• 제어로봇시스템학회논문지
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• 제9권12호
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• pp.977-983
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• 2003

An output feedback stabilizing controller far non-minimum phase nonlinear systems is presented. We first perform the standard input-output linearization of the system and then transform the zero dynamics into a special normal form in which the antistable part is not affected by the stable part and the antistable part is given in approximately linear form. Under the assumption that the nonlinear system satisfies the observability rank condition, we can design an observer f3r the extended system that is made of the augmentation of a chain of integrators. The proposed output feedback stabilizing controller can then be designed by combining the observer and the state feedback controller.

• 한국정밀공학회지
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• 제21권1호
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• pp.124-132
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• 2004

A hydraulic system is difficult to keep the performance due to non-linearity, load pressure which changes according to working condition and system parameter variation, the requirement of control algorithm has been risen in order to satisfy them. An adaptive control is a control method which is suggested to achieve a control object though plant characteristics change. In spite of the case that plant characteristics and the degree of variation are difficult to grasp, adaptive control can keep the characteristics of closed-loop system regularly. In this study GMVAC(generalized minimum variance adaptive control) combined with output error feedback is proposed in order to solve problems of non-minimum phase, vibration and overshoot in initial response of the plant. The control performance according to the variation of characteristics of the plant is evaluated by changing the supply pressure only.

• 한국정밀공학회지
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• 제23권12호
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• pp.38-45
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• 2006

In this work, optimal finish machining condition considering total time for mold or electrode manufacturing was investigated. First, manual finishing time according to the machining condition was analyzed for the work material. The effect of runout and phase shift of tool path on surface finish was also considered in those analyses. Secondly, optimal manual finishing processes were determined for various machining conditions. Finally, finish machining time and corresponding manual finishing time were taken into account for the estimation of the total time of manufacturing mold. Though small feed per tooth and pick feed reduced the manual finishing time, the finish machining time increased in such conditions. With a machining condition of feed per tooth of 0.2 mm and pick feed of 0.3 mm, the minimum total time of manufacturing mold was achieved in our machining condition.

• 전자공학회논문지S
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• 제34S권10호
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• pp.52-58
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• 1997

In this paper, we consider methods of robust stabilization of the interval plant with a PID controller. Suppose that we know apriori a sign of the coefficients of the numerator of the PID controller. Under this condition, it sufficies to make eight polynomials stable for robust stabilization of the interval plant with a minimum phase PID controller. In addition, with a nonminimum phase PID controller, it suffices to make different eight polynomials stable. Especially, with the nonminimum phase PID controller it is shown that stabilization of eight plants is necessary and sufficient for robust stabilization of the interval plants.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.1167-1170
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• 1999

We consider a negative unity feedback control system in which a controller and a given minimum phase transfer function are in cascade. This paper present a sufficient condition for the existence of a constant gain controller under which the overall closed loop characteristic polynomial is stable. This sufficient condition is based on Lehnigk's lemmas.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.129-131
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• 2007

In this paper, we research improvement in efficiency of single-phase induction motor by adapting the condition of the balanced and quasi-balanced operation. we maintain turns of auxiliary winding of the motor and adjust resistance and reactance. In this condition, resistance value and copper loss are much gloater. Namely, this is the condition only for balancing MMF without consideration of copper loss of stator winding. To make more practical design, therefore, we will perform winding design which is based on balanced operation condition and applies copper loss minimum. The problem of deterioration of starting torque is completed by rotor bar shape design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.137-139
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• 1991

This paper proposes a minimum power factor control for maximum efficiency operation of an induction motor, under low load condition. Minimum input or maximum efficiency operation is achived by properly adjusting the amplitude of the stator voltage, with the three phase AC voltage controller. Through the simulation, the relationships between the delay angle and input power under various load conditions are examined. Experimental results are also given, which show good coincidence with the simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.729-731
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• 2000

This paper presents a simple method for determining the minimum value of capacitance required for initiating self excitation in three-phase self-excited induction generator. Based on the steady-state equivalent circuit model, this paper presents simple and direct method to find the minimum capacitance requirement under R-L load. Using the loop impedance and nodal admittance. the minimum capacitance is determined by self excitation condition. These computed values can be used to predict practically the minimum value of the terminal voltage required for self-excitation. To maintain a constant terminal voltage, a method for determining the frequency, terminal capacitance, and exciting reactance is also described.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.367-369
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• 2002

We have designed ramp profile excitation pulse based on the Shinnar-Le Roux (SLR) algorithm. The algorithm provides many advantages to pulse designers. The first advantage is the freedom of deciding the amplitudes, frequencies, and ripple sizes of stopband, passband, and transition band of pulse profile. The second advantage is the freedom of deciding the pulse phase, more specifically, minimum phase, linear phase, maximum phase, and any phase between them. The minimum phase pulse is the best choice in the case of 3D TOF, because it minimizes the echo time, which implies the best image quality in the same MR examination condition. In addition, the half echo technique is slightly modified in our case. In general, using the half echo technique means that the acquired data size is half and the rest part can be filled with complex conjugate of acquired data. But in our case, the echo center is just shifted to left, which implies the reduction of echo time, and the acquired data size is the same as the one without using the half echo technique. In this case, the increase of right part of data leads to improvement of the resolution and the decrease of left part of data leads to decrease of signal to noise ratio. Since in the case of 3D TOF, the signal to noise ratio is sufficiently high and the resolution is more important than signal to noise ratio, the proposed method appears to be significantly affective and gives rise to the improved high resolution angiograms.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.311-315
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• 2001

In this paper synchronous whirl of bearing is employed as control algorithm of actively controlled hydrodynamic journal bearing to suppress the whirl instability and unbalance response of a rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis which uses the Reynolds condition. The stability and unbalance responses of a rotor-bearing system are investigated for various control gain and phase difference between the bearing and journal motion. It is shown that the unbalance response of a rotor-bearing system can be greatly improved by synchronous whirl of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, at given operating condition. It is also found that the speed at onset of instability can be greatly increased by synchronous whirl of the bearing.