Yedatore, Raghuram A · Civil War Book Review · 1996
A distributed system is a set of cooperating computers (processes) communicating with each other to achieve a common goal. They are broadly classified as centralized and decentralised systems. In a centralized system, a single computer plays the role of central coordinator and controls all the system activities. Whereas in a decentralized system, all the cooperating processes have an equal role to play, therefore solutions to problems involve instructing all the processes and coordinating their actions. Although a centralized system facilitates program development, it has serious drawbacks. If the coordinator fails, the system effectively breaks down. Also, the coordinator can become a performance bottleneck. On the other hand, a decentralized system does not suffer from these shortcomings, but program development is more difficult. In this research, we develop a paradigm for a distributed system that provides the view of a centralized system even though the underlying system is decentralized. Special processes called agents reside on all participating computers. One of the agents acts as a leader and coordinates activities of other agents. Agents communicate through a fault-tolerant agent-to-agent protocol. The paradigm defines a one-shot computation, a construct that enables the expression of programs in a simulated centralized environment, thus making program development easier. Programs, written in terms of one-shot computations that are encapsulated in templates which hide all the lower level details from the programmer. We show that every computation can be expressed as a one-shot computation. The proposed paradigm has a high degree of fault-tolerance. It tolerates up to $n-1$ failures in a system of n processors. A prototype has been implemented using PVM.
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Brian Johnson · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2023
Virtual oscillator control systems, devices, and techniques are provided. One example device includes a processor configured to implement a virtual oscillator circuit and output an oscillating waveform based on the virtual oscillator circuit and power electronics operatively coupled to the processor and configured to convert, based on the oscillating waveform, direct current (DC) electricity to alternating current (AC) electricity. The processor may be further configured to extract, from the virtual oscillator circuit, a virtual current based on an output current of the AC electricity, and output the oscillating waveform further based on an input voltage of the DC electricity.
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Raghuram Yedatore · 1996
A distributed system is a set of cooperating computers (processes) communicating with each other to achieve a common goal. They are broadly classified as centralized and decentralised systems. In a centralized system, a single computer plays the role of central coordinator and controls all the system activities. Whereas in a decentralized system, all the cooperating processes have an equal role to play, therefore solutions to problems involve instructing all the processes and coordinating their actions. Although a centralized system facilitates program development, it has serious drawbacks. If the coordinator fails, the system effectively breaks down. Also, the coordinator can become a performance bottleneck. On the other hand, a decentralized system does not suffer from these shortcomings, but program development is more difficult. In this research, we develop a paradigm for a distributed system that provides the view of a centralized system even though the underlying system is decentralized. Special processes called agents reside on all participating computers. One of the agents acts as a leader and coordinates activities of other agents. Agents communicate through a fault-tolerant agent-to-agent protocol. The paradigm defines a one-shot computation, a construct that enables the expression of programs in a simulated centralized environment, thus making program development easier. Programs, written in terms of one-shot computations that are encapsulated in templates which hide all the lower level details from the programmer. We show that every computation can be expressed as a one-shot computation. The proposed paradigm has a high degree of fault-tolerance. It tolerates up to $n-1$ failures in a system of n processors. A prototype has been implemented using PVM.
Cited by 0Open access
Mohit Sinha, Florian Dörfler, Brian Johnson et al. · 2015
In this paper we examine the amplitude and phase dynamics of power-electronic inverters in islanded microgrids that are controlled to emulate the dynamics of a class of weakly nonlinear Liénard-type oscillators. The general strategy of controlling inverters to emulate the behavior of Liénard-type oscillators is termed Virtual Oscillator Control (VOC), and it presents a compelling time-domain alternative to ubiquitous droop control methods which linearly trade off voltage frequencies and magnitudes with active and reactive power injections. In comparison to droop control, which assumes a priori that the network operates in a quasi-stationary sinusoidal steady state, VOC is a time-domain control strategy that globally stabilizes a desired sinusoidal steady state. The main, and somewhat surprising, result of this paper is that-when reduced to the sinusoidal steady state-the VOC dynamics correspond to those of droop control. Hence, VOC is a globally stabilizing control strategy that can deal with higher-order harmonics and includes droop control in the harmonic steady state. The results are intriguing, in that they suggest that droop control laws can be recovered from averaging the complex dynamics of a class of weakly nonlinear limit-cycle oscillators.
