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Communication Delays (communication + delay)
Selected AbstractsA stochastic load balancing algorithm for i-ComputingCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2003Yuk-Yin Wong Abstract This paper presents a stochastic dynamic load balancing algorithm for Internet computing, which is a new type of distributed computing involving heterogeneous workstations from different organizations on the Internet. To realize the practical environment, we assume the system to be comprised of heterogeneous, untrusted and non-dedicated workstations connected by a non-dedicated network. Our algorithm uses the product of the average processing time and the queue length of system jobs as the load index. Dynamic communication delay is included in the execution cost calculation. The transfer policy and the location policy are combined in a stochastic algorithm. State information exchange is done via information feedback and mutual updating. Simulations demonstrate that our algorithm outperforms conventional approaches over a wide range of system parameters. These results are reconfirmed by empirical experiments after we have implemented the algorithms on the Distributed Java Machine global virtual machine. Copyright © 2003 John Wiley & Sons, Ltd. [source] Bilateral teleoperation under time-varying communication time delay considering contact with environmentELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 7 2009Noriko Iiyama Abstract With recent popularization of the Internet, bilateral control systems which are robust to fluctuant and unpredictable time delay are desirable. In such a situation, communication disturbance observer (CDOB) has been proposed as a control method for fluctuant and unpredictable time delay in bilateral teleoperation. It compensates time delay using disturbance observer by considering the effect of communication delay on the system as acceleration dimensional disturbance. Since this method cannot separate network disturbance from contact force exerted on a slave, force response of the slave transmitted to the master side is not precise. This paper presents a method for separating network disturbance from the contact force exerted on the slave. By producing the compensation value using separated network disturbance the force response value of the slave is transmitted to the master side more precisely. The validity of the proposed method is verified by experimental results. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(7): 38,46, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10051 [source] A performance-oriented adaptive scheduler for dependent tasks on grids,CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2008Luiz F. Bittencourt Abstract A scheduler must consider the heterogeneity and communication delays when scheduling dependent tasks on a grid. The task-scheduling problem is NP-Complete in general, which led us to the development of a heuristic for the associated optimization problem. In this work we present a dynamic adaptive approach to schedule dependent tasks onto a grid based on the Xavantes grid middleware. The developed dynamic approach is applied to the Path Clustering Heuristic, and introduces the concept of rounds, which take turns sending tasks to execution and evaluating the performance of the resources. The adaptive extension changes the size of rounds during the process execution, taking task attributes and resources performance as parameters, and it can be adopted in other task schedulers. The experiments show that the dynamic round-based and adaptive schedule can minimize the effects of performance losses while executing processes on the grid. Copyright © 2007 John Wiley & Sons, Ltd. [source] Decisional autonomy of planetary roversJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 7 2007Félix Ingrand To achieve the ever increasing demand for science return, planetary exploration rovers require more autonomy to successfully perform their missions. Indeed, the communication delays are such that teleoperation is unrealistic. Although the current rovers (such as MER) demonstrate a limited navigation autonomy, and mostly rely on ground mission planning, the next generation (e.g., NASA Mars Science Laboratory and ESA Exomars) will have to regularly achieve long range autonomous navigation tasks. However, fully autonomous long range navigation in partially known planetary-like terrains is still an open challenge for robotics. Navigating hundreds of meters without any human intervention requires the robot to be able to build adequate representations of its environment, to plan and execute trajectories according to the kind of terrain traversed, to control its motions, and to localize itself as it moves. All these activities have to be planned, scheduled, and performed according to the rover context, and controlled so that the mission is correctly fulfilled. To achieve these objectives, we have developed a temporal planner and an execution controller, which exhibit plan repair and replanning capabilities. The planner is in charge of producing plans composed of actions for navigation, science activities (moving and operating instruments), communication with Earth and with an orbiter or a lander, while managing resources (power, memory, etc.) and respecting temporal constraints (communication visibility windows, rendezvous, etc.). High level actions also need to be refined and their execution temporally and logically controlled. Finally, in such critical applications, we believe it is important to deploy a component that protects the system against dangerous or even fatal situations resulting from unexpected interactions between subsystems (e.g., move the robot while the robot arm is unstowed) and/or software components (e.g., take and store a picture in a buffer while the previous one is still being processed). In this article we review the aforementioned capabilities, which have been developed, tested, and evaluated on board our rovers (Lama and Dala). After an overview of the architecture design principle adopted, we summarize the perception, localization, and motion generation functions required by autonomous navigation, and their integration and concurrent operation in a global architecture. We then detail the decisional components: a high level temporal planner that produces the robot activity plan on board, and temporal and procedural execution controllers. We show how some failures or execution delays are being taken care of with online local repair, or replanning. © 2007 Wiley Periodicals, Inc. [source] Robust load,frequency regulation: A real-time laboratory experimentOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 6 2007Hassan Bevrani Abstract This paper addresses a new method for robust decentralized design of proportional-integral-based load,frequency control (LFC) with communication delays. In the proposed methodology, the LFC problem is reduced to a static output feedback control synthesis for a multiple delays power system, and then the control parameters are easily carried out using robust H, control technique. To demonstrate the efficiency of the proposed control strategy, an experimental study has been performed on the Analog Power System Simulator at the Research Laboratory of the Kyushu Electric Power Co. in Japan. Copyright © 2007 John Wiley & Sons, Ltd. [source] Finite time agreement protocol design of multi-agent systems with communication delays,,ASIAN JOURNAL OF CONTROL, Issue 3 2009Li Wang Abstract In this paper, the finite-time agreement problem of continuous-time multi-agent systems with communication delays is considered. First, the multi-agent system researched in the paper is described. Second, some notations and lemmas used in the paper are given. Then, agreement protocols for continuous (but non-smooth) multi-agent systems are proposed, which ensure that the states of agents reach agreement in finite time. The stability analysis and simulations are presented to show the effectiveness of the method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] | ||||||||||