• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.109-114
• /
• 2007

Analytical method to analyze the effect of tolerance on the modal characteristic of multi-body systems in dynamic equilibrium position is suggested in this paper. Monte-Carlo Method is conventionally employed to perform the tolerance analysis. However, Monte-Carlo Method spends too much time for analysis and has a greater or less accuracy depending on sample condition. To resolve these problems, an analytical method is suggested in this paper. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivities of damped natural frequencies and the transfer function can be calculated at the dynamic equilibrium position. The effect of tolerance on the modal characteristic can be analyzed from tolerance analysis method.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.5
• /
• pp.363-373
• /
• 2014

In this study, computational multi-body dynamic analyses for the drivetrain system of a 5 MW class offshore wind turbine have been conducted using efficient equivalent modeling technique based on the design guideline of GL 2010. The present drivetrain system is originally modeled and its related system data is adopted from the NREL 5 MW wind turbine model. Efficient computational method for the drivetrain system dynamics is proposed based on an international guideline for the certification of wind turbine. Structural dynamic behaviors of drivetrain system with blade, hub, shaft, gearbox, supports, brake disk, coupling, and electric generator have been analyzed and the results for natural frequency and equivalent torsional stiffness of the drivetrain system are presented in detail. It is finally shown that the present multi-body dynamic analysis method gives good agreement with the previous results of the 5 MW class wind turbine system.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.3
• /
• pp.169-175
• /
• 2015

This study aims to improve the dynamic stiffness of an inspection robot frame to prevent derailment from transmission lines. Finite element models for the transmission lines and robot frame are developed for the multi-body dynamic simulation. Natural frequency analysis was conducted using the FE models. Three types of spacer damper clamps installed on 4-conductor transmission lines are used to evaluate the derailment of the robot. Multi-body dynamic simulations with FE models are demonstrated for sub-span oscillation. When the robot operates, derailment of inspection robot from the transmission lines is determined because of resonance. To prevent the resonance, body position was changed and thickness optimization was conducted. The results show that derailment was not occurred because of the natural frequency improvement.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.5
• /
• pp.51-55
• /
• 2002

This paper presents a systematic methodology and formulation for determining optimal strategies of multi-body dynamic systems, which is based on multi-body dynamics, design sensitivity, and optimization techniques, and is applicable to a wide variety of mechanical systems. The particular application discussed in this paper considers a vehicle model with four-wheel steeling capability, and the presented methodology determines an optimal steering angle ratio strategy for the vehicle. It is shown that such a strategy can improve the ride stability of the vehicle, during a variety of maneuvers, when compared against similar strategies obtained from linear and simplified vehicle models.

• Journal of Mechanical Science and Technology
• /
• v.19 no.spc1
• /
• pp.350-356
• /
• 2005

A method of dynamic analysis of mechanical systems considering probabilistic properties is proposed in this paper. Probabilistic properties that result from manufacturing tolerances can be represented by means and standard deviations (or variances). The probabilistic characteristics of dynamic responses of constrained multi-body systems are obtained by two ways : the proposed analytical approach and the Monte Carlo simulation. The formerpaper, necessitates sensitivity information to calculate the standard deviations. In this a direct differentiation method is employed to find the sensitivities of constrained multi-body systems. To verify the accuracy of the proposed method, numerical examples are solved and the results obtained by using the proposed method are compared to those obtained by Monte Carlo simulation.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.11
• /
• pp.1146-1154
• /
• 2008

This paper presents a method for the acceleration analysis of multi-legged walking robots in consideration of the frictional ground contact. This method is based on both unified dynamic equation for finding the acceleration of a robot's body and constraint equation for satisfying no-slip condition. After the dynamic equation representing relationship between actuator torques and body acceleration, is derived from the force and acceleration relationship between foot and body's gravity center, the constraint equation is formulated to reconfigure the maximum torque boundaries satisfying no-slip condition from given original actuator torque boundaries. From application of the reconfigured torques to the dynamic equation, interested acceleration boundaries are obtained. The approach based on above two equations, is adapted to the changes of degree-of-freedoms of legs as well as friction of ground. And the method provides the maximum translational and rotational acceleration boundaries of body's center that are achievable in every direction without occurring slipping at the contact points or saturating all actuators. Given the torque limits in infinite normsense, the resultant accelerations are derived as a polytope. From the proposed method, we obtained achievable acceleration boundaries of 4-legged and 6-legged walking robot system successfully.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.336-341
• /
• 2003

In this paper, resonance durability analysis technique is presented for the fatigue life assessment considering dynamic effect of a vehicle system. In the resonance durability analysis, the frequency response and the dynamic load on frequency domain are used. Multi-body dynamic analysis, finite element analysis, and fatigue life prediction method are applied for the virtual durability assessment. To obtain the frequency response and the dynamic load, the computer simulations running over typical pothole and Belgian road are carried out by utilizing vehicle dynamic model. The durability estimations on the rear suspension system of the passenger car are performed by using the presented technique and compared with the quasi-static durability analysis. The study shows that the fatigue life considering resonant frequency of vehicle system can be effectively estimated in early design stage.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.9 s.180
• /
• pp.2266-2273
• /
• 2000

Equations of motion of a multi-beam system undergoing overall rigid body motion are derived by employing finite element method. An orientation angle is employed to allow the arbitrary orientation o f the beam element. Modal coordinate reduction technique, which has been successfully utilized in the conventional linear modeling method, is employed for the present modeling method to reduce the computational effort. Different from the conventional linear modeling method, the present modeling method captures the motion-induced stiffness variations which are important for the dynamic analysis of structures undergoing overall rigid body motion. The numerical results are compared to those of a commercial program to verify the reliability of the present method.

• International Journal of Safety
• /
• v.6 no.1
• /
• pp.7-10
• /
• 2007

In this paper, we found that modification of the local flexibility (or local stiffness) of the 4 parts on which shock absorbers are mounted in the vehicle body has some influence the level of ride safety and comfort. Multi-body dynamic analysis considering the flexibility of the vehicle body is performed using MSC/ADAMS and MSC/NASTRAN. More concretely speaking, natural frequencies and mode shapes computed by MSC/NASTRAN are used as input data for multi-body dynamic analysis in MSC/ADAMS. It is confirmed that the ride comfort can be improved by appropriately changing the local stiffness of the vehicle body through several simulations using MSC/ADAMS.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.1
• /
• pp.28-38
• /
• 2012

The characteristics of vibration and noise of a compressor used for electric appliances have significant influence on the quality of the products. For improvement on the quality of electric appliances, investigations for understanding the dynamic behaviour of the compressor are essential. Since Virtual Lab for the dynamics model and MAXWELL for the electromagnetics model are separate software programs with no interface, the joint simulation of the models could not be performed. This study suggests a way to develop the compressor model capable of the joint simulation with MATLAB/SIMULINK linking a flexible multi-body dynamics model, a torque model, and an electricity control model. The compressor model is found to be able to perform I/O data transfer among the sub-models and joint simulation. The simulation results of the flexible body and rigid body dynamics models were compared to check availability of the joint simulation system. In addition, the simulated vibration and driving torque of the compressor mechanisms were compared with measurements. Through the simulations, the influence of springs and LDT on the dynamic behaviour of the compressor was examined. This study examines the influence of the dynamic behaviour of the compressor mechanisms through joint simulation of the flexible multi-body dynamics model and electromagnetic circuit allows analysis.