• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.25-32
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• 2000

A combination steering system was designed to provide the flexibility in controlling the steering wheel in fishing operations of the inshore and coastal fishing vessels. The designed steering system basically is consisted of three driving units, such as a electrically driven hydraulic pump unit with a solenoid control valve, a DC motor driven hydraulic pump unit and a manually driven hydraulic pump unit, and two controllers to provide remote steering on the deck, respectively. The steering torque was measured and analyzed to investigate the dynamic performance of the developed steering system. The steering system showed excellent linearity between the working pressure of cylinder and the torque of rudder post in case of increasing in rudder angle from $5^{\circ} to 35^{\circ}$ that is, the steering torque increased from $10.4 kgf{\cdot}m$ to $105.3 kgf{\cdot}m$ and then the working pressure of cylinder fluctuated from 6.3 kgf/cm super(2) to 16.4 kgf/cm super(2). The steering time of 3.2 sec in remote hydraulic steering by the on/off solenoid valve control was much faster than 13.2 sec in the manual steering by the helmsman and 11.6 sec in the electric steering by a DC motor, and then it was verified that operation of one unit does not affect other units in combination steering system in any way. Furthermore, the developed steering system can be remotely controlled in multiple stations of the deck during the fishing operation and the automatic pilot steering unit can be used to add hydraulic steering.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.106-112
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• 2005

Modern versions of supersonic jet fighter aircraft have several different weapon loading configuration to support air-to-air combat and air-to-ground delivery of weapon modes. These various aircraft loading conditions could result in asymmetric configurations to the aircraft once delivered. These asymmetric configurations could result in decreased handling qualities for the pilot maneuvering, stability, control issues and aerodynamic performance of the aircraft. In order to eliminate or decrease these adverse impacts on the pilot's ability, development of T-50 flight control law attempts to control the aircraft in both longitudinal and lateral-directional axes. Especially, the design of the lateral-directional roll axis control laws, utilizing a simple roll rate feedback structure and gains such as F-16, is developed for the T-50 aircraft to meet the aircraft's design requirements. Consequently, it is found that the improved control law decreases the roll-off phenomenon in lateral axes during pitch maneuver.

• Journal of Hydrogen and New Energy
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• v.27 no.1
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• pp.49-62
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• 2016

In this study, a solid oxide fuel cell (SOFC) system model including balance of plant (BOP) for building electric power generation is developed to study the effect of operating conditions on the system efficiency and power output. SOFC system modeled in this study consists of three heat-exchangers, an external reformer, burner, and two blowers. A detailed computational cell model including internal reforming reaction is developed for a planer SOFC stack which is operated at intermediate temperature (IT). The BOP models including an external reformer, heat-exchangers, a burner, blowers, pipes are developed to predict the gas temperature, pressure drops and flow rate at every component in the system. The SOFC stack model and BOP models are integrate to estimate the effect of operating parameters on the performance of the system. In this study, the design of experiment (DOE) is used to compare the effects of fuel flow rate, air flow rate, air temperature, current density, and recycle ratio of anode off gas on the system efficiency and power output.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.20-25
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• 2005

A high performance Viterbi decoder is designed using modified register exchange scheme and block decoding method. The elimination of the trace-back operation reduces the operation cycles to determine the merging state and the amount of memory. The Viterbi decoder has low latency, efficient memory organization, and low hardware complexity compared with other Viterbi decoding methods in block decoding architectures. The elimination of trace-back also reduces the power consumption for finding the merging state and the access to the memory. The proposed decoder can be designed with emphasis on either efficient memory or low latency. Also, it has a scalable structure so that the complexity of the hardware and the throughput are adjusted by changing a few design parameters before synthesis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1042-1049
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• 2014

In Military MicroWave communication, the distance of link, availability, transmission capacity is the important point in order to design the circuit. Currently, operated by fixed modulation, in the future it will be evolved to the modulation techniques enabled to increase the transmission capacity. It would be hard to consistently guarantee the transmission quality of the high-availability because the occurrence probability of fading increase in terms of the link distance for the case of the long distance. In the case of the modulation techniques for the transmission of high-capacity, as the distance is long, a falling-off in the fade margin from the link budget analysis cause the decrease in the availability. It is difficult to provide QoS guaranteed connection. In this paper, we propose the performance improvement technique of transmission by the variable allocation of the bandwidth and the higher priority transmission technique using setting the ratio of the higher priority capacity in association with the distance of link. Also we suggest the alternative of the calculation for channel transmission capacity to design the circuit.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1886-1900
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• 2018

