• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.45-53
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• 2009

Today, reduction of $CO_2$ exhaustion gas for global-warming prevention becomes important issues in all industrial fields. Hydraulic systems have been widely used in industrial applications due to high power density and so on. However hydraulic pump is always being operated by engine or electric motor in the conventional hydraulic system. Therefore most of the conventional hydraulic system is not efficient system. Recently, an electro-hydraulic hybrid system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. In the electro-hydraulic hybrid system, hydraulic pump is operated by electric motor only when hydraulic power is needed. Therefore the electro-hydraulic system can reduce the energy consumption drastically when compared to the conventional hydraulic systems. This paper presents a new kind of hydraulic load simulator which is composed of electro-hydraulic hybrid system. Disturbances in the real working condition make the control performance decrease or go bad. QFT controller is designed to eliminate or reduce the disturbance and improve the control performance of the electro-hydraulic load simulator. Experimental results show that the proposed controller is verified to apply for electro-hydraulic hybrid system with varied external disturbances.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1808-1817
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• 2017

Duties required for naval ship such as anti-submarine, anti-ship, and supply, etc are diversified, so the ECS (Enfineering Control System) is required for executing the mission effectively. The ECS monitors and controls the propulsion system in order that naval ship can perform the mission. As the in-country development of ECS is progressed, a test system for ECS is needed, and a naval ship propulsion system simulator based on CODOG was developed on this study. The naval ship propulsion system simulator based on CODOG which is divided into gas turbine model, diesel engine model, reduction gear model and controllable pitch propeller model, simulates to feedback of control commands of ECS. As a result of the experiment, it is able to confirm speed, torque and power, etc. of the gas turbine, diesel engine and shaft according to ECS propulsion mode.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.50-57
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• 2009

Lane Keeping Assistant Systems (LKAS) require the cooperative operation between drivers and active steering angle/torque controllers. An LKAS is proposed in this study such that the desired reference path generation (DRPG) system generates the desired path to minimize the trajectory overshoot. Based on the reference path from the DRPG system, an optimal controller is designed to minimize the cost function. A HIL (Hardware In the Loop) simulator is constructed to evaluate the proposed LKAS system. The single camera is mounted on the simulator and acquires the monitor images to detect lane markers. The performance of the proposed system is evaluated by HIL system using the Carsim and the Matlab Simulink.

• Design & Manufacturing
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• v.17 no.4
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• pp.8-13
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• 2023

In this study, it was studied whether a new measurement factor "frictional vibration" that occurs due to the material flow of the die and sheet metal in the flange area during deep drawing process, could be measured using an vibration sensor. The blank holder force acting on the flange area during drawing processing acts as a friction force in the opposite direction into which the sheet material flows and causes friction vibration. As the blank holder force increases, the friction force increases, and as the blank holder force decreases, the friction force also decreases. Because of this, friction vibration also increases and decreases in proportion to the size of the blank holder force. According to this theory, whether frictional vibration occurs was measured using a flange simulator and a vibration sensor. The initial pressure was created using a torque wrench, and it was confirmed that the amplitude increased by about 4 times when torque 6 Nm was increased. When the forming velocity was rapidly changed to 300 mm/min, the amplitude increased approximately 4 times. It was confirmed that the amplitude of frictional vibration according to the measurement location was greater the further away from the specimen. It was verified that a new measurement factor "friction vibration" in the flange area can be measured and used for online monitoring.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.187-187
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• 2010

풍력을 이용한 풍력발전기의 전력변환 시스템을 연구개발하기 위해서는 바람의 특성을 실내에서 구현할 수 있는 모의시험장치인 시뮬레이터가 요구된다. 모의시험장치는 바람을 받아 회전하는 블레이드 대신 풍속 값을 입력하여 전동기가 발전기에 토오크(torque)를 공급하게 된다. POSTECH 풍력에너지연구소는 2003년 750kW급 KBP-750D 풍력발전기용 모의시험장치에 이어, 2007년 2MW Gearless형 풍력발전기(KBP-2000M)의 400:1 축소모델인 5.83kW 모의시험 장치를 제작 완료하였다. (주)플라스포사는 모의시험장치를 이용하여 고효율의 전력변환장치 설계와 인버터 시스템 제어 알고리즘을 개발하였고, (주)유니슨은 2MW 풍력발전기용 통합연동제어 시스템을 제작 완료하여 2009년부터 대관령 실증단지에 초도품을 설치하고 실증운영 중에 있다. 본 논문은 대관령 실증단지에서 실시한 2MW 풍력시스템 실증과정에서 획득한 풍향과 풍속 데이터를 시각적으로 쉽게 보고 이해할 수 있도록 3D모델 처리방안을 적용하여 모의시험 장치에 구현한 내용이다. 풍력발전기 개발은 현재 대형화 추세에 있으며 연구개발 단계에서 풍력발전기의 발전 및 제어부분의 기능적 안정성 확보와 효율성 증대를 위한 적절한 시험은 필수적이다. 그러나 풍력발전기의 특성상 타워를 건설하고 회전자 블레이드를 사용하여 시험한다는 것은 설치 공간과 비용의 제약이 따른다. KBP-2000M (2MW) 모의시험장치는 풍력발전기와 같은 대형장비를 연구 개발하는데 필수적이며, 실증을 통해 획득한 Data를 적용함으로서 재품의 문제점을 찾아내고 성능향상을 도모하는데 필요하다. 실증 Data를 시각적으로 3D로 표현함으로서 현장의 풍속/풍향 변화를 사실감 있게 느끼게 되었다. 앞으로도 풍력발전기를 연구개발하거나 성능향상을 위해서는 적절한 제어와 안전을 위한 연동장치를 갖춘 스케일 다운된 모의시험장치 구축이 요구될 것이다. 풍력발전기의 실증과정에서 획득한 데이터를 모의시험장치에 적용(Feedback)하여 지속적인 성능향상을 높여나갈 것이다.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.31-46
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• 2009

