• Journal of Power Electronics
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• v.18 no.6
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• pp.1670-1682
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• 2018

The further improvement of submarine propulsion is associated with the modularity of accumulator-fed inverters, such as cascaded inverters (CIs). CI technology guarantees smooth output voltages with reduced switch frequencies under linear loads. However, the output voltages of CIs are distorted under rectifier loads. This distortion requires harmonic suppression technology. One such technology is the repetitive controller (RC), which is commonly applied but suffers from poor performance in propulsion systems. In this study, the FFT spectrum of a CI under rectifier load is analyzed, and the harmonic contents are uneven in magnitude. For the purpose of harmonic suppression, the control gains at each harmonic frequency should be seriously considered. A RC with a specific harmonic gain compensation (SHGC) for CIs is proposed. This method provides additional control gains at low-order harmonic frequencies, which are difficult to achieve with conventional RCs. This SHGC consists of a band-pass filter (BPF) and proportional element and is easy to implement. These features make the proposed method suitable for submarine propulsion. Experimental results verify the feasibility of the improved RC.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.268-272
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• 2012

A propulsion controller for vehicles should be designed to overcome a sensor failure during a flight, and it is necessary to control the system properly at any circumstances. Therefore, the vehicles need to retain reliability on the sensor measurements by implementing extra sensors to replace the original control sensors in case of their failure. This paper presents the MIMO NARX model by simulation which substitutes measured values with estimated ones by the state estimation technique in case of a sensor failure in a turbojet engine. It is also presented that the NARX model can be adapted as an engine model in HILS equipments.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.29-41
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• 2021

The PID controller with fin angle and thrust as control input was designed based on the aerodynamic data of scramjet system. Flight simulation following a given trajectory which strike the target point after climb and cruise with constant dynamic pressure was conducted. After that, the required thrust for the climb and cruise was calculated and the required fuel flow rate for the hydrogen fuel dual mode scramjet combustor was analyzed. The combustor analysis of this study which conducted on integrated model of independently developed inlet, combustor, nozzles and external aerodynamic models, laying the foundation for the integrated design of the air breathing hypersonic system.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.384-387
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• 1990

This paper describes the design of the power conversion system for the 3-ton prototype magnetic levitation system. Electric power needed for the propulsion and levitation system of the vehicle is supplied by the wayside rectifier through the power rail and is picked up by the on board power collector, and is supplied to the propulsion VVVF inverter and levitation chopper. In this paper, design characteristic of the VVVF inverter, chopper and power source unit which provides control power to the levitation controller and levitation power to the chopper is described.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.278-280
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• 1996

This paper presents a high performance AC propulsion system for electric car to improve traction capability. The presented VVVF inverter was composed of as GTO thyristor and the the controller was fully digitalized by using 32bit DSP. The improved PWM algorithms and the new adhesion control were adapted to improve traction characteristics. This system could be possible the higher reliability and flexibility. The field test results showed the higher performances characteristics of the presented system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.622-630
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• 2006

This paper is about the magnetic suspension stage based on the Switched Reluctance propulsion principle. Because the previous studies on contact-free stage adopted the Lorentz force for main force generation mechanism they have suffered from thermal problem deteriorating the precision. Thus, the magnetic suspension stage adopting SR principle which can achieve high force density is proposed. The main operating principle and structure for achieving high resolution and long travel range are represented. The magnetic force analysis of each actuator, providing back data for dynamic modeling and controller design are carried out. By conducting basic experiments, the feasibility of the proposed system is shown. In addition the problems which should be improved and their solutions are represented.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.427-432
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• 1998

There are many demands for ship control system and many studies have been proposed. For example, if a ship diesel engine is operated by consolidated control with Controllable Pitch Propeller(CPP), the minimum fuel consumption is achieved, satisfying the demanded ship speed. For this, it is necessary that the ship is operated on the ideal operating line which satisfies the minimum fuel consumption. In this context of view, this paper presents a controller design method for a ship propulsion system with CPP by Linear Matrix Inequality(LMI) which satisfies the given $H_{\infty}$ control performance and robust stability in the presence of physical parameter perturbations. The validity and applicability of this approach are illustrated through a simulation in the all operating ranges.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.642-645
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• 1997

This paper presents a propulsion control system for electric car to improve traction capability. The presented VVVF inverter was composed of as IGBT and the controller was full digitalized by using 32bit DSP. The improved PWM algorithms was adapted to improve traction characteristics. The system could be possible the higher reliablity, compact, light, low cost' and flexbility.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.3-3
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• 1997

미사일 수직발사 시스템은 공간을 작게 차지하고 간편하여 각국이 선호하고 있다. 그러나 수직발사 초기에는 매우 낮은 속도로 상승하므로 Fin의 공력이 발생하지 않기 때문에 추력방향을 직접제어하지 않으면 안된다. 추력방향 제어장치는 Gimbal, Jet Vane, Jet Tab, Secondary Injection 등 여러 방식이 있으나 Jet Vane Type의 추력 방향 제어장치는 응답이 빠르고 경량화가 가능하며 후방 Fin과의 연동 및 작동 후 분리가 가능하다는 장점으로 인해 수직발사 미사일의 초기 방향제어에 주로 사용한다. 이 장치는 Vane이 화염 속에서 직접 구동되므로 고내열성 재료의 기술이 필요하며 미사일의 전체 System에 요구되는 Side Force를 발생시키기 위한 Vane의 최대 받음각 및 회전속도를 결정해야 한다. 따라서 초음속 유동해석을 통해서 Vane의 받음각에 대한 Side Force와 Torque를 계산하며, 구조해석을 통해 Side Force가 가해지는 동안의 Housing의 굽힘, 비틀림 하중 등을 계산하였다. 또한 Controller는 기존의 유압방식보다도 소형이며 복잡하지 않고 가격이 싼 DC Motor와 감속기를 이용하여 빠른 응답성에 부합토록 설계하였다. 본론에서는 성능과 관련된 초기 요구조건에 대한 최적설계의 변수들을 해석하고. 그에 따른 개발사양, 개발 과정, 구조, 시험방법 등에 대해 고찰하고자 한다.

• Journal of Ship and Ocean Technology
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• v.11 no.1
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• pp.1-10
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• 2007

This study introduces the development of robot fish ROFI 1.1. Today, robot fish is one of strong candidates for next-generation UUV. The present paper describes the design, manufacturing, and operation tests of the robot fish developed at Seoul National University. The very first robot fish in Korea, ROFI 1.1 is operated by a wireless remote controller. Its overall length is 680mm, and weight is 8.8kg. The fore body contains main mechanical and electrical systems and is covered by a FRP skin. The aft body has a mechanical bone system that mimics fish bones, and its skin is made of flexible silicon sponge to allow elastic motion for propulsion. It is found that this mechanical system creates effective and realistic fish-like swimming mode. It is observed that the normal and maximum advancing speeds of ROFI 1.1 are about 1 and 2 m/sec, and the turning radius is between $0.7{\sim}2.5m$, depending on the turning mechanism.