• Proceedings of the KSME Conference
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• 2008.11a
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.99-108
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• 2005

This paper represents an efficient modeling method of a suspension system for the vehicle dynamic simulation. The suspension links are modeled as composite joints. The motion of wheel is defined as relative one degree of freedom motion with respect to car body. The unique relative kinematic constraint formulation between the car body and wheel enables to derive equations of motion in terms of wheel vertical motion. Thus, vehicle model has ten degrees of freedom. By using velocity transformation method, the equations of motion of the vehicle is systematically derived without kinematic constraints. Various vehicle simulation such as J-turn, slowly increasing steer, sinusoidal sweep steer and bump run has been performed to verify the validity of the suggested vehicle model.

• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.1-6
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• 2013

A SIM card socket is used for a cell phone to fix an USIM card and a push-push mechanism is typically employed in the SIM card socket for a user convenience. A SIM card is inserted with locking when a user pushes the card once and a SIM card is removed with unlocking when a user pushes the card again. A push-push mechanism is operated by a heart-cam structure and a main spring. A cam slider and a cam stick consisting a push-push mechanism may be broken because of the main spring. So, dynamic stress at a cam slider and a cam stick which is generated by a main spring during operating should be analyzed and considered in the push-push mechanism design. In this paper, a flexible multibody model of a push-push mechanism was developed to analyze dynamic stress at a cam slider and a cam stick.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.777-783
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• 2007

Since the performance of the circuit breaker mainly depends on the spring operating mechanism, the analysis of the spring operating mechanism is required. The spring, especially closing spring, stores the deformation energy due to the compression and then accelerates the big loads rapidly in the circuit breaker. To accurately carry out the kinematic and dynamic analysis of the circuit breaker, the precise modeling of the spring behavior is necessary. In this paper, the static stiffness of the spring is captured by using the tester. A simple mechanism similar to the spring operating mechanism was designed to generate the release motion of the spring. A high speed camera was used to capture the behavior of the spring. Three types of spring models such as a linear spring model, modal spring model, and nodal spring model are suggested and compared with the experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.686-689
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• 2005

A numerical simulation method is developed to analyze the dynamic response of a cantilever switch, which is driven by electrostatic force and a basic component of electro-mechanical coupled system. First, point-charges model on conductor is proposed as a lumped parameter of electrical part. Then, this model is easily incorporated into a multi-body dynamics analysis algorithm, the generalized recursive dynamics formula previously developed by our research group. The resulting motion of a coupled overall system is formulated as a differential algebraic equation form including electrical and mechanical variables together. The equation is simultaneously solved in every time step. To implement this approach into the useful dynamics analysis tool, we used multibody dynamics software (RecurDyn) based on the generalized recursive formula using relative coordinate. The developed numerical simulation tool is evaluated by applying to many different driving condition and switch configuration. The final analysis model will be added to RecurDyn as a basic module for dynamics analysis of electro-mechanical coupled system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.585-592
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• 2014

In this study, a multibody simulator was developed to analyze the bio-mimetic motion of a lizard robot design. A RecurDyn multibody dynamics model of a lizard was created using a micro-computerized tomography scan and motion capture data. The bio-mimetic motion simulator consisted of a trajectory generator, an inverse kinematics module, and an inverse dynamics module, which were used for various walking motion analyses of the developed lizard model. The trajectory generation module produces spinal movements and gait trajectories based on the lizard's speed. Using the joint angle history from an inverse kinematic analysis, an inverse dynamic analysis can be carried out, and the required joint torques can be obtained for the lizard robot design. In order to investigate the effectiveness of the developed simulator, the required joint torques of the model were calculated using the simulator.

• Journal of Biosystems Engineering
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• v.27 no.3
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• pp.185-194
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• 2002

The objective of this study was to analyze a stability of sideways overturning of a forwarder developed by the Forestry Research Institute. The stability analysis was conducted using a multibody dynamic analysis program. VisualNastran Desktop. A solid model of the forwarder was constructed and its physical properties such as mass, mass center and mass moment of inertia were determined on 3D CAD modeler of the Solid Edge 8.0. 3D simulations of sideways overturning of the forwarder were also performed on the Visual Nastran using the solid model when it traveled across the slope and traversed over an up-hill side obstacle. Stability comparison between a bogie-wheeled and a 6-wheeled forwarders was also made and found that the bogie-wheeled forwarder was more stable than the 6-wheeled one on slopes. The safety speeds of the forwarder predicted by the simulation under various conditions can be used as a guideline for safe operations of forwarders in mountainous area. The technique of using a solid model for the sability analysis can also be applied successfully to other vehicles like agricultural tractors, loaders and construction equipments.

• Journal of Drive and Control
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• v.14 no.2
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.132-139
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• 1997

It is difficult for most of passenger cars to attach various types of suspensions. The modular experimental vehicle, which is designed to exchange suspension systems, has been developed to evaluate the effect of design changes of a suspension upon ride and handling characteristics of a vehicle. In order to enable the assemblage between modules, the experimental vehicle design is based on a space frame construction through finite element analysis. Moreover, module frames and brackets are designed using three-dimensional solid modeler to check the interference between each part of a vehicle. Steady-state and transient road tests were performed. Multibody dynamic model and simplified linear vehicle model are made to compare with the tests. The results of simulations and tests show the performance and validity of this experimental vehicle.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.86-94
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• 1995

For a driving vehicle, a self-excited vibration of a pair of steerable wheels about their steering axis accompanied by tramp is called shimmy. Shimmy is caused by the coupling effects of the complicated actions of wheel and tire and the tramp motion of front wheel axle. Because front axle is no longer used on passenger cars shimmy occurring is not considerable. But in commercial vehicles using front wheel axle suspension system shimmy should be considered in design process. In this paper, the model closed to a practical vehicle was developed to analyze the shimmy of a commercial vehicle, and the effects of various design parameters to shimmy were observed by dynamic simulation with multibody dynamics program, DADS. The validity of developed model and analysis results were verified by practical vehicle experiments.