• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.735-740
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• 2010

This paper focuses on the effects of hydrodynamic forces between overtaking and overtaken vessels moving under the influences of external forces, such as strong wind and current in shallow water, in which condition the ship handling may become very complex. The purpose of this paper is to develop a guideline for safe conducting distance between two ships according to the velocity and the significance of external disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.497-497
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• 2000

This paper is concerned with the design of LMI based H$_{\infty}$ controller for a line of sight(LOS) stabilization system. This system which is even linearized to analyse nonlinear characteristic has also a lot of uncertainties. In addition, the angular velocity disturbance from the vehicle's driving deteriorates the stabilized LOS, main purpose of this system. In case of fast driving, particularly, all components which are ignored and skipped to make mathematical modelling act as the uncertainties against this system. The robustness against these uncertainties has been also continuously demanded including the well tracking performance for the target. Therefore, this paper employed H$_{\infty}$ control theory to satisfy these problems and LMI method to make suitable controller with few constraints for this system. Although this system matrix doesn't have full rank, this method make it possible to design H$_{\infty}$ controller and deal with R and S matrices for reducing its order. Consequently, this paper shows that the re-analyses on the real disturbances are achieved and the proposed robust controller for them has better disturbance attenuation and tracking performance. This paper contributes the applicability of reduced order H$_{\infty}$ controller to real system by handling LMI..

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.472-477
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• 1994

The lockup clutch is embeded on torque converter of automatic transmission to prevent the efficiency deterioration of torque converter in high speed. For improving fuel consumption rate, it is desirable to engage the lockup clutch earlier. But, it results in degrading shift quality, due to the transient torque. The transient clutch pressure which affects the shifting quality, should be controlled properly. In this study, to solve the problem, it is analysed the hydraulic circuit of lockup system including line pressure regulating circuit, established the nonlinear model, and designed the PID controller. The line pressure is supplied to the lockup clutch through the lockup control valve by switching the lockup solenoid valve on. In order to control the transient pressure actively, it is needed to control the lockup solenoid valve by closed loop control. The lockup solenoid valve is 2-way on-off valve, and is adequate for PWM control. To reduce the pressure chattering, the carrier frequency is increased. Target pressure profile is computed from optimized velocity difference profile throuth dynamic equation of vehicle system.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.193-203
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• 2001

The Monte Carlo method was used to evaluate the reliability of crash discrimination algorithms. Through the Fast Fourier Transformation, crash pulses obtained during frontal crash tests of a mini van and a sports utility vehicle were transformed to signals in the frequency domain, and the signals were divided into basic signals and changeable signals. The changeable signals were modified through random generation, and they were combined with the basic signals. Then, the combined signals were transferred back to the time domain. In this way numerous crash pulses could be generated. For the generated pulses, crash discrimination algorithms were evaluated by examining whether they did not result in air bag deployment for the pulses requiring no air bag deployment and whether they resulted in time-to-fires faster than required time-to-fires for the pulses requiring air bag deployment. The crash discrimination algorithm in which the absolute value of the deceleration change multiplied by the velocity change or the summation of the absolute value of the deceleration change was used as a metric was Proven to be highly reliable.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.3
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• pp.68-74
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• 1998

Performance and efficiency of deep seabed collector is a primary factor for feasibility of commercial deep ocean mining. The efficiency of manganese nodules collector depends on vehicle mobility relative to undulating seafloor and is attributed pickup head to keep altitude and elevation of it against seafloor. For this reason, motion control of pickup head relative to the changing deep-sea topography and other disturbances is of particular importance in design of pickup device. The concept of design axiom is applied to a pickup device of hybrid type in order to evaluate the concept design. Kinematic analysis conducted in absolute Cartesian coordinates gives position, velocity, and acceleration of the hydraulic cylinders which enable the pickup head to keep the preset optimal distance from seafloor. Inverse dynamic analysis provides the driving forces of hydraulic cylinders and the reaction forces at each joint. Design sensitivity analysis is performed in order to investigate the effects of possible design variables on the change of the maximum strokes of hydraulic cylinders. The direct differentiation method is used to obtain the design sensitivity coefficients.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.7
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• pp.603-609
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• 2015

