• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1571-1578
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• 2013

With the emergence of high-integration array and large area panel process, the need to minimize the generation of particles in the field of semiconductor, LCD and OLED has grown. As an alternative to the conventional roller system, a contactless magnetic conveyor has been proposed to reduce the generation of particles. An EM-PM hybrid which is one of magnetic levitation types is already proposed for the conveyor system. One of problems pointed out with this approach is the vibration caused by the dynamic interaction between conveyor and rail. To reduce the vibration, the introduction of a secondary suspension system which aims to decouple the levitation electromagnet from the main body is proposed. The objective of this study is to develop a dynamic model for the magnetically levitated conveyor, and to investigate the effect of the introduced suspension system. An integrated model of levitation system and rail based on 3D multibody dynamic model is proposed. With the proposed model, the dynamic characteristics of maglev conveyor system are analyzed, and the effect of the secondary suspension and the stiffness and damping are investigated.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.810-818
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• 2002

When the contribution of lightweight components to the total energy of a system is small, tole inertia effects are sometimes ignored by replacing them to massless links. For example, a revolute-spherical massless link generates two kinematic constraint equations between adjacent bodies and allows four relative degrees of freedom. In this paper, to implement a massless link systematically in a computer program using the velocity transformation technique, the velocity transformation matrix of massless links is derived and numerically implemented. The velocity transformation matrix for a revolute-spherical massless link and a revolute-universal massless link are appeared as a 6$\times$4 matrix and a 6$\times$3 matrix, respectively. A massless link model in a suspension composite joint transmitting external forces is also developed and the numerical efficiency of the proposed model is compared to a conventional multibody model. For a massless link transmitting external forces, forces acting on links are resolved and transmitted to the attached points with a quasi-static assumption. Numerical examples are presented to verify the formulation.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.699-722
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• 2019

It is difficult to observe the potential risks of lifting or turn-over operations in the early stages before a real operation. Therefore, many dynamic simulations have been designed to predict the risks and to reduce the possibility of accidents. These simulations, however, have usually been performed for predetermined and fixed scenarios, so they do not reflect the real-time control of an operator that is one of the most important influential factors in an operation; additionally, lifting or turn-over operations should be a collaboration involving more than two operators. Therefore, this study presents an integrated method for a collaborative simulation that allows multiple workers to operate together in the virtual world. The proposed method is composed of four components. The first component is a dynamic analysis that is based on multibody-system dynamics. The second component is VR (virtual reality) for the generation of realistic views for the operators. The third component comprises the control devices and the scenario generator to handle the crane in the virtual environment. Lastly, the fourth component is the HLA (high-level architecture)-based integrated simulation interface for the convenient and efficient exchange of the data through the middleware. To show the applicability of the proposed method, it has been applied to a block turn-over simulation for which one floating crane and two crawler cranes were used, and an offshore module installation for which a DCR (dual-crane rig) was used. In conclusion, the execution of the proposed method of this study is successful regarding the above two applications for which multiple workers were involved.

• International Journal of Automotive Technology
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• 제3권4호
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• pp.129-135
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• 2002

Durability estimation of a prototype vehicle has traditionally relied heavily on accelerated durability tests using predefined proving grounds or rig tests using a road simulator. By use of those tests, it is very difficult to predict durability failures in actual service environments. This motivated the development of an integrated CAE (Computer Aided Engineering) methodology for the durability estimation of a prototype vehicle in actual service environments. Since expensive computational costs such as computation time and hardware resources are required for a full vehicle simulation in those environments with a very long span of event time, the conventional CAE methodologies have little feasibility. An efficient computational methodology for durability estimations is applied with theoretical developments. The effectiveness of the proposed methodology is shown by the comparison of results of the typical actual service environment such as the city mode with those of the typical accelerated durability test over the Belgian road.

• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.550-559
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• 2004

In this paper, a recursive formulation for generating the equations of motion of spatial mechanical systems is presented. The rigid bodies are replaced by a dynamically equivalent constrained system of particles which avoids introducing any rotational coordinates. For the open-chain system, the equations of motion are generated recursively along the serial chains using the concepts of linear and angular momenta Closed-chain systems are transformed to open-chain systems by cutting suitable kinematic joints and introducing cut-joint constraints. The formulation is used to carry out the dynamic analysis of multi-link five-point suspension. The results of the simulation demonstrate the generality and simplicity of the proposed dynamic formulation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.718-723
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• 2007

A three dimensional multibody modeling of a launcher system was developed and dynamic characteristics of the system was carried out. All the components were modeled as rigid bodies, All the components of system, ie; chassis, turret, cage and suspension parts, are modeled as rigid. The force interaction between the ground and tire was modeled as a point contact model. The factors were selected as cause and effect diagram of the MINITAB. To see effect of the stiffness, damping, mass at the launcher system, several cases of suspension parameters were compared and optimal values were selected. The stiffness and the damping coefficient were selected as design variables to minimize the required time for the next fire. The dynamic simulation was carried out using the ADAMS, and the MINITAB was employed for data analysis.

• 농업과학연구
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• 제50권3호
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• pp.457-468
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• 2023

The purpose of this study is to develop a high-speed combine harvester. The performance was evaluated by composing a dynamic simulation model of a threshing cylinder and analyzing the amount of threshed rice grain during threshing operations. The rotational speed of the threshing cylinder was set at 10 rpm intervals from 500 rpm until 540 rpm, based on the rated rotational speed of 507 rpm. The rice stem model was developed using the EDEM software using measured rice stem properties. Multibody dynamics software was utilized to model the threshing cylinder and tank comprising five sections below the threshing cylinder, and the threshing performance was evaluated by weighing the grain collected in the threshing tank during threshing simulations. The simulation results showed that section 1 and 2 threshed more grains compared to section 3 and 4. It was also found that when the threshing speed was higher, the larger number of grains were threshed. Only simulation was conducted in this study. Therefore, the validation of the simulation model is required. A comparative analysis to validate the simulation model by field experiment will be conducted in the future.

• 대한기계학회논문집A
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• 제36권6호
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• pp.681-689
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• 2012

본 연구에서는 병렬 연결된 해상 크레인을 이용하여 5,000ton 이상의 기가 블록급 대형 중량물을 인양할 때 해상 크레인과 대형 중량물 사이에 연결된 와이어 로프에 작용하는 장력을 계산하기 위해 다물체계 동역학 시뮬레이션을 수행하였다. 이를 위해, 해상 크레인, 바지선, 대형 중량물은 각각 6 자유도 운동을 하고, 이들 사이에는 서로간의 구속에 의한 연성을 가지도록 모델링 하였다. 또한 해상 크레인 및 바지선에 작용하는 외력으로 유체 정역학 힘과 유체 동역학 힘을 고려하였고, 각각의 물체에 독립적으로 작용한다고 가정하였다. 본 시뮬레이션 결과, 향후 해상크레인을 병렬 연결하여 대형 중량물을 인양하는 공법의 안정성을 확인하고 공학적인 지침을 마련할 수 있는 근간이 될 수 있으리라 예상한다.

• 드라이브 ㆍ 컨트롤
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• 제14권2호
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• pp.23-29
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• 2017

In this study, a flexible multi-body dynamic simulation model of a knuckle boom crane is developed to evaluate the stress of spindle and rack gears under dynamic working conditions. It is difficult to predict potential critical damage to a knuckle boom crane if only the static condition is considered during the development process. To solve this issue, a severe working scenario (high speed with heavy load) was simulated as a boundary condition for testing the integrity of the dynamic simulation model. The crane gear model is defined as a flexible body so contact analysis was performed. The functional motion of a knuckle boom crane is generated by applying forces at each end of the rack gear, which was converted from hydraulic pressure measured for the experiment. The bending and contact stress of gears are theoretically calculated to validate the simulation model. In the simulation, the maximum stress of spindle and rack gears are observed when the crane abruptly stops. Peak impact force is produced at the contact interface between pinion and rack gears due to the inertia force of the boom. However, the maximum stress (bending/contact) of spindle and rack are under the yield stress, which is safe from damage. By using the developed simulation model, the experiment process is expected to be minimized.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.984-989
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• 2008

An estimation of high-order damping in flexible multibody dynamic simulation is introduced in this paper. The suggested damping model based on the experimental modal analysis leads to more accurate correlation results comparing to the traditional linear damping model because it directly uses the modal parameters of each mode achieved from experiment even high frequency modes. The modal parameters until the 5th mode are extracted from the experimental modal testing of the flexible beam using a high speed camera. And using the measured damping ratio and natural frequency until the 5th mode, the generic damping model is constructed. Then, the ANCF (absolute Nodal Coordinate Formulation) simulation results are compared to experimental results until the 5th mode.