• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.71-80
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• 2002

According to the rapid growth of high speed and precise industry, the application of synchronous motor has been increased. In the application fields, these fast dynamic response is of prime importance. In particular, since the PMLSM(Permanent Magnet Linear Synchronous Motor) has characteristics of high speed, high thrust, it has been used in high-performance servo drive. From these reasons, it is recently used for high precise position control, and machine tool. In this paper, a study of the sliding mode with VSS (Variable Structure System) design for a PMLSM is presented. For fast and precise motion control of PMLSM, the compensation of disturbance and parameter variation is necessary. Hence we eliminate the reaching phase use of VSS that is changed to switching function and vector control using the state observer. And we proposed to sliding mode control algorithm so that realize fast response without overshoot, disturbance and parameter variation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.333-342
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• 2016

Liquid rocket propulsion is a system that produces required thrust for satellites and space launch vehicles by using chemical reactions of a liquid fuel and a liquid oxidizer. Monomethylhydrazine/dinitrogen tetroxide, liquid hydrogen/liquid oxygen and RP-1/liquid oxygen are typical combinations of liquid propellants commonly used for the liquid rocket propulsion system. The objective of the present study is to investigate useful design and performance data of liquid rocket engine by conducting a numerical analysis of thermochemical reactions of liquid rocket propellants. For this, final products and chemical compositions of three liquid propellant combinations are calculated using equilibrium constants of major elementary equilibrium reactions when reactants remain in chemical equilibrium state after combustion process. In addition, flame temperature and specific impulse are estimated.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.92-97
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• 2012

The propulsion system of space launch vehicle generates thrust by supplying oxidizer and fuel to combustion chamber. KSLV-II 2nd stage engine, currently under development by KARI, is to use liquid oxygen as a oxidizer and JET-A1 as a fuel. The 2nd stage pump-fed engine is mainly composed of combustion chamber, turbo-pump and engine supply system. To develop liquid propulsion engine, the development of combustion chamber must be preceded. For performance validation of the combustion chamber, the designed and manufactured combustion chamber should be tested in combustion chamber test facility (CCTF). The detailed design for the planned CCTF in Naro Space Center was conducted. The oxidizer supply system modeling using AMESim was performed based on the results of the detailed design, and the oxidizer supply characteristics was analyzed in this paper.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.3
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• pp.313-314
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• 2009

To project military power, the paradigm of the modern warship aquisition has evolved with more large platform and high-technology equipment. For example, the Aegis combat system equipped warship is one of the most advanced and capable defense systems currently in use. Concurrently, if the warship attacked and disabled, it may worse the asymmetry of the battle field and it also depress the morale of the fleet. For that reason, to keep and protect few number of the big and high technology equipped warship from enemy is very important. At the present, the performance of unit weapon has enhanced remarkably. A Korean-built SS-209 class submarine, Lee Chun-ham, participated in Naval Exercise Tandem Thrust conducted in 1999, sink the target ship ex-USS Oklahoma by a single torpedo. USS Stark was struck on May 17, 1987, by two Exocet anti ship missiles and disabled. For this reason, susceptibility should be prior to vulnerability and recoverability. In this paper, deception ship which is small and chief but has very similar signatures to large and high technology equiped warship has conceptually studied by using systems engineering approach. And it may be a effective way to enhance the susceptibility of the key fighting power.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.197-204
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• 2005

A waterjet propulsion system has many advantages compared with a conventional screw propeller especially for amphibious armored wheeled vehicles because of a good maneuverability at low speed, good operation ability at shallow water, high thrust at low speed to aid maneuverability and exit from water, etc. The POD type waterjet is adequate for the present wheeled vehicle because the weight is lighter and L/B is longer than the conventional armored amphibious vehicle. Resistance and self-propulsion tests with a 1/3.5-scale model are conducted at PNU towing tank. Based on these measurements, the performance is analyzed according to ITTC 96 standard analysis method and also according to the conventional propulsive factor analysis method. Based on these two methods, the full-scale effective and delivered powers of amphibious armored wheeled vehicle are estimated. This paper emphasizes the analysis method of model test of the waterjet propulsion system for a amphibious armored wheeled vehicle and the model test technique together with the comparison of the two analysis methods.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.12-18
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• 2015

