Mallock platforms. In this study, the vibration isolation device has 3 degree order freedom, one translational and two rotational motions. The origin of the coordinate is located at the center-of-gravity of the upper plane. In this paper, adaptive notch filter finds the disturbance frequency and the reference signal in filtered-x least mean square is generated by the notch frequency. The design parameters of the notch filter are updated continuously using recursive least square algorithm. Therefore, the adaptive filtered-x least mean square algorithm is applied to the vibration suppressing experiment without reference sensor. This paper shows the experimental results of an active vibration control using an adaptive filtered-x least mean squares algorithm.

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Effects of Nanopowder Additives in Micro-electrical Discharge Machining

  • Tan, Peng-Cheong;Yeo, Swee-Hock;Tan, Yie-Voon
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.3
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    • pp.22-26
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    • 2008
  • The use of electrical discharge machining (EDM) for micro-machining applications requires particular attention to the machined surface roughness and discharge gap distance, as these factors affect the geometrical accuracy of micro-parts. Previous studies of conventional EDM have shown that selected types of semi-conductive and non-conductive powder suspended in the dielectric reduced the surface roughness while ensuring a limited increase in the gap distance. Based on this, an extension of the technique to micro-EDM was studied Such work is necessary since the introduction of nanopowders suspended in the dielectric is not well understood. The experimental results showed that a statistically significant reduction in the surface roughness value was achieved at particular concentrations of the powder additives, depending on the powder material and the machining input energy setting. The average reduction in surface roughness using a powder suspended dielectric was between 14-24% of the average surface roughness generated using a pure dielectric. Furthermore, when these additive concentrations were used for machining, no adverse increase in the gap distance was observed.

Development of simulation-based testing environment for safety-critical software

  • Lee, Sang Hun;Lee, Seung Jun;Park, Jinkyun;Lee, Eun-chan;Kang, Hyun Gook
    • Nuclear Engineering and Technology
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    • v.50 no.4
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    • pp.570-581
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    • 2018
  • Recently, a software program has been used in nuclear power plants (NPPs) to digitalize many instrumentation and control systems. To guarantee NPP safety, the reliability of the software used in safetycritical instrumentation and control systems must be quantified and verified with proper test cases and test environment. In this study, a software testing method using a simulation-based software test bed is proposed. The test bed is developed by emulating the microprocessor architecture of the programmable logic controller used in NPP safety-critical applications and capturing its behavior at each machine instruction. The effectiveness of the proposed method is demonstrated via a case study. To represent the possible states of software input and the internal variables that contribute to generating a dedicated safety signal, the software test cases are developed in consideration of the digital characteristics of the target system and the plant dynamics. The method provides a practical way to conduct exhaustive software testing, which can prove the software to be error free and minimize the uncertainty in software reliability quantification. Compared with existing testing methods, it can effectively reduce the software testing effort by emulating the programmable logic controller behavior at the machine level.

Experimental Verification of Multi-Sensor Geolocation Algorithm using Sequential Kalman Filter (순차적 칼만 필터를 적용한 다중센서 위치추정 알고리즘 실험적 검증)

  • Lee, Seongheon;Kim, Youngjoo;Bang, Hyochoong
    • Journal of Institute of Control, Robotics and Systems
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    • v.21 no.1
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    • pp.7-13
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    • 2015
  • Unmanned air vehicles (UAVs) are getting popular not only as a private usage for the aerial photograph but military usage for the surveillance, reconnaissance and supply missions. For an UAV to successfully achieve these kind of missions, geolocation (localization) must be implied to track an interested target or fly by reference. In this research, we adopted multi-sensor fusion (MSF) algorithm to increase the accuracy of the geolocation and verified the algorithm using two multicopter UAVs. One UAV is equipped with an optical camera, and another UAV is equipped with an optical camera and a laser range finder. Throughout the experiment, we have obtained measurements about a fixed ground target and estimated the target position by a series of coordinate transformations and sequential Kalman filter. The result showed that the MSF has better performance in estimating target location than the case of using single sensor. Moreover, the experimental result implied that multi-sensor geolocation algorithm is able to have further improvements in localization accuracy and feasibility of other complicated applications such as moving target tracking and multiple target tracking.