Cited by 42
Pavel Kučera, Petr Honzík, F. Zezulka · IFAC Proceedings Volumes · 2003
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Mulder, John C. · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2020
Abstract not provided.
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Alvarado Aldea, Ignacio, Gomez Stern, Fabio, Muñoz de la Peña, David et al. · Zenodo (CERN European Organization for Nuclear Research) · 2010
Este ejecutable contiene un laboratorio virtual de control de un servomecanismo que consiste en una antena de un telescopio. Está autocontenido, cuando lo ejecutas podrás ver el enunciado de los ejercicios propuestos. Además los parámetros del sistema dependen del valor del DNI por lo que cada alumno tiene un sistema diferente.
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Computer Communications · 1984
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William J. Dally · IEEE Transactions on Parallel and Distributed Systems · 1992
Network throughput can be increased by dividing the buffer storage associated with each network channel into several virtual channels. Each physical channel is associated with several small queues, virtual channels, rather than a single deep queue. The virtual channels associated with one physical channel are allocated independently but compete with each other for physical bandwidth. Virtual channels decouple buffer resources from transmission resources. This decoupling allows active messages to pass blocked messages using network bandwidth that would otherwise be left idle. The paper studies the performance of networks using virtual channels using both analysis and simulation. These studies show that virtual channels increase network throughput, by a factor of four for 10-stage networks, and reduce the dependence of throughput on the depth of the network.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Cited by 1,154
Jose ́ L. Lima, Jose ́ C. Gonçalves, Paulo G. Costa et al. · 2016
This paper describes a tool for interactive learning that can be used to improve control systems design. The developed system is ready to use and allows testing different control methods. It can be used by students for problem solving and individual learning. The virtual control laboratory was implemented as a teaching aid during lectures on control systems. As there is no need to do any special programming or debugging, the students can focus on the control items. Classical control methods such as PID and State-Space approaches are available and gains can be tuned. A friendly appearance based on openGL 3D shows a simulation of the real word: A cart with an inverted pendulum is ”bumped ” with a force. The dynamic equations of motion for the control system are linearized assuming that the pendulum does not move more than a few degrees away from the vertical allowing to apply linear control methods. Although, the simulated system is realistic and based on a Dynamics Engine.
Cited by 0
Valeriya Gribova, Leonid Fedorischev · Informatika i sistemy upravleniya · 2016
Cited by 1
Parisa Gazerani · touchREVIEWS in Neurology · 2016
Virtual Reality (VR) technology creates a sense of immersion in a virtual environment analogous to the real world. VR has increasingly gained attention for pain management based on current evidence demonstrating its analgesic effects in certain experimental, acute and chronic pain conditions. VR-based interventions shift the users’ attention towards active cognitive processing that can lead to higher pain threshold or tolerance. An understanding of neurobiological mechanisms underlying analgesic effects of VR will definitely facilitate optimal utility of this tool for pain control.
Cited by 2Open access
Yalong Hu, Wei Wei, Yonggang Peng et al. · 2016
The virtual synchronous generator (VSG) control scheme regulates the inverter as a synchronous generator (SG). As the SG plays an important role in the conventional grid by supporting system stability, the VSG can act the same role in a micro-grid. Additionally, the VSG can be more flexible on the parameters setting, such as the virtual inertia. Enlightened by this, a fuzzy controller is proposed with regulating the virtual inertia to enhance the dynamic response of the VSG. At last, the idea is verified by simulations.
