• ETRI Journal
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• v.17 no.1
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• pp.23-36
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• 1995

We present a performance evaluation model of cell reassembly mechanism in an ATM switching system. An ATM switching system may be designed so that communications between processors of its control part can be performed via its switching network rather than a separate inter-processor communications network. In such a system, there should be interface to convert inter-processor communication traffic from message format to cell format and vice versa, that is, mechanisms to perform the segmentation and reassembly sublayer. In this paper, we employ a continuous-time Markov chain for the performance evaluation model of cell reassembly mechanism with individual buffering, judicially defining the states of the mechanism. Performance measures such as message loss probability and average reassembly delay are obtained in closed forms. Some numerical illustrations are given for the performance analysis and dimensioning of the cell reassembly mechanism.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.2
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• pp.20-27
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• 1996

In this paper, we propose a coprime factor model reduction method to get a reduced order controller in $H^{\infty}$ mixed sensitivity problem with frequency weighting functions. for this purpose, the given $H^{\infty}$ mixed sensitivity problem is transformed into robust stabilization problem with coprime factor uncertainty of given plant. This method is to define frequency weighted coprime factors of plant in CSD (chain scattering description) form and reduce the coprime factors using weighted balanced truncation. then a controller is designed to the reduced order coprime factors using J-lossless coprime factorization method. Using this approach, the robust stability condition is derived and good performance is preserved in closed loop system with the given plant and the reduced order controller. Also the order of reduced controller for guaranteeing the robust stability can be determined before designing the reduced controller. The proposed method behaves well in both stable and unstable plant.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.4
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• pp.240-245
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• 2014

How well the self-interference cancellation (SIC) technique performs is a primary issue in realizing an in-band full-duplex (FD) wireless communication system. One factor affecting its performance is channel estimation error on the self-interference channel. We propose a new analog SIC scheme which is robust to channel estimation error. It uses phase rotators in the radio frequency (RF) chain. We also derive closed-form equations for the residual self-interference of the proposed and the conventional schemes. The analytical and numerical results show that the residual self-interference under the proposed SIC scheme is less than that using the conventional scheme, even though channel estimation error is present.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.144-147
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• 2001

The planar tracked vehicle model used in this investigation consists of two kinematically decoupled subsystem, i.e., the chassis subsystem and the track subsystem. The chassis subsystem include the chassis frame, sprocket, idler and rollers, while the track subsystem is represented as a closed kinematic chain consisting of rigid links interconnected by revolute joints, In this paper, the recursive kinematic and dynamic formulation of the tracked vehicle is used to find the vertical forces and the distances of the certain track moved in the driving direction along the track. These distances and vertical forces obtained are used to calculate the sinkage of a terrain. The FEM is adopted to analyze the interaction between the tracked vehicle and terrain. The terrain is represented by a system of elements with specified constitutive relationships and considered as a piecewise linear elastic, plastic and isotropic material. When the tracked vehicle is moving with different speeds on the terrain, the elastic and plastic deformations and the maximum sinkage for the four different types of a isotropic soil are simulated.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1156-1161
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• 1990

The concept of the manipulability measure of the robotic mechanism is extended to the dual arm holding a single object. This is a measure of manipulating ability of the dual arm forming a closed kinematic chain in positioning and orienting the object. Dual arm manipulability measure is defined and compared to the single arm manipulability measure, and some properties are investigated.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.145-148
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• 1990

In this paper, the problem of designing a feedback controller for a robotic manipulator, which is activated by a D.C. motor through a gear train and a flexible shaft or chain, is considered. When the response of the closed loop control system is relatively slow, a satisfactory controller may be designed as a PID controller. As the speed of the control system increases, however, the spring effect of the linkage becomes profound, and as a result, the transient response exhibits a substantial oscillation. To eliminate this oscillation, it is necessary to design the controller based on at least a fourth order system model. This, in turn, requires the feedback of the entire state variables. In practice, however, only the position of the manipulator and the velocity of the motor are readily measurable. The state variable reconstruction method or a state observer cannot be used because of the system nonlinearities such as the Coulomb frictions. In this study, an alternative controller, which is based on delayed feedback of the output variable only, is proposed, and a successful delayed feedback controller is designed and implemented on an actual experimental manipulator.

• Journal of the Korean Arthroscopy Society
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• v.1 no.1
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• pp.86-90
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• 1997

Good stability and complete range of motion should be the ultimate goal of a rehabilitation program after ACL reconstruction. In previous years. the rehabilitation of the ACL reconstructed knee focused on protecting the new ligament by blocking terminal knee extension, hut, despite good stability, this approach led to numerous postoperative complications. Nowadays, most of surgeons agree the accelerated rehabilitation program based on the concept of ligamentization and clinical experience. Accelerated rehabilitation program consists of maintain of full extension of the knee, early weight bearing and prompt recovery of ROM, and closed kinetic chain exercise. Meeting this goal requires effective communication between-members of the health care team-the physician, physical therapist, atheletic trainer, and the patient. We have to know the importance of rehabilitation, knowlege about the physical therapy, and to introduce for special physical therapist and equipment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.540-543
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• 2002

Conventional robot manipulators actuated by motors with the speed reducer such as the harmonic drive have weakness in the load capacity, since the speed reducer does not have enough strength. To overcome this, we proposed and constructed a new type of the robot actuator which is four-bar-link mechanism driven by the ball screw. We developed a new type of a revolute-jointed robot manipulator composed of four axes. The base axis is actuated with conventional speed reducer, but the others are actuated by the proposed actuators. We analyzed the mechanism of the actuators of the robot joints, and developed the dynamics model. The dynamics are expressed in the joint coordinates, and then they are mapped into the sliding coordinates of the ball screw. The structure specifications of the manipulator shown.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.24-31
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• 1998

In this study, a procedure is presented for the dynamic analysis of a multibody tracked vehicle system. The planar vehicle model used in this investigation is assumed to consist of two kinematically decoupled subsystems. i.e., the chassis subsystem and track subsystem. The chassis subsystem includes the chassis frame, sprocket, idler and rollers, while the track subsystem is represented as a closed kinematic chain consisting of rigid links interconnected by revolute joints. The nonlinear contact force modules describing the interaction between track links, and sprocket, idler, rollers and ground will be developed.

• The Journal of Korean Physical Therapy
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• v.12 no.2
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• pp.239-247
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• 2000

Knowledge of the anatomy and biomechanics of the knee is critical fur successful rehabilitation fellowing knee injury and surgery. Biomechanics of both the tibiofemoral and patellofemoral joints must be considered. The purpose of this paper is to provid framework for rehabilitation of the knee by reviewing the biomechanics of the tibiofemoral and patellofemoral joints. This will include discussion of the relevant arthrokinematics as well as the effects of open and closed chain exercises. The implications for rehabilitation of the knee will be highlighted.