• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.271-276
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• 1995

This paper presents a systematic method for the dynamic analysis of flexible mechanical systems containing closed kinematic loops. Kinematics between pairs of contiguous flexible bodies is described with the joint coordinates and the deformation modal coordinates. The cut-joint constraint equations associated with the closed kinematic loops are derived, simply using the geometric conditions. The equations of motions are initially written in terms of the joint and modal coordinates using the velocity transformation technique. Lagrange multipliers associated with the cut-joint constraints for closed-loop systems are then eliminated systematically using the generalized coordinate partitioning method, resulting to a minimal set of equations of motion.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.54-63
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• 2002

In recent years, mechanical systems such as high speed vehicles and railway trains moving on elastic beam structures have become a very important issue to consider. In this paper, a general approach, which can predict the dynamic behavior of a constrained mechanical system moving on a flexible beam structure, is proposed. Various supporting conditions for the foundation support are considered for the elastic beam structure. The elastic structure is assumed to be a non-uniform and linear Bernoulli-Euler beam with a proportional damping effect. Combined differential-algebraic equation of motion is derived using the multi-body dynamics theory and the finite element method. The proposed equations of motion can be solved numerically using the generalized coordinate partitioning method and predictor-corrector algorithm, which is an implicit multi-step integration method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1820-1826
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• 2016

This paper deals with dynamic characteristics of the experimental magnetic levitation vehicle employing LSM(Linear Synchronous Motor) for propulsion. To predict the dynamic characteristics of the system, the dynamic model which is composed of the electrical elements such as electromagnets and LSM and mechanical components and is developed based on multibody dynamics is developed. The resulting system equations of motion for the model are a coupled one representing all the mechanical and electrical parts. To verify the dynamic model of the system, air gaps are measured in both running tests and simulation, and the frequency characteristics of air gaps are analyzed. From the results, it can be seen that the frequency responses are almost the same. Finally, to evaluate the levitation stability and the designed controller, numerical simulations are carried out.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.865-874
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• 2016

This research is concerned with the experimental investigation on the vibrations of a flexible two-link system for verifying the theoretical result from simplified equations of motion for the system along with the kinematical synthesis are proposed to simulate the elastic vibrations of a previous study. The structure consists of flexible two-links; The link 2 is attached to the end of the link 1. The link 1 is made of composite fiber reinforced polymer and the link 2 is an aluminum beam. In order to verify the theoretical result, a flexible two-link system operated by the AC and RC servo motors was constructed. Experimental results show that the dynamic modeling approach and the kinematical synthesis proposed in this paper are effective.

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

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.112-119
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• 2001

Design sensitivity is an important is an important device in improving a mechanical system design. A continuum design consists of the shape and orientation design. This research develops the shape and orientation design sensitivity method. The configura-tion design variables of multibody systems define the shape and orientation changes. The equations of motion are directly differentiated to obtain the governing equations for the design sensitivity. The governing equation of the design sensitivity is formulated as an over determined differential algebraic equation and treated as ordinary differential equations on mani-folds. The material derivative of a domain functional is performed to obtain the sensitivity due to shape and orientation changes. The configuration design sensitivities of a fly-ball governor system and a spatial four bar mechanism are obtained using the proposed method and are validated against those obtained from the finite difference method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1265-1272
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• 1988

Kinematic and dynamic equations of open-loop mechanical systems are derived using the velocity transformation. The velocities of a link are defined by the velocities of the previous link and relative velocities between the links. The velocities and angular velocities are expressed with joint velocities and 6*1 velocity transformation vector. Using the velocity relations, recursive formula are derived and compared to the previous results. The derived recursive formula are modified and applied to the dynamic simulation of a vehicle. The computational efficiency of the vehicle simulation with the derived recursive formula is much enhanced.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.576-583
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• 2000

A robust position control using a sliding mode controller is adopted for the stable dynamic walking of the biped. For the biped robot that is modeled with 14 degrees of freedom rigid bodies using the method of the multibody dynamics, the joint angles for simulation are obtained by the velocity transformation matrix using the given Cartesian foot and trunk trajectories. Hertz force model and Hysteresis damping element which is used in explanation of the energy dissipation during contact with ground are used for modeling of the ground reactions during the simulation. By the obtained that forces which contains highly confused noise elements and the system modeling uncertainties of various kinds such as unmodeled dynamics and parameter inaccuracies, the biped system will be unstable. For that problems, we are adopting a nonlinear robust control using a sliding mode controller. Under the assumption that the esimation error on the unknown parameters is bounded by a given function, that controller provides a successful way to preserve stability and achieve good performance, despite the presence of strong modeling imprecisions or uncertainties.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.377-387
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• 2005

The equations of motion of two-wheeled vehicles, e.g. bicycles or motorcycles, are developed by using Lagrange's equations for quasi-coordinates. The pure rolling constraints between the ground and the two wheels are considered in the dynamical equations of the system. For each wheel, two nonholonomic and two holonomic constraints are introduced in a set of differential-algebraic equations (DAE). The constraint Jacobian matrix is obtained by collecting all the constraint equations and converting them into the velocity form. Equilibrium, an algorithm for searching for equilibrium points of two-wheeled vehicles and the associated problems are discussed. Formulae for calculating the radii of curvatures of ground-wheel contact paths and the reference point are also given.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.444-451
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• 2005

The analysis of human arm motion during steering maneuver is carried out for investigation of man-machine interface of driver and steering system Each arm is modeled as interconnection of upper arm, lower arm, and hand by rotational joints that can properly represents permissible joint motion, and both arms are connected to a steering wheel through spring and damper at the contact points. The joint motion law during steering motion is determined through the measurement of each arm movement, and subsequent inverse kinematic analysis. Combining the joint motion law and inverse dynamic analysis, joint stiffness of arm is estimated. Arm dynamic analysis model for steering maneuver is setup, and is validated through the comparison with experimentally measured data, which shows relatively good agreement. To demonstrate the usefulness of the arm model, it is applied to study the effect of steering column angle on the steering motion.