• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.5
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• pp.541-549
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• 2008

The dynamic contact between a high-speed wheel and an elastic beam is numerically analyzed by solving the whole equations of motion of the wheel and the beam subjected to the contact condition. For the stability of the numerical solution, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Through the numerical examples, it is shown that the acceleration contact constraint including the Coriolis and centripetal accelerations are crucial for the numerical stability.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.159-167
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• 2000

A computational method for the dynamic analysis of a constrained mechanical system is presented in this paper. The partial velocity matrix, which is the null space of the Jacobian of the constraint equations, is used as the key ingredient for the derivation of reduced equations of motion. The acceleration constraint equations are solved simultaneously with the equations of motion. Thus, the total number of equations to be integrated is equivalent to that of the pseudo generalized coordinates, which denote all the variables employed to describe the configuration of the system of concern. Two well-known conventional methods are briefly introduced and compared with the present method. Three numerical examples are solved to demonstrate the solution accuracy, the computational efficiency, and the numerical stability of the present method.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.6
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• pp.705-713
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• 1999

In this paper, we propose a new motion and force control methodology for constrained robots as an approach of hybrid discrete-continuous dynamical system. The hybrid dynamic system modeling of robotic manipulation tasks with constraints is presented, and the hybrid system control architecture for unconstrained and constrained motion system with parametric uncertainties is synthesized. The optimal reference stiffness of robot manipulator is generated by the hybrid automata as a discrete state system and the control behavior of constrained system which has poor modeling information and time-varying constraint function is improved by the constrained robots as a continuous state system. The performance of the proposed constrained motion control system is successfully evaluated via experimental studies to the constraint tasks.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.725-730
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• 2000

Genetic algorithms based on the theory of natural selection, have been applied to many different fields, and have proven to be relatively robust means to search for global optimum and handle discontinuous or even discrete data. Genetic algorithms are widely used for unconstrained optimization problems. However, their application to constrained optimization problems remains unsettled. The most prevalent technique for coping with infeasible solutions is to penalize a population member for constraint violation. But, the weighting of a penalty for a particular problem constraint is usually determined in the heuristic way. Therefore this paper proposes, the effective technique for handling constraints, the ranking penalty method and hybrid genetic algorithms. And this paper proposes dynamic mutation tate to maintain the diversity in population. The effectiveness of the proposed algorithm is tested on several test problems and results are discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.185-191
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• 2001

In many papers, the powertrain system generally has been madeled as one-dimensional torque model. One-dimensional powertrain model may calculate the torque correctly but it does not consider the non-rotational degrees-of-freedom of the powertrain components and the interaction of these degrees-of-freedom with the vehicle body frame and suspension. To consider the non-rotational degrees of freedom, the differential is modeled as a three-dimensional rigid body in this paper. A constant velocity joint is newly formulated and a relative constraint is also formulated to model the motion transfer due to gear ratio of the differential. Implementing the proposed powertrain system in the multibody model, more detail dynamic responses can be obtained. Obtained outputs such as reaction torques on the constant velocity joint and reaction forces on the rack can be useful data in the design of a powertrain.

• Journal of Industrial Technology
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• v.29 no.A
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• pp.183-190
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• 2009

This study deals with the single-product production and transportation model with dynamic demand over finite time horizon, in which the optimal production(order) quantities, transportation modes and the number of each vehicles are determined simultaneously. The finite number of identical vehicles with capacity constraint is given to each mode. Production and transportation costs are assumed to be concave function for generality. For a relevant mathematical model formulated, the theorems and properties are discussed to present the efficient algorithm. A numerical example is solved to illustrate the algorithm developed.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.673-674
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• 2011

본 논문에서는 OBS 망의 에지 라우터에서 소비되는 에너지를 절감하기 위한 통제 기반 동적 버스트 어셈블 알고리즘 (Constraint based Dynamic Burst Assemble algorithm : CDBA) 을 제안한다. 기존의 버스트 어셈블 알고리즘은 망의 성능 및 QoS (Quality of Service) 만을 고려한 고정된 버스트 어셈블 임계값을 사용하였으나 제시한 알고리즘은 에지 라우터에서 발생하는 에너지 소비율을 감소시키면서도 버스트 길이 및 패킷 지연과 같은 지표를 일정 수준이내로 유지함으로써 망의 성능을 보장한다. 제시한 알고리즘 평가를 위해 OPNET Modeler 를 사용하여 시뮬레이션을 수행하였으며, 에너지 절감율 및 패킷 지연 시간 관점에서 기존의 버스트 어셈블 알고리즘과 성능을 비교, 분석하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.415-426
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• 2007

