• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1474-1482
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• 2018

As an essential means of generator voltage regulation, excitation control plays an important role in controlling the stability of the power system. Therefore, the reasonable design of an excitation controller can help improve the system stability. In order to raise the robustness of the generator exciting system under outside interference and parametric perturbation and eliminate chattering in the sliding mode control, this paper presents a generator excitation control based on the quasi-sliding mode pseudo-variable structure control. A mathematical model of the synchronous generator is established by selecting its power, speed and voltage deviation as state variables. Then, according to the existing conditions of the quasi-sliding mode, a quasi-sliding mode pseudo-variable structure controller is designed, and the parameters of the controller are obtained with the method of pole configuration. Simulations show that compared with the existing methods, the proposed method is not only useful for accurate voltage regulation, but also beneficial to improving the robustness of the system at a time when perturbance happens in the system.

• Structural Engineering and Mechanics
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• v.18 no.6
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• pp.791-806
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• 2004

The inverse pseudo excitation method is used in the identification of random loadings. For structures subjected to stationary random excitations, the power spectral density matrices of such loadings are identified experimentally. The identification is based on the measured acceleration responses and the structural frequency response functions. Numerical simulation is used in the optimal selection of sensor locations. The proposed method has been successfully applied to the loading identification experiments of three structural models, two uniform steel cantilever beams and a four-story plastic glass frame, subjected to uncorrelated or partially correlated random excitations. The identified loadings agree quite well with actual excitations. It is proved that the proposed method is quite accurate and efficient in addition to its ability to alleviate the ill conditioning of the structural frequency response functions.

• Journal of Korean Association for Spatial Structures
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• v.13 no.4
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• pp.57-66
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• 2013

Spatial structures have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and seismic response for seismic design of spatial structure. Keel arch structure is used as an example structure because it has primary characteristics of spatial structures. In case of spatial structures with different ground condition and time lag, multiple support excitation may be subjected to supports of a keel arch structure. In this study, the response of the keel arch structure under multiple support excitation and with time lag are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. It is known that the seismic responses of spatial structure under multiple support excitation are different from those of spatial structure under simple excitation. And the seismic response of spatial structure with time lag are different from those of spatial structure without time lag. Therefore, it has to be necessary to analyze the seismic response of spatial structure under multiple support excitation and time lag because the spatial structure supports may be different and very long span. It is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation.

• Journal of Korean Association for Spatial Structures
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• v.14 no.4
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• pp.89-96
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• 2014

Spatial structures as like dome structure have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and effectively control of seismic response of spatial structure subjected to multi-supported excitation. In this study, star dome structure that is subjected to multi-supported excitation was used as an example spatial structure. The response of the star dome structure under multiple support excitation are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. And the application of passive tuned mass damper(TMD) to seismic response control of star dome structures has been investigated. From this numerical analysis, it is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation. And it is reasonable to install TMD to the dominant points of each mode. And it is found that the passive TMD could effectively reduce the seismic responses of dome structure subjected to multi-supported excitation.

• Structural Engineering and Mechanics
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• v.10 no.4
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• pp.359-369
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• 2000

Random loading identification has long been a difficult problem for Multi-Input-Multi-Output (MIMO) structure. In this paper, the Pseudo Excitation Method (PEM), which is an exact and efficient method for computing the structural random response, is extended inversely to identify the excitation power spectral densities (PSD). This identified method, named the Inverse Pseudo Excitation Method (IPEM), resembles the general dynamic loading identification in the frequency domain, and can be used to identify the definite or random excitations of complex structures in a similar way. Numerical simulations are used to reveal the the difficulties in such problems, and the results of some numerical analysis are discussed, which may be very useful in the setting up and processing of experimental data so as to obtain reasonable predictions of the input loading from the selected structural responses.

