• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1456-1470
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• 2017

This paper presents sensorless vector control of induction motor drives with an improved model reference adaptive system observer for rotor speed estimation and parameters identification from measured stator currents, stator voltages and estimated rotor fluxes. The aim of the proposed sensorless control method is to compensate simultaneously stator resistance and rotor time constant variations which are subject of large changes during operation. PI controllers have been used in the model reference adaptive system adaptation mechanism and in the closed loops of speed and currents regulation. The stability of the proposed observer is proved by the Lyapunov's theorem and its feasibility is verified by experimentation. The experimental results are obtained with an 1 kW induction motor using Matlab/Simulink and a dSPACE system with DS1104 controller board showing the effectiveness of the proposed approach in terms of dynamic performance.

• Asian-Australasian Journal of Animal Sciences
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• 제20권5호
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• pp.742-747
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• 2007

In order to investigate the mechanism of adaptation to long-term heat stress, six female buffalo calves of about 7 to 8 months age, were exposed to the cool-comfort environment (THI 65) for 21 days to obtain normal values of blood acid-base. An adaptive response of acid-base regulation was determined to long term (21 days) exposure of buffalo calves to hot-dry (THI 80) and hot-humid (THI 84) conditions. Higher rectal temperature and respiratory rate was recorded under hot-humid exposure compared to hot-dry. Significant reduction in the rectal temperature and respiratory rate on day 21 of hot-dry exposure indicated early thermal adaptation compared to hot-humid. Decreasing rectal temperature and respiratory rate from day 1 to 21 was associated with concurrent decrease in blood pH and pCO2. Increased plasma chloride concentration with low base excess in blood and in extracellular fluid suggested compensatory response to respiratory alkalosis. Reduced fractional excretion of sodium with increased fractional excretion of potassium and urine flow rate indicated renal adaptive response to heat stress.

• Journal of Power Electronics
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• 제9권3호
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• pp.343-353
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• 2009

In this paper, a nonlinear controller is proposed for Doubly-Fed Induction Machine (DFIM) drives. The nonlinear controller is designed based on an adaptive backstepping control technique, using a fifth order model of an induction machine in the synchronous d & q axis rotating reference frame, whose d axis coincides with the space voltage vector of the main AC supply, and using the rotor current and stator flux components as state variables. The nonlinear controller can perfectly track the torque reference signal measured in the stator terminals under the condition of unity power factor regulation, in spite of the stator and rotor resistance variations. In order to make the drive system capable of operating in the motoring and generating modes below and above the synchronous speed, two level Space-Vector PWM (SV-PWM) back-to-back voltage source inverters are employed in the rotor circuit. It is confirmed through computer simulation results that the proposed control approach is effective and valid.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.79-82
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• 1997

The current from the feed motor of a machine tool contains substantial information about the machining state. There have been many researches that investigated the current as a measure for the cutting forces. However it has not been reported that indirect measurement of the cutting forces from the current of the feed motor at rest is possible. The cutting force normal to the machined surface influences the machined surface of the workpiece, which makes it necessary to estimate this force to control the roughness of the machined surface. But the unpredictable behavior of the current prevents applying the current to prediction of the cutting state. In this paper, empirical approach was conducted to resolve the problem. Also parametric adaptive and fuzzy logic control strategies are applied to the force regulation problem. As a result, the current is shown to be related to the accumulation of the infinitesimal rotation of the motor, and besides the unpredictable behavior of the current is shown to be caused by the relationship. Subsequently the relationship between the current and the cutting force is identified, and it is presented that control of machined surface using the current of the feed motor at rest is possible.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.244-248
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• 2004

This paper proposes a new noise cancellation method for speech recognition in noise environments. We determine the time adaptive threshold value using standard deviations of wavelet coefficients after wavelet transform by frames. The time adaptive threshold value is set up by using sum of standard deviations of wavelet coefficients in cA3 and weighted cD1. cA3 coefficients represent the voiced sound with lower frequency components and cD1 coefficients represent the unvoiced sound with higher frequency components. In experiments, we removed noise after adding white Gaussian noise and colored noise to original speech. The proposed method improved SNR and MSE more than wavelet transform and wavelet packet transform does. As a result of speech recognition experiment using noise speech DB, recognition performance is improved by $2\sim4\;\%.$

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1740-1751
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• 2018

This paper proposes a novel fault tolerant tracking control (FTTC) scheme for a class of nonlinear systems with actuator failures based on the policy iteration (PI) algorithm and the adaptive fault observer. The estimated actuator failure from an adaptive fault observer is utilized to construct an improved performance index function that reflects the failure, regulation and control simultaneously. With the help of the proper performance index function, the FTTC problem can be transformed into an optimal control problem. The fault tolerant tracking controller is composed of the desired controller and the approximated optimal feedback one. The desired controller is developed to maintain the desired tracking performance at the steady-state, and the approximated optimal feedback controller is designed to stabilize the tracking error dynamics in an optimal manner. By establishing a critic neural network, the PI algorithm is utilized to solve the Hamilton-Jacobi-Bellman equation, and then the approximated optimal feedback controller can be derived. Based on Lyapunov technique, the uniform ultimate boundedness of the closed-loop system is proven. The proposed FTTC scheme is applied to reconfigurable manipulators with two degree of freedoms in order to test the effectiveness via numerical simulation.

