• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.337-342
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• 2011

Medical lift column controlling the vertical position while supporting heavy eccentric load should have the high fatigue strength as well as the extremely low structural deflection and vibration in order to maintain the positioning accuracy. The lift column driven by a induction motor is generally in a three-step sliding boom structure and exhibits the time-varying stress distribution according to the up-and-down motion. This study is concerned with the numerical prediction of the fatigue strength of the lift column subject to the time-varying stress caused by the up-and-down motion. The stress variation during a motion cycle is obtained by finite element analysis and the fatigue life is predicted making use of Palmgren-miner's rule and S-N curves. In order to secure the numerical analysis reliability, a 3-D FEM, model in which the detailed lift column structure and the fitting parts are fully considered, is generated and the interfaces between lift column and pads are treated by the contact condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.261-266
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• 1995

본 연구에서는 자기부상시스템에 대해 흡인식 자기부상방식을 채택하고 쇠구슬에 대한 운동을 상하 1자유도로 가정하여 운동방정식을 세운다. 이때 전자석이 자기 부상력은 전자석에 흐르는 전류와 인덕턴스의 함수라 가정하고, 모델의 불확실성은 자기부상계의 운동 방정식으로부터 선형화 할 때 발생하는 오차 및 파라미터 변동으로 생각한다. 또한 모델의 불확실성이 존재하더라도 정상편차 없이 부상하는 서보제어계를 설계한다. 그런데 저자등은 강인성 문제 및 정상편차 없는 것에 역점을 두어 H$_{\infty}$ 제어이론에 기초한 1형 로바스트 서보 제어기를 구하여 자기부상 시스템의 안정화 제어계로써 적용한 적이 있다. 이때 중심해 이외의 해를 이용하여 설계한 서보 제어계는 자기부상계의 과도상태시에 일어나는 오버슈트를 줄일 수 없었다. 따라서 시스템 내부 안정화를 위하여 H$_{\infty}$ 제어이론에 의해 설계된 피드백(feedback) 제어기와 물체가 부상할 때 오버슈트를 줄이고 제어량이 목표치에 잘 추종하기 위해 설계된 피드 포워드(feed forward) 제어기로써 2자유도를 갖는 제어계를 설계한다. 이렇게 설계한 2자유도 제어계를 가지고 모의 응답실험과 본 연구자들이 만든 자기부상 시스템의 실험결과를 비교함으로써 설계된 제어기의 타당성을 조사한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1122-1127
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• 2001

This paper proposed a speed adaptive control system with load torque observer and feed-forward compensation using neural network for air compressor system driven an induction motor. The motor receive impact load change under the influence of piston movement of up and down, and so it difficult to obtain good speed control characteristics. With real-time adjusting control gain estimated in neural network, control characteristics of motor is improved. The validity of the proposed system is confirmed through the theoretical analysis and computer simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1152-1158
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• 2004

In this study a MRAC(model reference adaptive control) for fluid power elevator model system was designed. The MRAC was compared with PI control in case of applying to the elevator model system with constant external load and changing external load. In this case external load was produced by a single fluid power cylinder combined with pressure control valve. In conclusion the MRAC control performance was better than PI control performance because overshoot and steady state error of the elevator model system controlled by the MRAC were not appeared for constant and changing external load.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.397-400
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• 2001

This paper proposed a speed adaptive control system with load torque observer and feed-forward compensation using neural network for air compressor system driven an induction motor. The motor receive impact load change under the influence of piston movement of up and down, and so it difficult to obtain good speed control characteristics. With real-time adjusting control gain estimated in neural network, control characteristics of motor is improved. The validity of the proposed system is confirmed through the theoretical analysis and computer simulation.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.1173-1174
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• 2023

Shock Absorber 는 Suspension 부품 중 하나로 감쇠력을 통해 스프링의 수축을 제어함으로써 차량의 승차감 및 안정성을 향상시키는 장치이다[1]. 그러나, 스프링의 상하운동을 억제하기 위해 Shock Absorber 가 압축·인장 됨으로써 소음이 발생하여 탑승객을 불편하게 한다. 본 논문에서는 이에 대한 계측을 통해 원인을 파악하고 NVH 를 개선하여 승차감 향상을 도모한다.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.503-505
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• 1986

