基于延时干扰的感应电能传输系统分岔频率输送控制

本文针对感应电能传输系统分岔频率的输送控制问题, 提出一种基于延时干扰的变轨控制方法. 该方法在反馈控制环节中加入一段延时干扰, 通过调节延时参数, 可使系统相轨迹流在各稳定极限环吸引子间自由切换. 文中以原副边均为串联谐振的感应电能传输系统为例, 对该方法的机理及实现方案进行了研究, 并通过仿真和实验验证了其有效性. 论文的研究结果对类似多吸引子分岔行为的输送控制可提供一定的理论参考. 关键词： 感应电能传输 频率分岔 输送控制 延时干扰     

随机扰动优化和多模型融合的目标密度非线性重建

针对高能闪光X射线图像线性重建结果受系统模糊影响的问题,提出一种随机扰动优化和多模型融合的非线性重建算法.构建非线性正向模型并推导相应的雅可比矩阵形式,结合贝叶斯理论考虑该反演问题的求解及不确定量化,引入基于弱信息先验的超参数构建非线性分层贝叶斯模型.通过加速求解随机扰动的优化问题对条件分布进行采样,结合雅可比矩阵投影...     

电压反馈型DC-DC变换器的稳定性研究

建立了电压反馈型DC-DC变换器连续运行模式下的频闪映射模型，利用离散映射方程的Jacobian矩阵的特征值分析了变换器在参数变化时不动点的失稳情况. 以具体的电压反馈型buck变换器为例， 通过理论分析与数值仿真，两者的结果具有很好的一致性，表明利用离散映射分析DC-DC变换器的稳定性是切实可行的. 关键词： 离散映射模型 DC-DC变换器 稳定性     

集成光波导陀螺双光路三角波调相谱脉冲噪声特性

基于三角波调相谱技术的谐振式集成光波导陀螺(RIOG)信号检测,光波相位调制引入的频谱分量所带来的光学噪声成为限制陀螺性能提升的主要因素。结合光波在三角波相位调制下的频率变化特性和波导谐振腔的光传输特性,给出了三角波调制下的同步解调信息;依据三角波调制下对背向散射噪声抑制的幅度调制参数和系统最大灵敏度工作点的频率调制参数,结合多光场叠加原理,理论仿真分析了谐振谱不同谐振区的输出脉冲噪声,这种脉冲噪声将对工作于不同调制频率下顺逆时针传输光波的信号采集区带来干扰;搭建了基于二氧化硅波导环形谐振腔的陀螺实验系统,分别测试了激光扫描下谐振腔不同谐振区的脉冲噪声和激光频率锁定在谐振腔谐振点时的脉冲噪声,与理论分析一致。分析结果表明,RIOG采用的三角波调相谱信号检测技术存在无法克服的脉冲噪声,针对不同要求的RIOG,给出了相应的调制技术方案,这为RIOG的工程化和性能优化提供了技术参考。     

谐振式磁耦合无线电能传输系统传输特性及实验仪设计

利用磁耦合理论,分析了谐振式磁耦合无线电能传输系统的传输特性,开发了一种谐振式双线圈磁耦合无线电能传输实验仪.利用LED负载直观定性地观测了系统的传输特性,实验测量了发射线圈高频等效电阻及系统输出功率与信号频率、传输距离和负载的关系,获到了最大传输功率条件和频率分裂规律.实验表明,线圈在MHz频率下趋肤效应明显,频率越高,等效电阻越大;磁耦合无线电能传输系统的谐振特性不仅与频率相关,还与耦合系数相关;最佳全谐振时输出功率和传输效率最大.本实验仪可拓展测量RLC串联电路稳态特性,工作稳定,实验与理论吻合好.     

二维均匀耦合映象格子中的时空周期图案

目的——构造二维均匀耦合映象格子中的时空周期图案;方法——通过一维耦合映象格子模型的相空间中已知低空间周期轨道,直接构造二维均匀耦合映象格子模型中一系列空间周期轨道,而不必求解其模型方程,并对构造轨道的稳定性进行分析;结果——L²×L²雅可比矩阵可化简为几个2×2矩阵组成的对角矩阵;结论——所构造轨道的稳定性不可能比原来轨道的稳定性高. 关键词： 耦合映象格子 时空周期图案 雅可比矩阵     

基于有限元分析电能无线传输实验的谐振传输特性

通过三维有限元电磁仿真软件设计了电能无线传输实验的仿真模型,研究了电能无线传输实验的谐振特性以及传输特性.通过合理设置参量,模拟电能无线传输实验的电磁能量传输过程.通过控制变量法,研究电能无线传输过程中,实验参数对其传输性能的影响,主要包括谐振线圈的匝数、线圈的间距、谐振状态等因素对传输距离和谐振频率的影响.     

