• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.445-449
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• 1989

Achievement of a straight line motion in the Cartesian space has a matter of great importance. Minimization of task execution time with linear interpolation in the joint space, accomplishing of a approximation of straight line motion in the Cartesian coordinate is considered as the prespecified task. Such determination yields minimum time joint-trajectory subject to input torque constraints. The applications of these results for joint-trajectory planning of a two-link manipulator with revolute joints are demonstrated by computer simulations.

• International Journal of Contents
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• 제1권2호
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• pp.31-34
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• 2005

The new realtime applications like multimedia and realtime services in a wireless network will be dramatically increased. However, many realtime services of mobile hosts in a cell cannot be continued because of insufficiency of useful channels. Conventional channel assignment approaches didn't properly consider the problem to serve realtime applications in a cell. This paper proposes a new realtime channel assignment algorithm based on time constraint analysis of channel requests. The proposed algorithm dynamically borrows available channels from neighboring cells. It also supports a smooth handoff which continuously serves realtime applications of the mobile hosts.

• Journal of Information Technology Applications and Management
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• 제23권2호
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• pp.61-80
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• 2016

The wireless mesh network (WMN) is a next-generation technology for data networking that has the advantage in cost and the flexibility in its construction because of not requiring the infra-structure such as the ethernet. This paper focuses on the optimal link scheduling problem under the wireless mesh network to effectuate real-time streaming by using the constraint programming. In particular, Under the limitation of half-duplex transmission in wireless nodes, this paper proposes a solution method to minimize the makespan in scheduling packet transmission from wireless nodes to the gateway in a WMN with no packet transmission conflicts due to the half-duplex transmission. It discusses the conflicts in packet transmission and deduces the condition of feasible schedules, which defines the model for the constraint programming. Finally it comparatively shows and discusses the results using two constraint programming solvers, Gecode and the IBM ILOG CP solver.

• 제어로봇시스템학회논문지
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• 제20권3호
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• pp.235-244
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• 2014

This article introduces recent trends in RHC (Receding Horizon Control), also known as MPC (Model Predictive Control), that has been well recognized in industry and academy as a systematic approach for optimal design and constraint management. Constrained and robust RHCs will be briefly reviewed with milestone results. Among the diverse developments and achievements of RHCs, implementation issues will be focused on, together with the latest applications. In particular, this article introduces results on how to solve a finite horizon open-loop optimal control problem in an efficient way, together with code generation for real-time execution and easy implementation. Instead of traditional applications such as refineries and petrochemical plants, this article highlights some selected emerging applications, such as energy management systems and mechatronics, that have resulted from state-of-the-art high performance computing power and advanced numerical schemes.

• Journal of information and communication convergence engineering
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• 제8권2호
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• pp.212-218
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• 2010

In wireless sensor networks (WSNs), both efficient energy management and Quality of Service (QoS) are important issues for some applications. For creating robust networks, real-time services are usually employed to satisfy the QoS requirements. In this paper, we proposed a hierarchical real-time MAC (medium access control) protocol for (m,k)-firm constraint in wireless sensor networks shortly called HRTS-MAC. The proposed HRTS-MAC protocol is based on a dynamic priority assignment by (m,k)-firm constraint. In a tree structure topology, the scheduling algorithm assigns uniform transmitting opportunities to each node. The paper also provides experimental results and comparison of the proposed protocol with E_DBP scheduling algorithm.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권2호
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• pp.196-200
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• 2008

최근 공간 네트워크 데이타베이스를 위한 질의처리 알고리즘에 관한 연구가 많이 진행되어 왔으나, 경로-기반 질의에 대한 연구는 매우 미흡한 실정이다. 공간 네트워크 데이타베이스에서는 이동객체가 공간 네트워크상에서만 이동하기 때문에 LBS(Location-Based Services) 및 Telematic와 같은 응용에서는 경로-기반 질의가 매우 유용하게 사용된다. 따라서 본 논문에서는 경로-기반 질의의 대표적인 방법인 경로 내 최근접(In-Route Nearest Neighbor, IRNN) 질의처리 알고리즘을 분석하고, 시간 제약을 지닌 새로운 경로 내 최근접 질의처리 알고리즘을 제안한다. 아울러, 성능 분석을 통하여 시간 제약을 지닌 제안하는 질의처리 알고리즘이 기존 경로 내 최근접 질의처리 알고리즘에 비하여 검색 성능이 우수함을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권1호
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• pp.185-201
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• 2023

