• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.646-650
• /
• 2004

This paper presents a novel method to detect the rotor position of the BrushLess DC(BLDC) motor at standstill and a start-up method to accelerate the rotor up to a certain speed where the conventional position sensorless control methods based on the back EMF could work reasonably The proposed initial rotor position estimation method is suitable to avoid the temporary reverse rotation or the starting failure. This method can be implemented using only one current sensor at DC link of the inverter. It does not depend on the model of the motor , and it is robust to motor parameter variations. By the proposed method, it is demonstrated experimentally that a stable starting can be achieved even with severe mechanical disturbance.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.39 no.4
• /
• pp.364-370
• /
• 1990

In this paper, we propose a self-tuning PID controller for unknown systems with time-varying delay. Using pole placement equations, we derive the controller that can be extended to the multi-step time delay case. The time-varying delays are estimated by a prediction error delay method using multiple predictors. Since the order of the estimation vector is not increased, the persistant exciting condition of control input is alleviated. Since the least square method gives biased parameter estimates for colored noise cases, the recursive instrumental variable method is used to estimate system parameters. The computational burden of the proposed method is less than the conventional adaptive methods. Computer simulations are performed to illustrate the efficiency of the proposed method.

• International Journal of Control, Automation, and Systems
• /
• v.1 no.4
• /
• pp.520-526
• /
• 2003

In the case of a strapdown inertial navigation system (SDINS) with sizeable attitude errors, the uncertainty caused by linearization of the system degrades the performance of the filter. In this paper, a robust filter and various error models for the uncertainty are presented. The analytical characteristics of the proposed filter are also investigated. The results show that the filter does not require the statistical property of the system disturbance and that the region of the estimation error depends on a freedom parameter in the worst case. Then, the uncertainty of the SDINS is derived. Depending on the choice of the reference frame and the attitude error state, several error models are presented. Finally, various in-flight alignment methods are proposed by combining the robust filter with the error models. Simulation results demonstrate that the proposed filter effectively improves the performance.

• Communications for Statistical Applications and Methods
• /
• v.23 no.2
• /
• pp.179-187
• /
• 2016

The fixed effects panel probit model faces "incidental parameters problem" because it has a property that the number of parameters to be estimated will increase with sample size. The maximum likelihood estimation fails to give a consistent estimator of slope parameter. Unlike the panel regression model, it is not feasible to find an orthogonal reparameterization of fixed effects to get a consistent estimator. In this note, a hierarchical Bayesian model is proposed. The model is essentially equivalent to the frequentist's random effects model, but the individual specific effects are estimable with the help of Gibbs sampling. The Bayesian estimator is shown to reduce reduced the small sample bias. The maximum likelihood estimator in the random effects model is also efficient, which contradicts Green (2004)'s conclusion.

• Journal of Preventive Medicine and Public Health
• /
• v.42 no.4
• /
• pp.215-222
• /
• 2009

Objectives : Vigorous physical activity is a well-known method to promote people s health. This research aims to investigate whether perceived neighborhood characteristics affect vigorous physical activity among adult Seoul residents (aged 19 to 64). Methods : Utilizing the 2005 Seoul Citizens Health Indicators Survey data, this study estimates the probability of vigorous physical activity. Particular attention is given to the effects of three perceived neighborhood characteristics satisfaction with relationship to the neighborhood, satisfaction with park and recreational facilities, and satisfaction with public security). Logistic regression models are analyzed separately by gender for the parameter estimation. Results : Vigorous physical activity is positively associated with three perceived neighborhood characteristics for women, while neither significant nor substantive association is found for men. Conclusions : As vigorous physical activity among Seoul citizens is differentially affected by perceived neighborhood characteristics and by gender, a different approach will be needed to increase vigorous physical activity of men and women in Seoul.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.12
• /
• pp.73-79
• /
• 2003

Recently, the tole-robot operations to an unstructured environment have been widely researched. The human's interaction with the tole-robot system can be used to improve robot operation and performance for an unknown environment. The exact modeling based on real environment is fundamental and important process for this interaction. In this paper, we propose an extrinsic parameter calibration and data augmentation method that only uses a circular jig in the hand-eye laser virtual environment. Compared to other methods, easier estimation and overlay can be done by this algorithm. Experimental results using synthetic graphic demonstrate the usefulness of the proposed algorithm.

• Communications for Statistical Applications and Methods
• /
• v.10 no.1
• /
• pp.89-99
• /
• 2003

The primary purpose of this paper is to estimate the wealth effect. We establish a linear relationships between household consumption, labor income, and stock price index. Each variable is nonstationary. And so, it contains a unit root. However, as the result of the test about cointegrating relations, the variables are cointegrated which implies the error term is stationary. The cointegrating parameter that the marginal propensity to consume out of stock price is 0.08%. The result of estimation shows the error correction is -0.62 and the significant level is also high. The error correction term indicates a rather rapid adjustment to deviations from the long run equilibrium relations.

• Communications for Statistical Applications and Methods
• /
• v.22 no.2
• /
• pp.105-120
• /
• 2015

A large family of distributions arising from distributions of ordered data is proposed which contains other models studied in the literature. This extension subsume many cases of weighted random variables such as order statistics, records, k-records and many others in variety. Such a distribution can be used for modeling data which are not identical in distribution. Some properties of the theoretical model such as moment, mean deviation, entropy criteria, symmetry and unimodality are derived. The proposed model also studies the problem of parameter estimation and derives maximum likelihood estimators in a weighted gamma distribution. Finally, it will be shown that the proposed model is the best among the previously introduced distributions for modeling a real data set.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.899-900
• /
• 2006

Using the MATLAB/SIMULINK, this paper presents dynamic simulation model for 6MW wind power generation systems with the DFIG considering distribution systems and performs the dynamic analysis of wind power systems.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.93-100
• /
• 2008

Recently, due to the advanced measurement techniques, long-term health monitoring systems have been frequently applied to existing bridges. It is known that damping ratios as one of dynamic properties would be an important parameter for evaluating the bridge condition. However, damping ratios may be normally varied depending on the external loading effects on bridges. In general, both the logarithmic decrement and the half-power band width method as a conventional method can be simply used for evaluating the damping ratios accurately when bridge response signals are measured under free vibration conditions. In this study, the Hilbert-Huang transform and the extended Kalman filter were applied to evaluate the damping ratio by using the bridge acceleration signals measured under ambient vibration condition. From the results under ambient vibration condition of bridges, it was examined that the damping ratios evaluated from both the Hilbert-Huang transform and the extended Kalman filter could be more reliable than those from conventional methods.