一类具有两个边界的分段光滑系统中边界碰撞分岔现象及混沌

以不连续运行模式下的电流反馈型Buck-Boost变换器为例，导出了一类具有三段形式的分段光滑迭代映射方程，数值仿真得到了输入电压变化时的分岔图.结果表明，发生分岔时映射雅可比矩阵的特征值以不连续的方式跳跃出复平面上的单位圆，而且映射总有某个或某些轨道点位于相平面中不同区域的边界上，即映射随输入电压的变化会发生边界碰撞分岔现象，如由周期态到周期态以及由周期态到混沌态的分岔. 关键词： 分段光滑系统 边界碰撞分岔 混沌     

光纤光栅传输矩阵研究

利用模耦合理论给出并分析了一般坐标系下相移布喇格光纤光栅中的传输矩阵及其特性,所给出的传输矩阵具有分段不变性,而且不能被分解为一个矩阵和一个相移矩阵的乘积.利用该传输矩阵可以研究均匀、相移、啁啾、超结构等光纤光栅及光栅的级联等.计算了相移光栅的反射谱和相移量的关系,以及两个光栅级联时的反射谱.结果表明,同样相移量时的反射谱和已有文献不同,两个光栅级联时,也不同于已有文献,各自的谐振波长与光栅的级联没有关系.     

基于磁耦合谐振式的无线电能传输系统

提出了一种基于磁耦合谐振式的无线电能传输系统,该系统能够提高电能的传输效率和传输距离,具有良好的发展前景.     

LCC谐振变换器的电路建模与参数设计

对用于高压场合的LCC谐振变换器进行了分析和研究,采用基波近似法推导等效模型,建立了谐振电路的大信号模型和等效模型,对LCC谐振变换器的稳态特性进行分析,采用了一种以输入阻抗角为限定条件的参数设计方法,该方法可以实现谐振变换器零电压开关的同时兼顾谐振电流对效率的影响。在大信号模型的基础上,建立了小信号模型,得到输出电压与输入占空比之间的传递函数,从而建立闭环系统,实现电压的宽范围输出。通过Simulink仿真验证了所设计的LCC谐振变换器可实现全负载范围的零电压开关(ZVS),说明了设计方法的可行性。     

A transient method for measuring the gas volume fraction in a mixed gas-liquid flow using acoustic resonance spectroscopy

In this paper, the feasibility of measuring the gas volume fraction in a mixed gas-liquid flow by using an acoustic resonant spectroscopy (ARS) method in a transient way is studied theoretically and experimentally. Firstly, the effects of sizes and locations of a single air bubble in a cylindrical cavity with two open ends on resonant frequencies are investigated numerically. Then, a transient measurement system for ARS is established, and the trends of the resonant frequencies (RFs) and resonant amplitudes (RAs) in the cylindrical cavity with gas flux inside are investigated experimentally. The measurement results by the proposed transient method are compared with those by steady-state ones and numerical ones. The numerical results show that the RFs of the cavity are highly sensitive to the volume of the single air bubble. A tiny bubble volume perturbation may cause a prominent RF shift even though the volume of the air bubble is smaller than 0.1% of that of the cavity. When the small air bubble moves, the RF shift will change and reach its maximum value as it is located at the middle of the cavity. As the gas volume fraction of the two-phase flow is low, both the RFs and RAs from the measurement results decrease dramatically with the increasing gas volume, and this decreasing trend gradually becomes even as the gas volume fraction increases further. These experimental results agree with the theoretical ones qualitatively. In addition, the transient method for ARS is more suitable for measuring the gas volume fraction with randomness and instantaneity than the steady-state one, because the latter could not reflect the random and instant characteristics of the mixed fluid due to the time consumption for frequency sweeping. This study will play a very important role in the quantitative measurement of the gas volume fraction of multiphase flows.     

