• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.614-622
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• 2011

In this study, the computational structural dynamic modeling of floating offshore wind turbine system is presented using efficient equivalent modeling technique. Structural dynamic behaviors of the offshore floating platform with 5MW wind turbine system have been analyzed using computational multi-body dynamics based on the finite element method. The considered platform configuration of the present offshore wind turbine model is the typical spar-buoy type. Equivalent stiffness and damping properties of the floating platform were extracted from the results of the baseline model. Dynamic responses for the floating wind turbine models are presented and compared to investigate its structural dynamic characteristics. It is important shown that the results of the present equivalent modeling technique show good and reasonable agreements with those by the fully coupled analysis considering complex floating body dynamics.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.937-943
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• 2017

To design an automatic steering controller with high performance for autonomous vehicle, it is necessary to have a precise model of the lateral dynamics with respect to the steering command input. This paper presents an empirical modeling of the steering system for an autonomous vehicle. The steering system here is represented by three individual transfer function models: a steering wheel actuator model from the steering command input to the steering angle of the shaft, a dynamic model between the steering angle and the yaw rate of the vehicle, and a dynamic model between the steering command and the lateral deviation of vehicle. These models are identified using frequency response data. Experiments were performed using a real vehicle. It is shown that the resulting identified models have been well fitted to the experimental data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제29권10호
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• pp.89-96
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• 2015

Explicit numerical integration methods for power system transient stability simulation require very small time steps to avoid numerical instability. The EXST1 exciter model is a primary source of fast dynamics in power system transients. In case of the EXST1, the required small integration time step for entire system simulation increases the computational demands in terms of running time and storage. This paper presents a practical exciter model reduction approach which allows the increase of the required step size and thus the method can decrease the computational demands. The fast dynamics in the original EXST1 are eliminated in the reduced exciter model. The use of a larger time step improves the computational efficiency. This paper describes the way to eliminate the fast dynamics from the original exciter model based on linear system theory. In order to validate the performance of the proposed method, case studies with the GSO-37 bus system are provided. Comparisons between the original and reduced models are made in simulation accuracy and critical clearing time.

• Journal of Institute of Control, Robotics and Systems
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• 제7권5호
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• pp.432-437
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• 2001

Korea High Speed Train(KHST) is supposed to run up 350km/h, in which the braking system has a crucial role for the safety of the train. In the design st데 of the braking system, its very hard to ac-quire information data for design guidelines. A HILS(Hardware-In-the-Loop Simulation) system can be used to get design data which could simulate the braking system of the real train in real-time. In this paper, cars are modelled including car dynamics, brake blending algorithms, pneumatic actuator dynamics, the models of each braking devices, adhesive coefficients, and soon. Real-time braking time, distance, and other design parameters are simulated using a DSP board and C language which shows the validity of the proposed method.

• International Journal of Control, Automation, and Systems
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• 제4권6호
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• pp.782-787
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• 2006

The role of Unmanned Aircraft Vehicles(UAVs) has been increasing significantly in both military and civilian operations. Many complex systems, such as UAVs, are difficult to model accurately because they exhibit nonlinearity and show variations with time. Therefore, the control system must address the issues of uncertainty, nonlinearity, and complexity. Hence, identification of the mathematical model is an important process in controller design. In this paper, attitude dynamics identification of UAV is investigated. Using the flight data, nonlinear state space model for attitude dynamics of UAV is derived and verified. Real time simulation results show that the model dynamics match experimental data.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제24권4호
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• pp.830-838
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• 2000

The paper addresses an application of molecular dynamics technique for fracture mechanics. Molecular dynamics simulation is an atomistic approach, while typical numerical methods such as finite element methods are macroscopic. Using the potential functions, which express the energy of a molecular system, a virtual specimen with molecules is set up and the trajectory of every molecule can be calculated by Newton's equation of motion. Several three-dimensional models with various types of cracks are considered. The stress intensity factors, the sizes of plastic zone as well as the dislocation emission are sought to be compared with the analytical solutions, which result in good agreement.

• Journal of Power System Engineering
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• 제13권5호
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• pp.34-39
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• 2009

In this paper, the CFD analysis using various turbulent models has been performed to evaluate which type of turbulent models can predict well the mixing flow structure of $45^{\circ}$ impinging round jet. This CFD analysis has been carried out through the commercial Fluent software. As a result, any of turbulent models cannot predict the experimental results definitely all over the flow range. However, as compared with the experimental results, the turbulent model of realizable(RLZ) k-$\varepsilon$ only predicts well in the limited range between X/$X_0=1.1$ and X/$X_0=2.0$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.932-937
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• 2002

The polyimide nozzle and silicon restrictor inside a thermal micro actuator have been fabricated using state of the art laser micromachining methods. Numerical models of fluid dynamics inside the actuator chamber and nozzle are presented. The models include fluid flow from reservoir, bubble formation and growth, ejection through the nozzle, and dynamics of refill through restrictor. Since high tapered nozzle and restrictor are very important parameters for overall actuator performance design, a special setup for the beam delivery system has been developed. The effects of variations of nozzle thickness, diameter, taper angles, and restrictor shapes are simulated and some results are compared with the experimental results. It is fecund that the fluid ejection through the thinner and high tapered nozzle is more steady, fast, and robust and the tapered restrictor shows more satisfying refill than the zero taper one.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1623-1629
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• 2001

This parer presents a CVT line pressure control strategy for the increased shift speed. Firstly, an algorithm to increase the CVT shift speed is suggested based on a modified CVT shift dynamics and shift speed maps are constructed. In addition, simplified dynamic models of the line pressure and the ratio control valve are derived by considering the CVT shift dynamics, and low level control algorithms for the ratio and the line pressure control are proposed. Using the shift speed maps and the simplified dynamic models of the CVT system, shift performance is investigated. It is found from the experimental and simulation results that improved shift speed can be achieved by increasing the lilly pressure.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.162-165
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• 1995

For an accurate on-line measurement of the ship's attitude the paper develops an intelligent sensing system which uses one servo-type accelerometer and two servo-type inclinometers appropriately located on the ship. By considering the dynamics of the servo-controlled rigid pendulums of the inclinometers, linear equations for the rolling and pitching of the ship are derived separately from each other. Moreover, one accelerometer is used for extracting the heaving signal. Through the introduction of linear dynamic models and the linear observation equations for the heaving, rolling and pitching, the on-line measurement of the three signals can be reduced to the state estimation of the linear dynamic systems. A bank of Kalman filters is adaptively used to achieve the on-line accurate state estimation and to overcome changes in parameters in the linear dynamic models.