• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1690-1695
• /
• 2003

In order to investigate the mechanism of brake squeal noise, the sound and vibration of an actua1 brake system were measured using a brake dynamometer. The experimental results show that disc run-out varies with brake line pressure and the factor of squeal generation is the run-out due to the misalignment of brake disk. A three degrees of freedom friction model is developed for the disk brake system where the run-out effect and nonlinear friction characteristic are considered. The results of numerical analysis of the model agree well with the experimental results. Also, the stability analysis of the model was performed to predict the generation of brake squeal due to the design parameter modification of brake systems. The results show that the squeal generation depends on the nm-out rather than the friction characteristic between the pad and the disk of brake.

• Journal of the Korean Society for Railway
• /
• v.6 no.4
• /
• pp.294-299
• /
• 2003

Using a conventional railway, a tilting train was applied as a means of improving vehicle speed during curve negotiation without any modification of infrastructure. As a study for the optimum design of the tilting mechanism of a tilting vehicle, the kinematics sensitivity of the tilting mechanism was analyzed. Using the geometric relationship of the linkage-type tilting mechanism, the relationship of the parameters and the performance index was defined using nonlinear algebraic equations. With the defined relation, the effect of change in the parameters on the performance was analyzed. The analysis result can be used in the optimum design of a tilting mechanism that considers the track environment, vehicle and operational condition in which the tilting vehicle is applied.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.12
• /
• pp.3007-3019
• /
• 1993

For the same configuration, the stiffness of 6-node two dimensional isoparametric is stiffer than that of 8-node two dimensional isoparametric element. This phenomenon may be called 'Relative Stiffness Stiffening Phenomenon.' In this paper, the relative stiffness stiffening phenomenon was studied, and could be corrected by modifying the position of Gauss integral points used in the numerical integration of the stiffness matrix. For the same deformation (bending) energy of 6-node and 8-node two dimensional isoparametric elements, Gauss integral points of 6-node element have to move closer, in comparison with those of 8-node element, in the case of numerical integration along the thickness direction.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 1998.03a
• /
• pp.35-38
• /
• 1998

Abstracts In this paper, we propose a robust adaptive fuzzy control scheme using a sliding control input for tracking of a class of MISO nonlinear systems with unknown bounded external disturbances. In the proposed scheme, the nonlinearity is estimated adaptively via a fuzzy inference based on a fuzzy model. A sliding control input is introduced such that boundedness of all signals in the system is guaranteed even though the existence of a fuzzy approximation error and external disturbances. The controller parameters are updated by using a proposed adaptation law, which is similar 1-modification method. Computer simulation shows the effectiveness of the proposed control scheme.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2000.05a
• /
• pp.195-198
• /
• 2000

We propose a new wavelet neural network structure, for which we apply new recurrent nodes to the network, in this paper for the dynamic system identification and control. We will construct the wavelet neural network by using wavelet frame function. The function does not have the best approximation property, but it may be possible to apply some modification to the structure of the network because the constriction of orthogonality is loosened a little. This wavelet neural network we propose can obtain previous state information by its structure of the network without any addition of input, though the conventional wavelet network needs additional previous state input for the improvement of the dynamic performance. In numerical experience, the performance of the new wavelet neural network we propose in the nonlinear system with uncertainity of parameter Is equal to that of the wavelet network which used the additional previous information input, superior to that of the conventional wavelet network.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2000.10a
• /
• pp.190-197
• /
• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Structural Engineering and Mechanics
• /
• v.55 no.1
• /
• pp.1-27
• /
• 2015

This article presents a theoretical parametric analysis on the ultimate torsional behaviour of axially restrained reinforced concrete (RC) beams. This analysis is performed by using a computing procedure based on a modification of the Variable Angle Truss Model. This computing procedure was previously developed to account for the influence of the longitudinal compressive stress state due to the axial restraint conditions provided by the connections of the beams to other structural members. The presented parametric study aims to check the influence of some important variable studies, namely: torsional reinforcement ratio, compressive concrete strength and axial restraint level. From the results of this parametric study, nonlinear regression analyses are performed and some design charts are proposed. Such charts allow to correct the resistance torque of RC beams (rectangular sections with small height to width ratios) to account for the favorable influence of the axial restraint.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.04a
• /
• pp.61-68
• /
• 1999

In the nonlinear dynamic structural analysis the given ground excitation as an input should be well defined. Because of the lack of recorded accelerograms in Korea it is required to generate an artificial earthquake by a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms. It is well known that earthquake motions are generally non-stationary with time-varying intensity and frequency content. Many researchers have proposed non-stationary random process models. Yeh and Wen (1990) proposed a non-stationary modulation function and a power spectral density function to describe such non-stationary characteristics. Satio and Wen(1994) proposed a non-stationary stochastic process model to generate earthquake ground motions which are compatible with design reponse spectrum at sites in Japan. this paper shows the process to modify power spectrum compatible with target design response spectrum for generating of nonstationary artificial earthquake ground motions. Target reponse spectrum is chosen by ATC14 to calibrate the response spectrum according to a give recurrence period.

• Journal of Communications and Networks
• /
• v.6 no.2
• /
• pp.112-122
• /
• 2004

A nonlinear spectral-line method utilizing the fourth absolute moment of the receiver discrete Fourier transform output is proposed as a non-data-aided fine carrier frequency synchronization algorithm for OFDM receivers. A simple modification of the algorithm resulting in low implementation complexity is also developed. Analytic expressions are derived for the steady-state frequency error variances of the algorithms and verified to be very accurate via computer simulations over AWGN and frequency selective multipath channels. Numerical results show that the proposed algorithms provide reliable and excellent steady-state performance, especially with PSK modulation. Also, the proposed algorithms are insensitive to symbol timing offsets, only requiring a coarse symbol timing recovery.

• Proceedings of the KIEE Conference
• /
• 1996.07b
• /
• pp.1205-1207
• /
• 1996

The computed-torque method (CTM) shows good trajectory tracking performance in controlling robot manipulator if there is no disturbance or modelling errors. But with the increase of a payload or the disturbance of a manipulator, the tracking errors become large. So there have been many researchs to reduce the tracking error. In this paper, we propose a new control algorithm based on the CTM that decreases a tracking error by generating new reference trajectory to the controller. In this algorithm we used a fuzzy system based on the rule bases. For the numerical simulation, we used a 2-link robot manipulator. To simulate the disturbance due to a modelling uncertainty, we added errors to each elements of the inertia matrix and the nonlinear terms and assumed a payload to the end-effector. In the simulations of several cases, our method showed better trajectory tracking performance compared with the CTM.