共查询到20条相似文献，搜索用时 15 毫秒
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Moustafa Ahmed Safwat W. Z. Mahmoud Minoru Yamada 《International Journal of Numerical Modelling》2007,20(3):117-132
This paper demonstrates numerical analysis of the dynamics and intensity noise of fibre‐grating semiconductor lasers (FGSLs). The induced phenomenon of strong optical feedback (OFB) is analysed. The simulations are based on an improved time‐delay rate equations model of a single‐mode laser that takes into account the multiple round‐trips of the lasing field in the fibre cavity. The analyses are performed in terms of the temporal trajectory of the laser intensity, bifurcation diagram and relative intensity noise (RIN). We explore influence of the fibre‐cavity length on the dynamics and RIN. The results show that when the fibre cavity is short, the regime of strong OFB is characterized by either continuous‐wave (CW) operation or periodic pulsation. The pulsation frequency is locked at the frequency separation of either the compound‐cavity modes or the external fibre‐cavity modes. The corresponding RIN level is close to or higher than the level of the solitary laser depending on pulse symmetry. When the fibre cavity is long, the laser exhibits unstable dynamics over wider range of OFB. Moreover, the strong‐OFB pulsation becomes beating quasi‐periodic at the relaxation oscillation frequency and the fibre‐cavity mode‐separation frequency. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Moustafa Ahmed Minoru Yamada Salah Abdulrhmann 《International Journal of Numerical Modelling》2009,22(6):434-445
This paper investigates numerically influence of the external‐cavity length on the type of the route‐to‐chaos of semiconductor lasers under external optical feedback. The study is based on numerical solution of a time‐delay model of rate equations, and the solutions are employed to construct bifurcation diagrams and to examine the Fourier frequency spectrum of the laser output. The ratio of the relaxation frequency to the external‐cavity resonance frequency is employed to measure the influence of the length of the external cavity. The route‐to‐chaos is period doubling when this frequency ratio is less than unity. The route is sub‐harmonic when the frequency ratio increases up to 2.25. When the frequency ratio increases further, the transition to chaos becomes quasi‐periodic characterized by the compound‐cavity frequency and the relaxation frequency as well as their difference. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Moustafa Ahmed 《International Journal of Numerical Modelling》2004,17(2):147-163
This paper reports on a numerical approach to model the field fluctuations, spectral lineshape and linewidth in semiconductor lasers. The approach is based on numerical solution of the laser rate equations augmented by Langevin noise sources that account for fluctuations in the lasing field. The paper newly examines contributions of intensity and frequency noises to the spectral characteristics of the lineshape and its linewidth over a wide range of injection current. The model is applied to InGaAsP lasers emitting in a wavelength of 1.5 μm as the most representative light sources in optical communication systems. Accuracy of approximated models of calculating linewidth from low‐frequency components of the frequency noise is checked. Effect of non‐linear gain suppression on the lineshape is also explored. The spectral lineshape promotes and the linewidth decreases as the laser is injected far from the near‐threshold region. The lineshape changes mainly with changes in the frequency noise spectrum while the linewidth is sensitive to variation in the low‐frequency levels of both intensity and frequency noises. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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考虑一类半线性驱动-响应系统，提出了一种实用的输出反馈控制方法并研究了相应的同步条件。通过构造误差动力系统的二次Lyapunov函数并令其导数负定，证明了当非线性项对有界自变量有界且线性部分及输出矩阵也满足一定条件时存在反馈控制使系统同步。然后将主要结果推广至多变量情形。最后通过具体实例说明了文本结果。 相似文献
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蔡氏电路混沌系统的自适应反馈控制 总被引：2，自引：0，他引：2
