共查询到20条相似文献，搜索用时 31 毫秒
1.
LU Guang WANG Yong-chao ZHU Miao-liang 《浙江大学学报(A卷英文版)》2007,8(6):849-856
The Internet evolves to incorporate very-high-bandwidth optical links and more large-delay satellite links. TCP faces new challenges in this unique environment. Theory and experiments showed that TCP becomes inefficient and is prone to be unstable as the per-flow product of bandwidth and latency increases, regardless of the queuing scheme. Variable-structure congestion Control Protocol (VCP) is proposed to address these problems. However, VCP has problem in terms of convergence time, i.e., it takes a long time for a new VCP flow to achieve fair bandwidth allocation if the existing VCP flows have large con- gestion windows. This paper proposed an Extended Variable-structure congestion Control Protocol (EVCP), which adopted a convergence controller. The basic idea of convergence controller is that if a flow has larger window than its fair window, its congestion window should be decreased more aggressively than usual in Multiplicative Decrease (MD) phase. Simulations showed that EVCP has better performance in terms of convergence time while keeping the advantages of VCP. 相似文献
2.
A new chaos control method is proposed to take advantage of chaos or avoid it. The hybrid Internal Model Control and Proportional Control learning scheme are introduced. In order to gain the desired robust performance and ensure the system's stability, Adaptive Momentum Algorithms are also developed. Through properly designing the neural network plant model and neural network controller, the chaotic dynamical systems are controlled while the parameters of the BP neural network are modified. Taking the Lorenz chaotic system as example, the results show that chaotic dynamical systems can be stabilized at the desired orbits by this control strategy. 相似文献
3.
INTRODUCTIONOneoftheoldestresearchesofchaosincon trolfieldscanbeseeninthepaperbyKalman(1956) ,whofirstfoundnon synchronousoscil lationsinatwo dimensionalsampled datacontrolsystem .IntheOGYmethoddevelopedbyOttetal.(1990 ) ,chaoticphenomenawaseliminatedbyadjustingparametersofthesystemswhenthechaoticorbitcomesnearaperiodicalorbit.ButtheOGY’smethodrequiresmonitoringthesys temlongenoughtodeterminealinearizationmodeintheneighborhoodofthedesiredunstableperiodicorbitbeforeitcanbeapplied .Besi… 相似文献
4.
To prevent the oxygen starvation and improve the system output performance, an adaptive inverse control (AIC) strategy is developed to regulate the air supply flow of a proton exchange membrane fuel cell (PEMFC) system in this paper.The PEMFC stack and the air supply system including a compressor and a supply manifold are modeled for the purpose of performance analysis and controller design. A recurrent fuzzy neural network (RFNN) is utilized to identify the inverse model of the controlled system and generates a suitable control input during the abrupt step change of external disturbances. Compared with the PI controller, numerical simulations are performed to validate the effectiveness and advantages of the proposed AIC strategy. 相似文献
5.
Control design is important for proton exchange membrane fuel cell （PEMFC） generator. This work researched the anode system ofa 60-kW PEMFC generator. Both anode pressure and humidity must be maintained at ideal levels during steady operation. In view of characteristics and requirements of the system, a hybrid intelligent PID controller is designed specifically based on dynamic simulation. A single neuron PI controller is used for anode humidity by adjusting the water injection to the hydrogen cell. Another incremental PID controller, based on the diagonal recurrent neural network （DRNN） dynamic identification, is used to control anode pressure to be more stable and exact by adjusting the hydrogen flow rate. This control strategy can avoid the coupling problem of the PEMFC and achieve a more adaptive ability. Simulation results showed that the control strategy can maintain both anode humidity and pressure at ideal levels regardless of variable load, nonlinear dynamic and coupling characteristics of the system. This work will give some guides for further control design and applications of the total PEMFC generator. 相似文献
6.
针对网络控制系统(NCS)存在时延的情况下如何设计控制器问题,提出了一种新的网络闭环控制系统建模方法-离散模糊T-S模型,并在此模型的基础上应用平行分布补偿原理设计了NCS模糊控制器;应用Lyapunov理论和LMI方法,研究了系统的模糊稳定控制问题,给出了基于线性矩阵不等式的不依赖时滞的状态反馈模糊控制器的设计方法,并获得了NCS模糊控制的稳定充分条件为求解一组线性矩阵不等式;通过仿真验证了该控制方法的有效性。 相似文献
7.
HU Jia-bing HE Yi-kang 《浙江大学学报(A卷英文版)》2006,7(10):1757-1764
INTRODUCTION Due to concerns about emissions from fossil fuels and the depletion of fossil fuel resources, re- newable energy systems are becoming a topic of great interest and investment in the world. In particular, wind energy has been the subject of much recent research and development. In order to overcome the problems associated with fixed-speed wind-turbine system and to maximize the wind energy capture, many new wind farms will employ wind turbines based on Doubly-Fed Induction Ge… 相似文献
8.
