• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.241-250
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• 2022

This paper addresses the Feasible Angular Momentum(FAM) chart that can be used as an indicator for maneuverability analysis of spacecraft installed with control moment gyros(CMGs). Recently, as the demands for high agility of spacecraft has been increasing in order to perform the space mission given to spacecraft more effectively, interest in CMGs, which is a high torque generator is increasing. However, since the CMG has a singularity problem that does not generate the control torque in the specific directions, in this paper, we consider the two pairs of parallel control moment gyros(TPCMGs) that follows the roof-type configuration. The Gimbal space was newly defined except for the space where singularity can be generated and the space where torque error is generated due to the hardware limits. The feasible angular momentum space is defined as a FAM chart, and it is very meaningful that it is possible to analyze the spacecraft's rotational maneuverability effectively by deriving the spacecraft's 3-axis parameters in the corresponding gimbal space mathematically.

• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.3
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• pp.70-78
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• 2004

The aerial photographic mission is a difficult work because aircraft must be flown along the specified flight lines, not marked on the ground. This study has been carried out for the development of aerial photographic guidance system, which enables us to make aerial photographic task easier. Such a flight guidance system is able to display a variety of map informations in a quick and efficient way in order to guide pilot. For this purpose, we first developed the nationwide aerial navigation map database that provides the topographic map information used for topographic interpretation and aeronautical chart information used for the flight security. Next, we developed the aerial photographic guidance system which uses the aerial navigation map as base map. It is concluded that the developed system can display the various map informations quickly and do any other photographing guidance tasks well in fast moving airplane.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.3
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• pp.403-410
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• 2020

Continuous industrial development has led to a better quality of life for everyone, even further accelerating industrial growth. Industrial development, however, has also caused environmental degradation, which is posing a serious threat to humanity. It has also encouraged the indiscriminate use of limited resources, causing resource depletion. Efficient resource management based on resource circulation is critical to saving resources. Resource circulation methods are as follows: reducing the use of resources in the manufacturing process, recycling used or reprocessed products and reusing used resources without being reprocessed, remanufacturing with end-of-life products with disassembled parts. Furthermore, remanufacturing process including cleaning, inspection, repairing, and reassembling facilitate performance level as well as new typical products. It is noteworthy that the remanufacturing of machine tools can significantly save resources because their structural parts are substantially large in size. Machine tools have served as a foundation for the manufacturing industry, which has driven Korea's industrial development. Nevertheless, a few research has been reported for remanufacturing technology with used machine tools. Relevant research of developing a remanufacturing process chart and method is prerequisite for saving the resource and environments.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.157-166
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• 2016

Aerodynamic loads for a horizontal axis wind turbine of the National Renewable Energy Laboratory (NREL) Phase VI rotor in yawed condition were predicted by using the blade element momentum theorem. The classical blade element momentum theorem was complemented by several aerodynamic corrections and models including the Pitt and Peters' yaw correction, Buhl's wake correction, Prandtl's tip loss model, Du and Selig's three-dimensional (3-D) stall delay model, etc. Changes of the aerodynamic loads according to the azimuth angle acting on the span-wise location of the NREL Phase VI blade were compared with the experimental data with various yaw angles and inflow speeds. The computational flow chart for the classical blade element momentum theorem was adequately modified to accurately calculate the combined functions of additional corrections and models stated above. A successive under-relaxation technique was developed and applied to prevent possible failure during the iteration process. Changes of the angle of attack according to the azimuth angle at the specified radial location of the blade were also obtained. The proposed numerical procedure was verified, and the predicted data of aerodynamic loads for the NREL Phase VI rotor bears an extremely close resemblance to those of the experimental data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.135-140
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• 2010

A new treatment is proposed to handle a deflection limit in the open-loop-onset-point (OLOP), which is commonly used in the prediction of pilot in-the-loop oscillation (PIO) due to a rate saturation. The new approach is motivated by the frequency response of a stand-alone actuator in that, unlike the suggestion by the original OLOP procedure, the rate limit onset is not delayed to a higher frequency by a deflection limit. Indeed, if a feedback control loop is closed, the rate limit onset can be shifted to a lower frequency since the controller tends to react with larger commands when deflection limited. The amplitude of the command at this onset frequency is combined with the deflection limit to estimate the associated gain reduction in the open-loop-onset-point in the final step of the OLOP process. The comparison of the new approach with the previous method reveals that an inaccurate optimism which can occur in the previous method is corrected by the proposed treatment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.9
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• pp.816-825
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• 2007

With a view to building up a program used in conceptual design of liquid rocket engine system, a preliminary performance-based code for an integrated engine system has been developed by incorporating sub-modular programs for each essential engine component. Modular descriptions for each component were formulated mathematically with essential parameters. In the whole iterative circuits for predicting engine performance, matching conditions of mass flow rate and pressure drop through each engine component have been considered. Mass balance calculations at each inter-component boundary are found smoothly converged. All the pressure drops through engine components as a function of mass flow rate are added up to provide turbo-pump outlet condition. In this paper, the flow chart for each iterative circuit and design methodologies are presented. Resultant predictions are validated with real engine data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.110-116
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• 2003

With the growth of aircraft performance and needs for light aircraft, the problems associated with hail impacts on aircraft during flights and grounding become and important issue. These hail encounters can cause severe damages to aircraft and result in major concerns in safety and cost. Since nearly all external components of the commercial and military aircraft-in particular, the nose section and the leading edge of the wing and tail-are subject to damages, much effort has been put into understanding of this problem. However, most of the previous studies have focused on the composite components and few results have been reported for the metallic components. In this paper, we study the ice impacts on the aluminum component with the finite element analysis method utilizing commercial non-linear dynamics solver LS-DYNA. The results are compared with the experimental data and a simple measure of the ice impact effects is proposed.