• The Journal of Korea Robotics Society
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• v.13 no.3
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• pp.198-204
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• 2018

Quadrotor with limited flight time due to battery level can have the extended mission life by applying energy harvesting technology. Bio-inspiration from the birds' locomotion of flight and perch-and-stare can make energy consumption efficient, and energy harvesting technology can generate energy. In order to charge the battery with solar power, the drones are required to be in a position without shade. In the mountainous terrain, a novel mechanism is required in order to be located stably at the top of the tree or the inclined rock. In this study, we propose an analysis of the origami structure and the concept design of the perching mechanism with two stable equilibrium states. The origami structure composed of compliant material can be applied to the perching mechanism that can be locked passively. Moreover, the experimental results of the trajectory and perching test are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.11-15
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• 2005

Compared with the conventional ground rocket launching, air-launching has many advantages. However, comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. The system design has been performed using two different approaches: the sequential optimization and the multidisciplinary feasible(MDF) optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. MDF optimization shows better result than sequential optimization. As a result of system optimization, a supersonic air launching rocket with total mass of 1244.91 kg, total length of 6.18 m, outer diameter of 0.60 m and the payload mass of 7.5 kg has been successfully designed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.26-32
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• 2005

Compared with the conventional ground rocket launching, air-launching has many advantages. However, a comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. The system design has been performed using two different approaches: the sequential optimization and the multidisciplinary feasible(MDF) optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. MDF optimization shows better results than the sequential optimization. As a result of system optimization, a supersonic air launching rocket with total mass of 1244.91kg, total length of 6.36m, outer diameter of 0.60m and the payload mass of 7.5kg has been successfully designed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.544-551
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• 2014

A program of launch vehicle performance analysis is composed for the education of the conceptual design of launch vehicles and the requirement analysis for the propulsion system design. The program is applied for the mission analysis of space launch vehicles based on KSLV-II with liquid rocket boosters. The 75-ton class liquid rocket engine is assumed for the boosters by referring the mass ratio of KSLV-II second stage. The launch performance analysis is carried out for KSLV-II with 2, 3 and 4 boosters by targeting the circular orbit of 700 km altitude. The trajectory is assumed as two-dimension considering the variation of the flight environment. Payload of advanced KSLV-II could be increased to maximum 3 tons, though it is limited by the thrust performance of the upper stage.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.3
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• pp.441-450
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• 2022

The introduction of autonomous underwater gliders (AUGs) specifically addresses the reduction of operational costs that were previously prohibited with conventional autonomous underwater vehicles (AUVs) using a "scaling-down" design philosophy by utilizing the characteristics of autonomous drifters to far extend operation duration and coverage. Long-duration, wide-area missions raise the cost and complexity of in-water testing for novel approaches to autonomous mission planning. As a result, a simulator that supports the rapid design, development, and testing of autonomy solutions across a wide range using software-in-the-loop simulation at faster-than-real-time speeds becomes critical. This paper describes a faster-than-real-time AUG simulator that can support high-resolution bathymetry for a wide variety of ocean environments, including ocean currents, various sensors, and vehicle dynamics. On top of the de facto standard ROS-Gazebo framework and open-sourced underwater vehicle simulation packages, features specific to AUGs for ocean mapping are developed. For vehicle dynamics, the next-generation hybrid autonomous underwater gliders (Hybrid-AUGs) operate with both the buoyancy engine and the thrusters to improve navigation for bathymetry mappings, e.g., line trajectory, are is implemented since because it can also describe conventional AUGs without the thrusters. The simulation results are validated with experiments while operating at 120 times faster than the real-time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.330-339
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• 2008

Ground-based interceptors(GBI) comprise a major element of the strategic defense against hostile targets like Intercontinental Ballistic Missiles(ICBM) and reentry vehicles(RV) dispersed from them. An optimum design of the subsystems is required to increase the performance and reliability of these GBI. Propulsion subsystem design and optimization is the motivation for this effort. This paper describes an effort in which an entire GBI missile system, including a multi-stage solid rocket booster, is considered simultaneously in a Genetic Algorithm(GA) performance optimization process. Single goal, constrained optimization is performed. For specified payload and miss distance, time of flight, the most important component in the optimization process is the booster, for its takeoff weight, time of flight, or a combination of the two. The GBI is assumed to be a multistage missile that uses target location data provided by two ground based RF radar sensors and two low earth orbit(LEO) IR sensors. 3Dimensional model is developed for a multistage target with a boost phase acceleration profile that depends on total mass, propellant mass and the specific impulse in the gravity field. The monostatic radar cross section (RCS) data of a three stage ICBM is used. For preliminary design, GBI is assumed to have a fixed initial position from the target launch point and zero launch delay. GBI carries the Kill Vehicle(KV) to an optimal position in space to allow it to complete the intercept. The objective is to design and optimize the propulsion system for the GBI that will fulfill mission requirements and objectives. The KV weight and volume requirements are specified in the problem definition before the optimization is computed. We have considered only continuous design variables, while considering discrete variables as input. Though the number of stages should also be one of the design variables, however, in this paper it is fixed as three. The elite solution from GA is passed on to(Sequential Quadratic Programming) SQP as near optimal guess. The SQP then performs local convergence to identify the minimum mass of the GBI. The performance of the three staged GBI is validated using a ballistic missile intercept scenario modeled in Matlab/SIMULINK.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.127-133
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• 2004

This paper described development of the portable ground control system(PGCS) for unmanned aerial vehicle. In the design of GCS, it upload mission planning that aircraft has to perform and has to receive position, attitude, state, navigation information all about the aircraft. Aircraft states and trajectory are displayed using this system on line. The PGCS is composed of commercial notebook computer, RF modem for communication between aircraft and PGCS, input/output board, remote control receiver, switches and lamps. Performance of this system is verified by flight test of small unmanned aerial vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.448-454
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• 2008

This paper deals with a behavior based decentralized control strategy for UAV swarming utilizing the artificial potential functions and the sliding mode control technique. Individual interactions for swarming behavior are modeled using the artificial potential functions. The motion of individual UAV is directed toward the negative gradient of the combined potential. For tracking the reference trajectory of UAV swarming, a swarming center is considered as the object of control. The sliding-mode control technique is adopted to make the proposed swarm control strategy robust with respect to the system uncertainties and the varying mission environment. Numerical simulation is performed to verify the performance of the proposed controller.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.97-104
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• 2014

In this study, preliminary thermal sizing was performed with the aim of developing a fuel supply and cooling system design to solve the heating problems in high-speed vehicles. First, an analysis model was used to satisfy an optional mission profile. The heat loads were computed under boundary conditions. The results were verified using the precedent design case. Then, fuel consumption rates were estimated for the analysis trajectory. Accordingly, the cooling capacity in the system was calculated using the heat sink capacity of the endothermic fuel. Lastly, the fulfillment of the design requirements was confirmed in comparison to the cooling needs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.41-47
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• 2005

Conceptual design process is defined for the air-launching rocket by including analysis modules like mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. As a result of the conceptual design, the supersonic(M=1.5) air-launching rocket with hybrid engine for first stage propulsion system is designed. For the best system alternative selection, trade study for the 1st stage engine type and launching speeds using sequential optimization and confirming feasibility of baseline air-launching rocket has been performed. As a result of trade study, all alternatives are competitive in total weight and show only small difference in total weight per unit payload weight. Therefore, it is confirmed that the baseline air-launching rocket which has advantage in system safety especially in supersonic launching is feasible.