针对一类简单的三维自治系统一蔡氏电路(Chau’s circuit)混沌系统，提出了一种反馈控制方法和一种自适应反馈控制方法。对于两种控制方法都利用Lyapunov原理证明了闭环系统的渐进稳定性，将提出的控制方法用于蔡氏电路混沌系统稳定于其不动点的控制。仿真结果表明，控制方法是有效的，自适应技术提高了系统的控制性能。 相似文献
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Micha&#x; Szyma&#x;ski 《International Journal of Numerical Modelling》2010,23(6):492-502
The solution of non‐linear carrier diffusion equation associated with the axial direction of broad‐area laser has been achieved by a hybrid asymptotic‐numerical method that combines WKB approximation and the variation of constants method. The non‐linearity has been taken into account by using an iterative scheme: carrier lifetime has been linearized and calculated as a function of carrier density known from the previous iteration. Non‐uniform photon density has been taken into account. As the new method is based on analytical solutions, it is very fast and not vulnerable to large gradients of carrier concentration usually occurring in the vicinity of laser facets. Therefore, it can be useful in complicated self‐consistent thermal models of broad‐area lasers. The obtained results are compared with two simplified cases: solution of linear diffusion equation with constant coefficients and calculations neglecting the diffusion. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Hussein Taleb Kambiz Abedi Saeed. Golmohammadi 《International Journal of Numerical Modelling》2014,27(1):79-88
In this article, quantum‐dot semiconductor optical amplifiers (QD‐SOAs) have been modelled using state space method. To derive this model, we have manipulated the rate equation model of the QD‐SOA, where the average values of the occupation probabilities along the QD‐SOA cavity are considered as the state variables of the system. Using these variables, the distance dependence of the rate equations is eliminated. The derived state space model gives the optical gain and output signal of the amplifier with a high accuracy. Simulation results show that the derived model is not only much simpler and faster than conventional rate equation models, but also the optical gain and output signal of the investigated QD‐SOA are calculated with a higher precision compared to the rate equation model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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电力系统混沌振荡的自适应补偿控制 总被引：7，自引：1，他引：7
提出了电力系统混沌振荡自适应控制的一种方法。电力系统混沌振荡状态和它的微分信号由微分跟随器实时提取,并通过微分跟随器对非线性周期性负荷扰动的影响进行自适应补偿。在此基础上,设计线性状态反馈控制规律,使得电力系统的运动状态保持稳定。计算机仿真验证了该方法的正确性。 相似文献
10.
永磁直流电机的混沌反控制 总被引：2，自引：1，他引：1
以永磁直流电机为例,在开环控制电压的基础上,分别叠加电机转速和电枢电流的延迟反馈电压构成电机输入电压,成功地使电机转速出现混沌运动,并且使得电机转速以及在这个转速附近产生的混沌振荡的幅值范围可控。对实施混沌反控制的电机系统,进行理论分析和推导,给出了开环控制和延迟反馈电压设计的解析表达式。进行了系统仿真,并进一步验证理论推导的结果。画出周期和混沌电机转速的波形和相空间重构相轨迹。而且还计算了李雅普诺夫指数,验证电机存在混沌运动。 相似文献
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Syed Ali Asad Rizvi Zongli Lin 《International Journal of Adaptive Control and Signal Processing》2019,33(12):1825-1842
This paper focuses on solving the adaptive optimal tracking control problem for discrete‐time linear systems with unknown system dynamics using output feedback. A Q‐learning‐based optimal adaptive control scheme is presented to learn the feedback and feedforward control parameters of the optimal tracking control law. The optimal feedback parameters are learned using the proposed output feedback Q‐learning Bellman equation, whereas the estimation of the optimal feedforward control parameters is achieved using an adaptive algorithm that guarantees convergence to zero of the tracking error. The proposed method has the advantage that it is not affected by the exploration noise bias problem and does not require a discounting factor, relieving the two bottlenecks in the past works in achieving stability guarantee and optimal asymptotic tracking. Furthermore, the proposed scheme employs the experience replay technique for data‐driven learning, which is data efficient and relaxes the persistence of excitation requirement in learning the feedback control parameters. It is shown that the learned feedback control parameters converge to the optimal solution of the Riccati equation and the feedforward control parameters converge to the solution of the Sylvester equation. Simulation studies on two practical systems have been carried out to show the effectiveness of the proposed scheme. 相似文献