Recently, the development trend of turbomachinery is high capacity and high efficiency. Most of turbomachinery in the market are adopting ball bearings or air foil bearings. However, ball bearings have a limit for high speed product over $2.0{\times}10^6DN$(product of the inner diameter of the bearing in mm (D) and the maximum speed in rpm (N)). Air foil bearings have a limit for high axial load for high power products over 200~300 HP(horse power). Magnetic bearing is one of the solutions to overcome the limits of high speed and high axial load. Because magnetic bearings have no friction between the rotor and the bearings, they can reduce the load of the motor and make it possible to increase the rotating speed up to $5.0{\times}10^6DN$. Moreover, they can have high axial load capacity, because the axial load capacity of magnetic bearing depends on the capacity of the designed electromagnet. In this study, the radial and thrust magnetic bearings are designed to be applied to the 200 HP class turbo blower, and their performance was evaluated by the experiment. Based on the tests up to 26,400 rpm and 21,000 rpm under the no-load and load condition, respectively, it was verified that the magnetic bearings are stably support the rotor of the turbo blower.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.42-49
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• 2017

The solid rocket motor(SRM) consists of a motor case, igniter, propellants, nozzle, insulation, controller, and driving device. The liquid rocket propulsion systems(LRPSs) cools the nozzle by the fuel and oxidizer but SRM does not cool the nozzle. The nozzle of SRM is high temperature condition and high velocity condition so occurs the erosion by combustion gas. This erosion occurs the change of nozzle throat and reduces thrust performance of rocket. The material of Rocket nozzle is minimization of erosion and insulation effect and endure the shear force, high temperature and high pressure. The purpose of this study is to investigate the erosion characteristics of solid rocket nozzles by each combustion time. Through the structure inspection of Graphite and C-C composite, identify the characteristics of the microstructure before and after erosion.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.156-164
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• 2010

As part of preliminary study for development of 1,200 N-class bipropellant rocket engine with the concentrated hydrogen peroxide, bipropellant engine elements were designed and experimentally tested. The catalysts of $MnO_2$ and $MnO_2$ added Pb as an addictive were compared to achieve high decomposition performance and the catalytic reactor with $MnO_2$ added Pb was designed and its decomposition efficiency of 97.2% was achieved. The autoignition tests of kerosene by decomposed hydrogen peroxide were carried out under various equivalence ratios to ignite without additional ignition sources. Autoignition were achieved in all experimental conditions and $C^*$ efficiencies at each condition were at or above 90%. From the measured thrust results, the highest value was 830 N which is in corresponds with 1,035 N at vacuum level using 94.1% theoretical $I_{sp}$.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.476-482
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• 2010

In this paper, we propose a robust path tracking control method for autonomous underwater vehicle with variable speed. The proposed path tracking controller consists of a kinematic controller and a dynamic controller. First, the kinematic controller computes the surge speed and yaw rate to follow the reference path with variable speed. Then the dynamic controller controls the thrust force and yaw torque to move the AUV actually. In the dynamic control, we assume that the sway speed is a disturbance. In addition the dynamic controller is designed based on sliding mode conrol. We also demonstrate the stability of the proposed control method by Lyapunov stability theory. Finally, simulation results illustrate the performance of the proposed control method.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.73-82
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• 2015

A high altitude test facility which includes supersonic diffuser and ejector has been developed to simulate atmospheric pressure at 25 km using a 500 N class small scale liquid rocket engine. Also high altitude simulation test for the small scale liquid rocket engine was performed to verify the facility's performance. The experimental facility consists of high altitude simulation device, propellants supply system and coolant supply system. Low pressure condition corresponding to about 27 km(0.021 bar) altitude atmosphere was successfully simulated and a small scale liquid rocket engine thrust level was confirmed at the simulated condition by the high altitude test facility verification test.