• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.6-12
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• 2008

The dispersion and attenuation of Lamb and Leaky Lamb waves propagating in a 1 mm-thick steel plate were investigated. For acquiring a long(or large) range inspection capability, the fundamental symmetric and anti-symmetric wave modes(S0 and A0) over law frequencies were studied. Based on the dispersion curves, as well as pitch-catch and multi-mode simulations, it was shown that the S0 mode over law frequencies is the proper mode to minimize the dispersion and attenuation. In addition, it was shown that the S0 mode couldbe easily distinguished under multi-mode simulation since it has a larger group velocity than the A0 mode.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.311-317
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• 1997

DTG(dynamically tuned gyroscope) is a sensor detecting disturbance in angle velocity control loop of EOTS(electro optical tracking system), which is used for the stabilization of gimbal. DTG is classified into rate mode or rate integrated mode according to operating mode. In this paper, basic principles and characteristics of DTG, depending on to operating mode, are compared and the model of rate integrated mode DTG is proposed. Also, the validity of the presented model is verified by computer simulations and experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.768-773
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• 2011

The prediction method of future events using the time histories of velocity or pressure, etc., is a useful way for controlling various air vehicles. For example, the sensors of velocity or pressure can be used to extract the time mode coefficients of eigenmode of flow field, and then the result is applied to suppress wake or drag. The velocity information is mapped to the entire flow field, so this mapping function can be used to predict the future events based on the current information. The mapping function is composed of the huge amount of weight parameters, so the efficient way of finding these parameters is needed. Here, the neural network algorithm is studied to draw a mapping function using the number and location of velocity sensors.

• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.357-370
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• 2024

Due to the fact that the mechanism of the effects of temperature and initial geometric imperfection on low-velocity impact problem of axially moving plates is not yet clear, the present paper is to fill the gap. In the present paper, the nonlinear dynamic behavior of axially moving imperfect graphene platelet reinforced metal foams (GPLRMF) plates subjected to lowvelocity impact in thermal environment is analyzed. The equivalent physical parameters of GPLRMF plates are estimated based on the Halpin-Tsai equation and the mixing rule. Combining Kirchhoff plate theory and the modified nonlinear Hertz contact theory, the nonlinear governing equations of GPLRMF plates are derived. Under the condition of simply supported boundary, the nonlinear control equation is discretized with the help of Gallekin method. The correctness of the proposed model is verified by comparison with the existing results. Finally, the time history curves of contact force and transverse center displacement are obtained by using the fourth order Runge-Kutta method. Through detailed parameter research, the effects of graphene platelet (GPL) distribution mode, foam distribution mode, GPL weight fraction, foam coefficient, axial moving speed, prestressing force, temperature changes, damping coefficient, initial geometric defect, radius and initial velocity of the impactor on the nonlinear impact problem are explored. The results indicate that temperature changes and initial geometric imperfections have significant impacts.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.230-241
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• 2008

Characteristics of transfer responses for arrays like triangle, hexagon and semicircle were investigated. To characterize the site near Izmit city with ambient noise measurement, dispersion curves of surface waves were derived with using array technique like F-K, High resolution F-K, MSPAC and H/V ratio was calculated. Also, MASW was surveyed to get the high frequency part of dispersion curves. The transition from fundamental mode to first high mode of surface waves for dispersion curve was observed. Dispersion curve of fundamental mode of ambient noise and first higher mode of MASW was used in inversion to get S-wave velocity structure of subsurface. None-unique problem of results of surface wave inversion was solved with comparison of result of refraction tomography performed with first arrivals of MASW data.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.97-100
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• 2006

Accelerating ability is one of the most important performance of the vehicle. Unlike conventional internal combustion vehicles and power-assist hybrid vehicles, the maximized acceleration of dual mode hybrid vehicles is not simply. achieved by maximizing engine or motor torque Because of the dynamic stability of planetary gear, speeds and torques control of engine, motor 1 and motor 2 is essential and according to control value, acceleration performance is changed There are two control values which are velocity and torque for each component totalling six. These six values can be variables for an objective function. However, because three velocity variables can be regarded as only one variable speed ratio and the remaining three torque variables can be solved analytically, without complicated numerical algorithm the solution for the objective function can be obtained. This optimized solution shows the best performance possible to the specified dual mode system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.44-53
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• 2007

In this paper, the Sliding Mode Controller is applied to reduce the starting current of the single phase induction motor. The input voltage to the single phase induction motor is controlled so that the starting current of the motor may be maintained within the rating value and the velocity is also controlled, by adjusting the switching function of the Sliding Mode Controller. The switching of sliding control made appropriately with regard to velocity error signal and acceleration signal. It is shown that the starting characteristics of the single phase induction motor(SPIM) can be greatly enhanced through the sliding control of single phase induction motor.

• Fire Science and Engineering
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• v.20 no.3 s.63
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• pp.9-14
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• 2006

In this study boundary velocity which is one of the important boundary conditions for numerical simulation for subway station on fire are experimentally obtained. The tests were conducted according to its operating mode of the ventilation systems in the platform: smoke extraction ventilation mode in occurrence of fire and normal ventilation mode for air conditioning. Velocities are measured at various points on the platform. To examine smoke extraction and air supply capacity in the platform level, air velocities were checked on opening vents. Numerical analysis under normal ventilation mode without fire is conducted by using measured boundary conditions, and the numerical results are compared with the measured velocities on the platform.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.576-583
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• 2000

A robust position control using a sliding mode controller is adopted for the stable dynamic walking of the biped. For the biped robot that is modeled with 14 degrees of freedom rigid bodies using the method of the multibody dynamics, the joint angles for simulation are obtained by the velocity transformation matrix using the given Cartesian foot and trunk trajectories. Hertz force model and Hysteresis damping element which is used in explanation of the energy dissipation during contact with ground are used for modeling of the ground reactions during the simulation. By the obtained that forces which contains highly confused noise elements and the system modeling uncertainties of various kinds such as unmodeled dynamics and parameter inaccuracies, the biped system will be unstable. For that problems, we are adopting a nonlinear robust control using a sliding mode controller. Under the assumption that the esimation error on the unknown parameters is bounded by a given function, that controller provides a successful way to preserve stability and achieve good performance, despite the presence of strong modeling imprecisions or uncertainties.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.137-146
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• 2001

A robust controller with the sliding mode is proposed for stable dynamic walking of the biped robot in this paper. For the robot system to be controlled, which is modeled as 14 DOF rigid bodies by the method of multi-body dynamics, the joint angle trajectories are determined by the velocity transformation matrix. Also Hertz force model and Hysteresis damping element are utilized for the ground reaction and impact forces during the contact with the ground. The biped robot system becomes unstable since those forces contain highly confused noise components and some discontinuity, and modeling uncertainties such as parameter inaccuracies. The sliding mode control is applied to solve above problems. Under the assumption of the bounded estimation errors on the unknown parameters, the proposed controller provides a successful way to achieve the stability and good performance in spite of the presence of modeling imprecisions of uncertainties.