共查询到20条相似文献,搜索用时 187 毫秒
1.
永磁同步风力发电机在运行过程中不可避免地会受到风能的随机干扰,本文建立了在输入机械转矩存在随机干扰情况下永磁同步风力发电机的数学模型,采用胞映射方法分析了随机干扰强度变化时系统全局结构的演化行为,并通过数值模拟对理论分析进行验证.研究结果表明,随着随机干扰强度的增大,系统中会出现随机内部激变和随机边界激变,即由于随机吸引子与其吸引域内的随机鞍发生碰撞而产生的随机分岔现象和由于随机吸引子与其吸引域边界发生碰撞而产生的随机分岔现象.研究结果揭示了随机干扰对永磁同步风力发电机运行性能影响的机理,为永磁同步风力发电系统的运行和设计提供了理论依据. 相似文献
2.
研究了叉形分岔系统和FitzHugh Nagumo(FHN)细胞模型两种非线性动力系统分岔点邻域内 随机共振的特性.研究结果表明:这两种系统在分岔发生时具有由一个吸引子变为两个吸引 子或者由两个吸引子变为一个吸引子共同的分岔特性,即在分岔点的邻域内, 系统在分岔点 的两侧有分岔前吸引子和分岔后吸引子存在,在噪声的作用下,系统的运动除了像传统随机 共振的机理那样在分岔点一侧共存的吸引子之间跃迁,还在分岔点两侧三个吸引子(分岔前 一个吸引子和分岔后两个吸引子)之间跃迁,并且这种跃迁单独诱发了随机共振 ;在两种 跃迁都发生的情况下, 在其分岔点的邻域内,由第二种跃迁诱发的随机共振在引起第一种跃 迁噪声的强度很大的范围内变化仍可维持, 而第一种跃迁诱发的随机共振在引起第二种跃迁 噪声的强度很小的范围内变化即迅速消失.
关键词:
随机共振
吸引子
分岔点
跃迁 相似文献
3.
4.
利用荷控忆阻器和一个电感串联设计一种新型浮地忆阻混沌电路.用常规动力学分析方法研究该系统的基本动力学特性,发现系统可以产生一对关于原点对称的"心"型吸引子.将观察混沌吸引子时关注的电压、电流推广到功率和能量信号,观察到蝴蝶结型奇怪吸引子的产生.理论分析Hopf分岔行为并通过数值仿真进行验证,结果表明系统随电路参数变化能产生Hopf分岔、反倍周期分岔两种分岔行为.相对于其它忆阻混沌电路该电路采用的是一个浮地型忆阻器,并且在初始状态改变时,能产生共存吸引子和混沌吸引子与周期极限环共存现象. 相似文献
5.
应用广义胞映射方法研究了参激和外激共同作用的Duffing-van der Pol振子的随机分岔.以 系统参数通过某一临界值时,如果系统的随机吸引子或随机鞍的形态发生突然变化,则认为 系统发生随机分岔为定义,分析了参激强度和外激强度的变化对于随机分岔的影响.揭示了 随机分岔的发生主要是由于系统的随机吸引子与系统的随机鞍碰撞产生的.分析表明,广义 胞映射方法是分析随机分岔的有力工具,这种全局分析方法可以清晰地给出随机分岔的发生 和发展.
关键词:
随机分岔
全局分析
广义胞映射方法
随机吸引子
随机鞍 相似文献
6.
7.
强流电子束时间分辨测量系统在直线感应加速器(LIA)环境中会受到一些短暂的高能脉冲干扰,这些瞬态脉冲干扰既针对电路又针对测量系统,这对测量系统电子设备危害很大。介绍了时间分辨测量系统的原理,分析了瞬态脉冲干扰的成因和抑制方法,给出了束参数测量系统的实验布局和特点,分析瞬态脉冲干扰对LIA中测量系统电子器件电性能的影响和变化规律,并进一步探讨电子器件电性能受瞬态脉冲干扰后的抑制措施。通过采用光纤传输控制信号的措施,能很好地传输窄脉冲,信号延时抖动小,达到了高速信号的可靠传输要求,利用紧凑嵌入式方法,提高了抗电磁干扰的能力,这样可以更好地保护束参数测量电子器件,提高了整个系统的抗干扰能力及可靠性。 相似文献
8.
9.
