• Korean Journal of Psychosomatic Medicine
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• v.13 no.1
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• pp.41-48
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• 2005

Objectives : The aim of this study was to investigate the attitudes and opinions toward psychiatry of students and professionals for social welfare. Methods : 67 students and 34 social workers joined to this study completed the attitudes and opinions scale and the quality of life scale successfully. Results : On the attitude scale, in factor 'overall merits of field of psychiatry' and factor 'possible abuses and social criticisms', and factor 'career and personal rewards', the social workers have more positive attitude than other group, in factor 'role definition and functioning of psychiatrists', the female sex have more positive attitude than the other sex. It showed significant correlation between activity factor in quality of life scale and possible abuses and social criticisms in attitude scale. Conclusion : The contact with patients with psychiatric disorders will have a good impact on the personal attitude toward patients. It is important that the students for social welfare would receive appropriate psychiatric education program.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.116-127
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• 2003

In this paper, a new fully digital control method for UPS inverter, which is based on the double control loop such as the outer voltage control loop and inner current control loop, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The inner current control loop is adopted by an Internal model controller The Internal model controller is designed to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. The outer voltage control loop employing P-Resonance controller is proposed. The resonance controller has an infinite gain at resonant frequency, and the resonant frequency is set to the fundamental frequency of the reference voltage in this paper. Thus the outer voltage control loop causes no steady state error as regard to both magnitude and phase. The effectiveness of the proposed control system has been verified by the simulation and experimental results respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.171-178
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• 2008

Pressure control of hydraulic pump using SRM with pressure predictor and direct torque control method is presented in this paper. Nowadays, high efficiency and high performance motor drive is much interested in hydraulic pump system. But the hydraulic pump system has an inherent defect that its dynamic behavior causes by interaction between the sensor and hydraulic load. It will make low performance of whole system, even unstable and oscillatory. Proposed system integrates pressure predictor and direct instantaneous torque control (DITC). The pressure predictor includes Smith predictor, which is easy to improve unstable or long oscillation in traditional negative feedback control and popular PID control architectures. And DITC method can reduce inherent torque ripple of SRM, and develop smooth torque to load, which can increase stability and improve the torque response of SR drive. So high dynamic performance and stabilization can achieved proposed hydraulic system. At last, the proposed hydraulic system is verified by simulation and experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.761-770
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• 2008

Impedance or admittance inverter is a conceptual 2-port device frequently used in microwave filter design. In this paper, the equivalent circuit using inverter for general loss less 2-port circuit is presented. Our equivalent circuit can be directly and easily represented with z- or y-parameters compared with the conventional methods. Based on the representation, the derived results for various coupled lines such as parallel coupled line and anti-parallel coupled lines are compared ours. In addition, the results of other workers for improvement of the distortion in frequency response of microstrip coupled line filter are derived using our representation and compared. The proposed equivalent circuit shows the difference with conventional equivalent circuit so the conventional design method can not be applied to parallel coupled line filter with our representation. So in this paper the novel design method is proposed and we showed the method yields more accurate design results.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.4 s.310
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• pp.35-44
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• 2006

The network induced transmission delay deteriorates the performance and stability of the real-time distributed control system on LonWorks over IP (LonWorks/IP) virtual device network (VDN). LonWorks/IP virtual device network is an integrated form of LonWorks device network and IP data network. The time delay in servo control on the LonWorks/IP-based VDN has highly stochastic nature. In the real-time distributed servo applications for predictive maintenance on the factory floor, timely response is essential.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.1
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• pp.1-11
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• 2007

In this paper, a new fully digital control method for UPS inverter, which is based on the double control loop such as the outer voltage control loop and inner current control loop, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The inner current control loop is adopted by an internal model controller. The internal model controller is designed to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. The outer voltage control loop employing P-Resonance controller is proposed. The resonance controller has an infinite gain at resonant frequency, and the resonant frequency is set to the fundamental frequency of the reference voltage in this paper. Thus the outer voltage control loop causes no steady state error as regard to both magnitude and phase. The effectiveness of the proposed control system has been verified by the simulation and experimental results respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.70-79
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• 2005

In this paper, improvement method of control performance by a full-order observer using reduced-order state equation is proposed in the low speed range. Full-order observer using reduced-order state equation is the motor speed and the disturbance torque observer. The proposed algorithm is very stable in the low speed range about 1.9[rpm]. The disturbance torque in the motor drive system degrades speed control performance in the low speed range. The proposed algorithm estimated both motor speed and disturbance torque. The estimated disturbance torque is used as a feedforward value in output of the speed controller, As a result, it improves the response of load torque in the low speed range(1.9rpm).

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.935-939
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• 2015

This paper describes sensorless speed control of brushless DC motors by using direct torque control. Direct torque control offers fast torque response, robust specification of parameter changes, and lower hardware and processing costs compared to vector-controlled drives. In this paper, the current error compensation method is applied to the sensorless speed control of a brushless DC motor. Through this control technique, the controlled stator voltage is applied to the brushless DC motor such that the error between the stator currents in the mathematical model and the actual motor can be forced to decay to zero as time proceeds, and therefore, the motor speed approaches the setting value. This paper discusses the composition of the controller, which can carry out robust speed control without any proportional-integral (PI) controllers. The simulation results show that the control system has good dynamic speed and load responses at wide ranges of speed.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.427-436
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• 2002

This paper presents an implementation of high-dynamic performance of position sensorless motion control system of Reluctance Synchronous Motor(RSM) drives for an industrial servo system with direct torque control(DTC). The problems of high-dynamic performance and maximum efficiency RSM drives controlled by DTC are saturation of stator linkage flux and nonlinear inductance characteristics with various load currents. The accurate estimation of the stator flux and torque are obtained using stator flux observer of which a saturated inductance $L_d$ and $L_q$ can be compensated by adapting from measurable the modulus of the stator current and rotor position. To obtain fast torque response and maximum torque/current with varying load current, the reference command flux is ensured by imposing $I_{ds} = I_{qs}$. This control strategy is proposed to achieve fast response and optimal efficiency for RSM drive. In order to prove rightness of the suggested control algorithm, the actual experiment carried out at $\pm$20 and $\pm$1500 rpm. The developed digitally high-performance motion control system shown good response characteristic of control results and high performance features using 1.0kW RSM which has 2.57 Ld/Lq salient ratio.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.335-342
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• 2000

A new control method for a single-phase active power filter, based on a load current estimation using a DC capacitor voltage of active power filter without sensing nonlinear load current, is proposed in this paper. Because the method proposed can remove the load current sensor in comparison with a conventional method sensing the load current and DC capacitor voltage together, it can make the active power filter easy installation, low cost, small size with no performance detriment. In addition, sample-hold technique and proportional control method is adopted to control the DC capacitor voltage and as no delay element such as LPF or PI control in the conventional method is used, the transient response is fast and good. Operation of a single-phase active power filter which consist of eight mode is explained according to utility voltage, compensation current and switch state, and compensation characteristics of active power filter using proposed method is verified by experiment.