• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.627-634
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• 1998

This paper proposes an algorithm which improves capacity of a state observer and low speed driving characteristics of a induction motor by inertia moment identification. In induction motet driving systems, it is difficult to obtain the accurate speed information by a low resolution encoder because the encoder pulses are very few in a low speed range. To improve this problem, state observer based on the Gopinath' theory which estimates speed and disturbance was designed, and disturbance rejection control was realized by application of the observer. Also, inertia moment of the motor was estimated and the nominal inertia of the observer was identified to minimize the error of estimated speed and disturbance. From the simulation and experimental results, it is showed that the proposed observer improved the transient response characteristics in low speed region below 6［rpm］.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.5
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• pp.317-325
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• 2003

The vibration, which often occurred in a two inertia motor system, makes it difficult to achieve a quick response of speed and disturbance rejection. This paper provides an autonomous pole assignment technique for three kinds of speed controllers (I-P, I-PD, and State feedback) using GAs(Genetic Algorithms) for a two-inertia motor system. Firstly, the optimal parameters are chosen using GAs in view of reducing overshoot and settling time, then those are used in computing the gains of each controller. Some simulation results verify the effectiveness of the proposed design. The proposed controller is expected to be the autonomous design way for controlling a two-inertia motor system with flexible shaft.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.143-149
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• 2003

다목적위성 1호(KOMPSAT-1, The first Korea Multi-Purpose Satellite)에 장착된 위성 자세제어용 3축 자력계(TAM, Three-Axis Magnetometer)로부터 2000년 6월 19일에서 21일 사이에 측정된 지구자기장을 분석하였다. TAM Telemetry 값을 지구관성좌표계에서 지구고정좌표계로 우선 변환시킨 후에 다시 구면좌표계로 변환하여 자료를 처리하였다. 지구자기장의 영향 이외의 위성내의 유도 전류나 온도변화로 인한 에러, 태양풍의 영향 등을 제거하였고 태양에 의한 영향을 제거하기 위해 제도를 지방시에 따라 상승 및 하강과 두 그룹으로 나눈 후 파동수대비법을 이용해 두 그룹 사이에 서로 역으로 대비되는 (inversely-correlated) 성분을 제거하였다. 측선 잡음을 제거하기 위하여 파동수 영역에서 Quadrant Swapping법을 도입하였고, 이로부터 연구 기간 중 최종적인 지구자기장을 추출하였다. KOMSAT TAM 으로부터 추출된 자기장의 주성분(corefield)을 동일 기간 중 KOMSAT과 유사한 고도에서 지구자기장 관측을 전문적으로 수행한 Ørsted 위성 관측값과 비교한 결과 이들 사이의 상관계수는 0.97로 매우 높게 나타났다 위성 자세보정용 자력계로 부터 관측된 자기장으로부터 신뢰도 있는 주성분 추출이 가능해짐에 따라 이로부터 전지구 구면조화계수를 유도할 경우 지구자기장 전문 관측위성이 존재하지 않는 기간 및 고도에 대한 자기장 연구가 가능하다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.75-80
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• 2004

Vehicle structures are composed of many substructure connected to one another by various types of mechanical joints. In vehicle engineering it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. It is difficult to obtain the accurate load history of specified positions because of the errors such as modeling, measurement and etc. In the beginning of design exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the procedure of practical dynamic force determination is developed by the combination of the principal stresses of F. E. Analysis and experiment. Least square pseudo inverse matrix is adopted to obtain in inverse matrix of analyzed stresses matrix. The error minimization method utilizes the inaccurate measured error and the shifting error that the whole data is stiffed over real data. The least square criterion is adopted to avoid these non. Finally, to verify the proposed procedure, a bus is analyzed. This measurement and prediction technology can be extended to the structural modification of any geometric shape in complex structure.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.118-123
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• 2001

Most structures of automobile are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic farces for the evaluations of fatigue life and stress concentration exactly. It is rarely obtained the accurate load history of specified positions because of the errors such as modeling, measurement, and etc. In the beginning of design, exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the procedure of practical dynamic load determination is developed by the combination of the principal stresses of F.E. analysis and experiment. Inverse problem and least square pseudo inverse matrix are adopted to obtain an inverse matrix of analyzed stresses matrix. Pseudo-Practical dynamic load was calculated for Lab. Test of sub-structure. GUI program(PLODAS) was developed for whole of above procedure. This proposed method could be extended to any geometric shape of structure.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.287-290
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• 2003