• Structural Engineering and Mechanics
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• v.11 no.1
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• pp.71-87
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• 2001

A frequency domain response analysis is presented for building frames passively controlled by viscoelastic dampers, under harmonic ground excitation. Three different models are used to represent the linear dynamic force-deformation characteristics of viscoelastic dampers namely, Kelvin model, Linear hysteretic model and Maxwell model. The frequency domain solution is obtained by (i) an iterative pseudo-force method, which uses undamped mode shapes and frequencies of the system, (ii) an approximate modal strain energy method, which uses an equivalent modal damping of the system in each mode of vibration, and (iii) an exact method which uses complex frequency response function of the system. The responses obtained by three different methods are compared for different combinations of viscoelastic dampers giving rise to both classically and non-classically damped cases. In addition, the effect of the modelling of viscoelastic dampers on the response is investigated for a certain frequency range of interest. The results of the study are useful in appropriate modelling of viscoelastic dampers and in understanding the implication of using modal analysis procedure for building frames which are passively controlled by viscoelastic dampers against base excitation.

• Structural Engineering and Mechanics
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• v.24 no.2
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• pp.213-225
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• 2006

The propagation of non-uniformly modulated, evolutionary random waves in viscoelastic, transversely isotropic, stratified materials is investigated. The theory is developed in the context of a multi-layered soil medium overlying bedrock, where the material properties of the bedrock are considered to be much stiffer than those of the soil and the power spectral density of the random excitation is assumed to be known at the bedrock. The governing differential equations are first derived in the frequency/wave-number domain so that the displacement response of the ground may be computed. The eigen-solution expansion method is then used to solve for the responses of the layers. This utilizes the precise integration method, in combination with the extended Wittrick-Williams algorithm, to obtain all the eigen-solutions of the ordinary differential equation. The recently developed pseudo-excitation method for structural random vibration is then used to determine the solution of the layered soil responses.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.9
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• pp.1436-1443
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• 1989

In this paper, we propose a maximum-likelihood estimation(MLE) method to obtain the location and the amplitude of the pulses in MPE( multi-pulse excitation)-LPC speech synthesis using multi-pulses as excitation source. This MLE method computes the value maximizing the likelihood function with respect to unknown parameters(amplitude and position of the pulses) for the observed data sequence. Thus in the case of overlapped pulses, the method is equivalent to Ozawa's crosscorrelation method, resulting in equal amount of computation and sound quality with the cross-correlation method. We show by computer simulation: the multi-pulses obtained by MLE method are(1) pseudo-periodic in pitch in the case of voicde sound, (2) the pulses are random for unvoiced sound, (3) the pulses change from random to periodic in the interval where the original speech signal changes from unvoiced to voiced. Short time power specta of original speech and syunthesized speech obtained by using multi-pulses as excitation source are quite similar to each other at the formants.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.1931-1939
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• 2000

Operating excitation forces of the linear vibratory system are normally determined by direct measurement techniques using load cells, strain gauges, etc. But, hydraulic forces of the rotating turbomachinery such as centrifugal pumps are exerted on an impeller due to asymmety of the flow by the interaction between pump impeller and volute. So, investigations of wide range of hydraulic designs and geometric deviations are difficult by direct method. This paper presents a hybrid approach for fourier transformed operational excitation forces, which uses pseudo-inverse matrix of the transfer matrix for the system and the measured vibrational data with standard installed pump. The determination of the transfer function matrix is based on a linear rotor/stationary system and steady state harmonic response in finite element analysis. And, vibrational data is collected in both vertical and horizontal directions at inboard and outboard bearing housings. The results of the process may be enhanced by making acceleration measurements at many more locations than there are forces to be determined.

• Journal of Korean Association for Spatial Structures
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• v.13 no.1
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• pp.113-119
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• 2013

Spatial structures have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and seismic response of spatial structure for seismic design of spatial structure. An arch structure is used as an example structure because it has primary characteristics of spatial structures. Multiple support excitation may be subjected to supports of a spatial structure because ground condition of spatial structures is different. In this study, the response analysis of the arch structure under multiple support excitation and simple support excitation is studied. By means of the pseudo excitation method, the seismic response is analyzed for long span spatial structure. It shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. It is known that the seismic response of spatial structure under multiple support excitation and simple support excitation are the different in some case. Therefore, it has to be necessary to analyze the seismic response of spatial structure under multiple support excitation because the spatial structure supports may be different.