• Journal of Power Electronics
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• v.16 no.6
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• pp.2173-2181
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• 2016

Permanent magnet synchronous motors (PMSMs) have higher torque and superior output power per volume than other types of AC motors. They are commonly used for applications that require a large output power and a wide range of speed. For precise control of PMSMs, knowing the accurate position of the rotor is essential, and normally position sensors such as a resolver or an encoder are employed. On the other hand, the position sensors make the driving system expensive and unstable if the attached sensor malfunctions. Therefore, sensorless algorithms are widely researched nowadays, to reduce the cost and cope with sensor failure. This paper proposes a sensorless algorithm that can be applied to a wide range of speed. The proposed method features a robust operation at low-speed as well as high-speed ranges by employing a gain adjustment scheme and intermittent voltage pulse injection method. In the proposed scheme the position estimation gain is tuned by a closed loop manner to have stable operation in tough driving environment. The proposed algorithm is fully verified by various experiments done with a 1 kW outer rotor-type PMSM.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1838-1842
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• 2004

Gain and phase margins of a first order plus delayed time (FOPDT) process controlled by generalized predictive controller (GPC) are related to the control parameters ${\lambda}$ (control move suppression parameter) and ${\alpha}$ (smoothing filter coefficient) and the normalized delay of the process. Variation ranges of gain and phase margins are determined. It is shown that the margins cannot be assigned independently for a wide range of variation and the range is narrowing by increase of the normalized delay of the process. And finally curves are given to use for adjustment of the controller parameters in order to obtain a specific pair of gain and phase margins.

• Research in Community and Public Health Nursing
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• v.30 no.1
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• pp.90-98
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• 2019

Purpose: The purpose of this study is to identify the association between maternal feeding practices and excessive weight gain in infants. Methods: This study adopted a cross-sectional design and included 240 pairs of mothers and their infants (129 boys and 111 girls) in public healthcare centers in the Daejeon area in South Korea. Via multivariate analyses, the association between maternal feeding practices and excessive weight gain in infants was identified. Results: Among 240 infants in this study, 39 (16.3%) infants gained excessive weight during 12 months after birth. Using multivariate logistic regression with adjustment for covariates, more than 7 months of exclusive breastfeeding was associated with a reduced likelihood of excessive weight gain in infants during the 12 months after birth (adjusted odds ratio: 0.39, 95% confidence interval: 0.02~0.81, p=.029). Conclusion: Based on these results, nurses in communities and clinics should educate mothers on the importance of longer durations of exclusive breast feeding and develop strategies for encouraging such behavior. Furthermore, support for exclusive breast feeding should be provided in various settings.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.140-149
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• 2016

For visual measurement under dynamic scenarios, a zoom lens camera is more flexible than a fixed one. However, the challenges of distortion prediction within the whole focal range limit the widespread application of zoom lens cameras greatly. Thus, a novel sequential distortion correction method for a zoom lens camera is proposed in this study. In this paper, a distortion assessment method without coupling effect is depicted by an elaborated chessboard pattern. Then, the appropriate distortion correction model for a zoom lens camera is derived from the comparisons of some existing models and methods. To gain a rectified image at any zoom settings, a global distortion correction modeling method is developed with bundle adjustment. Based on some selected zoom settings, the optimized quadratic functions of distortion parameters are obtained from the global perspective. Using the proposed method, we can rectify all images from the calibrated zoom lens camera. Experimental results of different zoom lens cameras validate the feasibility and effectiveness of the proposed method.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.36-44
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• 2005

In this paper, we present a retransmission power adjustment (RPA) scheme for DS/SSMA ALOHA packet radio systems with packet combining. In the proposed RPA scheme, retransmission power is adjusted in such a way that the erroneously-received packet can be recovered with a minimized interference to other user packets. We analyze the performance of the system with the RPA by employing the equilibrium point analysis (EPA), and confirm that the results obtained from the EPA are very close to the simulation results in low power cases. Simulation results demonstrate that the RPA scheme brings forth performance gain in the throughput and the average delay while saving a significant amount of transmission power. We also investigate the stability of the system from the EPA results, and conclude that the system becomes stable as the offered load increases or the level of retransmission power decreases.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2725-2730
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• 2003

In this study we present a vibration controller for articulated robots that has flexible joints modeled as a 2-mass system. Most of articulated robots have time varying load inertias for each axis according to its motion. Moreover, the inertias vary drastically; for the base axis of articulated robots it may vary about 10 times of its minimum value. But, for industrial robots and many mechatronic devices, it is desirable to maintain control performance in spite of load inertia variation. So we propose a control gain adjustment rule considering the time-varying nature of load inertia. In this gain-adjusting algorithm, the pole locations are in proportion to the anti-resonance frequency of the 2-mass system. The simulation and experimental results show uniform properties in overshoot in spite of the variation of load.

