• Journal of Mechanical Science and Technology
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• v.17 no.9
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• pp.1287-1296
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• 2003

In this paper the dynamic analysis of the Macpherson strut motor-vehicle suspension system is presented. The equations of motion are formulated using a two-step transformation. Initially, the equations of motion are derived for a dynamically equivalent constrained system of particles that replaces the rigid bodies by applying Newton's second law The equations of motion are then transformed to a reduced set in terms of the relative joint variables. Use of both Cartesian and joint variables produces an efficient set of equations without loss of generality For open chains, this process automatically eliminates all of the non-working constraint forces and leads to an efficient solution and integration of the equations of motion. For closed loops, suitable joints should be cut and few cut-joints constraint equations should be included for each closed chain. The chosen suspension includes open and closed loops with quarter-car model. The results of the simulation indicate the simplicity and generality of the dynamic formulation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.155-162
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• 2015

Abalone (Haliotis discus hannai) is a shellfish that feeds on kelp and, as a product, it can often achieve a high market value. However, the dissolved oxygen (DO) levels in coastal waters in Korea have been negatively impacted by pollution from many anthropogenic sources. Herein, a computational fluid dynamics (CFD) software package was used to analyze the distribution of the DO concentration within an abalone containment structure. A finite volume approach was used to solve the Reynolds-averaged Navier-Stokes equations combined with a $k-{\varepsilon}$ turbulence model to describe the flow. The distribution of DO was determined within the control volume domain, and the transport equations of the pollutants were interpreted using a CFD model. The CFD analysis revealed that more than 60% and 30% of the relative oxygen concentration in one and two containers, respectively, was maintained when the flow acts along the six sheets of polyethylene plates. Therefore, it is clear that the abalone plate shelters should be placed parallel to the flow.

• Journal of KSNVE
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• v.7 no.3
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• pp.387-392
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• 1997

This paper concerns a SCARA robot with the flexible forearm linked to the rigid upper arm. The equations of motion are derived by the Lagrangian mechanics. For controller design, the perturbation approach is taken to separate the original equations of motion into linear equations describing small perturbed motions and nonlinear equations describing purely rigid motion of the robot. To effect the desired payload motion, open loop control inputs are determined based on the inverse dynamics of the latter. In order to reduce the positional error during maneuver, an active vibration suppression is done. To this end, a feedback control is designed for robustness against disturbance on the basis of the linear equations and the LQR theory modified to have a prescribed degree of stability. The proposed control scheme shows satisfactory performances in experiments as well as in numerical simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.809-818
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• 1997

An efficient non-recursive formulation of dynamic force analysis has been developed for serially connected multibody systems. Although derivation of equations of motion is based on a recursive dynamic formulation with joint relative coordinates, in the proposed formulation, dynamic forces such as joint reaction forces and driving force are computed non-recursively for specified joints. The efficiency of the proposed formulation has been proved by the operational count and the CPU time measure, comparing with that of the conventional recursive Newton-Euler formulation. A simulation of 7-DOF RRC robot arm has been carried out to validate solutions of reaction forces by comparing with those from a commercial dynamic analysis program DADS.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1090-1096
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• 2001

In this paper, new methods for efficiently solving linear acceleration equations of multibody dynamic simulation exploiting sparsity for real-time simulation are presented. The coefficient matrix of the equations tends to have a large number of zero entries according to the relative joint coordinate numbering. By adequate joint coordinate numbering, the matrix has minimum off-diagonal terms and a block pattern of non-zero entries and can be solved efficiently. The proposed methods, using sparse Cholesky method and recursive block mass matrix method, take advantages of both the special structure and the sparsity of the coefficient matrix to reduce computation time. The first method solves the η$\times$η sparse coefficient matrix for the accelerations, where η denotes the number of relative coordinates. In the second method, for vehicle dynamic simulation, simple manipulations bring the original problem of dimension η$\times$η to an equivalent problem of dimension 6$\times$6 to be solved for the accelerations of a vehicle chassis. For vehicle dynamic simulation, the proposed solution methods are proved to be more efficient than the classical approaches using reduced Lagrangian multiplier method. With the methods computation time for real-time vehicle dynamic simulation can be reduced up to 14 per cent compared to the classical approach.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.352-360
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• 1997

An inverse dynamic procedure for spatial multibody systems containing flexible bodies is developed in the relative joint coordinate space. Constraint acceleration equations are derived in terms of relative coordinates using the velocity transformation technique. An inverse velocity transformation operator, which transforms the Cartesian velocities to the relative velocities, is derived systematically corresponding to the types of kinematic joints connecting the bodies and the system reference matrix. Using the resulting matrix, the joint reaction forces and moments are analyzed in the Cartesian coordinate space. The formulation is illustrated by means of two numerical examples.

• Journal of applied mathematics & informatics
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• v.31 no.1_2
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• pp.111-118
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• 2013

External excitations are employed to investigate properties of optical media, with measurement data often analyzed via linear response theory. In this respect, external forcing is modeled here by well-known Poisson and negative-binomial distributions. Ensuing dynamics is examined with a special attention to the relative decay rates of damped harmonic oscillators to such external forcing, along with its relationship to other physical phenomena.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.289-292
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• 1994

In this paper, the equations of motion are constructed systematically for multibody systems containing closed kinematic loops. For the displacement analysis of the closed loops, we introduce a new mixed coordinates by adding to the reference coordinates, relative coordinates corresponding to the degrees of freedom of the system. The mixed coordinates makes easy derive the explicit closed form solution. The explicit functional relationship expressed in closed form is of great advantages in system dimension reduction and no need of an iterative scheme for the displacement analysis. This forms of equation are built up in the general purpose computer program for the kinematic and dynamic analysis of multiboty systems.

• Bulletin of the Korean Mathematical Society
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• v.35 no.1
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• pp.157-172
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• 1998

A numerical method is proposed for dynamical systems. We utilize the fact that special matrix exponentials can be exactly evaluated by the intrinsic library functions. Numerical examples are given, which show that the relative error s of the proposed method converge to a small constant and that the method faithfully approximates the dynamics of the nonlinear differential equations.

• Wind and Structures
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• v.6 no.6
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• pp.451-470
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• 2003

The classical two-degree-of-freedom (2-d-o-f) "sectional model" is of common use to study the dynamics of suspension bridges. It takes into account the first pair of vertical and torsional modes of the bridge and describes well global oscillations caused by wind actions on the deck, yielding very useful information on the overall behaviour and the aerodynamic and aeroelastic response; however, it does not consider relative oscillations between main cables and deck. On the contrary, the 4-d-o-f model described in the two Parts of this paper includes longitudinal deformability of the hangers (assumed linear elastic in tension and unable to react in compression) and thus allows to take into account not only global oscillations, but also relative oscillations between main cables and deck. In particular, when the hangers go slack, large nonlinear oscillations are possible; if the hangers remain taut, the oscillations remain small and essentially linear: the latter behaviour has been the specific object of Part I (Sepe and Augusti 2001), while the present Part II investigates the nonlinear behaviour (coexisting large and/or small amplitude oscillations) under harmonic actions on the cables and/or on the deck, such as might be generated by vortex shedding. Because of the discontinuities and strong nonlinearity of the governing equations, the response has been investigated numerically. The results obtained for sample values of mechanical and forcing parameters seems to confirm that relative oscillations cannot a priori be excluded for very long span bridges under wind-induced loads, and they can stimulate a discussion on the actual possibility of such phenomena.