• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.39-43
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• 2005

In this paper, we describe the contents of the achievement of basic experiments for manufacturing and evaluating a micro-rocket using solid propellant, as the device of the micro thrust generator which can be used for attitude control of satellites. We try to analyze performance of the rocket through visualization of the motor jet, and adopt various ignition methods to obtain confidence in ignition problem. For this purpose, we develop and test two different types of thrust measurement system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.92-98
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• 2006

An 1 lbf of NASA standard monopropellant thruster, MRE-1, is used for KOMPSAT (Korea Multi-Purpose Satellite) which is launched in 2006 and provides reliable and cost-effective means for attitude and maneuvering control system. The monopropellant thruster obtains required thrust by thermal decomposition process of propellant through catalyst bed. During firing, the decomposition plays a role of a heat source that may occur an excessive radiation heat transfer to peripheral structures and electronics in relatively low temperature condition.Therefore, the radiation heat shield is needed to prevent the critical radiative heat exchange between thruster and satellite during firing. This paper summarizes an overall development process of radiation heat shield from the design engineering up to the manufacturing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.89-95
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• 2003

Propulsion system of the current developing satellite is roughly composed of propellant tank and four major modules. Each module prevides the pulse momentum for spacecraft attitude control, filling/draining of propellant and pressurant, propellant filtering, and the change of flow passage in the spacecraft emergency situation, respectively. These modules will be fixed on the propulsion platform with their suitable mounting brackers, so the brackets shall be designed sufficiently to support a function of the modules under launch environment and on-orbit condition. The purpose of this article is to check if all the bracket designs satisfy the defined structural requirements through finite element analysis, and then to verify structural safety.

• The Journal of Fisheries Business Administration
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• v.26 no.1
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• pp.55-77
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• 1995

This study analyzed the structure of imported fisheries, focusing especially on the following factors of live fisheries import : First of all, it is confirmed that the import of live fisheries expands when domestic production decreases. To put it concretely, the structure of domestic live fish supply is based upon the production of aquaculture, the shift from export to domestic use, and imported live fisheries. These all coexist, expand, and grow together. Secondly, the structure of the consumer's market - the background of expanding and growing live fisheries-is currently diversifying with quality and quantity from a local area consumer system based upon regional markets, to a wider ranged system based upon the food industry and retailing market. The existence of the consumer markets is premised upon a stable supply structure, in terms of material and price. Thirdly, in terms of trade policy, control of imports instantly reduces import goods. But it is reasonable to say that there is not any logical effectiveness of denying the stable growth of low market capital under the background of strong consummer expansion. Fourthly, the attitude of the import related managener organization is directly related to the degree to which it is connected to live fish import. It is demanded that such a managing organization possess suitable facilities, specializaed knowledge, and management skill of live fisheries. So it is predicted that newly introducing the importing of live fisheries is not simple. It indirectly shows that the capital which relates to live fisheries are connected with the importing og live fish fisheries.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.61-70
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• 2017

Robust thrust distribution method of solid DACS is researched. For the case of the system which has higher number of actuation nozzles than the degree of freedom of thrust to be controlled, the robust thrust allocation law which accommodate the abnormal operation is suggested. Assuming the situation that some nozzles are uncontrollable, the error between nozzle throat area command and response can be calculated. The error is used for realtime reshaping of weighting matrix. From the weighting effect, the nozzle which operated abnormally has low responsibility for the command then, the thrust error is reduced. The suggested algorithm is verified by the simulation of abnormal operation condition of DCS and ACS nozzle respectively.

• Journal of Aerospace System Engineering
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• v.11 no.1
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• pp.41-46
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• 2017

A new test bench for small multi-rotor type drones has been developed. Six degrees of freedom (DOF) motion is possible due to a ball bushing, wheels, and rotating plates. An FPGA (field programmable gate array) based controller, that supports realtime parallel processing, is used to measure attitude with an accelerometer and a gyro to adjust motor speed. Several tests were performed to check the operational properties of the test bench and the controller. The results show that this test bench is proper for verifying controllers and the control methods of small multi-rotor drones.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.263-271
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• 2010

A reaction wheel is commonly used, as an important actuator, to control the attitude of a satellite. Operation of the reaction wheel plays a role of an excitation source to loading equipment inside the satellite. As requirements for environmental vibration to manifest the performance of precision equipment are getting more stringent, the research for analysis or reduction of unwanted action force in high frequency range when operating the reaction wheel is necessary. In this paper, the procedure to extract input forces and damping of a rotor system of reaction wheel is suggested. The analysis for measured action forces of reaction wheel is accomplished and important higher harmonics of action forces are determined. The input forces and damping of the rotor system are, then, extracted by curve-fitting and a particular solution for input force.

• Convergence Security Journal
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• v.17 no.5
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• pp.71-76
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• 2017

Today, it is an information society where a large number of users access and view important data in a large number of information assets as needed. In this complexity, techniques related Identify Management are being applied, in order to verify authorized user access to important information assets and manage of history. But, the ability access to sensitive information using account has the disadvantage of being able to open the way for information to the attacker when it is hijacked. Thus, in this paper, we propose a secure Identify Management System that can control the use of accounts based on the attitude of the account holder, but also enhances the security and does not hinder the convenience.

• Journal of Multimedia Information System
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• v.8 no.2
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• pp.121-130
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• 2021

Foot bionic robot could be supported and towed through a series of discrete footholds and be adapted to rugged terrain through attitude adjustment. The vibration isolation of the robot could decouple the fuselage from foot-end trajectories, thus, the robot walked smoothly even if in a significant terrain. The gait programming and foot end trajectory algorithm were simulated. The quadruped robot of parallel five linkages with eight degrees of freedom were tested. The kinematics model of the robot was established by setting the corresponding coordinate system. The forward and inverse kinematics of both supporting and swinging legs were analyzed, and the angle function of single leg driving joint was obtained. The trajectory planning of both supporting and swinging phases was carried out, based on the control strategy of compound cycloid foot-end trajectory planning algorithm with zero impact. The single leg was simulated in Matlab with the established kinematic model. Finally, the walking mode of the robot was studied according to bionics principles. The diagonal gait was simulated and verified through the foot-end trajectory and the kinematics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.9
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• pp.639-646
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• 2022

Landing site searching algorithms are developed for a quadrotor using a depth map in unknown environment. Guidance and control system of Unmanned Aerial Vehicle (UAV) consists of a trajectory planner, a position and an attitude controller. Landing site is selected based on the information of the depth map which is acquired by a stereo vision sensor attached on the gimbal system pointing downwards. Flatness information is obtained by the maximum depth difference of a predefined depth map region, and the distance from the UAV is also considered. This study proposes three landing methods and compares their performance using various indices such as UAV travel distance, map accuracy, obstacle response time etc.