Based on variable structure control (VSC) and fuzzy local controller network (FLCN), a new design method of robust gain-scheduling
control is proposed in this paper. The proper sliding-modes and the tendency-rates for general operation-points are introduced
such that the system gets into the sliding-modes’ motion as soon as possible and has the desired performance. Its good performance
is due to the robustness of VSC. However, any local controller works well only in the local region of a specified operation-point.
In this paper functions similar to the fuzzy-attributed function in fuzzy-systems are introduced to form FLCN. The simulation
results showed that the presented method is feasible and acceptable.
Project supported by the Natural Science Foundation of China (NSFC: 69934030) and the Zhejiang Provincial Natural Science
Foundation of China (ZJPNSFC: ZD9905). 相似文献
9.
Optimal distributed resource allocation in a wireless sensor network for control systems 总被引：1，自引：0，他引：1
MAO Jian-lin WU Zhi-ming 《浙江大学学报(A卷英文版)》2007,8(1):106-112
INTRODUCTION With the rapid development of wireless com-munication technology, the combination of wireless communication and control systems becomes a new trend of networked control systems. Among the kinds of wireless technologies, wireless sensor network (WSN) has attracted a lot of interest and visibility due to its huge application space. WSN is a kind of wire-less ad-hoc network which connects embedded sen-sors, actuators, and processors and in which each node consists of a wireles… 相似文献
10.
A new neural network model termed ＇standard neural network model＇ （SNNM） is presented, and a state-feedback control law is then designed for the SNNM to stabilize the closed-loop system. The control design constraints are shown to be a set of linear matrix inequalities （LMIs）, which can be easily solved by the MATLAB LMI Control Toolbox to determine the control law. Most recurrent neural networks （including the chaotic neural network） and nonlinear systems modeled by neural networks or Takagi and Sugeno （T-S） fuzzy models can be transformed into the SNNMs to be stabilization controllers synthesized in the framework of a unified SNNM. Finally, three numerical examples are provided to illustrate the design developed in this paper. 相似文献
11.
M.Tahir Khaleeq Lang Wenpen He Guosen 《上海大学学报(英文版)》1998,2(3):226-236
ＮｏｍｅｎｃｌａｔｕｒｅｓＡＡｒｅａ（ｍ２）ＥＥｎｅｒｇｙＣｏｎｔｒｏｌ（Ｊ）ｆＰｒｅｓｓｕｒｅＬｏｓｓＣｏｅｆｉｃｉｅｎｔａＶｏｉｄＦｒａｃｔｉｏｎＨＳｐｅｃｉｆｉｃＥｎｔｈａｐｌｙ（Ｊ／ｋｇ）ＩＩｎｅｒｔａｎｃｅ（ｍ）ＫＦｒｉｃｔｉｏｎＬｏｓｓＣ... 相似文献
12.
ZOU Jun FU Xin YANG Hua-yong 《浙江大学学报(A卷英文版)》2007,8(9):1429-1434
The highly nonlinear behavior of the system limits the performance of classical linear proportional and integral (PI) controllers used for hot rolling. An active disturbance rejection controller is proposed in this paper to deal with the nonlinear problem of hydraulic servo system in order to preserve fast response and small overshoot of control system. The active disturbance rejection (ADR) controller is composed of nonlinear tracking differentiator (TD),extended state observer (ESO) and nonlinear feedback (NF) law. An example of the hydraulic edger system case study is investigated to show the effectiveness and robustness of the proposed nonlinear controller,especially,in the circumstance of foreign disturbance and working condition variation,compared with classic PI controller. 相似文献
13.
Radar leveling system is the key equipment for improving the radar mobility and survival capability. A combined quantitative feedback theory(QFT)controller is designed for the radar truck leveling simulator in this paper, which suffers from strong nonlinearities and system parameter uncertainties. QFT can reduce the plant uncertainties and stabilize the system, but it fails to obtain high-precision tracking. This drawback can be solved by a robust QFT control scheme based on zero phase error tracking control(ZPETC)compensation. The combined controller not only possesses high robustness, but greatly improves the system performance. To verify the effectiveness and the potential of the proposed controller, a series of experiments have been carried out. Experimental results have demonstrated its robustness against a large range of parameters variation and high tracking precision performance, as well as its capability of restraining the load coupling among channels. The combined QFT controller can drive the radar truck leveling platform accurately, quickly and stably. 相似文献
14.
