基于非线性匹配追踪的激光微多普勒信号特征参数提取

针对振动目标的激光微多普勒信号特征参数提取问题,引入一种新的时频分析方法即非线性匹配追踪算法(NMP),但该算法在强噪声和弱调制条件下存在较大局限性。由此提出一种加权平均频率算法(WAFA-NMP)对其抗噪性能进行改进,通过滑动矩形窗对NMP所提取本征函数的瞬时频率和幅度进行加权平均,得到其对应的时频分布。同时,对于弱调制条件下参数提取困难的问题,提出欠采样的WAFA-NMP来提取弱调制下的微动参数。仿真实验表明,与Wigner-Ville分布及平滑伪Wigner-Ville分布比较,提出的WAFA-NMP方法性能更好,其平均估值精度高达96%,抗噪性能在-10 d B以上。

非匹配不确定非线性系统的滑模跟踪控制

在非匹配不确定非线性系统中 ,系统状态之间无通常的积分关系 ,从而无法得到系统状态的各阶导数 .因此 ,那些基于系统状态各阶导数的滑模控制方法也就无法实现 .为此 ,在利用多级滑模观测器对系统状态的各阶导数进行估计的基础上 ,针对非匹配不确定非线性系统 ,采用合成输入这一概念来构造滑动面 ,将其选取为跟踪误差及其积分、微分的线性组合 .利用 Lyapunov方法对滑模控制律进行设计 ,以实现滑动模 ,进而实现此类系统的跟踪控制 .设计过程同时也证明了 ,利用多级观测器 ,该滑模控制方法对非线性不确定性因素具有鲁棒性 ,闭环系统在有限时间内进入滑动模态 .

基于禁止搜索的非线性时间匹配优化算法

动态时间规整算法DTW(Dynamic Time Warping)作为一种非线性时间匹配技术已成功地应用于语音识别系统中。DTW算法使用动态规划技术来搜索两个时间序列的最优规整路径,虽然这种算法计算量小,运算时间较短,但只是一种局部优化算法。禁止搜索TS(Tabu Search)算法是一种具有短期记忆的广义启发式全局搜索技术,适用于解决许多非线性优化问题。本文将该技术用于语音识别系统中,提出了基于禁止搜索的非线性时间规整的优化算法TSTW,使得时间规整函数尽可能逼近全局最优。仿真结果表明,TSTW比DTW有更高的识别率,且运行时间比遗传时间规整算法GTW大大减少。

非匹配不确定非线性系统的反演变结构控制

讨论一类非匹配不确定的非线性系统的输出跟踪问题。结合反演 ( Backstepping)设计方法和变结构控制 ,提出了反演变结构控制策略。对存在非匹配不确定性和未知干扰的系统 ,设计的反演变结构控制器实现鲁棒输出跟踪 ,闭环系统在有限时间进入滑动模态。

非匹配非线性系统的ACPID控制方法

非匹配扰动是工程实际问题中常见的干扰类型,传统的控制方法难以达到理想的控制效果,在此背景下,针对一类非匹配非线性系统,提出一种基于自耦PID(ACPID)控制理论的控制方法。首先,将非匹配通道的外部扰动与内部状态定义为一个未知状态,同时将内部动态、外部扰动定义为一个总和扰动,从而将非匹配非线性系统映射为一个等价的未知线性系统。其次,构建一个受总和扰动反相激励的受控误差系统,结合ACPID控制理论设计ACPD控制器,构造闭环控制系统模型,并分析闭环控制系统的鲁棒稳定性。最后,以二阶非匹配非线性系统为例验证所提方法的有效性。仿真结果表明,ACPID控制系统不仅具有良好的动态品质和稳态性能,而且还具有良好的抗扰动鲁棒性和快的响应速度,在电力、交通、航空航天等广泛领域具有实际应用前景。

一种用于预失真线性化器的宽带匹配技术

由于放大链路的增益波动以及不同频点之间非线性特性的差异,预失真器难以在不同的频点同时实现非线性特性匹配,即令整个频带内不同频点的线性度指标同时满足要求。由于预失真器和放大器之间的非线性失配,放大器在某些频点的非线性特性还会恶化。本文从线性化器与预失真器的宽带匹配出发,讨论了预失真线性化器与行波管放大器宽带匹配的条件以及非线性失配所带来的影响,当增益失配误差不大于1 dB时,在行波管放大器自身的三阶交调值不大于40 dB的非线性动态范围内,三阶交调下降幅度最大值为4.1 dB;通过采用级联增益补偿电路的方式,降低链路增益波动,实现预失真器和放大器的非线性匹配,真正拓展预失真线性化器的工作带宽。

