• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.35-43
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• 1996

A computer program for automatic deriving the symbolic equations of motion for robots using the programming language MATHEMATICA has been developed. The program, developed based on the Lagrange formalism, is applicable to the closed chain robots as well as the open chain robots. The closed chains are virtually cut open, and the kinematics and dynamics of the virtual open chain robot are analyzed. The constraints are applied to the virtually cut joints. As a result, the spatial closed chain robot can be considered as a tree structured open chain robot with kinematic constraints. The topology of tree structured open chain robot is described by a FATHER array. The FATHER array of a link indicates the link that is connected in the direction of base link. The constraints are represented by Lagrange multipliers. The parallel robot, DELTA, having three-dimensional closed chains is modeled and simulated to illustrate the approach.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2543-2554
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• 1993

In this paper, the kinematic and dynamic analyses of spatial complex kinematic chain are studied. Through the new method both using the set of identification numbers and applying the DenavitHartenberg link representation method to the spatial complex kinematic chain, the kinematic configuration of the chain is represented. Some link in the part of closed chain being fictitiously cutted, the complex kinematic chain is transformed to the branched chain. The kinematic constraint equations are derived from the constraint conditions which the cutted sections of the link have to satisfy. And the joint variables being partitioned in the independent joint variables and the dependent joint variables, the dependent variables are calculated from the independent variables by using the Newton-Raphson iterative method and the pseudoinverse matrix. The equations of motion are derived under the independent joint variables by using the principle of virtual work. Algorithms for dynamic analysis are presented and simulations are done to verify accuracy and efficiency of the algorithms.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2099-2108
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• 2016

The cascaded multilevel converter is widely adopted to medium/high voltage and high power electronic applications due to the small harmonic components of the output voltage and the facilitation of modularity. In this paper, the operation principle of a T-type H-bridge topology is investigated in detail, and a carrier phase shifted pulse width modulation (CPS-PWM) based control method is proposed for this topology. Taking a virtual five-level waveform achieved by a unipolar double frequency CPS-PWM as the output object, PWM signals of the T-type H-bridge can be obtained by reverse derivation according to its switching modes. In addition, a control method for the T-type H-bridge based cascaded multilevel converter is introduced. Then a single-phase T-type H-bridge cascaded multilevel static var generator (SVG) prototype is built, and a repetitive controller based compound current control strategy is designed with the DC-link voltage balancing control scheme analyzed. Finally, simulation and experimental results validate the correctness and feasibility of the proposed modulation method and control strategy for T-type H-bridge based cascaded multilevel converters.

• Proceedings of the IEEK Conference
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• 2000.06c
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• pp.31-34
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• 2000

Genetic Algorithm is well known as the efficient algorithm which can solve a difficult optimization problem. Recently, there has been increasing interest in applying genetic algorithm to problem related to network design. In this paper, we propose a two-step genetic algorithm for designing a optimum virtual path network(VPN) for a given physical network and traffic demand. The first step is a routing step in which a route is found between every node pair in the network. In the second step, paths are assigned as VPs so as to minimize the total number of VPs configured, the number of VPs carried by a link, and the VP hopcount. We study the performance of the propose algorithm through simulation. The result shows that the VPN generated by the proposed algorithm is good in minimizing the number of VPs configured, the load on a link, and the VP hopcount.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.31-32
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• 2015

본 논문에서는 컴퓨터 망에서 동적라우팅 프로토콜로 다중영역을 지원하는 OSPF (Open Shortest Path First)를 중심으로 망 축약(summary), 타 프로톨과의 연동을 위한 재분배(redistribution), Virtual Link 등 복잡한 설정 기법을 연구하고 이를 신라대학교 LAN 구성에 적용한다. 시스코의 망 시뮬레이터 장비인 패킷트레이서를 활용하여 라우터와 스위치는 각각 2620XM Router, 2950T-24 Switch를 사용하고, 라우팅 프로토콜은 OSPF, EIGRP(Enhanced Interior Gateway Routing Protocol)를, 또한 이들 간의 연결을 위해서는 재분배를 이용하고, 다중 영역 중 백본 area에 인접하지 않는 area에 대한 연결을 위해서는 Virtual Link 등 여러 설정 기법을 사용한다. 전체 망 구성 연결 후에는 이들 설정에 대한 통신상태를 확인한다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.3
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• pp.13-20
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• 1983

A method for the detecting defined vertices is described in this paper. An alogrithm detecting vertex position by means of calculating an error and distinguishing the defined inner and outer corners by the chain code of line segments is described. To calculate the error, virtual links are detected by means of a jointing relations of line segments for a contour. And so an error is calculated by measuring a minimum distance from a jointing point between the line segments to virtual link. As a result, this method is more flexible and effective than conventional Freeman's method.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.982-985
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• 2000

This paper presents channel estimation of an asynchronous W-CDMA reverse link using the interpolation and moving average algorithm in frequency-selective Rayleigh fading channel. The proposed algorithm is an interpolated decision-directed (IDD) block-wise moving average (BWMA) algorithm. The IDD-BWMA algorithm performs two- stage processes. The first stage performs data decision to make a virtual pilot channel by using linear interpolation channel estimation scheme. Then, the second stage performs the channel estimation of the “block-wise moving average” type by using a virtual pilot channel obtained in the first stage. By using Monte-Carlo computer simulations, we show that the proposed channel estimator is superior to other estimation schemes such as the WMSA(K=1) and DD-RAKE at higher Doppler frequencies, especially.

• Proceedings of the KIEE Conference
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• summer
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• pp.1161-1165
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• 2004

The fundamental digital control of utility-connected PV inverter are presented with detailed analysis and simulation and experimental results. PLL controller using virtual two phase detector, current controller of DC-DC converter, dc link voltage controller and inverter current controller are discussed. The novel PLL controller using virtual two phase detector can detect the information of utility voltage instantaneously and is not sensitive to the noise. Current controller of DC-DC converter, dc link voltage controller and inverter current controller are the conventional methods. We have constructed utility-Connected PV Inverter and applied to those controllers. The simulation and experimental results demonstrate an excellent performance in the single-phase grid-connected operation.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2510-2512
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• 2002

In this paper, we investigated 2-DOF haptic device and the method of virtual environment modeling for virtual reality. We designed an modified five bar link system to improve the performance. The haptic control system is composed of calculating kinematics and statics, controlling actuator, and describing the virtual environment. Using this system, we realized the virtual spring model and the freely falling ball model.

• The Journal of Korea Robotics Society
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• v.8 no.3
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• pp.186-196
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• 2013

Since its introduction (e.g., [4, 6]), virtual coupling technique has been de facto way to connect a haptic device with a virtual proxy for haptic rendering and control. However, because of the single dependence on spring-damper feedback action, this virtual coupling suffers from the degraded transparency particularly during contact tasks when large device/proxy-forces are involved. In this paper, we propose a novel virtual coupling technique, which, by utilizing passive decomposition, reduces device-proxy position deviation even during the contact tasks while also scaling down (or up) the apparent inertia of the coordinated device-proxy. By doing so, we can significantly improve transparency between multiple degree of freedom (possibly nonlinear) haptic device and virtual proxy. In other to use passive decomposition, disturbance observer of [3] is adopted to estimate human force with some dead-zone modification to avoid "winding-up" force estimation in the presence of device torque saturation. Some preliminary experimental results are also given to illustrate efficacy of the proposed technique.