• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8C
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• pp.793-800
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• 2005

Computation of multimedia data increases in portable devices with the advances of the mobile and personal communication services. The energy management of such devices is very important for the battery-powered operation hours. The motion estimation in a video encoder requires huge amount of computation, and hence, consumes the largest portion of the energy consumption. In this paper, we propose a novel architecture that a low energy management scheme can be applied with several fast-search algorithms. The energy-constrained Vdd hopping (ECVH) technique reduces power consumption of the motion estimation by adaptively changing the search algorithm, the operating frequency, and the supply voltage using the remaining slack time within given power-budget. We show that the ECVH can be applied to the architecture, and that the power consumption can be efficiently reduced.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.550-559
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• 2004

In this paper, a recursive formulation for generating the equations of motion of spatial mechanical systems is presented. The rigid bodies are replaced by a dynamically equivalent constrained system of particles which avoids introducing any rotational coordinates. For the open-chain system, the equations of motion are generated recursively along the serial chains using the concepts of linear and angular momenta Closed-chain systems are transformed to open-chain systems by cutting suitable kinematic joints and introducing cut-joint constraints. The formulation is used to carry out the dynamic analysis of multi-link five-point suspension. The results of the simulation demonstrate the generality and simplicity of the proposed dynamic formulation.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.8 no.2
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• pp.75-86
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• 2004

In this study, a recursive algorithm for generating the equations of motion of a chain of rigid rods is presented. The methods rests upon the idea of replacing the rigid body by a dynamically equivalent constrained system of particles. The concepts of linear and angular momentums are used to generate the rigid body equations of motion without either introducing any rotational coordinates or the corresponding transformation matrices. For open-chain, the equations of motion are generated recursively along the serial chains. For closed-chain, the system is transformed to open-chain by cutting suitable kinematic joints with the addition of cut-joints kinematic constraints. An example of a closed-chain of rigid rods is chosen to demonstrate the generality and simplicity of the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.619-624
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• 2007

Spectral element method (SEM) is introduced for the fully coupled structural dynamic problems, In this paper, the beam with passive constrained layered damping (PCLD) treatments is considered as a representative problems. The beam consists of a viscoelastic layer that is sandwiched between the base beam structure and an elastic layer, The fully coupled equations of motion for a PCLD beam are derived, The equations of motion are derived first by using Hamilton's principle, From this equations of motion, the spectral element is formulated for the vibration analysis by use of the SEM, As an illustrative example, a cantilevered beam is considered. It is shown that, as the thickness of VEM layer vanishes, the results become a simple layer beam's that.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.8 s.197
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• pp.122-129
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• 2007

To evaluate the effect of artificial disc implantation and fusion on the biomechanics of adjacent motion segment, a nonlinear three-dimensional finite element model of whole lumbar spine (L1-S1) was developed. Biomechanical analysis was performed for two different types of artificial disc, ProDisc and SB $Charit{\acute{e}}$ III model, inserted at L4-L5 level and these results were also compared with fusion case. Angular motion of vertebral body, forces on the spinal ligaments and facet joint under sagittal plane loading with a compressive preload of 150 N at a nonlinear three-dimensional finite element model of Ll-S1 were compared. The implant did not significantly alter the kinematics of the motion segment adjacent to the instrumented level. However, $Charit{\acute{e}}$ III model tend to decrease its motion on the adjacent levels, especially in extension motion. Contrast to motion and ligament force changes, facet contact forces were increased in the adjacent levels as well as implanted level for constrained instantaneous center of rotation model, i.e. ProDisc model.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.176-184
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• 2000

Recently, it becomes a very important issue to consider the mechanical systems such as high-speed vehicle and railway train moving on a flexible beam structure. Using general approach proposed in the first part of this paper, it tis possible to predict planar motion of constrained mechanical system and elastic structure with various kinds of foundation supporting condition. Combined differential-algebraic equations of motion derived from both multibody dynamics theory and Finite Element Method can be analyzed numerically using generalized coordinate partitioning algorithm. To verify the validity of this approach, results from simply supported elastic beam subjected to a moving load are compared with exact solution from a reference. Finally, parameter study is conducted for a moving vehicle model on a simply supported 3-span bridge.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.71-78
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• 2003