This paper proposes a confronting feedback control structure and controllers for positive output elementary super lift Luo converters (POESLLCs) working in discontinuous conduction mode (DCM). The POESLLC offers the merits like high voltage transfer gain, good efficiency, and minimized coil current and capacitor voltage ripples. The POESLLC working in DCM holds the value of not having right half pole zero (RHPZ) in their control to output transfer function unlike continuous conduction mode (CCM). Also the DCM bestows superlative dynamic response, eliminates the reverse recovery troubles of diode and retains the stability. The proposed control structure involves two controllers respectively to control the voltage (outer) loop and the current (inner) loop to confront the time-varying ON/OFF characteristics of variable structured systems (VSSs) like POESLLC. This study involves two different combination of feedback controllers viz. the proportional integral controller (PIC) plus sliding mode controller (SMC) and the fuzzy logic controller (FLC) plus SMC. The state space averaging modeling of POESLLC in DCM is reviewed first, then design of PIC, FLC and SMC are detailed. The performance of developed controller combinations is studied at different working states of the POESLLC system by MATLAB-Simulink implementation. Further the experimental corroboration is done through implementation of the developed controllers in PIC 16F877A processor. The prototype uses IRF250 MOSFET, IR2110 driver and UF5408 diodes. The results reassured the proficiency of designed FLC plus SMC combination over its counterpart PIC plus SMC.

• Journal of Power Electronics
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• v.14 no.3
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• pp.444-457
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• 2014

This paper presents the design and realization of a digital PV simulator with a Push-Pull Forward (PPF) circuit based on the principle of modular hardware and configurable software. A PPF circuit is chosen as the main circuit to restrain the magnetic biasing of the core for a DC-DC converter and to reduce the spike of the turn-off voltage across every switch. Control and I/O interface based on a personal computer (PC) and multifunction data acquisition card, can conveniently achieve the data acquisition and configuration of the control algorithm and interface due to the abundant software resources of computers. In addition, the control program developed in Matlab/Simulink can conveniently construct and adjust both the models and parameters. It can also run in real-time under the external mode of Simulink by loading the modules of the Real-Time Windows Target. The mathematic models of the Push-Pull Forward circuit and the digital PV simulator are established in this paper by the state-space averaging method. The pole-zero cancellation technique is employed and then its controller parameters are systematically designed based on the performance analysis of the root loci of the closed current loop with $k_i$ and $R_L$ as variables. A fuzzy PI controller based on the Takagi-Sugeno fuzzy model is applied to regulate the controller parameters self-adaptively according to the change of $R_L$ and the operating point of the PV simulator to match the controller parameters with $R_L$. The stationary and dynamic performances of the PV simulator are tested by experiments, and the experimental results show that the PV simulator has the merits of a wide effective working range, high steady-state accuracy and good dynamic performances.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.1-11
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• 2020

Behaviors of wake vortices generated by an aircraft affect the performance and flight stability of flying aircraft in formation flight. In the present study, the trajectories of the wake vortices behind airplanes in close formation flight were computed using a Fourier spectral method. The behavior of wake vortices showed complex patterns depending on the initial circulation and the relative positions between the vortices. In the initial stage, the wake vortex movement was affected by the nascent vortex. When the vortex becomes closer to the other vortex, then a new trajectory is formed. When the viscous effect becomes dominant, the core radius increases. Thus, a new vortex moving near the existing vortex can have strong interaction with each other, resulting in the complicated behavior of wake vortices. In the future, the ground effect on the behavior of the wake vortices during take-off and landing will be studied.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.1
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• pp.177-186
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• 2017

Recently, Autonomous vehicles are getting hot attention. Amazon, the biggest online shopping service provider is developing a delivery system that uses drones. This kinds of platforms are need accurate attitude information for navigation. In this paper, a structure design of AHRS using low-cost inertia sensor is proposed. To estimate attitudes a Kalman filter which uses a quaternion based dynamic model, bias-removed measurements from MEMS Gyro, raw measurements from MEMS accelerometer and magnetometer, is designed. To remove bias from MEMS Gyro, an additional Kalman filter which uses raw Gyro measurements and attitude estimates, is designed. The performance of implemented AHRS is compared with high price off-the-shelf 3DM-GX3-25 AHRS from Microstrain. The Gyro bias was estimated within 0.0001[deg/s]. And from the estimated attitude, roll and pitch angle error is smaller than 0.2 and 0.3 degree. Yaw angle error is smaller than 6 degree.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.11
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• pp.523-530
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• 2018

It has been studied over the long time for the high efficiency and high power density of the power converter. It is possible to obtain higher power conversion efficiency and small volume by increasing switching frequency, however, the switching loss is also increased. The soft switching technique can overcome of the above deficiency. The design and analysis method for ZVS(Zero Voltage Switching) Phase Shifte Full bridge converter is presented in this paper. The power transfer depends on the phase difference between two legs of the power stage and the maximum power conversion efficiency is achieved by the optimum leakage inductance value. The waveform of the current and voltage of the operational mode is analysed and the corresponding switch status is plotted as on/off status. A ZVS full bridge converter for a communication rectifier with 2kW output power is implemented and its performance are verified through PSIM software simulation and experimental results.