• International Journal of Control, Automation, and Systems
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• 제1권1호
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• pp.68-75
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• 2003

This paper presents an effective trajectory planning algorithm for industrial robot manipulators. Given the end-effector trajectory in Cartesian space, together with the relevant constraints and task specifications, the proposed method is capable of planning the optimum end-effector trajectory. The proposed trajectory planning algorithm considers the joint acceleration limit, end-effector velocity limits, and trajectory allowance. A feedforward compensator is also incorporated in the proposed algorithm to counteract the delay in joint dynamics. The algorithm is carefully designed so that it can be directly adopted with the existing industrial manipulators. The proposed algorithm can be easily programmed for various tasks given the specifications and constraints. A three-dimensional test trajectory was planned with the proposed algorithm and tested with the Performer MK3s industrial manipulator. The results verified effective manipulator performance within the constraints.

• International Journal of Control, Automation, and Systems
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• 제1권4호
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• pp.474-483
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• 2003

Belt drives provide freedom to position the motor relative to the load and this phenomenon enables reduction of the robot arm inertia. It also facilitates quick response when employed in robotics. Unfortunately, the flexible dynamics deteriorates the positioning accuracy. Therefore, there exists a trade-off between the simplicity of the control strategy to reject time varying disturbance caused by flexibility of the belt and precision in performance. Resonance of the system further leads to vibrations and poor accuracy in positioning. In this paper, accurate positioning of a belt driven mechanism using a feed-forward compensator under maximum acceleration and velocity constraints is proposed. The proposed method plans the desired trajectory and modifies it to compensate delay dynamics and vibration. Being an offline method, the proposed method could be easily and effectively adopted to the existing systems without any modification of the hardware setup. The effectiveness of the proposed method was proven by experiments carried out with an actual belt driven system. The accuracy of the simulation study based on numerical methods was also verified with the analytical solutions derived.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5191-5211
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• 2016

It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.

• 한국시뮬레이션학회논문지
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• 제24권3호
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• pp.17-26
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• 2015

생산성과 웨이퍼의 품질을 향상하기 위해 다양한 공정에서 사용되는 클러스터 장비는 단순한 구성에도 불구하고 병렬 공정모듈, 중간버퍼의 부재, 시간 제약 때문에 스케줄이 쉽지 않다. 그래서 스케줄링에 대한 많은 연구가 진행되었지만 대부분 시간이 변동되지 않는다는 가정 하에서 주기별로 동일한 스케줄이 반복되는 안정 상태를 연구하였다. 본 연구에서는 시간 제약을 만족시키면서도 원하는 안정 상태의 스케줄로 안착할 수 있는 스케줄 전략을 제시한다. 제안된 스케줄 전략은 작업시간이 지속적으로 변동되는 상황에서도 강건하다. 마지막으로 이 전략들이 실제로 강건하고, 원하는 안정 상태로 갈 수 있다는 것을 보여주기 위하여 시뮬레이션을 수행한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2529-2547
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• 2012

In this paper, we use a quadrotor-based mobile sink to gather sensor data from the terrestrial deployed wireless sensor network. By analyzing the flight features of the mobile sink node, we theoretically study the flight constraints of height, velocity, and trajectory of the mobile sink node so as to communicate with the terrestrial wireless sensor network. Moreover, we analyze the data amount which the mobile sink can send when it satisfies these flight constraints. Based on these analysis results, we propose a data acquisition approach for the mobile sink node, which is discussed detailed in terms of network performance such as the transmission delay, packet loss rate, sojourning time and mobile trajectory when given the flying speed and height of the mobile sink node. Extensive simulation results validate the efficiency of the proposed scheme.

