• 대한안전경영과학회지
• /
• 제4권2호
• /
• pp.11-22
• /
• 2002

In this study, an asymmetric lifting posture prediction model was developed, which was a three-dimensional model with 12 links and 23 degrees of freedom open kinematic chains. Although previous researchers have proposed biomechanical, psychophysical, or physiological measures as cost functions, for solving redundancy, they lack in accuracy in predicting actual lifting postures and most of them are confined to the two-dimensional model. To develop an asymmetric lifting posture prediction model, we used the resolved motion method for accurately simulating the lifting motion in a reasonable time. Furthermore, in solving the redundant problem of the human posture prediction, a moment weighted Joint Range Availability (JRA) was used as a cost function in order to consider dynamic lifting. However, it is known that the moment weighted JRA as a cost function predicted the lower extremity and L5/S1 joint motions better than the upper extremities, while the constant weighted JRA as a cost function predicted the latter better than the former. To compensate for this, we proposed a hybrid moment weighted JRA as a new cost function with moment weighted for only the lower extremity. In order to validate the proposed cost function, the predicted and real lifting postures for various lifting conditions were compared by using the root mean square(RMS) error. This hybrid JRA reduced RMS more than the previous cost functions. Therefore, it is concluded that the cost function of a hybrid moment weighted JRA can be used to predict three-dimensional lifting postures. To compare with the predicted trajectories and the real lifting movements, graphical validations were performed. The results also showed that the hybrid moment weighted cost function model was found to have generated the postures more similar to the real movements.

• 대한기계학회논문집A
• /
• 제32권7호
• /
• pp.549-555
• /
• 2008

Analytical method to analyze the tolerance effect on the vehicle ride comfort is suggested in this paper. Ride comfort is one of the most important performance indices which decide the vehicle design quality. In general, the ride comfort is affected by the variations of parameters of a vehicle model. Therefore, the effects of the parameters on the ride comfort need to be evaluated statistically based on the whole-body vibration of the vehicle. In this paper, weighted RMS values of the acceleration PSD of a seat position are used to define the ride comfort. The equations of motion and the sensitivity equations are derived based on a 5-DOF vehicle model. By employing the sensitivity information of the acceleration at the seat position, the tolerance effect on the vehicle ride comfort could be effectively analyzed.

• 한국철도학회논문집
• /
• 제18권3호
• /
• pp.194-202
• /
• 2015

본 연구에서는 수직 진동에 노출된 승객의 승차감을 정량적으로 분석하기 위해 점탄성 특성을 가진 시트에 기댄 인체의 동적 모델링을 제시한다. 시트 위 인체의 운동을 기술하기 위해 문헌에서 찾은 5자유도계 다물체 동역학 모델이 이용되었다. 철도차량 시트에 사용되는 점탄성 특성은 비선형 강성 특성과 시간 지연을 표현하는 컨볼루션 적분으로 수식화된다. 바닥 가진에 대한 전달함수를 분석 결과 시트의 비선형 특성으로 인해 입력 가진의 크기에 따라 전달함수는 변하는 것으로 나타났다. 측정된 철도차량의 바닥 가진을 이용하여 실제적인 인체 진동 특성을 분석한다. 주파수 가중치 자승평균치 값을 계산하고 시트 설계 파라미터가 이 주파수 가중치 자승평균치에 미치는 영향을 제시한다.

• 한국지역지리학회지
• /
• 제10권2호
• /
• pp.389-406
• /
• 2004

최근 지역 연구의 활성화와 더불어 지역 자료의 중요성이 점점 강조되고 있다. 그런데 실제 이용가능한 지역 자료의 공간단위는 연구 분석을 위한 기능지역 단위와 일치하지 않는 경우가 종종 발생하며, 이로 인해 발생하는 문제를 해결하기 위해 이용가능한 지역 단위 자료를 연구 분석을 위한 공간 단위로 재구성하는 방법이 요구된다. 본 연구는 면적 가중치 내삽법, pycnophylactic 방법, dasymetric 방법, Area-to-point 내삽법 등을 검토하고 도시지역 자료의 효율적인 재구성 방법으로 면적 가중치 내삽법을 수정하여 인구 가중치 내삽법(population weighted interpolation)을 제안하였다. 인구 가중치 내삽법은 미국 뉴욕주 이리 카운티(Erie County)를 연구 사례로 면적 가중치 방법 pycnophylactic 방법을 RMS 에러, 자료 분포 유형, 공간 자기상관의 측면에서 비교되었다.

