• 대한기계학회논문집
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• 제14권6호
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• pp.1365-1381
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• 1990

본 연구에서는 Kant 등이 제안한 고차판이론의 C연속변위 유한요소 모델을 사 용하여 충격자와 적층판의 저속 충격 응답에 대하여 연구하여 그 결과를 Mindlin의 판 이론에 의한 계산 결과와 비교하고, 경계 조건의 영향 및 충격자의 충격속도, 질량변 화에 대한 접촉력의 변화를 고찰하고자 한다.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.29-34
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• 2017

본 논문에서는 압연 공정을 통해 리드용 와이어를 생산할 때 생산성을 향상시키기 위해 와이어의 직진 속도를 증가시키는 방법을 연구했다. 직진 속도를 증가시킬 때 가장 중요한 점은 와이어가 원래의 목적을 바르게 수행할 수 있는 것이다. 즉, 와이어의 직진 속도가 증가함과 동시에 균열이 발생하지 않으며, 치수 공차를 만족시켜야 한다. 하지만 와이어의 직진속도를 증가시키게 되면 기존의 압하량 보다 더 큰 수치를 주어야 하고 이는 와이어에 보다 큰 손상을 주어 표면에 무리를 주게 된다. 따라서 기존의 2단계 평압연 공정을 통해 생산되었던 와이어의 필요스펙을 충족시키면서 생산성 향상까지 도모할 수 있는 3단계 평압연 공정에 관해 연구하였다. 본 연구에서는 3단계 평압연 롤러의 압하량만을 변수로 가정하고 다른 조건은 현장 조건과 일치시킨다. 상용 PIDO(Process Integration and Design Optimization) 툴인 PIANO (Process Integration, Design and Optimization)를 통해 지정한 변수 3가지를 조작하면서 실험점을 분포하고 이를 바탕으로 최적설계를 진행하여 와이어의 생산성을 향상시킴과 동시에 필요 스펙인 최대 응력의 최소화가 가능하도록 설계되었다.

• 대한기계학회논문집
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• 제19권5호
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• pp.1243-1250
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• 1995

For the numerical solution of frictional dynamic contact problems, correct contact points and displacements are determined by iteratively reducing the displacement error vector monotonically toward zero And spurious oscillations are prevented from the solution by enforcing the velocity and acceleration compatibilities of the contact points with the corresponding error vectors. Numerical simulations are conducted to demonstrate the accuracy of the solution and the necessity of the velocity and acceleration compatibilities on the contact surface.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.969-974
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• 1994

The dynamic behavior of graphite/epoxy laminated composite shell structure due to low-velocity impact is investigated using the finite element method. In this analysis, the Newmark's constant-acceleration time integration algorithm is used. The impact response such as contact force, central deflection and dynamic strain history form shell structure analysis are compared with those form the plate non-linear analysis. The effects of curvature, impact velocity and mass of impactor on the composite shell are discussed.

• Structural Engineering and Mechanics
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• 제48권5호
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• pp.711-736
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• 2013

In this paper new implicit time integration called N-IHOA is presented for dynamic analysis of high damping systems. Here, current displacement and velocity are assumed to be functions of the velocities and accelerations of several previous time steps, respectively. This definition causes that only one set of weighted factors is calculated from the Taylor series expansion which leads to a simple approach and reduce the computational efforts. Moreover a comprehensive study on stability of the proposed method i.e., N-IHOA compared with IHOA integration which is performed based on amplification matrices proves the ability of the N-IHOA in high damping vibrations such as control systems. Also, wide range of numerical examples which contains single/multi degrees of freedom, damped/un-damped, free/forced vibrations from finite element/finite difference demonstrate that the accuracy and efficiency of the proposed time integration is more than the common approaches such as the IHOA, the Wilson-${\theta}$ and the Newmark-${\beta}$.

• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.716-722
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• 2016

Coordinate estimation is an essential function for autonomous navigation of a mobile robot. The optical mouse sensor is convenient and cost-effective for the coordinate estimation problem. It is possible to overcome the position estimation error caused by the slip and the model mismatch of robot's motion equation using the optical mouse sensor. One of the simple methods for the position estimation using the optical mouse sensor is integration of the velocity data from the sensor with time. However, the unavoidable noise in the sensor data may deteriorate the position estimation in case of the simple integration method. In general, a mobile robot has ready-to-use motion information from the encoder sensors of driving motors. By combining the velocity data from the optical mouse sensor and the motion information of a mobile robot, it is possible to improve the coordinate estimation performance. In this paper, a coordinate estimation algorithm for an autonomous mobile robot is presented based on the well-known Kalman filter that is useful to combine the different types of sensors. Computer simulation results show the performance of the proposed localization algorithm for several types of trajectories in comparison with the simple integration method.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.378-386
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• 2002

Multi-path ultrasonic Sow measurement system uncertainty is determined by assigning an expected error of each component of flow measurement and then defining the total flow measurement uncertainty as square root of the sum of squared values of the individual error. Sources of uncertainty for flow measurement are geometry, transit time and velocity profile integration uncertainty. A theoretical uncertainty model for multi-path ultrasonic transit time flowmeter configured with parallel 5 chords, is derived from and calculated by dry calibration method.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.460-470
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• 2004

A computational analysis of engineering problems with moving domain or/and boundary according to either Lagrangian or Eulerian approach may encounter inherent numerical difficulties, the extreme mesh distortion in the former and the material boundary indistinctness in the latter. In order to overcome such defects in classical numerical approaches, the ALE(arbitrary Lagrangian Eulerian) method is widely being adopted in which the finite element mesh moves with arbitrary velocity. This paper is concerned with the ALE finite element formulation, aiming at the dynamic response analysis of baffled fuel-storage container in yawing motion, for which the coupled time integration scheme, the remeshing and smoothing algorithm and the mesh velocity determination are addressed. Numerical simulation illustrating theoretical works is also presented.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.488-493
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• 2006

Accurate river discharge is the most important factor in managing river basins and for successfully maintaining total maximum daily loads in Korea. It is not easy to measure the discharge directly in large rivers owing to physical and environmental constraints, even after investing much time and money. Recently, to overcome these historical drawbacks in river discharge measurement, we have developed the Automatic Discharge Acquisition & Management System (ADAMS) that scans the river cross-section and measures each cell $(1m{\times}1m)$ velocity using HADCP. The hardware system is composed of an HADCP sensor and winch, as well as a PC and software system for the discharge calculation module and hardware control module. It is controlled remotely via the internet and uses the velocity-depth integration method and the velocity-contour method for calculating river discharges. The characteristics of ADAMS are a ubiquitously accessible system, featuring real time automatic discharge measurement, remote control via the internet. The results using ADAMS at the Jindong stage site show less than 5% uncertainty and are 4 times more efficient than the ADCP & Q-boat system. This system can be used to measure any large river, river mouth or tributary river affected by backwater, all of which have a very difficult measuring real time discharge. The next generation of ADAMS will feature an upgrade to increase portability and GPS integration.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1253-1267
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• 2005

Misalignment can be an important problem in the integration of GPS/INS. Observability analysis of the alignment errors in the integration of low-grade inertial sensors and multi-antenna GPS is presented in this paper. A control-theoretic approach is adopted to study the observability of time-varying error dynamics models. The relationship between vehicle motions and the observability of the errors in the lever arm and relative attitude between GPS antenna array and IMU is given. It is shown that alignment errors can be made observable through maneuvering. The change of acceleration makes the components of the relative attitude error that are orthogonal to the direction of the acceleration change observable. The change of angular velocity makes the components of the lever arm error that are orthogonal to the direction of the angular velocity observable. The motion of constant angular velocity has no influence on the estimation of the lever arm.