다모선 계통의 정확한 과도 안정도 직접해석을 위해 댐핑영향은 고려해야 할 중요한 요소 중의 하나이나 일반화가 어려워 최근까지 무시되어 왔다. 본 논문에서는 시스템을 나타내는 함수들의 적분 관계식들을 고려함으로써 다모선 계통에서의 댐핑영향을 반영한 에너지 함수를 유도하였으며 유도 과정에 있어 최근 다모선 계통에 보편적으로 적용되고 있는 관성중심(Center of Inertia :COI) 표현법으로 전개를 시도하였다. 유도된 에너지함수를 PEBS(Potential Energy Boundary Surface) 직접법에 적용하여 임계위치에너지를 산출하였으며, 임계고장제거시간을 계산함으로써 과도안정도직접해석법을 수행하였다. 제안된 에너지 함수를 WSCC 3기 9모선 샘플 시스템에 적용하여 댐핑이 고려된 에너지함수가 실제 계통을 보다 정확하게 표현하고 있음을 시뮬레이션을 통해 검증하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.442-449
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• 2009

A two-dimensional cross-section analysis program based on the finite element method has been developed for composite blades with solid, thin-walled and compound cross-sections. The weighted-modulus method is introduced to determine the laminated composite material properties. The shear center and the torsion constant for any given section are calculated according to the Trefftz' definition and the St. Venant torsion theory, respectively. The singular value problem of cross-section stiffness properties faced during the section analysis has been solved by performing an eigenvalue analysis to remove the rigid body mode. Numerical results showing the accuracy of the program obtained for stiffness, offset and inertia properties are compared in this analysis. The current analysis results are validated with those obtained by commercial software and published data available in the literature and a good correlation has generally been achieved through a series of validation study.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.583-590
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• 2015

Automobile crash optimization is nonlinear dynamic response structural optimization that uses highly nonlinear crash analysis in the time domain. The equivalent static loads (ESLs) method has been proposed to solve such problems. The ESLs are the static load sets generating the same displacement field as that of nonlinear dynamic analysis. Linear static response structural optimization is employed with the ESLs as multiple loading conditions. Nonlinear dynamic analysis and linear static structural optimization are repeated until the convergence criteria are satisfied. Nonlinear dynamic crash analysis for frontal analysis may not have boundary conditions, but boundary conditions are required in linear static response optimization. This study proposes a method to use the inertia relief method to overcome the mismatch. An optimization problem is formulated for the design of an automobile frontal structure and solved by the proposed method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.8-9
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• 2011

본 논문에서는 수상 및 수중운동체의 안정성 및 안정화기법에 관해 고찰한다. 선박이 운동을 하게 되면 부가질량이 변하게 되고 대칭인 시스템행렬이 비대칭이 된다. 비대칭성에 따라 시스템의 안정성해석방법도 달라지는데 예를 들어 가속도 피드백을 통해 비대칭요소를 제거하여 대칭으로 변환시키는 것이 가장 대표적인 해석 및 안정화 기법이다. 시스템 모델자체는 어디까지나 모델이기 때문에 대상시스템을 명확하게 수식으로 표현할 수 없으므로 피드백에 의한 비대칭요소를 소거시키는 방법은 타당하지 못하다. 따라서 본 논문에서는 대칭행렬이 비대칭행렬로 변하는 제약에 구애받지 않는, 보다 일반성을 갖는 안정성해석법을 제안한다.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.2
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• pp.161-168
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• 2015

In this paper, we present an inertial sensor-based gait distance measurement system using accelerometer, gyroscope, and magnetometer. To minimize offset and gain error of inertial sensors, we performed the calibration using the self-made calibration jig with 9 degrees of freedom. For measuring accurate gait distance, we used gradient descent algorithm to remove gravity error and used analysis of gait pattern to remove drift error. Finally, we measured a gait distance by double-integration of the error-removed acceleration data. To evaluate the performance of our system, we walked 10m in a straight line indoors to observe the improvement of removing error which compared un-calibrated to calibrated data. Also, the gait distance measured by the system was compared to the measurement of the Vicon motion capture system. The evaluation resulted in the improvement of $31.4{\pm}14.38%$(mean${\pm}$S.D.), $78.64{\pm}10.84%$ and $69.71{\pm}26.25%$ for x, y and z axis, respectively when walked in a straight line, and a root mean square error of 0.10m, 0.16m, and 0.12m for x, y and z axis, respectively when compared to the Vicon motion capture system.