• Journal of Power Electronics
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• 제19권3호
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• pp.691-701
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• 2019

To solve the problems in the contact charging of inspection robots, a wireless charging system for inspection robots and a control strategy are introduced in this paper. Circuit models of a wireless power system with a compound compensation circuit and a three-phase Class-D resonant inverter are set up based on circuit theory. An output voltage control method based on the equal spread regulation of the phase difference between adjacent phases and the parameter correction method in the primary compound compensation circuit are proposed. The dynamic characteristics of the key parameters varying with the secondary coil position are obtained to further investigate the adaptive location scheme during the access and exit processes of moving robots. Combining the output voltage control method and the adaptive location scheme, a transition control strategy for the standby and operation modes of the wireless charging systems for inspection robots is put forward to realize the system characteristics including the low standby power in the standby mode and the high receiving power in the operation mode. Finally, experiments are designed and conducted to verify the correctness of the theoretical research.

• IMMUNE NETWORK
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• 제14권4호
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• pp.171-181
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• 2014

Asthma is a common pulmonary disease with several different forms. The most studied form of asthma is the allergic form, which is mainly related to the function of Th2 cells and their production of cytokines (IL-4, IL-5, and IL-13) in association with allergen sensitization and adaptive immunity. Recently, there have been many advances in understanding non-allergic asthma, which seems to be related to environmental factors such as air pollution, infection, or even obesity. Cells of the innate immune system, including macrophages, neutrophils, and natural killer T cells as well as the newly described innate lymphoid cells, are effective producers of a variety of cytokines and seem to play important roles in the development of non-allergic asthma. In this review, we focus on recent findings regarding innate lymphoid cells and their roles in asthma.

• IMMUNE NETWORK
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• 제11권6호
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• pp.406-411
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• 2011

Background: Invariant Natural killer T (iNKT) cells, a distinct subset of CD1d-restricted T cells with invariant $V{\alpha}{\beta}$ TCR, functionally bridge innate and adaptive immunity. While iNKT cells share features with conventional T cells in some functional aspects, they simultaneously produce large amount of Th1 and Th2 cytokines upon T-cell receptor (TCR) ligation. However, gene expression pattern in two types of cells has not been well characterized. Methods: we performed comparative microarray analyses of gene expression in murine iNKT cells and conventional $CD4^+CD25^-$ ${\gamma}{\delta}TCR^-$ T cells by using Gene Set Enrichment Analysis (GSEA) method. Results: Here, we describe profound differences in gene expression pattern between iNKT cells and conventional $CD4^+CD25^-$ ${\gamma}{\delta}TCR^-$ T cells. Conclusion: Our results provide new insights into the functional competence of iNKT cells and a better understanding of their various roles during immune responses.

• 한국전자파학회논문지
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• 제23권5호
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• pp.632-639
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• 2012

Ad-hoc 네트워크는 음영 지역, 재난 지역, 전쟁 시와 같은 통신 인프라가 구축되기 어려운 상황에서 유용하게 사용될 수 있다. 그러나 음성 및 데이터 서비스 등과 같은 무선 서비스의 제공을 위해 많은 양의 네트워크 용량이 필요하게 되지만, 기존의 제한된 주파수 자원에 따른 주파수 부족 상황 및 주파수 자원 정책의 규제에 따라 원활한 주파수 사용이 어려운 상황이다. 이에 따라 높은 주파수 활용을 제공하는 인지 무선 시스템을 ad-hoc 네트워크에 적용하여 보다 다양하고 확장된 네트워크 서비스를 제공할 수 있다. 하지만 기존 스펙트럼 센싱에 있어 임계치가 정적으로 작용하므로 detection probability가 낮게 검출되는 단점이 있다. 이러한 점을 보완하여 신호들의 detection probability를 향상시키기 위해 adaptive threshold를 이용할 것이다. 본 논문에서는 동적인 임계치를 이용하여 수신 신호의 power에 따라 임계치가 변화하여 신호들의 detection probability를 향상시키는 센싱 성능을 보여 준다.