Railway vehicles driven by wheels obtain force required for propulsion and braking by adhesive force between wheels and rails, this adhesive force is determined by multiplying adhesion coefficient of the friction surface by the applied axle load. Because the adhesion coefficient has a peak at certain slip velocity, it is important to determine the maximum values of the friction coefficient on the contact area. But this adhesive phenomenon is not clearly examined or analyzed. Thus we have developed new test procedure using the scaled adhesion test-bench for analyzing of the adhesion coefficient between wheel and rail. This adhesion test equipment is an experimental device that contacts mutually with twin disc which are equivalent to wheels and rails of railway vehicles.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.147-153
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• 2017

PURPOSES : This research aims to estimate the occurrence of hydroplaning on roads based on the road alignment types and rainfall intensity in Seoul. METHODS : Three types of data were used for estimation of hydroplaning in this study. The Inner Circulation Road (12.5 km) to the Bukbu Expressway (7.4 km) in Seoul was selected as the test road and data was collected for road information using a probe-vehicle. Precipitation was observed from Automatic Weather System in Seoul. These data were interpolated by applying Inverse Distance Weighted Methodology for hydroplaning estimation. Finally, the water depth information of the roads was observed using an RCM411 device. RESULTS : This study demonstrated that the cross slope with small-angle-tilt or vertical section with large-angle-tilt are the primary factors causing hydroplaning on the roads. The flow velocity on steep slope is high; however, large drainage lengths result in hydroplaning on the roads. CONCLUSIONS : This result can contribute towards the reduction of car accidents on rainy days. Furthermore, information regarding hydroplaning can be delivered to drivers more rapidly and precisely in the future.

• Journal of the Korean Society of Visualization
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• v.8 no.1
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• pp.39-45
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• 2010

The optimal design is needed for the blade geometry of the quad-rotor blades which is mainly used for Unmanned Aerial Vehicle. To do this, it is important to analyze the wakes under the blades. In the present study, the flow around the rotating blades was analyzed using PIV(Particle Image Velocimetry) and CFD(Computational Fluid Dynamics). The maximum axial velocity was measured at about 60% position toward the radial direction of the blade. The positions of vorticities in the test section obtained by PIV and CFD were turned out to be almost alike. The values in the difference of pressure coefficients at the upper and the lower blades were increased depending on the radial direction. Then, the values were decreased at the blade tip. The data of the flow analysis in the present study are expected to be served as the design of blades and ducts for the thrust improvement in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.277-282
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• 2006

Road traffic noise is not produced by any one factor rather occurs as a composition of various factors. Its occurrence is made by running engine noise, tire frictional, and exhaust noise etc. The quality of the noise depends on the size of the vehicles, rotation and engine speed, vehicle load, package state of the road and incline etc. The occurrence of noise level of heavy trucks appears louder than smaller vehicles and the noise levels produced differs according to speed and load etc between similar size vehicles. Other factors such as traffic density, average speed, mixing rate of heavy vehicles, and the distance between vehicles also generate road traffic noise. In this paper we examine 2, 4, and 6-lane roads in Jeonju. Consequently, this study examined the means used to measure road traffic noise. It was found that when there is a large traffic density and the average velocity is below 70 km/hr, the noise level could receive a relative proper value by the current measuring means. But in the case of night-time, it was found that the current measuring method is inapposite.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.61-67
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• 2011

The cooling module needs enough space (or distance) from hood to absorb the energy from any pedestrian collision. Downsized cooling module for pedestrian protection is important to reduce the severity of pedestrian injury. When a vehicle collision happens, the downsized cooling module is required to reduce the risk of injury to the upper legs of adults and the heads of children. In this study, the performance of cooling module to cool the engine was investigated under 25% height reduction. The heat dissipation and pressure drop characteristics have been experimentally studied with the variation of coolant flow rate, air inlet velocity and A/C operation ON/OFF for the downsized cooling module. The results indicated that the cooling performance was about 94% level compared to that of the conventional cooling module. Therefore, we checked that the cooling module had good performance, and expected that the cooling module could meet the same cooling performance as conventional cooling module through optimization of components efficiency.