• Information and Communications Magazine
• /
• v.16 no.10
• /
• pp.64-74
• /
• 1999

무선 채널에서 제한된 주파수 대역폭을 최대로 활용하여 비디오 데이터를 전송하기 위해서는 고효율의 변복조 기법, 페이딩 보상 기업 및 효율적인 오류 정정 기법이 요구된다. 본 고에서는 RF 주파수가 2GHz 대역이고 주파수 대역폭이 200 KHz를 갖는 TDMA 방식에 의한 WLL 모뎀(이하 AdWiLL$^{TM}$이라 한다) 설계에 대하여 기술한다. AdWiLL$^{TM}$모뎀의 핵심 기술로는 채널 특성을 실시간으로 분석하여 최적의 송수신 조건을 결정하는 channel probing 기술, 페이딩 환경에서 다중 레벨 QAM변복조를 가능하게 하는 적응출력제어 기술, WLL전파 환경과 서비스가 고려된 연접 부호(concatenated coding)를 통한 순방향 오류 정정(FEC) 기술, 송수신 성능 향상을 위한 범포밍 기술이 포함된다. 구현된 모뎀으 고정 무선 채널 환경에서 16 채널에서 32Kbps ADPCM 음성 신호를 동시에 송신할 수 있으며, 협대역 ISDN에서 제공하는 전송속도로 비디오 데이터의 전송이 가능함을 보였다.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.5 no.1
• /
• pp.13-19
• /
• 2008

The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, counter balance valve, and flow control valves. The flow capacity coefficients of flow control valves should be adjusted so that the hoist is operated at moderate speed and the hydraulic energy loss is minimized. However, it is difficult to adjust the flow coefficients of flow control valves by trial and error for optimal operation. Here, the steady state model of the hoist hydraulic system including the differential cylinder circuit is derived and the optimal flow capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.1
• /
• pp.85-92
• /
• 1989

For feedback control of a linear dynamic system the optimum linear state regulator (OLSR) can be implemented only if all states are available for feedback. This work demonstrates that when only the output state is available for feedback, a nonlinear controllers can give improved performance over that obtained by a proportional controller. This paper found the optimal control law by dynamic programming and principles of optimalityl. This, performances of both proportional and nonlinear controllers are compared with performance of optimum linear state regulator.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.5
• /
• pp.779-787
• /
• 2001

The multi degree of freedom system using magnetic levitation has been implemented successfully. Differently from another noncontact systems, the developed system was focused on the maximization of the system stiffness under the constraint of a limited input. The variation of a relative adopting point between the magnetic pair, its location on the fixed base, and the selection of optimal specifications for the main active magnetic elements give us another chance to realize the increased robustness against external disturbances with the less control inputs. In this paper, the overall development procedures are given including the optimal design, the dynamic modeling, the various control tests, and the main issues to be solved.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.5 s.98
• /
• pp.578-585
• /
• 2005

In this paper, we present a schematic method estimating the tracking vibration quantity occurring in the track-following system of an optical recording device. A tracking loop gain adjustment algorithm is introduced to estimate accurately the tracking vibration quantity in spite of the uncertainties of the tracking actuator, Accordingly, the tracking vibration quantity can be estimated from the tracking error, the controller output, the nominal actuator model, and a compensated gain. An optimal tracking controller can be designed from a minimum tracking open-loop gain calculated by the estimated tracking vibration quantity The proposed vibration quantity estimation and controller design method are applied to the track-following system of an optical recording device and are evaluated through the experimental result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.203-206
• /
• 2006

In this study, the method of designing the flexible wing model which will be used for wind tunnel testing of gust response alleviation system was presented. The design concept proposed herein was validated by performing the modal testing of the flexible wing model manufactured for demonstration purpose. In addition, the study on the gust response alleviation using flexible wing control surface was performed. For this purpose, optimal control with output feedback was adopted for designing the control surface controller, and the effects of gust response alleviation was validated by performing the numerical simulation for the representative flexible wing model. The methods proposed and validated in this study can be applied for wind tunnel testing of the flexible wing for gust response alleviation.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.10
• /
• pp.41-50
• /
• 1998

In this study, to investigate a characteristics of slip ratio control of H.C.U for ABS, half car model tester were developed and a new H.C.U. was compactly designed comparing to the commercical H.C.U. for ABS. In half car model tester, variable inertia wheel has been used to load the car weights and braking forces according to the road surface conditions which were realized by pneumatic cylinder. And solenoid valves using P.W.M. (Pulse Width Modulation) method were installed in the new H.C.U The slip ratio characteristics of tire had been measured using half car model tester and the results were used in the control simulation for a new H.C.U.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.11a
• /
• pp.91-92
• /
• 2012

본 연구에서는 $NaHCO_3$, $CaCl_2$ 용액 중 $Mg^{2+}$의 농도를 조절하며 전착프로세스에 의해 다양한 결정구조의 환경친화적인 탄산칼슘 막을 제작할 수 있었다. 특히, 여기서는 이들 막의 효율-실용적 설계 제작을 위해 상기한 용액 조건 중 NaCl의 첨가 농도를 달리하여 탄산칼슘 막의 석출량을 도출함으로써 최적 석출 속도를 제시할 수 있었다.

• Proceedings of the KIEE Conference
• /
• 1998.07b
• /
• pp.549-551
• /
• 1998

In this paper, we design the optimal satellite-tracking antenna $H_{\infty}$ control system using genetic algorithm(GA). To do this, we give gain and dynamics parameters to the weighting functions and apply GA with reference model to the optimal determination of weighting functions and design parameter ${\gamma}$ that are given by Glover-Doyle algorithm which can design $H_{\infty}$ controller in the state space. These weighting functions and design parameter ${\gamma}$ are simultaneously optimized in tile search domain guaranteeing the robust stability of closed-loop system. The effectiveness of this satellite-tracking antenna $H_{\infty}$ control system is verified by computer simulation.

• Proceedings of the KIEE Conference
• /
• 1998.07b
• /
• pp.446-448
• /
• 1998

In this paper, a novel sliding surface is proposed by introducing a virtual state. This sliding surface has nominal dynamics of an original system and makes it possible that the Sliding Mode Control(SMC) technique is used with the various types of controllers. Its design is based on the augmented system whose dynamics have one higher order than that of the original system. The reaching phase is removed by using an initial virtual state which makes the initial switching function equal to zero.