Grant-free random access (GFRA) can reduce the access delay and signaling cost, and satisfy the short transmission packet and strict delay constraints requirement in internet of things (IoT). IoT is a major trend in the future, which is characterized by the variety of applications and devices. However, most existing studies on GFRA only consider a single type of device and omit the effect of access delay. In this paper, we study GFRA in multicell massive multipleinput multiple-output (MIMO) systems where different types of devices with various configurations and requirements co-exist. By introducing the backoff mechanism, each device is randomly activated according to the backoff parameter, and active devices randomly select an orthogonal pilot sequence from a predefined pilot pool. An analytical approximation of the average spectral efficiency for each type of device is derived. Based on it, we obtain the optimal backoff parameter for each type of devices under their delay constraints. It is found that the optimal backoff parameters are closely related to the device number and delay constraint. In general, devices that have larger quantity should have more backoff time before they are allowed to access. However, as the delay constraint become stricter, the required backoff time reduces gradually, and the device with larger quantity may have less backoff time than that with smaller quantity when its delay constraint is extremely strict. When the pilot length is short, the effect of delay constraints mentioned above works more obviously.

• Journal of Mechanical Science and Technology
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• 제16권8호
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• pp.1072-1078
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• 2002

The constrained motion requires the determination of constraint force acting on unconstrained systems for satisfying given constraints. Most of the methods to decide the force depend on numerical approaches such that the Lagrange multiplier method, and the other methods need vector analysis or complicated intermediate process. In 1992, Udwadia and Kalaba presented the generalized inverse method to describe the constrained motion as well as to calculate the constraint force. The generalized inverse method has the advantages which do not require any linearization process for the control of nonlinear systems and can explicitly describe the motion of holonomically and/or nongolonomically constrained systems. In this paper, an explicit equation to describe the constrained motion is derived by minimizing the performance index, which is a function of constraint force vector, with respect to the constraint force. At this time, it is shown that the positive-definite weighting matrix in the performance index must be the inverse of mass matrix on the basis of the Gauss's principle and the derived differential equation coincides with the generalized inverse method. The effectiveness of this method is illustrated by means of two numerical applications.

• 정보처리학회논문지C
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• 제16C권1호
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• pp.65-72
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• 2009

모바일 장치의 증가와 무선 네트워크 기술의 발전으로 인해 새롭게 모바일 애드혹 네트워크에 대한 관심이 증가하고 있다. 최근까지의 연구는 데이터 접근성(Accessibility) 향상을 위해 데이터 복사본 활용이 효율적임을 증명하였다. 그러나, 데이터 복사본이 모바일 애드혹 네트워크에서 활용되기 위해서는 원본과 복사본 사이에 일관성(Consistency)이 확보되어야만 한다. 기존의 연구에서 사용되고 있는 일관성 확보 기법은 원본을 가진 노드에게 복사본 사용 노드들이 매번 일관성을 가지는지 확인하는 기법이 활용되었다. 그러나, 시간제약을 가지는 응용의 경우 원본을 가진 노드에게 확인하는 기법은 효율적이지 못하거나 때로는 심각한 문제를 일으킬 수도 있다. 본 논문에서는 시간제약응용을 위한 캐쉬 무효화 기법을 제안하고 있다. 제안하는 기법을 통해 기존의 일관성 확인 기법에서 일어나는 ‘롤백(Rollback)’ 문제를 해결할 수 있었으며, 접근시간(Access time) 측면에서 성능향상을 얻을 수 있었다. 또한 본 논문에서는 임계값 기반의 보완 기법을 제안한다. 우리는 실험 결과를 통해 제안하는 기법이 약간의 현재성(Currency) 손해는 있지만, 접근시간 측면에서 효율적임을 증명하여 준다.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제22권1호
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• pp.1-7
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• 2016

동일하지 않은 주기와 시작 시간을 가지는 여러 개의 어플리케이션을 멀티프로세서 시스템에서 동시에 수행하면 어플리케이션 간의 간섭이 발생하게 되고, 이에 따라 각 어플리케이션이 실시간 시간 제약을 만족시키는지에 대한 보장이 어려워진다. 본 연구에서는 데이터 플로우 어플리케이션을 대상으로 하여, 주어진 시간 제약 조건을 지키면서 프로세서를 공유할 수 있도록 하는 간섭 분석 모델을 제안하였다. 그리고 이 기법을 바탕으로 여러 개의 어플리케이션들이 프로세서 공유를 통하여 자원사용량을 최소화하는 스케줄링 방법을 제안하였다. 그리하여 태스크 그래프를 실시간 태스크로 변환하여 스케줄 하는 최근의 동시 스케줄링 기법과 비교해보았을 때, 어플리케이션의 반응시간 제약이 빠듯할 때 제안한 기법이 더 적은 자원을 사용하는 스케줄을 생성함을 실험을 통해 확인하였다.