This research proposes an implementation method of linearized equations of motion for multibody systems with closed loops. The null space of the constraint Jacobian is first pre-multiplied to the equations of motion to eliminate the Lagrange multiplier and the equations of motion are reduced down to a minimum set of ordinary differential equations. The resulting differential equations are functions of all relative coordinates, velocities, and accelerations. Since the variables are tightly coupled by the position, velocity, and acceleration level coordinates, direct substitution of the relationships among these variables yields very complicated equations to be implemented. As a consequence, the reduced equations of motion are perturbed with respect to the variations of all variables, which are coupled by the constraints. The position velocity and acceleration level constraints are also perturbed to obtain the relationships between the variations of all relative coordinates, velocities, and accelerations and variations of the independent ones. The Perturbed constraint equations are then simultaneously solved for variations of all variables only in terms of the variations of the independent variables. Finally, the relationships between the variations of all variables and these of the independent ones are substituted into the variational equations of motion to obtain the linearized equations of motion only in terms of the independent variables variations.

• Journal of Mechanical Science and Technology
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• v.16 no.1
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• pp.83-93
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• 2002

This paper presents a motion control method and its simulation results of a mobile robot for a lattice type welding. Its dynamic equation and motion control methods for welding speed and seam tracking are described. The motion control is realized in the view of keeping constant welding speed and precise target line even though the robot is driven for following straight line or curve. The mobile robot is modeled based on Lagrange equation under nonholonomic constraints and the model is represented in state space form. The motion control of the mobile robot is separated into three driving motions of straight locomotion, turning locomotion and torch slider control. For the torch slider control, the proportional-integral-derivative (PID) control method is used. For the straight locomotion, a concept of decoupling method between input and output is adopted and for the turning locomotion, the turning speed is controlled according to the angular velocity value at each point of the corner with range of 90$^{\circ}$ constrained to the welding speed. The proposed control methods are proved through simulation results and these results have proved that the mobile robot has enough ability to apply the lattice type welding line.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1303-1308
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• 2003

This research proposes an implementation method of linearized equations of motion for multibody systems with closed loops. The null space of the constraint Jacobian is first pre-multiplied to the equations of motion to eliminate the Lagrange multiplier and the equations of motion are reduced down to a minimum set of ordinary differential equations. The resulting differential equations are functions of ail relative coordinates, velocities, and accelerations. Since the coordinates, velocities, and accelerations are tightly coupled by the position, velocity, and acceleration level constraints, direct substitution of the relationships among these variables yields very complicated equations to be implemented. As a consequence, the reduced equations of motion are perturbed with respect to the variations of all coordinates, velocities, and accelerations, which are coupled by the constraints. The position, velocity and acceleration level constraints are also perturbed to obtain the relationships between the variations of all relative coordinates, velocities, and accelerations and variations of the independent ones. The perturbed constraint equations are then simultaneously solved for variations of all coordinates, velocities, and accelerations only in terms of the variations of the independent coordinates, velocities, and accelerations. Finally, the relationships between the variations of all coordinates, velocities, accelerations and these of the independent ones are substituted into the variational equations of motion to obtain the linearized equations of motion only in terms of the independent coordinate, velocity, and acceleration variations.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.893-898
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• 2004

This research proposes an implementation method of linearized equations of motion for multibody systems with closed loops. The null space of the constraint Jacobian is first pre multiplied to the equations of motion to eliminate the Lagrange multiplier and the equations of motion are reduced down to a minimum set of ordinary differential equations. The resulting differential equations are functions of all relative coordinates, velocities, and accelerations. Since the coordinates, velocities, and accelerations are tightly coupled by the position, velocity, and acceleration level constraints, direct substitution of the relationships among these variables yields very complicated equations to be implemented. As a consequence, the reduced equations of motion are perturbed with respect to the variations of all coordinates, velocities, and accelerations, which are coupled by the constraints. The position, velocity and acceleration level constraints are also perturbed to obtain the relationships between the variations of all relative coordinates, velocities, and accelerations and variations of the independent ones. The perturbed constraint equations are then simultaneously solved for variations of all coordinates, velocities, and accelerations only in terms of the variations of the independent coordinates, velocities, and accelerations. Finally, the relationships between the variations of all coordinates, velocities, accelerations and these of the independent ones are substituted into the variational equations of motion to obtain the linearized equations of motion only in terms of the independent coordinate, velocity, and acceleration variations.