• International Journal of Automotive Technology
• /
• 제6권2호
• /
• pp.141-148
• /
• 2005

In order to reduce the time and costs of improving the performance of vehicle suspensions, the techniques for optimizing damping and air spring characteristic were proposed. A full vehicle model for a bus is constructed with a car body, front and rear suspension linkages, air springs, dampers, tires, and a steering system. An air spring and a damper are modeled with nonlinear characteristics using experimental data and a curve fitting technique. The objective function for ride quality is WRMS (Weighted RMS) of the power spectral density of the vertical acceleration at the driver's seat, middle seat and rear seat. The objective function for handling performance is the RMS (Root Mean Squares) of the roll angle, roll rate, yaw rate, and lateral acceleration at the center of gravity of a body during a lane change. The design variables are determined by damping coefficients, damping exponents and curve fitting parameters of air spring characteristic curves. The Taguchi method is used in order to investigate sensitivity of design variables. Since ride and handling performances are mutually conflicting characteristics, the validity of the developed optimum design procedure is demonstrated by comparing the trends of ride and handling performance indices with respect to the ratio of weighting factors. The global criterion method is proposed to obtain the solution of multi-objective optimization problem.

• 한국소음진동공학회논문집
• /
• 제20권3호
• /
• pp.249-256
• /
• 2010

This paper presents performance analysis of a quarter-vehicle magneto-rheological(MR) suspension system with respect to different tire pressure. As a first step, MR damper is designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial mid-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the manufactured MR damper, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR damper is constructed in order to investigate the ride comfort. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, vertical tire stiffness with respect to different tire pressure is experimentally identified. The skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. Ride comfort characteristics such as vertical acceleration RMS and weighted RMS of sprung mass are evaluated under various road conditions.

• 한국통신학회논문지
• /
• 제36권5C호
• /
• pp.317-325
• /
• 2011

OFDM (Orthogonal Frequency Division Multiplexing) 시스템에서 2-D MMSE (2-Dimensional Minimum Mean Square Error) 채널 추정 기법은 주파수/시간 선택적 특성을 가지는 채널에서 우수한 성능을 나타내는 것으로 알려져 있다. 하지만 2-D MMSE 채널 추정 방식은 주파수 축 뿐만 아니라 시간 축 까지 고려하기 때문에 행렬 크기가 커지고, 이로 인해 복잡도가 크게 증가한다는 문제점이 있다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해 l-D MMSE 채널 추정 구조를 기반으로 가중치 합을 이용하여 기존의 2-D MMSE 채널 추정 방식보다 낮은 복잡도를 갖는 방식을 제안한다. 뿐만 아니라 2-D MMSE 채널 추정을 적용하기 위해 필요한 파라미터인 RMS 지연 확산과 도플러 주파수를 추정하는 기법을 고려한다. 성능 검증 결과 제안하는 방식은 기존의 2-D MMSE 방식에 비해서 복잡도를 크게 줄일 수 있을 뿐만 아니라, 2-D MMSE 채널 추정 방법과 유사한 성능을 나타내는 것을 확인하였다.

• Journal of Positioning, Navigation, and Timing
• /
• 제7권4호
• /
• pp.245-253
• /
• 2018

The current SBAS service does not provide a method to integrate multiple SBAS corrections. This paper proposes a positioning method to effectively integrate multiple SBAS and multiple GNSS. In the method, the final position is obtained by the weighted sum of the positions obtained from the combination of GNSS and SBAS. Since each position is independently computed and combined using flexible weights, it has a simple structure that can easily cope with various environments. In order to verify the operation and performance of the proposed method, raw measurements of GNSS and SBAS were collected using commercial receivers. The experiments using real signals show that the combined use of two SBAS corrections was more accurate by 0.05~0.4m(2dRMS) than using only one SBAS correction. To improve the position accuracy, this paper considered the integration of multi-GNSS and multi-SBAS, which was not found in other existing studies. The proposed method is expected to be a core technology for designing multi-GNSS navigation receivers considering multi-SBAS corrections. The importance of the method will be increased as KPS and KASS also available in near future.

• Bulletin of the Korean Chemical Society
• /
• 제35권3호
• /
• pp.749-752
• /
• 2014

New software was developed for the assignment of elemental formulae based on high-resolution mass spectra and subsequent hydrogen/deuterium exchange data. Entire peaks in high-resolution mass spectra were grouped by their Kendrick mass defect values, and the weighted RMS deviations between theoretical and experimental values were used to determine elemental formulae. After this initial assignment, formulae containing deuterium atoms were sorted in order to interpret hydrogen/deuterium exchange spectra. The software was successfully applied to hydrogen/deuterium exchange spectra of resins and aromatic fractions from heavy crude oil.

• 대한기계학회논문집
• /
• 제12권1호
• /
• pp.163-172
• /
• 1988

본 논문에서는 GAC방법을 이용하여 공작기계의 안내면오차를 수치제어 공작기계가 가지고 있는 가공조건의 조절 능력을 이용하여 가공오차를 보상제어 함으로써 규명(identification)할 수 있는 방법을 제시한다.