• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
• /
• pp.160-163
• /
• 1993

In this paper, design of an automatic grinding robot system for car brazing bead is introduced. Car roof and side panels are joined using brazing, and then the brazing bead is processed so that the bead is invisible after painting. Up to now the grinding process is accomplished manually. The difficulties in automation of the grinding process are induced by variation of position and shape of the bead and non-uniformity of the grinding area due to surface deformation. For each car, the grinding area including the brazing bead is sensed and then modeled using a 2-D optical sensor system. Using these model data, the position and the direction of discrete points on the car, body surface are obtained to produce grinding path for a 6 degrees of freedom grinding robot. During the process, it is necessary to sense the reaction forces continuously to prepare for the unexpected circumstances. In addition, to meet the line cycle time it is necessary to reduce the required time in sensing, signal processing, modeling, path planning and data transfer by utilizing real-time communication of the information. The key technique in the communication and integration of the complex information is obtaining in-field reliability. This automatic grinding robot system may be regarded as a jump in the intelligent robot processing technique.

• 한국추진공학회지
• /
• 제26권6호
• /
• pp.10-20
• /
• 2022

본 연구에서는 케로신 다단연소사이클 엔진용 예연소기를 설계하기 위해, 고압의 산화제 과잉 조건에서 예연소가스를 계산하고 냉각유로에서 극저온 유체의 복합열전달 및 수력 특성을 해석할 수 있는 설계코드를 개발하였다. 사용자 편의성과 범용성을 가진 오픈 소스 라이브러리 Cantera를 활용하였으며, 실제유체의 열역학/전달 상태량을 정확히 계산하기 위해 관련 소스 코드들을 새로 작성하여 Cantera에 추가하였다. 현재 예비설계 중인 100톤급 부스터 엔진용 예연소기에 적용하였으며, CFD 해석결과와 비교를 통해 설계코드로서의 예측 정확도와 활용성을 확인하였다.

• 한국유체기계학회 논문집
• /
• 제14권5호
• /
• pp.48-54
• /
• 2011

Structural modifications of a ship may cause a fatal accident such as sinking and wrecking of ship. Especially, barge ship can be easily reconstructed to load more bulk cargo. In this study, for a real accident case, change of mooring force due to structural modification was analyzed to evaluate accident risk. A two dimensional dynamic model for the barge ship was constructed to compute mooring forces with related to floating motion. The equation of motion was established in Matlab code and buoyancy was calculated by using direct integration of submerged volume. The results showed that wind force, current force, and mooring force after rebuilding was approximately 4.3 kN, 14 kN, 1,561 kN respectively. The maximum force of mooring force according to the length of mooring cable were 1,614 kN at 30 m of mooring cable. Thus, an arbitrary modification of ship lead instability and unreliable result so that illegal rebuilding of ship should be avoided.

• 터널과지하공간
• /
• 제30권4호
• /
• pp.320-334
• /
• 2020

본 수치해석연구에서는 국제공동연구프로젝트 DECOVALEX2019의 Task B의 일환으로 PFC3D를 기반으로한 수리역학연계모델을 개발하여 스위스 Mont Terri 지하연구시설에서 수행된 단층의 유체주입으로 인한 슬립시험을 모사하였다. 이를통해, 개발한 PFC3D 수리역학연계모델이 가진 한계점과 향후 보완할 점을 검토하고자 하였다. PFC3D를 기반으로한 3차원 입자결합모델 내 공극-유동통로모델을 생성하였으며 이를 사용하여 Mont Terri Step 2 단층내 유체주입실험을 모사하였다. 모델링결과 단층대를 따라 주입유체의 유동에 의한 단층대의 변형을 확인하였지만, 관측정에서의 시간에 따른 수압변화는 현장측정치와 부분적으로 일치하는 경향을 확인하였다. 현장측정 관측수압은 초기 유체주입 압력증가에 거의 변화를 보이지 않고 주입수압이 최대치에 도달할때쯤 급격한 증가를 보이는반면, 모델링에서는 주입압력이 증가함에 따라 관측수압도 부드럽게 증가하는 경향을 보였다. 이러한 부분적으로 일치하는 결과의 원인으로는 Mont Terri 현장의 단층을 모사하는 방법에 기인하는 것으로 판단하다. PFC3D에서는 단층을 손상대와 코어균열의 조합으로 모사하였고 단층대의 두께가 약 2 m로 주입유체가 단층대를 통해 유동하도록 모사하였기에 현장에서의 주입유체의 단층내 유동보다 그 유동범위가 크게 모사되었다고 판단한다. 또한, 현장단층에서와 같이 단층내부에 존재하는 충진물질로 인해 단층내 수리유동이 제한되어 국부적으로 과잉공급수압이 형성될 수 있는 기재를 모사하지 못한 점 또한 모델링 결과와 현장측정결과가 부분적으로 일치하는 원인일 수 있다. 단층변형의 경우는 모델링결과와 현장측정결과 유사한 수준으로 일치하는 결과를 확인하였다. 수치모델을 변형하여 단층대의 두께를 감소시키고 단층내 충진 물질의 비균질적인분포를 모사할 수 있는 방법론에 대한 후속 연구를 통해 PFC3D 수리역학연계모델의 유체주입으로 인한 단층활성화 연구로의 적용성을 향상시키는 것을 제안하고 한다.

