• Earthquakes and Structures
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• v.3 no.1
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• pp.17-35
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• 2012

Simplified equations for fundamental period of vibration of skeletal structures provided by most seismic design provisions suffer from the absence of any associated confidence levels and of any reference to their empirical basis. Therefore, such equations may typically give a sector of designers the false impression of yielding a fairly accurate value of the period of vibration. This paper, although not addressing simplified codes equations, introduces a set of mathematical equations utilizing the theory of error propagation and First-Order Second-Moment (FOSM) techniques to determine bounds on the relative error in theoretically calculated fundamental period of vibration of skeletal structures. In a complementary step, and for verification purposes, Monte Carlo simulation technique has been also applied. The latter, despite involving larger computational effort, is expected to provide more precise estimates than FOSM methods. Studies of parametric uncertainties applied to reinforced concrete frame bents - potentially idealized as SDOF systems - are conducted demonstrating the effect of randomness and uncertainty of various relevant properties, shaping both mass and stiffness, on the variance (i.e. relative error) in the estimated period of vibration. Correlation between mass and stiffness parameters - regarded as random variables - is also thoroughly discussed. According to achieved results, a relative error in the period of vibration in the order of 19% for new designs/constructions and of about 25% for existing structures for assessment purposes - and even climbing up to about 36% in some special applications and/or circumstances - is acknowledged when adopting estimates gathered from the literature for relative errors in the relevant random input variables.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.3
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• pp.240-246
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• 1992

In the paper, the differential detection techniques of 3-h CPM signals whose modulation index is varied periodically are proposed and their error performances are analyzed. We select the modulation index sets which are proper to the differential detection and propose the differential detectors which detect symbol with 3 bits per smapling period of 3T and detect a bit per sampling period of T. Applying the nonredundant error correction circuit and viterbi algorithm to differential detection of 3-h CPM. We ascertain the error performances are improved.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.1
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• pp.34-39
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• 2013

In this study, the quantitative analysis and pattern analysis of the error bounds with respect to recording period were carried out using the wave climate data from coastal areas. Arbitrary recording periods were randomly sampled from one month to six years using the bootstrap method. Based on the analysis, for recording periods less than one year, it was found that the error bounds decreased rapidly as the recording period increased. Meanwhile, the error bounds were found to decrease more slowly for recording periods longer than one year. Assuming the absolute estimate error to be around 10% (${\pm}0.1m$) for an one meter significant wave height condition, the minimum recording period for reaching the estimate error for Sokcho and Geoje-Hongdo stations satisfied this condition with over two years of data, while Anmado station was found to satisfy this condition when using observational data of over three years. The confidence intervals of the significant wave height clearly show an increasing pattern when the percentile value of the wave height increases. Whereas, the confidence intervals of the mean wave period are nearly constant, at around 0.5 seconds except for the tail regions, i.e., 2.5- and 97.5-percentile values. The error bounds for 97.5-percentile values of the wave height necessary for harbor tranquility analysis were found to be 0.75 m, 0.5 m, and 1.2 m in Sokcho, Geoje-Hongdo, and Anmado, respectively.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1203-1215
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• 2019

Sensorless brushless DC (BLDC) motor drive systems are often subjected to inaccurate commutation signals and can produce high current peaks and conduction consumption. To achieve accurate commutation, a fast commutation shift regulation method for sensorless BLDC motor drive systems considering the influence of the inductance freewheeling process is presented to compensate inaccurate commutation signals. The regulation method is effective in both steady speed and variable speed operations. In the proposed method, the commutation error is gained from the line-voltage difference integral in a 60 electrical-degree conduction period and the outgoing phase current before commutation. In addition, the detection precision of the commutation error is improved due to the consideration of the freewheeling period. The commutation error is directly obtained, which avoids successive optimization and accelerates the convergence rate of the proposed method. Moreover, the commutation error features a positive or negative sign, which can be utilized as an indicator of advanced or delayed commutation. Finally, experiments are conducted to validate the effectiveness and feasibility of the proposed method. The results obtained show that the proposed method can accurately regulate commutation signals.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.181-183
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• 1996