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基于变量反馈的电力系统混沌振荡控制 总被引：6，自引：2，他引：4
混沌运动是一种普遍存在的现象,表现了系统内部的复杂性、随机性和无序性。电力系统也存在混沌现象,对系统的稳定运行是有害的。采用变量反馈控制法（VFC）控制互联电力系统由周期性负荷扰动引起的混沌振荡,根据混沌运动对初值敏感依赖性,仅采用单一状态变量反馈就能有效地抑制系统的混沌振荡,使系统从混沌或不稳定状态进入稳定的运动状态。该方法具有良好的稳定性和轨道跟踪能力,不改变被控系统的结构,不需要使用除系统输出或状态变量以外的任何有关被控系统的信息。在仿真分析时比较了反馈控制器投入前后的系统动态行为,得到的结果与理论分析相一致。 相似文献
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为了抑制超声波电机转速控制系统中的混沌行为,设计了比例延时反馈控制器,采用基于模糊逻辑的方法在线自适应调节延迟时间。结果表明,该方法可以快速有效地将超声波电机转速控制系统的混沌行为稳定为周期或固定点运动,使系统从混沌状态进入稳定状态,从而实现混沌控制。 相似文献
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利用延迟反馈进行异步电动机混沌反控制 总被引：4，自引：2，他引：4
目前已有实验证明，某些系统在混沌运动下可获得更好的效果。因此，具有混沌运动特性的电机传动系统成为新的研究热点之一。本文探讨了通过延迟反馈控制对异步电动机传动系统进行混沌反控制的技术，实现了将异步电动机的稳态由通常的固定在某个转速控制到周期的甚至混沌的运动。本文分析了应用延时反馈控制实现异步机混沌运动的原理，给出了仿真实现和分析。 相似文献
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Abdelali El Aroudi Mohamed Orabi 《International Journal of Circuit Theory and Applications》2012,40(1):15-35
Power factor correction converters are power electronics circuits used as AC‐DC power supplies. These systems are well known to exhibit nonlinear phenomena such as subharmonic oscillations and chaotic regimes. These undesirable behaviors increase the THD and therefore can jeopardize enormously the system performances. In this paper, time delay feedback control is applied to stabilize a two‐stage power factor correction AC‐DC converter when it exhibits these instabilities under traditional controllers. This control technique introduces many advantages to the most and widely used average current mode control through widening the stability domain of the system. By appropriately selecting the time delay feedback gain and the time delay period, the undesirable subharmonic components are eliminated, whereas the desired ones remain unchanged. A harmonic balance approach is used for studying the dynamics of the system under the new control scheme and to obtain the stabilization domain. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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RYO ISHIDA YASUSHI YAMANO SHINICHI KOBAYASHI ATSUSHI KOJIMA MASAYA HANADA YOSHIO SAITO 《Electrical Engineering in Japan》2016,196(3):3-12
Dark current based on field emission current is considered to be a factor causing the vacuum electrical breakdown between multiaperture acceleration grids in the JT‐60 negative ion source. In this paper, we focus on field enhancement factor, which is a key parameter of field emission from the electrode. Vacuum breakdown testing for small‐sized electrodes simulating the multiaperture acceleration grids of the negative ion source was performed. We found the field enhancement factor and breakdown field for multiaperture electrodes, and we investigated the dependence of each parameter on the number of apertures. The results revealed that an increase in the average field enhancement factor after the end of conditioning resulting from an increase in the number of apertures led to a decrease in the dielectric strength of the multiaperture electrodes. 相似文献
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Ali Dadashi 《International Journal of Circuit Theory and Applications》2013,41(8):818-830
A new operational amplifier is presented based on the conventional telescopic amplifier structure. A novel method is used to increase the DC gain of the telescopic amplifier. This method does not degrade the output swing, bandwidth, settling time and the phase margin of the telescopic amplifier. Proposed structure has been simulated by HSPICE software using level 49 parameters (BSIM3v3) in a typical 0.18 µm Complementary metal‐oxide‐semiconductor (CMOS) technology. HSPICE simulation confirms the theoretical estimated improvements. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献