• 전기의세계
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• v.18 no.5
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• pp.12-19
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• 1969

The sensitivity of transistorized d.c. amplifiers is mainly limited by drift at operating point caused by ambient temperature changes. A chopper-type transistorized amplifier is necessary to obtain a high sensitivity without recourse to drift compensation which requires the adjustment of several balancing controls. A chopper-stabilized system consisting of an electro-mechanical chopper for input and output and a high-gain a.c. amplifier is designed and analyzed. The gain of the a.c. amplifier, expressed as the ratio of voltages, is larger than 80db in the band of 50C/S - 100KC/S. The complete system gives an open-loop gain of 68db at direct current. The offset voltage is 20.mu.V referred in input and the voltage drift at the input is less than 10.mu.V/hr at 25.deg.C. This type of amplifier would be useful for the high-gain transistorized d.c. amplifier for analog computers. Also, due to the high input impedance, it is suitable for amplification of signals from wide range of source impedances.

• Journal of the Korean Statistical Society
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• v.33 no.4
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• pp.381-399
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• 2004

Statistical process control (SPC) and engineering process control (EPC) are based on different strategies for process quality improvement. SPC re-duces process variability by detecting and eliminating special causes of process variation, while EPC reduces process variability by adjusting compensatory variables to keep the quality variable close to target. Recently there has been need for an integrated process control (IPC) procedure which combines the two strategies. This paper considers a scheme that simultaneously applies SPC and EPC techniques to reduce the variation of a process. The process model under consideration is an IMA(1,1) model with a step shift. The EPC part of the scheme adjusts the process, while the SPC part of the scheme detects the occurrence of a special cause. For adjusting the process repeated adjustment is applied according to the predicted deviation from target. For detecting special causes the exponentially weighted moving average control chart is applied to the observed deviations. It was assumed that the adjustment under the presence of a special cause may increase the process variability or change the system gain. Reasonable choices of parameters for the IPC procedure are considered in the context of the mean squared deviation as well as the average run length.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.187-190
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• 1998

The values of physical components of the plants and controllers as well as the relevant environmental conditions change in time, thus the output performance can be deteriorated during the operating span of the system. Naturally the duty of calibration or the prevention of performance deterioration due to excessive component sensitivity should be provided to the control system. The proposed controller, whenever necessary, measures the open-loop and close-loop characteristics, and then calculates the offset and sensor gain correction values based on the prepared standard measurements It is applied to the control of a flexible link system with the gain and offset calibration problems in the light sensor module for position to show the applicability. In this paper, we propose a digital controller which has the capability of calibration gain and offset adjustment using fuzzy methods.

• The Korean Journal of Rehabilitation Nursing
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• v.3 no.2
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• pp.127-140
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• 2000

The purpose of this study is to identify the effect of sexual rehabilitation education on the knowledge and adjustment of sexual of spinal cord injury clients by the method of nonequivalant control group pretest-posttest group. The data were collected from Jan. 19 though Feb. 16, 2000. The experimental group was 26 spinal cord injury client from one rehabilitation center, and the control group was 26 spinal cord injury client from two rehabilitation center. Sexual rehabilitation education was done with manuals, videotapes and chart. Education time was 120 minutes a week for 2 weeks. The study tool was about Sexual Knowledge, designed Song, Chung Sook(1990) and SIAC(Sexual, Interest, Activity, & Satisfaction) designed Kruter, Sullivan, Siosteen(1994) translated by Kang, Hyun Sook, Koh, Jung Eun, Suh, Yeon Ok, Yee, Oon Hee(1999). The collected data were analyzed SPSS program. The Data were analyzed descriptive statistics and $X^2$ test, Pearson's Correlation Coefficient, t-test, F-test (ANOVA), Duncan's multiple comparison test. The result were as follows. 1. The first hypothesis was accepted : The group educated about sexual rehabilitation has more sexual knowledge than those of the uneducated group(t = 7.412, p = .001). 2. The second hypothesis was accepted : The group educated about the sexual rehabilitation has more adjustment of sexual than those of the uneducated group(t = 5.524, p= .001). 3. The third hypothesis was accepted: The higher sexual knowledge state, the higher sexual adjustment(r= .449, p= .003). According to results, sexual rehabilitation education helps Spinal cord Injury Clients to gain knowledge and adjustment of sexual.