주어진 제어대상 모델에 대하여 제어기를 구성하여 실제로 적용하는 경우 모델의 불일치, 모델링에서 고려하지 않은 외란(disturbance), 측정잡음등에 의하여 성능이 설계시와 달라진다. 실제적용에서도 성능을 계속 유지하기 위하여 제어기는 안정성, 계수변화(parameter variation)에 대한 강인성(robustness), 외란상쇄(disturbance rejection) 및 측정잡음에 둔감함등의 특성을 가져야 한다. 귀환(feedback)을 사용하여 제어기를 구성하는 경우 위의 모든 조건을 만족 시킬 수 없으므로 제어목적에 따라 적당한 조건을 선정하여 중요한 특성을 주로 갖게 한다. 본 논문에서는 쌍동선(small waterplane area twin hull ship-SWATHS)에 대하여 PID, LQ, LQG 제어기를 구성하여 안정성, 계수 변화에 대한 강인성, 외란 상쇄 및 측정잡음의 영향을 비교하였다. 쌍동선의 경우 다른 단동선(mono hull ship)에 비하여 접수면(waterplane)이 적으므로 무게증변을 흡수할 수 있는 복원력이 약하여 적은 외력에도 상하동요(heave)와 종동요(pitch)가 심하게 일어난다. 이러한 동요를 줄이는 것이 쌍동선의 제어목적이다. 본 연구에서는 먼저 선형화된 수직축 운동방정식을 이용하여 선체운동의 모델을 구했으며 중첩의 원리(super-position theorem)에 의하여 주파수 응답의 합으로 파도입력을 모델링 하였으며 제어를 위하여 필요한 측정치는 IMU(Inertial Measurement Unit)에서 제공된다고 가정하였다. 쌍동선의 동요의 원인은 파도, 바람, 조류 등이 있으나 파도에 의한 영향이 가장 크므로 본 논문에서는 파도에 의한 영향만을 고려하였다. 파도는 쌍동선에 외란으로 작용하며 측정할 수 없는 양이므로 PID, LQ 제어에서는 제어모델에 포함되지 않지만 LQG 제어에서는 제어모델에 포함된다. LQG 제어의 경우 제어모델에 파도를 백색잡음으로 가정하고 제어기를 구성한 것 (LQG1)과 2차의 쉐이핑필터(shaping filter)를 사용하여 구성한 것(LQG2)으로 나누었다.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.36-43
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• 1996

An Attitude Control System for a high speed catamaran with contorl fins in waves is designed and investigated by the experimental methods. An optimal control theory is applied to design the automatic attitude control system of the high speed catamaran for its good seaworthiness. The experimental results performed in KRISO model basin for the displacements and accelerations for the model ship are measured in regular hear waves. Form the epxerimental results the effect of control planes is thought to be incroeasing with speed.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.485-491
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• 2017

An experimental study on the reduction of vertical motion of floating body using floating-submerged body interaction was performed in a two-dimensional wave channel. The system consisting of a floating and submerged body that only move vertically was modeled. This experiment was designed based on the results of theoretical analysis of two-body interaction. The results showed a tendency to significant reduction of heave RAO of floating body due to submerged body. Various connection line stiffness and dimension of the submerged body were applied to investigate the effect of two-body interaction on the vertical motion of the bodies, Heave RAOs of the floating-submerged body were compared with those of single body. From the comparison study, we obtained an optimum condition of connection line and dimension of submerged body for maximum heave reduction at the resonant period of single body.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.65-77
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• 1994

This paper presents a derailed application procedure of the linear quadratic(LQ) theory for a SWATH heave and pitch control. A time domain model of coupled, linear time-invariant second order differential equations is derived from the frequency response model with the frequency dependent added mass and damping approximated as constant values at the heave natural frequency. Wave exciting forces are modeled as a sum of sinusoids. A systematic selection procedure of state and control weighting matrices is presented to obtain good transient behavior and acceptable fin movement. The validity of this controller design process is throughly investigated by simulations both in time domain and frequency domain and singular value plots of transfer function matrices. The finally designed control system shows good overall performances revealing that the applicability of the present study is proved successful.