• 한국통신학회논문지
• /
• 제26권10B호
• /
• pp.1464-1469
• /
• 2001

본 논문에서는 디지털 하이브리드 위상고정루프(Digital Hybrid Phase-Locked Loop, DHPLL) 주파수 합성기 구조에서 고 순도 스펙트럼과 초고속 스위칭 속도를 위한 설계기술을 제안한다. D/A 변환기 출력으로 전압제어발진기(Voltage Controlled Oscillator, VCO)를 구동하는 개 루프(open-loop) 구성 방식과 기존 위상고정루프(Phase Locked Loop, PLL)의 폐 루프(closed-loop) 구성 방식을 혼합한 하이브리드 구조의 주파수 합성기를 고려하여, 시스템 변수(개 루프 대역과 위상 여유)와 성능 파라미터(정착시간, 위상 잡음, 그리고 최대 오버슈트(Max. overshoot)의 관계를 연구하였다. 그리고 이 관계를 통해 스펙트럼 순도와 스위칭 속도를 향상시키기 위한 최적의 3가지 설계방안을 제시한다. 컴퓨터 시뮬레이션 결과, 주파수 스위칭 과정에서 발생하는 최대 오버슈트가 0.0991%이고 완전 정상상태 도달시간은 0.288msec이다. offset 주파수 10KHz에서 위상 잡음은 -128.15dBc이다.

• 전기의세계
• /
• 제28권5호
• /
• pp.44-48
• /
• 1979

For ordinary systems the receding horizon method has beer proved by the author as a very useful and easy tool to find stable feedback controls. In this paper an open-loop optimal control which minimizes the control energy with a suitable upper limit and terminal control and state constraints is derived and then transformed to the closed-loop control. The stable feedback control law is obtained from the closed-loop control. The stable feedback control law is obtained from the closed-loop control by the receding horizon concept. It is shown by the Lyapunov method that the control law derived from the receding, horizon concept is asymtotically stable under the complete controllability condition. The stable feedback control which is similar to but more general than the receding horizon control is presented in this paper To the author's knowledge the control laws in this paper are easiest to stabilize systems with delay in control.

• 한국정밀공학회지
• /
• 제15권1호
• /
• pp.60-68
• /
• 1998

Parallel link manipulators have an ability of more precise positioning than serial open-loop manipulators. However. general parallel link manipulators have been restricted to the real applications since they have limited workspace due to interference among actuators. In this study, we suggest a closed-loop manipulator with 6 degrees-of-freedom and with enlarged workspace. It consists of two parts for minimizing the interference among actuators. One part is lower structure with planar 3 degrees-of-freedom and the other is upper one with spatial 3 degrees-of-freedom. Forward kinematics and inverse kinematics are solved, research about singularity points are carried out and workspace is evaluated. The comparison of workspace between Stewart platform, which is the typical parallel link manipulator, and the suggested manipulator shows that the workspace of the latter is wider than that of the former. Especially, simulation results also show that the suggested manipulator is more suitable when there needs rotation in the end-effector.

• Journal of Advanced Marine Engineering and Technology
• /
• 제25권4호
• /
• pp.833-845
• /
• 2001

Quantitative Feedback Theory(QFT) has been used to design a robust power system stabilizer(PSS) to improve transient and dynamic stabilities of a power system. This design technique is basically accomplished in frequency domain. The most important feature of QFT is that it is able to deal with the design problem of complicated uncertain plants. A basic idea in QFT design is the translation of closed-loop frequency-domain specifications into Nichols chart domains specifying the allowable range of the nominal open-loop response and then to design a controller by using the gain-phase loop shaping technique. This paper introduces a new algorithm to compute QFT bounds more efficiently. The propose QFT design method ensures a satisfactory performance of the PSS under a wide range of power system operating conditions.

• 설비공학논문집
• /
• 제27권4호
• /
• pp.207-212
• /
• 2015

The use of groundwater and ground_heat is one of the ways to use natural and renewable energy, and it has been considered as a technology to reduce greenhouse gas emissions and increase energy-saving. There are a few researches on the optimum design for the open-loop geothermal system. In this study, to develop the optimal design method numerical simulation of the open-loop geothermal system with two-wells was performed by a groundwater and heat transfer model. In this paper, a study was performed to analyze the system performance according to well distance and pumping flow rate. In the result, average heat exchange rate and heat source temperature were calculated and it was found that they were dependent on the pumping rate.

• 한국소음진동공학회논문집
• /
• 제21권12호
• /
• pp.1104-1111
• /
• 2011

This paper investigates the filtered velocity feedback(FVF) controller for the reduction of the acoustic power radiated from a clamped beam. The instability problem due to the non-collocated sensor/actuator configuration when using PZT actuator should be sorted out. The roll-off property of the FVF controller at high frequency helps to alleviate the instability. The dynamics of clamped beams under forces and moments pair and the FVF controller are first formulated. The formulation of the sound radiated power is followed. The open loop transfer function(OLTF) synthesized with 100 modes is used to determine the stability of the control system. The control performance is finally estimated. The levels of the vibration and the sound radiated power are reduced in the wide bandbelow the tuning mode of the FVF controller.

• 제어로봇시스템학회논문지
• /
• 제5권4호
• /
• pp.385-393
• /
• 1999

An open loop vibrational control for an underactuated mechanical system with amplitude and frequently modulation is investigated. Since there is no direct external input to an unactuated joint, the dynamic coupling between the actuated and unactuated joints is utilized for controlling the unactuated joint. Feedback linearization has been performed to incorporate fully the known nonlinearities of the underactuated system considered. The actuated joints are firstly positioned to their desired locations, and the periodic oscillatory inputs are applied to the actuated joints to move the remaining unactuated joints to their target positions. The amplitudes and frequencies of the vibrations introduced are determined through averaging analysis. A systematic way of obtaining an averaged system for the underactuated system via a coordinate transformation is developed. A control design example of 2R planer manipulator with a free joint with no brake is provided.

• 소성∙가공
• /
• 제11권3호
• /
• pp.246-254
• /
• 2002

A simple method to derive an optimal pressure curve, characterized by initial pressure, final pressure and pressure path, has been proposed. The initial pressure has been determined from the condition to prevent recoiling phenomenon in the early stage, while the final pressure is from the FE analysis and pressure path is from the punch penetration volume. In order to realize the pressure curve, an open loop control system based on a proportional relief valve has been developed for the renovated CNC hydroforming press. Through the comparison of experiment and analysis, the predicted pressure curve has been verified optimal curve since no defect has been observed.

• 전기학회논문지
• /
• 제59권12호
• /
• pp.2324-2328
• /
• 2010

In this paper we proposed a new algorithm that can reduce the open-loop pitch estimation time of G.723.1. The time domain cross-correlation method is simple but has long processing time by recursive multiplication. For reduction of processing time, we use the method that compute the cross-correlation by multiplying the Fourier value of speech by it's complex conjugate. Also, we can reduce the processing time by omitting the bit-reversing of FFT and IFFT for time-frequency domain transform. As a result, the processing time of improved hybrid domain cross-correlation algorithm is reduced by 67.37% of conventional time domain cross-correlation.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2011년도 전력전자학술대회
• /
• pp.294-295
• /
• 2011

This paper presents the design and development of Web control algorithm of continuous process control system using vector inverter. Web algorithm used tension control without the tension sensor, and it is to calculate the diameter of Web materials with maintain Web tension. The performance of Web control in this paper is verified by experiment.