中心流形理论提供了一个将高维系统降维研究的方法,应用该理论研究了一个新的混沌系统的基本特性,给出中心流形上流方程,分析这个新的混沌系统的叉式分岔.通过构建电路实现了该混沌系统,从而验证了系统的混沌行为,证实了混沌吸引子的存在.同时说明了由于电路信号频率与数值信号频率的不同所带来的数值仿真与物理实现之间在应用上有着重要区别.最后利用单变量反馈控制方法实现了新系统的同步控制,并给出了完整的同步实现电路.
关键词:
三维混沌系统
中心流形
电路实现
同步 相似文献
10.
11.
以串联型感应电能传输(IPT)系统为例,用非线性动力学的方法研究了IPT系统的多谐振点的判断及稳定性分析问题.建立了系统的频闪映射模型,根据不动点理论推导出了系统的稳态响应分段解析函数式,并在此基础上,给出了系统谐振工作点的理论判据,结合系统庞加莱映射的雅可比矩阵特征值分布情况,给出了谐振点的稳定性判据.结合具体实例系统,讨论了其多谐振点现象,并通过仿真和实验进行了验证,证明了本文理论分析结果的正确性.本文所提出的分析方法也可为其他类似谐振变换电路的建模及稳态工作点分析提供一定的理论参考.
关键词:
感应电能传输(IPT)
频闪映射
雅可比矩阵
稳定性 相似文献
12.
研究了弹性轨道条件下,控制回路中位置反馈信号存在时滞的磁浮系统在亚谐轨道激励作用下的响应问题. 将动力学模型在平衡点处线性化,以时滞为分岔参数,得到了系统出现Hopf分岔的条件. 用中心流形约化方法得到了包含轨道扰动系统的Poincaré规范型. 用多尺度法从理论上推导了时滞磁浮系统的亚谐共振周期解,得到了自由振动的分岔响应方程,分析了周期解中自由振动项的存在条件,研究了控制参数和激励参数与周期解的关系. 最后用数值仿真的方法分析了时滞参数、控制参数对系统响应的影响,分析结果指出,使系统保持稳定的亚谐响应的时滞边界小于无扰动时的时滞边界,时滞参数不但可以抑制亚谐响应,还能够控制混沌的产生,而控制参数可以控制系统响应中自由振动项的出现和受迫振动的幅值,适当选择这些参数可以有效抑制亚谐振动响应.
关键词:
亚谐共振响应
位置时滞反馈控制
非自治磁浮系统
分岔 相似文献
13.
R.?Aust P.?H?vel J.?Hizanidis E.?Sch?ll 《The European physical journal. Special topics》2010,187(1):77-85
We consider a simple paradigmatic system of type-I excitability subject to noise and time-delayed feedback. This system is
governed by a global bifurcation, namely a saddle-node bifurcation on a limit cycle. In the absence of noise, delay can induce
complex dynamics including multiple stable and unstable periodic orbits. Random fluctuations result in coherence resonance
in dependence on the noise strength. We show that this effect can be enhanced by delayed feedback control with suitably chosen
feedback strength and time delay. 相似文献
14.
This paper undertakes a nonlinear analysis of a model for a maglev system with time-delayed feedback. Using linear analysis, we determine constraints on the feedback control gains and the time delay which ensure stability of the maglev system. We then show that a Hopf bifurcation occurs at the linear stability boundary. To gain insight into the periodic motion which arises from the Hopf bifurcation, we use the method of multiple scales on the nonlinear model. This analysis shows that for practical operating ranges, the maglev system undergoes both subcritical and supercritical bifurcations, which give rise to unstable and stable limit cycles respectively. Numerical simulations confirm the theoretical results and indicate that unstable limit cycles may coexist with the stable equilibrium state. This means that large enough perturbations may cause instability in the system even if the feedback gains are such that the linear theory predicts that the equilibrium state is stable. 相似文献
15.
The purpose of this Letter is to show how a border-collision bifurcation in a piecewise-smooth dynamical system can produce a direct transition from a stable equilibrium point to a two-dimensional invariant torus. Considering a system of nonautonomous differential equations describing the behavior of a power electronic DC/DC converter, we first determine the chart of dynamical modes and show that there is a region of parameter space in which the system has a single stable equilibrium point. Under variation of the parameters, this equilibrium may collide with a discontinuity boundary between two smooth regions in phase space. When this happens, one can observe a number of different bifurcation scenarios. One scenario is the continuous transformation of the stable equilibrium into a stable period-1 cycle. Another is the transformation of the stable equilibrium into an unstable period-1 cycle with complex conjugate multipliers, and the associated formation of a two-dimensional (ergodic or resonant) torus. 相似文献
16.
