• Journal of the Korean Mathematical Society
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• 제52권5호
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• pp.929-944
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• 2015

We give a quotient of the ring ${\mathbb{Q}}[A^{{\pm}1},\;t^{{\pm}1]$ so that the Miyazawa polynomial is a non-trivial invariant of welded links. Furthermore we show that this is also an invariant under the other forbidden move $F_u$, and so it is a fused isotopy invariant. Also, we give some quotient ring so that the index polynomial can be an invariant for welded links.

• Journal of Power System Engineering
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• 제5권2호
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• pp.79-86
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• 2001

A method is presented for generating the path which significantly reduces residual vibration of the redundant, flexible robot manipulator in the presence of obstacles. The desired path is optimally designed so that the system completes the required move with minimum residual vibration, avoiding obstacles. The dynamic model and optimal path are effectively formulated and computed by using special moving coordinate, called VLCS, to represent the link flexibility. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of design variables. A planar three-link manipualtor is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate path, in the presence of obstacles.

• Proceedings of the KIEE Conference
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.500-503
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• 1990

Neural network is a computational model of the biological nervous system developed to exploit its intelligence and parallelism. Applying neural networks to robots creates many advantages over conventional control methods such as learning, real-time control, and continuous performance improvement through training and adaptation. In this paper, dynamic control of a six-link robot will be presented using neural networks. The neural network model used in this paper is the backpropagation network. Simulated control of the PUMA 560 arm shows that it can move at high speed as well as adapt to unforseen load changes. The results are compared with the conventional PD control scheme.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.534-539
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• 1988

This paper presents a method to balance the links of an articulated robot for an unknown payload using an automatic balancing mechanism. The balancing masses are controlled to move in their appropriate locations so that the joint torques of the links are eliminated. After balancing the mass of the payload is obtained from the balancing conditions. Based upon a series of simulation studies some results are discussed.

• The KIPS Transactions:PartC
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• 제10C권5호
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• pp.647-656
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• 2003

In Webspace, mining traversal patterns is to understand user's path traversal patterns. On this mining, it has a unique characteristic which objects (for example, URLs) may be visited due to their positions rather than contents, because users move to other objects according to providing information services. As a consequence, it becomes very complex to extract meaningful information from these data. Recently discovering traversal patterns has been an important problem in data mining because there has been an increasing amount of research activity on various aspects of improving the quality of information services. This paper presents a Dynamic Link Recommendation (DLR) algorithm that recommends link sets on a Web site through mining frequent traversal patterns. It can be employed to any Web site with massive amounts of data. Our experimentation with two real Weblog data clearly validate that our method outperforms traditional method.

• Journal of Satellite, Information and Communications
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• 제2권1호
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• pp.14-20
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• 2007

The Korean Military Satellite Communication System (KMILSATCOM) is composed of military payload of KOREASAT 5 and military satellite terminals. The military satellite terminals communicate with each other in satellite service area. The satellite terminal management system is developed for centralized management of satellite terminals and communications link. The satellite terminal management system dose not use terrestrial networks (i.e. Fiber optic, Microwave) for management because the KMILSATCOM is system for emergency (i.e. war time) and the satellite terminals has to move to operational area, so the management link must use satellite link. The management link is composed of 1 to N communication scheme for one manager and multiple terminals. This paper describes the satellite terminal management protocol architecture and the performance of the protocol of the KMILSATCOM system.

• Journal of Advanced Navigation Technology
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• 제14권2호
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• pp.198-205
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• 2010

Any user in Ubiquitous environments have to be able to access networks in anywhere and anytime. Thus interests and researches are increasing. In this paper, we propose an interface selection scheme that adaptively utilizes a proper interface, as the wireless channel condition changes, instead of utilizing only one interface while the node is in move. The proposed scheme can determine which interface would be the most proper one by measuring data rate, packet error rate (PER), and end-to-end delay of each interface. From the simulation results, it is verified that the proposed scheme is able to enhance packet transmission about 20% better.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 춘계학술대회
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• pp.810-815
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• 2004

In this paper, we propose new parallel mechanism of a 3 dimensional biped robot whose each leg is composed of two 3-dof parallel platforms linked serially. This proposed parallel mechanism is able to move freely in the man-made environment and is applied to various fields, such as medical, welfare, and so on. And a total weight of each leg is expected to be lighter than serial linked leg. One side leg consists of a 3-dof orientation platform and 3-dof asymmetric parallel platform. The former consists of three active linear actuators and seven passive joints, and the latter of two active linear actuators, one active rotational actuator and eight passive joints. Thus, there are two kinds of parallel platforms each chain's elements and active joint's positions are different for the biped robot to move freely like a serial link without the kinematics constraints. The effectiveness and the performance of the proposed parallel mechanism and locomotion trajectory are shown in computer simulations with a 12-DOF parallel biped robot.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제39C권9호
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• pp.757-766
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• 2014

To compensate signal loss due to the channel blockage in satellite communication link, we propose a cooperative communication scheme for OTM(On-The-Move) terminal in next generation satellite communication systems. The proposed scheme configures cooperation subnet with adjacent OTM terminal with the help of ground communication equipment. Shared data is spread by orthogonal spreading code, then the spread sequences are transmitted simultaneously. The receiver combines the power of received signals by EGC(Equal gain combining). The OTM terminal blockage channel is modeled by 2-state Markov chain. We evaluate the bit error rate according to the blockage channel of the channel state for the performance analysis of the proposed scheme. As a result, the proposed scheme shows better BER performance than traditional scheme with the help of subset members. In particular, the proposed scheme shows superior performance as the channel block probability is higher. However, as the number of subset members is increasing, there is a constraint because of the higher multiple access interference.

• Journal of the Korea Institute of Military Science and Technology
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• 제10권1호
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• pp.44-54
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• 2007

In the military field, according to the MIL-STD-188-220, which is an Ad-Hoc communication protocol used for sending out or receiving data and voice smoothly among nodes in the situation that wireless communication nodes move arbitrarily, data communication is cut off because nodes can not know topology changes perpetually in the link disconnection state due to node movement in the case that transmitters do not confirm whether data is delivered to receivers or not, and transmit only the data having routine precedence continuously. In order to solve this problem, we have proposed the technique that makes efficient data communication possible by achieving a rapid topology change detection and link information update using TEST frame. We have analyzed TEST frame application effects in the two aspects of the topology update delay time and the data transmission success ratio.