• 한국가시화정보학회지
• /
• 제7권1호
• /
• pp.3-8
• /
• 2009

Most vehicles have a heating, ventilating and air conditioning (HVAC) device to control the thermal condition and to make comfortable environment in the passenger compartment. The improvement of ventilation flow inside the passenger compartment is crucial for providing comfortable environment. For this, better understanding on the variation of flow characteristics of ventilation air inside the passenger compartment with respect to various ventilation modes is strongly required. Most previous studies on the ventilation flow in a car cabin were carried out using computational fluid dynamics (CFD) analysis or scale-down water-model experiments. In this study, whole ventilation flow discharged from the air vent of a real passenger car was measured using a special PIV (particle image velocimetry) system for large-size FOV (field of view). Under real recirculation ventilation condition, the spatial distributions of stream-wise turbulence intensity and mean velocity were measured in the vortical panel-duct center plane under the panel ventilation mode. These experimental data would be useful for understanding the detailed flow structure of real ventilation flow and validating numerical predictions.

• 설비공학논문집
• /
• 제6권3호
• /
• pp.282-290
• /
• 1994

A numerical model for the analysis and design of orifice pulse tube refrigerators has been developed. Heat transfer coefficient and friction factors in the model vary with time, and the real physical properties such as thermal conductivity and viscosity were used to improve the accuracy of the model. Thermodynamic behavior of the working fluid within pulse tube refrigerators was investigated and the effect of design parameters, such as reservoir volume, orifice diameter, and NTU of regenerator, on the cooling load and COP was shown.

• 드라이브 ㆍ 컨트롤
• /
• 제12권2호
• /
• pp.14-20
• /
• 2015

This paper focuses on the issue of force synchronizing control for the injection servomechanism of injection molding machines. Prior to the controller design, a virtual design model was developed for the injection mechanism with an AC servomotor-ball screw. A synchronizing controller is designed and combined with the PID control to accommodate the mismatches between the real plant and the linear model plant used. Due to the plant uncertainty, the stiffness and the damping of the mechanism were considered. From the tracking control simulations based on the virtual design model, it is shown that a significant reduction in force synchronizing error is achieved through the use of a proposed control scheme.

• 드라이브 ㆍ 컨트롤
• /
• 제14권4호
• /
• pp.23-28
• /
• 2017

Time-delay control with internal model (TDCIM) is the controller for robot manipulators that applies the time-delay estimation and the concept of internal model control (IMC). TDCIM is robust against unknown dynamics and non-linear friction like coulomb friction and static friction. It is simple and computationally efficient. This study presents the relationship between the discrete TDCIM and the discrete PID controller. The PID controller is the most popular control law in the real application. But often the PID controller can be difficult to achieve the desired level of control performance. The result in this study provides a good candidate solution to these situations.

• Structural Engineering and Mechanics
• /
• 제76권3호
• /
• pp.355-365
• /
• 2020

In this study, considering the hydroelastic response represented by the springing and whipping phenomena, we propose a method of estimating the fatigue damage in the longitudinal connections of ships. First, we screened the design sea states using a load transfer function based on the frequency domain. We then conducted a time domain fluid-structure interaction (FSI) analysis using WISH-FLEX, an in-house code based on the weakly nonlinear approach. To obtain an effective and robust analytical result of the hydroelastic response, we also conducted an experimental model test with a 1/50-scale backbone-based model of a ship, and compared the experimental results with those obtained from the FSI analysis. Then, by combining the results obtained from the hydroelastic response with those obtained from the numerical fatigue analysis, we developed a fatigue damage estimation method. Finally, to demonstrate the effectiveness of the developed method, we evaluated the fatigue strength for the longitudinal connections of the real ship and compared it with the results obtained from the model tests.

• 한국항공우주학회지
• /
• 제30권4호
• /
• pp.84-91
• /
• 2002

Shroud로 감싸여 있는 제트베인의 추력 방향 조종 특성은 shoroud가 없는 제트베인의 조종 특성보다 매우 복잡하며 그 특성이 매우 특이하다. 이러한 제트 베인 시스템의 조종 특성을 파악하기 위하여 베인과 shroud 고유의 공력 특성은 물론 shroud/베인간의 유동 간섭에 대한 연구가 요구된다. 본 연구에서는 이를 위하여 반실험적인 모델링을 개발하고, 실제 기하학적 모델을 고려한 삼차원 유동해석과 실기형 연소시험을 수행하여 복잡한 물리적현상을 도출하여 shroud로 감싸여 있는 제트베인의 측력 특성을 제시하였다.