Stability and Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback 下载免费PDF全文
The stability and the Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback are studied.By considering the energy in the air-gap field of the AC motor,the dynamical equation of the electromechanical coupling transmission system is deduced and a time delay feedback is introduced to control the dynamic behaviors of the system.The characteristic roots and the stable regions of time delay are determined by the direct method,and the relationship between the feedback gain and the length summation of stable regions is analyzed.Choosing the time delay as a bifurcation parameter,we find that the Hopf bifurcation occurs when the time delay passes through a critical value.A formula for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions is given by using the normal form method and the center manifold theorem.Numerical simulations are also performed,which confirm the analytical results. 相似文献
17.
Zhanybai T. Zhusubaliyev Olga O. Yanochkina Erik Mosekilde 《Physica D: Nonlinear Phenomena》2011,240(4-5):397-405
Pulse modulated power electronic converters represent an important class of piecewise-smooth dynamical systems with a broad range of applications in modern power supply systems. The paper presents a detailed investigation of a number of unusual bifurcation phenomena that can occur in power converters with multilevel control. In the first example a closed invariant curve arises in a border-collision bifurcation as a period-6 saddle cycle collides with a stable fixed point of focus type and transforms it into an unstable focus point. The second example involves the formation of a structure of coexisting tori through the interplay between border-collision and global bifurcations. We examine the behavior of the system in the presence of two coexisting stable resonance tori and finally show how an existing torus can develop heteroclinic bubbles that connect the points of a stable resonance cycle with an external pair of saddle and focus cycles. The appearance of these structures is explained in terms of a sequence torus-birth bifurcations with pairs of stable and unstable tori folding one over the other. 相似文献
18.
A feedback control method is proposed to create a degenerate Hopf bifurcation in three-dimensional maps at a desired parameter point. The particularity of this bifurcation is that the system admits a stable fixed point inside a stable Hopf circle, between which an unstable Hopf circle resides. The interest of this solution structure is that the asymptotic behavior of the system can be switched between stationary and quasi-periodic motions by only tuning the initial state conditions. A set of critical and stability conditions for the degenerate Hopf bifurcation are discussed. The washout-filter-based controller with a polynomial control law is utilized. The control gains are derived from the theory of Chenciner's degenerate Hopf bifurcation with the aid of the center manifold reduction and the normal form evolution. 相似文献
19.
宽输入范围的Boost电路会跨越稳定和不稳定工作区,产生的混沌现象导致电路工作异常.以连续电流传导模式为基础,讨论Boost电路的参数正弦扰动调整与镇定过程,分析稳定状态和不稳定状态在不同正弦扰动幅度下的相互转化过程,推导电路工作状态转化的临界条件,研究宽输入范围时电路的可稳定条件.数字仿真说明参数正弦扰动不仅可以抑制不稳定电路的混沌现象,也可以使本身稳定的电路进入不稳定状态.对宽输入电压范围的Boost电路,可在一定区域内选择合适的扰动幅度,保证电路稳定可靠地起动、调整和镇定. 相似文献
20.
Finn JM 《Chaos (Woodbury, N.Y.)》2002,12(2):508-517
The effect of an externally imposed perturbation on an unstable or weakly stable shear flow is investigated, with a focus on the role of Lagrangian chaos in the bifurcations that occur. The external perturbation is at rest in the laboratory frame and can form a chain of resonances or cat's eyes where the initial velocity v(x0)(y) vanishes. If in addition the shear profile is unstable or weakly stable to a Kelvin-Helmholtz instability, for a certain amplitude of the external perturbation there can be an unlocking bifurcation to a nonlinear wave resonant around a different value of y, with nonzero phase velocity. The interaction of the propagating nonlinear wave with the external perturbation leads to Lagrangian chaos. We discuss results based on numerical simulations for different amplitudes of the external perturbation. The response to the external perturbation is strong, apparently because of non-normality of the linear operator, and the unlocking bifurcation is hysteretic. The results indicate that the observed Lagrangian chaos is responsible for a second bifurcation occurring at larger external perturbation, locking the wave to the wall. This bifurcation is nonhysteretic. The mechanism by which the chaos leads to locking in this second bifurcation is by means of chaotic advective transport of momentum from one chain of resonances to the other (Reynolds stress) and momentum transport to the vicinity of the wall via chaotic scattering. These results suggest that locking of waves in rotating tank experiments in the presence of two unstable modes is due to a similar process. (c) 2002 American Institute of Physics. 相似文献