Generally, While position type fuzzy controller has good performance in transient period, it has uniform steady state error of response. While velocity type fuzzy controller is capable of reducing steady state error of response, it is hard to develop the performance in transient period. In order to have both good performance in transient period and ability to reduce the steady state error of response, weighting fuzzy controller, which is composed of these two fuzzy controllers, is proposed. For the decision of weight to each fuzzy controller, Weighting fuzzy set is established according to the system state variables and applied to each fuzzy controller. The proposed weighted fuzzy controller has the merits of both position type fuzzy controller and velocity type fuzzy controller simultaneously.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.3
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• pp.245-248
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• 2010

Almost all of control schemes proposed so far have been designed in the continuous-time domain theoretically. Actual systems, however, have been implemented in the discrete-time domain since Micro Control Unit(MCU) and/or microprocessors have been used for the controllers. Thus, the overall system turned to be a sampled-data system, and generally speaking, the ultimate error cannot converge to zero in the actual system even though the proposed control algorithm showed the asymptotic stability in the continuous-time domain. In this paper, therefore, the ultimate error bound of a sampled data system with a short sampling period has been investigated. The ultimate error is shown to be related in the sampling period.

• Journal of Bio-Environment Control
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• v.13 no.3
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• pp.178-184
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• 2004

This study carried out to develope the vision system which automatically finds out a optimum transferring period of plants (Perilla, Platycodon grandifloums and Lactuca sativa) by using image process-ing. This system mearsured a height, long diameter and short diameter of the three plants with 20 replications. Following results were obtained on each plant. Compared with real data to be measured by hand with the vernier calipers, height, long diameter and short diameter of Perilla showed 0.5 mm average error rate with 1.7%, 4.7 mm average error rate with 3.9% and 5.5 mm average error rate with 6.9% respectively. Those of Platycodon grandifloums showed 2.4 mm with 8.1%, 3.4 mm with 7.2% and 4.0 mm with 10.4% respectively. Those of Lactuca sativa showed 4.0 mm with 9.1 %,3.4 mm with 7.2% and 3.6 mm with 9.4% respectively. The system could be used to transfer accurately the plant seedling, if the system were improved enough to reduce error rate for the optimum transferring period of a plant in the greenhouse.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.86-93
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• 2002

In this study, numerical experiments were performed to decide the proper size off finite element for the analysis of harbor resonance problems. Various sizes of finite elements were considered from 1/3 to 1/60 of wavelength to model a fully opened rectangular harbor. Through the numerical results, the proper number of finite elements per wavelength were revealed to be nine within two percents errors allowed in resonant period and amplification ratio, while twelve within one percent error. It was fecund that error rates of resonant periods decrease linearly, while those of amplification ratio decrease with oscillating form as the size of an element decreases. The error of amplification ratio increases more rapidly than that of resonant period in case of element numbers below nine.

• Journal of KSNVE
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• v.11 no.3
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• pp.455-460
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• 2001

An exact spectrum wish no leakage error could be obtained when the period of the signal coincides perfectly with the record length. However, the record length will be determined regardless of the period of signal. The Leakage error due to this problem will gibe a distorted spectrum. In the conventional research, the method was proposed to estimate the three parameters, frequency, amplitude and phase angle, from the spectrum data for anundamped sinusoidal signal. In this paper, some techniques are proposed to estimate frequency, amplitude and damping ratios from the frequency response functions for damped signals. The validation of the proposed techniques is verified by several numerical examples.

• Journal of Power Electronics
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• v.16 no.1
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• pp.388-397
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• 2016

An error-compensated pulse width modulator (ECPWM) is proposed to improve the baseband harmonic performance and the switching loss of voltage source inverters (VSIs). Selecting between harmonic distortion and switching loss is a design tradeoff in the conventional space vector pulse width modulation. In this work, an accumulated difference in produced and desired phase voltages is considered to adjust the reference signal. This mechanism can compensate for the voltage error in the previous carrier period. With error compensation every half-carrier period, the proposed ECPWM allows one-half reduction in carrier frequency without scarifying baseband harmonic distortion. The proposed modulator is applied to a three-phase VSI with R-L load and a motor-speed-control system for experiments. The measured efficiency and operating temperature of switches confirm the effectiveness of the proposed scheme.