• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.424-430
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• 2013

This paper presents a new design works for the braking chopper system which is included in the propulsion system of KTX high speed train. Due to the current fed type synchronous motors used in the propulsion system, some different behaviors are shown comparing to the voltage type other chopper systems. Specially this chopper system acts either braking controlling or regenerative power controlling system with a parallel resistive load in the propulsion system. In this paper, an improved simple high power IGBT brake chopper system has proposed which is able to be replaced with an existing complicated GTO chopper system. The analytical approaches to the parallel load type current chopper system and the propper snubber circuits calculation were explained in this paper to control new chopper system. In addition, the thermal resistance of the cooling system for power dissipation of IGBT modules was calculated also. Finally several PC simulations have been done to clarify its availability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.742-748
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• 2004

In this paper are presented TSTO system analysis including some controlled variables on the engine operation such as a fuel flow rate and a pressure ratio of compressor, as well as variables on the trajectory. TSTO studied here is accelerated up to Mach 6 by a fly-back booster powered by air breathing engines. Three different types of engine cycle were treated for propulsion system of the booster, such as a turbo ramjet, a precooled turbojet and an EXpander cycle Air Turbo Ramjet (ATREX). The history of the controlled variables on the engine operation was optimized by Sequential Quadratic Programming (SQP) to accomplish the minimum fuel consumption. The trajectory was also optimized simultaneously. The results showed that the turbo ramjet gave the best fuel consumption. The optimal trajectory was almost the same except in the transonic range and just before reaching to Mach 6. The history of the pressure ratio of compressor considerably depended on the engine type. It is concluded that simultaneous optimization for engine control and trajectory is effective especially for a high-speed airplane propelled by turbojets like the TSTO booster.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.339-342
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• 2010

Dual throat nozzle(DTN) is recently attracting much attention as a new concept of the thrust vectoring technique of propulsion jet. This DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze the performance of a dual throat nozzle(DTN) at various mass flow rate of secondary flow. Two-dimensional, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. The present computational results were validated with some experimental data available. Based upon the present results, Thrust-vector control using a DTN is discussed in terms of the thrust coefficient and the coefficient of discharge.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.38-46
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• 1998

A theoretical and an empirical application of the speed control of a single-shaft turbo-jet engine was done using an observer for Linear Quadratic Gausian(LQG) that is one of the robust control fields. Based on a general controller design with state feedback, a controller with output feedback was designed to find out a sufficient condition in finding an Asymptotic Stability After defining of the total system through the modeling of a real turbo-jet engine, a Tracking Control was carried out. Furthermore, a saturation of the control input was theoretically considered in the output feedback controller to simulate more similar real condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.427-430
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• 2005

The precision control valve flow of satellite attitude control device was analyzed in this paper, Then, force of flow in valve was calculated for plunger surface. We made an offer about basic data for optimal plunger design.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.1
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• pp.71-81
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• 2020

This paper proposes a possibility of using active front-end rectifier with the SVPWM method for induction motor speed control, which is applicable to small electric propulsion boats. The proposed method can produce a more precise sinusoidal input current waveform and a higher power factor than conventional methods. Its speed, torque, input current, DC voltage, and load current control performance are similar to or better than those of conventional methods. Through computer simulations using the PSIM program, the validity of the proposed method was verified by comparing and analyzing the characteristics of the conventional methods and the proposed method.

• Journal of Power Electronics
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• v.8 no.1
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• pp.23-34
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• 2008

This paper deals with a Direct Torque Control (DTC) of an Interior Permanent Magnet Synchronous Motor (IPMSM) for the Electric Vehicle (EV) propulsion system using a Neural Network (NN). The Conventional DTC with optimized switching lookup table and three level torque controller generates relatively large torque ripples in an electric vehicle motor drive. For reducing the torque ripples, a three level torque controller is hereby replaced by the five level torque controller. Furthermore, the switching lookup table of the five level torque controller based DTC is replaced with a Neural Network. These DTC schemes of an IPMSM drive are simulated using MATLAB/SIMULINK. The simulated results are compared with the conventional DTC and it is found that the ripples in the torque, as well as in the stator current, are reduced drastically.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.373-375
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• 1997

In this paper, we present IGBT VVVF inverters as a 1C1M propulsion system for electric car. These inverters are composed of high power IGBT's and controlled by compact control units. The control unit performs full digital control by using 32bit DSP and microcontroller. By using CAN-bus, high speed network is constructed within four control units. The stack is simplified and optimized by using plate bus and IGBT driver units of hybrid-type.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.18-21
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• 2011

In this study, basic research on the pressure control using driven pintle of modulatable thruster is presented. For this purpose, pintle thruster and pintle shape was developed. The actuator model was selected by calculating pintle load using Fluent software. Preliminary unsteady experimental results show that huge pressure oscillation is occurred as the pintle approach toward nozzle wall. From the preliminary experimental results, we could see possibility of pressure control of the modulatable thruster.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.131-136
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• 2004

Thermal control of satellite propellant tank is achieved by patch heaters enabled by thermostat's behavior. It is important to attach the thermostat on the appropriate position of the propellant tank. However its position cannot be given with exact numerics because tank is spherical. Actually the position for thermostat is designated in relevant drawing approximately, therby, the engineer practices depending on his own experience and intuition. The sensitivity analysis for the position of thermostat is performed such that the influence on the thermal behavior and control of tank is examined quantatively. When assembling tank module, the reasonable performance on the thermal control is believed with possible human errors if the uncertainty in the position of thermostat is not quite large.