• 한국컴퓨터정보학회논문지
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• 제22권2호
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• pp.37-44
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• 2017

Wireless sensor networks are composed of many wireless sensor nodes that are sensing the environments. These networks have many constraints that are resource constraints, wireless communication, self-construction, etc. But they have many applications that are monitoring environment, tracking the object, etc. In this paper, a mechanism of finding QoS Satisfied multi-path is proposed in wireless sensor networks. In order to satisfy the QoS requirement, the proposed mechanism extends the AODV protocol to find multiple paths from a source node to a destination node by using the additional AODV message types that are proposed. This mechanism will be used to support many QoS applications such as minimum delay time, the better reliability and the better throughput by using the QoS satisfied multi-path. Overheads of the proposed mechanism are evaluated using simulation, and it is showed that QoS satisfied multiple paths are found with a little more overhead than the AODV mechanism.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.171-173
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• 2005

To date, the IEA DSM Programme has not undertaken any work on the potential for DSM to cost-effectively relieve electricity network constraints Such constraints are becoming a significant problem in countries where electricity demand is increasing and network infrastructure ('poles and wires') is ageing. As loads grow and infrastructure reaches the end of its economic life, the potential cost of augmenting electricity networks is increasing exponentially. In many situations, network-driven DSM can delay the need for network augmentation. In some limited situations, mainly at the distribution level, network-driven DSM may be able to cost-effectively eliminate the requirement to build a 'poles and wires' solution. In this paper, the concept of network-driven DSM program is surveyed.

• Journal of Communications and Networks
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• 제12권1호
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• pp.86-94
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• 2010

In this paper, we present a decentralized algorithm to find minimum cost quality of service (QoS) flow subgraphs in network coded multicast schemes. The main objective is to find minimum cost subgraphs that also satisfy user-specified QoS constraints, specifically with respect to rate and delay demands. We consider networks with multiple multicast sessions. Although earlier network coding algorithms in this area have demonstrated performance improvements in terms of QoS parameters, the proposed QoS network coding approach provides a framework that guarantees QoS constraints are actually met over the network.

• 산업경영시스템학회지
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• 제14권23호
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• pp.19-25
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• 1991

In this paper, constrained resource project scheduling problems schedule project activities subject to finite constraints on the availability of non-storable resource. Further, resources are assumed to be available per period in constant amounts, and are also demanded by an activity in constant amounts throughout the duration of the activity. We describe formulation which minimizes the combined cost of fluctuations in resource demand and delay of project completion. Cost bounding procedures are augmented by dominance relationships presented as theorems. This paper presents algorithm for solving the problem. And numerical examples are presented. Sensitivity analysis to evaluate the effect of changes of cost efficients is conducted.

• 대한전자공학회논문지TC
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• 제45권12호
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• pp.74-82
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• 2008

본 논문에서는 다중 체인구조를 이용한 P2P 기반 IPTV 시스템을 제안한다. 제안하는 시스템은 P2P 네트워크의 특징인 peer의 빈번한 가입과 탈퇴 상황에서 단순한 과정으로 네트워크를 재구성하는 장점이 있다. 인터넷과는 달리 ISP가 관리하는 IPTV 환경은 전송회선의 속도와 안정성이 일정수준으로 보장되어 있다. 따라서 IPTV 환경에서의 P2P 네트워크는 단순성 측면을 우선적으로 고려해야 한다. 기존에 제안되어있는 단일 체인구조는 단순성을 강조하였으나 같은 채널을 시청하는 peer의 개수가 증가하면 체인의 끝 부분에 연결되어 있는 peer는 상당한 delay가 발생한다. 제안하는 시스템은 이러한 delay 문제를 해결하기 위하여 체인을 여러 개의 레벨로 분리하고 각 레벨은 다시 span으로 나누었다. 레벨과 span으로 분리를 하였지만 기본적인 구조는 체인구조이므로 peer가 join 하거나 departure 할 경우에 단순한 네트워크의 재구성 과정을 제공한다. 수치적인 해석을 통해 본 논문에서 제안한 다중 체인구조를 이용한 P2P 시스템이 단일 체인구조 방식에 비해 delay 및 신뢰도 성능이 우수하다는 것을 보여준다.