Cited by 54
Mir Nahidul Ambia, Yuchen Zhang, Ke Meng et al. · 2024
In recent years, the power industry has seen a significant uptick in renewable energy integration, including solar and wind farms, accompanied by energy storage systems.While this has increased overall generation capacity, it has also posed challenges to grid security and vulnerability.Key issues such as low short circuit ratios due to renewable integration and the retirement of synchronous machines have weakened grids.Grid forming inverters therefore have emerged as a vital solution, aiding solar and wind farms in maintaining stability during low short circuit ratio conditions.However, traditional Virtual Synchronous Generation (VSG) controllers, while beneficial, often introduce oscillations during disturbances, threatening network stability.This paper introduces an innovative approach that integrates Virtual Synchronous Generation Control with a Virtual Impedance Strategy to address stability challenges in solar and wind farms under low short circuit ratio conditions.By eliminating the need for Phase-Locked Loops (PLL), this method effectively mitigates oscillations during faults and voltage disturbances, thereby ensuring grid stability, with compliance to grid codes such as those of NER and AEMO Australia serving as guidelines.Implementation in PSCAD, which is widely used in the power system industry, validates its capability to meet stringent grid code requirements.
Cited by 0Open access
Jonathan Clarke · IEEE Power Engineering Society General Meeting, 2004. · 2004
This paper describes the implementation of a single "virtual" control centre to manage the New Zealand power system. With a single virtual centre the New Zealand power system is operated from two physically separate control centres simultaneously.
Cited by 1
Ari Glezer · Defense Technical Information Center (DTIC) · 2007
This experimental research has focused on modifying the global aerodynamic characteristics of lifting surfaces at cruise (low) angles of attack when the baseline flow is fully attached. Using hybrid actuators, trapped vorticity concentrations at the leading and trailing edges affect aerodynamic forces and moment without control surfaces. Hybrid actuators employ miniature obstructions with integrated synthetic jet actuators. Actuation on the pressure surface near the leading edge results in a substantial (up to 50%) reduction in pressure drag and total drag (29%) with virtually no loss in lift, leading to a higher lift to drag ratio. When the actuation is applied near the trailing edge, the effects are bi-directional changes in pitching moments, which can be continuously varied by controlling the actuation amplitude. Moreover, the same performance can be achieved at substantially reduced actuation power by exploiting transitory aerodynamic effects through pulse modulation. PIV studies of the flow in the vicinity of the actuators, in the boundary layer and the wake, were used in this investigation.
Cited by 0
Martin Klesen, Patrick Gebhard · 2007
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Yumin Chen, Liyong Ma, Xianmin Meng et al. · The Open Cybernetics & Systemics Journal · 2015
Digital control experiments are important parts of electrical engineering course in modern electrical schools. A virtual digital control experimental system is developed for undergraduates to learn digital control principals and to practice online. Based on the digital control hardware experiment platform, the practical circuit model is developed. And some digital control algorithms are employed for virtual digital control operations, these algorithms include PID and some varies algorithms, Smith predictor algorithm, Dahlin algorithm and Kalman algorithm. The development of the Kalman filtering algorithm in the virtual experimental system is detailed. The experimental parameters of the plant and the controller can be flexible configured by the users in the terminal online, and the control results can be quickly displayed online. The virtual digital control experimental system is efficient for undergraduates to pre-practice the digital control experiments and to learn the control principals.
Cited by 0Open access
Majid M. Moghaddam, M. Buehler · 2002
The authors introduce a new control problem: the control of motion simulating devices (virtual motion systems (VMS)) for walking and running humans and robots in a fashion that feels most realistic, that is, like locomoting on ground. After developing simplified dynamical models for the VMS, the human/robot and the resulting coupled system, the authors cast the problem in terms of a performance index. This approach permits application of standard optimal control theory. They present two solutions and discuss upcoming problems in the task domain of virtual motion control.
Cited by 11
Drla, Michal · Brno University of Technology Digital Library (Brno University of Technology) · 2021
Tato práce si kladla za cíl implementovat aplikaci, ve které je možné ovládat virtuálního robota pomocí EEG. V práci je vysvětlena teorie nutná k pochopení, jak fungují BCI systémy, které zpracovávají signály EEG. Jsou zde uvedeny nejen základy analýzy EEG, ale také ukazuje biologii lidského mozku a signály, které lze získat. Další důležitou části je teorie neuronových sítí, které byly v implementaci využity. V implementaci jsou popsané skripty, které byly využity pro sbírání dat, návrh neuronové sítě a tvorba demonstrační aplikace. Výsledky testování jsou uspokojivé. Neuronová síť vyhodnocovala správně signály EEG a uživatel byl schopen ovládat virtuálního robota.
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