CHEN Yue-hua CAO Guang-yi ZHU Xin-jian 《浙江大学学报(A卷英文版)》2007,8(5):748-754
This paper describes a nonlinear model predictive controller for regulating a molten carbonate fuel cell (MCFC). In order to improve MCFC’s generating performance, prolong its life and guarantee safety, it must be controlled efficiently. First, the output voltage of an MCFC stack is identified by a least squares support vector machine (LS-SVM) method with radial basis function (RBF) kernel so as to implement nonlinear predictive control. And then, the optimal control sequences are obtained by applying genetic algorithm (GA). The model and controller have been realized in the MATLAB environment. Simulation results indicated that the proposed controller exhibits satisfying control effect. 相似文献
15.
1Introduction Moltencarbonatefuelcell(MCFC)isaclearelec tricitygeneratingtechniquewithhighefficiency,which istobeusedwidely.Withoutcombustion,MCFCcon vertschemicalenergycontainedinfuelandoxidantin toelectricenergyviaelectro chemicalreaction.Per formanceof… 相似文献
16.
Jun Li Nan Gao Guang-yi Cao Heng-yong Tu Ming-ruo Hu Xin-jian Zhu Jian Li 《浙江大学学报(A卷英文版)》2010,11(1):61-70
In this paper, an application of a nonlinear predictive controller based on a self recurrent wavelet network （SRWN） model for a direct internal reforming solid oxide fuel cell （DIR-SOFC） is presented. As operating temperature and fuel utilization are two important parameters, the SOFC is identified using an SRWN with inlet fuel flow rate, inlet air flow rate and current as inputs, and temperature and fuel utilization as outputs. To improve the operating performance of the DIR-SOFC and guarantee proper operating conditions, the nonlinear predictive control is implemented using the off-line trained and on-line modified SRWN model, to manipulate the inlet flow rates to keep the temperature and the fuel utilization at desired levels. Simulation results show satisfactory predictive accuracy of the SRWN model, and demonstrate the excellence of the SRWN-based predictive controller for the DIR-SOFC. 相似文献
17.
讨论了一类不确定时滞系统的指数稳定弹性控制器设计问题。基于李亚普诺夫稳定性理论,采用线性矩阵不等式方法,给出系统指数稳定条件和状态反馈弹性控制器设计方法,使系统指数稳定。所得条件具有较小的保守性,且可以很方便的求解指数稳定度。 相似文献
18.
One of the main problems in controlling the shape of active structures (AS) is to determine the actuations that drive the structure from the current state to the target state. Model-based methods such as stochastic search require a known type of load and relatively long computational time, which limits the practical use of AS in civil engineering. Moreover, additive errors may be produced because of the discrepancy between analytic models and real structures. To overcome these limitations, this paper presents a compound system called WAS, which combines AS with a wireless sensor and actuator network (WSAN). A bio-inspired control framework imitating the activity of the nervous systems of animals is proposed for WAS. A typical example is tested for verification. In the example, a triangular tensegrity prism that aims to maintain its original height is integrated with a WSAN that consists of a central controller, three actuators, and three sensors. The result demonstrates the feasibility of the proposed concept and control framework in cases of unknown loads that include different types, distributions, magnitudes, and directions. The proposed control framework can also act as a supplementary means to improve the efficiency and accuracy of control frameworks based on a common stochastic search. 相似文献
19.
A dynamic velocity feed-forward compensation control (DVFCC) approach with RBF neural network (RBF-NN) dynamic model identification was presented for the adaptive trajectory tracking of industrial robots.The proposed control approach combined the advantages of traditional feedback closed-loop position control and computed torque control based on inverse dynamic model.The feed-forward compensator used a nominal robot dynamics as accurate dynamic model and on-line identification with RBF-NN as uncertain part to improve dynamic modeling accuracy.The proposed compensation was applied as velocity feed-forward by an inverse velocity controller that can convert torque signal into velocity in the standard industrial controller.Then,the need for a torque control interface was avoided in the real-time dynamic control of industrial robot.The simulations and experiments were carried out on a gas cutting manipulator.The results show that the proposed control approach can reduce steady-state error,suppress overshoot and enhance tracking accuracy and efficiency in joint space and Cartesian space,especially under highspeed condition. 相似文献
20.
In order to improve the output efficiency of a photovoltaic (PV) energy system, the real-time maximum power point (MPP) of the PV array should be tracked closely. The non-linear and time-variant characteristics of the photovoltaic array and the non-linear and non-minimum phase characteristics of a boost converter make it difficult to track the MPP as in traditional control strategies. A neural fuzzy controller (NFC) in conjunction with the reasoning capability of fuzzy logical systems and the learning capability of neural networks is proposed to track the MPP in this paper. A gradient estimator based on a radial basis function neural network is developed to provide the reference information to the NFC. With a derived learning algorithm, the parameters of the NFC are updated adaptively. Experimental results show that, compared with the fuzzy logic control algorithm, the proposed control algorithm provides much better tracking performance. 相似文献