Structured H∞ Control for Spacecraft with Flexible Appendages

Spacecraft with large flexible appendages are characterized by multiple system modes. They suffer from inherent low-frequency disturbances in the operating environment that consequently result in considerable interference in the operational performance of the system. It is required that the control design ensures the system’s high pointing precision, and it is also necessary to suppress low-frequency resonant interference as well as take into account multiple performance criteria such as attitude stability and bandwidth constraints. Aiming at the comprehensive control problem of this kind of flexible spacecraft, we propose a control strategy using a structured H-infinity controller with low complexity that was designed to meet the multiple performance requirements, so as to reduce the project cost and implementation difficulty. According to the specific resonant mode of the system, the design strategy of adding an internal mode controller, a trap filter, and a series PID controller to the structured controller is proposed, so as to achieve the comprehensive control goals through cooperative control of multiple control modules. A spacecraft with flexible appendages (solar array) is presented as an illustrative example in which a weighted function was designed for each performance requirement of the system (namely robustness, stability, bandwidth limit, etc.), and a structured comprehensive performance matrix with multiple performance weights and decoupled outputs was constructed. A structured H-infinity controller meeting the comprehensive performance requirements is given, which provides a structured integrated control method with low complexity for large flexible systems that is convenient for engineering practice, and provides a theoretical basis and reference examples for structured H-infinity control. The simulation results show that the proposed controller gives better control performance compared with the traditional H-infinity one, and can successfully suppress the vibration of large flexible appendages at 0.12 Hz and 0.66 Hz.     

Lambda-scheme spectroscopy in the cat-state field

We investigate the spectroscopical scheme of a three-level system in a Λ-configuration utilizing resonant optical field being a superposition of two Glauber coherent states. The source of the field is explicitly included into the theoretical model. In the limit of strong non-classical field we propose an ansatz for solution of the master equation and calculate the steady-state density matrix. The work of both classical and nonclassical field in the steady-state regime was calculated. It was found that the presence of non-classical field creates strong atom-field correlations that results in absence of dark resonances.     

Multiple flux difference effect in the lattice hydrodynamic model

Considering the effect of multiple flux difference, an extended lattice model is proposed to improve the stability of traffic flow. The stability condition of the new model is obtained by using linear stability theory. The theoretical analysis result shows that considering the flux difference effect ahead can stabilize traffic flow. The nonlinear analysis is also conducted by using a reductive perturbation method. The modified KdV (mKdV) equation near the critical point is derived and the kink-antikink solution is obtained from the mKdV equation. Numerical simulation results show that the multiple flux difference effect can suppress the traffic jam considerably, which is in line with the analytical result.     

基于混杂自动机的电容器充电电源建模方法

针对串联谐振电容器充电电源具有高阶、多模态、强非线性的特点,提出了一种基于混杂自动机的建模方法,该方法通过描述系统的连续时间变量和离散状态变量之间的关系来展现系统的混杂特性。基于该方法建立了系统的混杂自动机模型,并提出了一种基于上述模型的分段线性充电控制策略,通过搭建仿真模型验证了该模型和控制策略的有效性。     

Principal resonance response of a stochastic elastic impact oscillator under nonlinear delayed state feedback

In this paper, the principal resonance response of a stochastically driven elastic impact(EI) system with time-delayed cubic velocity feedback is investigated. Firstly, based on the method of multiple scales, the steady-state response and its dynamic stability are analyzed in deterministic and stochastic cases, respectively. It is shown that for the case of the multivalued response with the frequency island phenomenon, only the smallest amplitude of the steady-state response is stable under a certain time delay, which is different from the case of the traditional frequency response. Then, a design criterion is proposed to suppress the jump phenomenon, which is induced by the saddle-node bifurcation. The effects of the feedback parameters on the steady-state responses, as well as the size, shape, and location of stability regions are studied. Results show that the system responses and the stability boundaries are highly dependent on these parameters. Furthermore, with the purpose of suppressing the amplitude peak and governing the resonance stability, appropriate feedback gain and time delay are derived.     

基于参数展开的同伦分析法在强非线性随机动力系统中的应用

将基于参数展开的同伦分析法(PE-HAM)进行了推广，使之适用于谐和激励与随机噪声联合作用下的强非线性随机动力系统. 通过构造合适的同伦映射，将对强非线性随机动力系统响应的求解转化为对一组线性随机微分方程的求解. 进一步研究了受到谐和与Gauss白噪声激励的强非线性Duffing振子，由PE-HAM得到了该系统的解过程和稳态概率密度的解析表达式. 数值模拟的结果说明了PE-HAM方法的精确性. 关键词： PE-HAM方法 强非线性随机动力系统 稳态概率密度 解过程 随机激励     

A nonlinear system under combined periodic and random excitation

The anharmonic oscillator under combined sinusoidal and white noise excitation is studied using the Gaussian closure approximation. The mean response and the steady-state variance of the system is obtained by the WKBJ approximation and also by the Fokker-Planck equation. The multiple steadystate solutions are obtained and their stability analysis is presented. Numerical results are obtained for a particular set of system parameters. The theoretical results are compared with a digital simulation study to bring out the usefulness of the present approximate theory.