In a link motion punch press, numerous links are interconnected and each link executes a constrained motion at high speed. As a consequence, dynamic unbalance force and moment are transmitted to the main frame of the press, which results in unwanted vibration. This degrades productivity and precise stamping work of the press. This paper presents an effective method for reducing dynamic unbalance in a link motion punch press based upon kinematic and dynamic analyses. Firstly, the kinematic analysis is carried out in order to understand the fundamental characteristics of the link motion mechanism. Then design variable approach is presented in order to automate the model setup for the mechanism whenever design changes are necessary. To obtain the inertia properties of the links such as mass, mass moment of inertia, and the center of mass, 3-dimensional CAD software was utilized. Dynamic simulations were carried out for various combinations of design changes on some links having significant influences on kinematic and dynamic behavior of the mechanism.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.8
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• pp.875-881
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• 2014

The redundancy resolution of the seven DOF (Degree of Freedom) upper limb exoskeleton is key to the synchronous motion between a robot and a human user. According to the seven DOF human arm model, positioning and orientating the wrist can be completed by multiple arm configurations that results in the non-unique solution to the inverse kinematics. This paper presents analysis on the kinematic and dynamic aspect of the human arm movement and its effect on the redundancy resolution of the seven DOF human arm model. The redundancy of the arm is expressed mathematically by defining the swivel angle. The final form of swivel angle can be represented as a linear combination of two different swivel angles achieved by optimizing two cost functions based on kinematic and dynamic criteria. The kinematic criterion is to maximize the projection of the longest principal axis of the manipulability ellipsoid of the human arm on the vector connecting the wrist and the virtual target on the head region. The dynamic criterion is to minimize the mechanical work done in the joint space for each of two consecutive points along the task space trajectory. The contribution of each criterion on the redundancy was verified by the post processing of experimental data collected with a motion capture system. Results indicate that the bimodal redundancy resolution approach improved the accuracy of the predicted swivel angle. Statistical testing of the dynamic constraint contribution shows that under moderate speeds and no load, the dynamic component of the human arm is not dominant, and it is enough to resolve the redundancy without dynamic constraint for the realtime application.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.68-70
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• 1998

본 논문에서는 클록들을 주기적으로 동기화하는 분산 실시간 시스템에서 주어진 태스크의 시간 제약(timing constraint)을 변환시는 구가지 기법을 제안한다. 전형적인 이산 클록 동기화(discrete clock synchronization)알고리즘은 클록의 값을 순간적으로 보정(correct)하여 클록의 시간이 불연속적으로 진행학 한다. 이러한 시간상의 불연속성은 태스크의 시작제한시간(release time)이나 종료시한(deadline)과 같은 이벤트를 잃어버리거나 다시 발생시키는 오류를 범하게 한다. 클록 시간의 불연속성을 피하기 위해 일반적으로 연속 클록 동기화(continuous clock synchronization) 기법이제안되었지만 소프트웨어적으로 구현되기에는 많은 오버헤드를 유발시키는 문제점이 있다. 이에 따라 연속 클록 동기화는 PLL (Phase-Locked Loop)을 이용한 별도의 하드웨어를 사용하는 것이 보통이다. 본 논문에서는 연속 클록 동기화 기법을 사용하는 대신, 태스크의 시간 제약을 동적으로 변환시키는 DCT (Dynamic Constraint Transformation) 기법을 제안하였다. DCT는 소프트웨어 으로 구현이 가능하여 새로운 하드웨어를 필요로 하지 않으며, 이를 통해 기존의 이산적으로 동기화된 시스템에서 클록 시간의 불연속성에 의한 문제점들을 해결할 수 있다. 또 다른 문제점으로서, 클록의 물리적인 특성으로 인해 동기화된 클록들이 상한된(bounded from the above)오차(skew)를 갖는다는 것이다. 이러한 오차는 지역 클록(local clock)에 대해 만족될 수 있는 임의의 실기간 제약 조건이 전역 클록(global clock)에 대해서는 만족되지 않을 수 있음을 의미한다. 본 논문에서는 이를 위해 먼저 두 가지의 스케줄링 가능성, 지역적 스케줄링 가능서(local schedulability)과 전역적 스케줄링 가능성(global schedulability)을 정의하고, 실시간 제약을 정적으로 변환시키는 SCT (Static Constraint Transformation)기법을 제안하였다. SCT를 통해 지역적으로 스케줄링 가능한 태스크는 전역적으로 스케줄링이 가능하므로, 단지 지역적 스케줄링 가능성만을 검사하면서 스케줄링 문제를 해결할 수 있도록 하였다.