An Unscented Kalman Filter (UKF) for estimation of the attitude and rate of a spacecraft using only magnetometer vector measurement is developed. The attitude dynamics used in the estimation is the nonlinear Euler's rotational equation which is augmented with the quaternion kinematics to construct a process model. The filter is designed for small satellite in low Earth orbit, so the disturbance torques include gravity-gradient torque, magnetic disturbance torque, and aerodynamic drag torque. The magnetometer measurements are simulated based on time-varying position of the spacecraft. The filter has been tested not only in the standby mode but also in the detumbling mode. Two types of actuators have been modeled and applied in the simulation. The PD controller is used for the two types of actuators (reaction wheels and thrusters) to detumble the spacecraft. The estimation error converged to within 5 deg for attitude and 0.1 deg/s for rate respectively when the two types of actuators were used. A joint state parameter estimation has been tested and the effect of the process noise covariance on the parameter estimation has been indicated. Also, Monte-Carlo simulations have been performed to test the capability of the filter to converge with the initial conditions sampled from a uniform distribution. Finally, the UKF performance has been compared to that of the EKF and it demonstrates that UKF slightly outperforms EKF. The developed algorithm can be applied to any type of small satellites that are actuated by magnetic torquers, reaction wheels or thrusters with a capability of magnetometer vector measurements for attitude and rate estimation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.861-869
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• 2020

A dynamo set for a high-power induction motor drive is expensive and needs a long time to manufacture. Therefore, the development of a simulator that functions as the induction motor and load equipment is required. A load simulator of an inverter for a high-power three-phase induction motor consists of a reactor and three-phase PWM inverter. Therefore, it cannot simulate the dynamic characteristics of an induction motor and functions only as a load. In this paper, a real-time simulator is proposed to simulate a model of an induction motor and the load characteristics based on an LCL filter and three-phase PWM rectifier for a three-phase induction motor. The currents of a PWM inverter that simulate the stator currents of the motor are controlled by the inductor currents and capacitor voltages of the LCL filter. The capacitor voltages of the LCL filter simulate the induced voltages in the stator windings by the rotating rotor fluxes of the motor, and the capacitor voltages are controlled by the inductor currents and a PWM rectifier. The rotor currents, the stator and rotor flux linkages, the electromagnetic torque, the slip frequency, and the rotor speed are derived from the inverter currents and the motor parameters. The electrical and mechanical model characteristics and the operation of vector control were verified by MATLAB/Simulink simulation.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.164-173
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• 2009

Purpose: The purpose of this study was to evaluate the effect of abutment material on screw-loosening before and after cyclic loading. Among the different materials of abutments, zirconia and metal abutment were used. Material and methods: Two types of implant systems: external butt joint(US II, Osstem Implant, Korea) and internal conical joint(GS II, Osstem Implant, Korea) were used. In each type, specimens were divided into two different kinds of abutments: zirconia and metal(n=5). The implant was rigidly held in a special holding to device ensure fixation. Abutment was connected to 30 Ncm with digital torque gauge, and was retightened in 30 Ncm after 10 minutes. The initial removal torque values were measured. The same specimens were tightened in 30 Ncm again and held in the cycling loading simulator(Instron, USA) according to ISO/FPIS 1480. Cycling loading tests were performed at loads 10 to 250 N, for 1 million cycles, at 14 Hz,(by subjecting sinusoidal wave from 10 to 250 N at a frequency of 14 Hz for 1 million cycles,) and then postload removal torque values were evaluated. Results: 1. In all samples, the removal values of abutment screw were lower than tightening torque values(30 Ncm), but the phenomenon of the screw loosening was not observed. 2. In both of the implant systems, initial and postload removal torque of zirconia abutment were significantly higher than those of metal abutment(P<.05). 3. In both of the implant systems, the difference in removal torque ratio between zirconia abutment and metal abutment was not significant(P>.05). 4. In metal abutments, the removal torque ratio of GS II system(internal conical joint system) was lower than that of US II system(external butt joint system)(P<.05). 5. In zirconia abutments, the difference in removal torque ratio between the two implant systems was not significant(P>.05). Conclusion: Zirconia abutment had a good screw joint stability in the condition of one million cycling loading.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.376-381
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• 2011

CVT(Continuously Variable Transmission) is one of the most promising candidates for the future automobile transmission because of its continuously variable gear ratio and reduced shift shock. It is also possible to operate the power source at its high efficiency region with CVT. The CVT system consists of thrust plate, driving pulley, belt, driven pulley, and preload spring of output shaft. In this paper, the dynamic modeling of a CVT system is completed to obtain the static performances of CVT system. A simulator is implemented on Matlab(Simulink), which can analyse the static performances of a CVT system. The methods for improving the total efficiency of a motorcycle system are also proposed based on the simulation results. In this study we increase the capacity factor of CVT up to the three times of default specification.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.46-51
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• 2009

In this paper, the two-axis theory is adopted to analyze the secondary excited induction generator applied to random wave input generation system. The analysis by the two-axis theory helps to know the transmitted power of the induction machine. The electric variables, like as primary and secondary currents, voltages, and electric output power, were able to express as equations. These equations are help to simulate the generation system numerical model and to know the transient state of the system. As it is preferred to stabilize the output voltage and frequency in the constant level, microcomputer controlled VSI connected to the secondary windings supplies the secondary current with slip frequency. For testing the appropriateness of this method, the input torque simulator in the laboratory to drive the secondary excited results show the advantage of secondary excited induction generator system for the random input wave generation system.