• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.167-178
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• 2017

The steering wheel of a vehicle has a typical characteristic of automatically returning to its neutral state when the driver releases it. Steering returnability originated from the tire forces and kingpin moments. It is proportional to the reaction torque that is generated through the rack and column, which are dependent on suspension and steering geometry. It is also important to accurately predict and design it because steering returnability is related to steering performance. In this study, a detailed multibody dynamics model of a vehicle was designed by using ADAMS/Car and simulated for steering returnability. In addition, a tolerance analysis of the chassis system in terms of part dimension and properties has been performed in order to minimize the design parameters. The sensitivity of the selected design parameters was then analyzed via Design of Experiments(DOE). As a result, we were able to obtain the main parameters through a contribution analysis. It can be used to predict steering returnability and improve its performance, which is represented by the angle of restoration and laterality.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.80-88
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• 2000

This paper presents a method to optimize the bump steer characteristics (the change of toe angle with vertical wheel travel) with respect to hard points in the double wishbone front suspension of the four-wheel-drive vehicle using the design of experiment, multibody dynamics simulation, and optimum design program. Front and rear suspensions are modeled as the interconnection of rigid bodies by kinematic joints and force elements using DADS. The design variables with respect to the kinematic characteristics are obtained through the experimental design sensitivity analysis. An object function is defined as the area of absolute differences between the desired and experimental toe angle. By the design of experiment and regression analysis, the regression model function of bump steer characteristics is extracted. The design variables that make the toe angle optimized are selected using the optimum design program DOT. The lane change simulations and tests of the full vehicle models are implemented to evaluate the improvement of vehicle handling performances by the optimization of front bump steer characteristics. The results of the lane change simulations show that the vehicle with optimized bump steer has the weaker understeer tendency than the vehicle with initial bump steer.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.997-1002
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• 2007

A guideway vehicle is used in automobile, semiconductor and LCD manufacturing industries to transport products efficiently. Since the operating speed of the guideway vehicle should be increased for maximum productivity, the weight of the vehicle has to be reduced. This may cause parts in the system to fail before the life of the system. Therefore estimation of the fatigue life of the parts becomes an important problem. In this study, the fatigue life of the driving wheel in the guideway vehicle is estimated using a S-N curve. To obtain the fatigue life of a part, the S-N curve, load time history applied on a driving wheel and material property are required. The S-N curve of the driving wheel is obtained using the fatigue experiment on wheels. Load time history of the wheel is obtained from multibody dynamics analysis. To obtain the material properties of the driving wheel, which is composed of aluminum with urethane coating, a compression hardware testing has been done with the static analysis of the FE model. The fatigue life prediction using computational analysis model guarantees the safety of the vehicle at the design stage of the product.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.10
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• pp.261-268
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• 2021

Cloud computing is a computing paradigm in which users can utilize computing resources in a pay-as-you-go manner. In a cloud system, resources can be dynamically scaled up and down to the user's on-demand so that the total cost of ownership can be reduced. The Modeling and Simulation (M&S) technology is a renowned simulation-based method to obtain engineering analysis and results through CAE software without actual experimental action. In general, M&S technology is utilized in Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), Multibody dynamics (MBD), and optimization fields. The work procedure through M&S is divided into pre-processing, analysis, and post-processing steps. The pre/post-processing are GPU-intensive job that consists of 3D modeling jobs via CAE software, whereas analysis is CPU or GPU intensive. Because a general-purpose desktop needs plenty of time to analyze complicated 3D models, CAE software requires a high-end CPU and GPU-based workstation that can work fluently. In other words, for executing M&S, it is absolutely required to utilize high-performance computing resources. To mitigate the cost issue from equipping such tremendous computing resources, we propose HEMOS-Cloud service, an integrated cloud and cluster computing environment. The HEMOS-Cloud service provides CAE software and computing resources to users who want to experience M&S in business sectors or academics. In this paper, the economic ripple effect of HEMOS-Cloud service was analyzed by using industry-related analysis. The estimated results of using the experts-guided coefficients are the production inducement effect of KRW 7.4 billion, the value-added effect of KRW 4.1 billion, and the employment-inducing effect of 50 persons per KRW 1 billion.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.590-595
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• 2007

It is important to predict the collision behavior of a train consist to improve its crashworthiness. To analyze crash behavior of train, four kinds of methods are mainly used so far. The first is method using multibody dynamics to predict the gross motion of the train set. The second uses 3D FE model to apply the section analysis method in order. The third is used to deduce design specification and evaluate the crashworhiness of a train by using 1D model. The last is to constitute 2D model to check overriding and coupling devices. The train evaluation procedures are so complex that it is difficult to understand or deal with. In this study, VTM for railway train was introduced to simplify the procedures. VTM involves 3D models, 1D models and dynamic components such as suspension and coupling. The method using hybrid concept model makes it possible to do all the things that are mentioned above. To analyze crash behavior tendency of VTM, the model was simulated and the simulation results were discussed.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.5
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• pp.491-496
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• 2015

Electric handbike can be easily detachable to various sizes of manual wheelchair and the elderly and people with disabilities can use them easily. Therefore, connectors used for coupling between the handbike and manual wheelchair must secure structural stability for occupant safety. However, related research is rare. The aim of this study is to find the connector with highly structural stability by comparing static and dynamic mechanical characteristics among three typical connectors(a snatch lock, a slide latch, and a fastener) by computational simulations. To perform static and dynamic simulation, we referred to durability test based on Korean Standards and then calculated mechanical stresses in connectors. The results showed that the snatch lock addressed the lowest von-mises stress under the same mechanical condition. Therefore when using the combination of a handbike and a wheelchair, we concluded that the snatch lock is considered as the structurally stable connector to structural stability and usability.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.5-11
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• 2011

In this paper, the dynamic response analysis of a floating crane with elastic booms and a cargo is performed. The objective is to consider the effects of the elastic boom in the lifting design stage. Governing equations of the motion for the system which consists of interconnected rigid and flexible bodies are derived based on the formulation of flexible multibody system dynamics. To model the boom as a flexible body, floating reference frame and nodal coordinates are used. Coupled surge, pitch, and heave motion of the floating crane with the cargo which has 3 degree of freedom is simulated by solving the equation numerically. Finally, the effects of the elastic boom for the lifting design that the floating crane is required to lift a heavy cargo are discussed by comparing the simulation result between with the elastic boom and with the rigid one.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.62-68
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• 2019

The aim of this study was to interpret the structure and dynamics of a transfer shuttle system as a material supply device for small machine tools. The following conclusions were obtained by performing a structural interpretation of the material supply equipment with respect to workload and the dynamical interpretation of a flexible multibody carriage shuttle. When a 1,000-kg workload was applied to a fork lift, the safety factor was approximately 1.86. To conservatively assess the integrity of the structure, a 1,000-kg workload would be proper. In the case of a deflection of the fork system, the width increased with increasing time. The greatest deflection occurred at 5.5 s, which was the largest increase in the time point of the fork system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.7-14
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• 2019

A marine turning gear controls the position of the piston-crank mechanism by rotating the flywheel of the marine engine at a low speed, which is the main auxiliary machine that enables the disassembly and maintenance of the engine. In this study, the safety factor for surface durability and tooth bending strength was improved by the design modification of the marine turning gear based on the spur planetary gear. Angular velocity, torque, and efficiency of the turning gear were measured using a reliability evaluation tester, and a multibody dynamics model for analysis corresponding to the test results was developed. Finally, it was confirmed that the design improvements improved the tooth surface damage of the sun gear in the 3^rd reduction stage.

• Korean Journal of Agricultural Science
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• v.50 no.3
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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.