高阶非线性未知系统的ACPI控制方法

针对一类含有非匹配干扰的高阶非线性未知系统的控制问题,采用一种基于自耦比例-积分(ACPI)控制理论的虚拟递推控制方法,该方法通过引入未知状态和总和扰动的概念,将非匹配非线性系统映射为等价的线性未知系统,并构建了一个在总和扰动反相激励下的受控误差系统,结合ACPI控制理论构造了以速度因子为核心联系因子的ACPI虚拟指令,为了有效避免反步控制中存在的“微分爆炸”问题,将各虚拟指令的微分定义为未知有界扰动。仿真结果表明了ACPI控制系统不仅具有良好的动态品质和稳态性能,而且具有良好的抗扰动鲁棒性,因而在高阶非线性未知系统控制领域具有广泛的应用前景。

基于一致空间映射的改进ORB特征匹配算法

针对传统ORB(Oriented Fast and Rotated BRIEF)算法误匹配率高、抗视角变换能力弱等问题,提出一种融合交叉验证ORB和一致空间映射的快速图像匹配算法。在ORB算法的框架下分别检测模板图像和目标图像的特征点集,并利用每个特征点的描述符建立两个特征点集之间的对应关系;利用每对特征点邻域的支持点集交叉验证对应特征点对的准确性;在粗剔除低准确性的对应特征点对后,通过一致空间映射对经过筛选的特征点集进行稳健的非线性匹配。实验结果表明,该算法优于当前主流的图像特征匹配算法,并且在处理大视角变换和现实场景下的图像特征匹配问题时稳健性较强。

党政机关文秘工作人岗匹配研究--以邢台市X区办公室为例

现阶段,我国党政机关文秘机构在人岗匹配上缺少具体的量化标准,不能有效评估文秘工作人员的任职资格,未能充分发挥人才在岗位上的最佳价值。文章基于胜任力冰山模型,结合邢台市X区办公室现行运行机制,构建了文秘人员素质模型,探究X区党政机关文秘工作的发展成效与人岗匹配的现实困境,并就构建非线性人岗匹配模型提出解决路径,期望对党政机关文秘工作人岗相适提供借鉴。

考虑杆臂效应和挠曲变形的大失准角快速传递对准

提出一种非线性'速度'+'姿态'的匹配模型,具体采用无迹卡尔曼滤波器,仿真在杆臂效应和挠曲变形两大因素综合作用下大失准角的估计精度。结果表明,该模型能够在60 s内估算出失准角的大小并满足战术级武器的精度要求。

基于蒙皮模型和WEOPA的人体外形和运动跟踪

为了解决多关节人体三维外形和运动跟踪问题,提出了一种基于蒙皮模型(skinned model)和加权扩展正交普鲁克分析(weighted extended orthogonal procrustes analysis,WEOPA)的三维人体外形和运动跟踪方法。首先使用Shape-From-Silhouettes方法从当前帧多目视频图像轮廓中计算出被跟踪人物的可视外壳,然后建立人物先验蒙皮模型并与之匹配,其中蒙皮模型的引入使得多关节人体三维外形和运动跟踪问题被转化为一个分层非线性最小二乘匹配问题。考虑到在先验模型获取中肢体间连接部位产生的网格顶点粘连问题,采用WEOPA算法来进行求解,其中通过引入4种不同的权值分配策略,克服了顶点粘连对匹配的影响,并有效利用了匹配点对的几何法线信息。实验结果表明,该方法能对人物外形和运动进行有效的跟踪。

投影模板耦合遗传算法的红外图像点目标检测

当前基于模板匹配的红外图像点目标定位检测技术难以扑获图像的高阶统计特性,无法描述图像的非线性结构,且此类算法直接将图像作为模板,使算法稳定性不佳,为此提出非线性模板匹配耦合遗传算法的红外图像点目标定位检测技术。定义参数约束边界,改进2D高斯强度函数,获取目标训练图像;引入主成分分析(principal component analysis,PCA),利用其特征提取函数,通过预设阈值,将目标训练矢量投影到该函数的特征向量中,设计PCA加权投影系数模板;考虑图像的高阶统计特性,嵌入内核函数,联合非线性映射与相关系数,构造特征空间内的归一化非线性相关系数计算模型,估算投影系数模板与测试模板之间的相似度;引入遗传算法,快速求解相关匹配。实验结果表明,与当前红外图像微小目标检测技术相比,该算法拥有最佳的稳定性与定位性能,在复杂背景下,成功检测出了点目标,且其信杂比值最高,时耗最短。

L_1 adaptive controller of nonlinear reference system in presence of unmatched uncertainties

An extension of L_1 adaptive control is proposed for the unmatched uncertain nonlinear system with the nonlinear reference system that defines the performance specifications. The control law adapts fast and tracks the reference system with the guaranteed robustness and transient performance in the presence of unmatched uncertainties. The interval analysis is used to build the quasi-linear parameter-varying model of unmatched nonlinear system, and the robust stability of the proposed controller is addressed by sum of squares programming. The transient performance analysis shows that within the limit of hardware a large adaption gain can improve the asymptotic tracking performance. Simulation results are provided to demonstrate the theoretical findings of the proposed controller.

Seismic-inversion method for nonlinear mapping multilevel well–seismic matching based on bidirectional long short-term memory networks

In this paper,the recurrent neural network structure of a bidirectional long shortterm memory network(Bi-LSTM)with special memory cells that store information is used to characterize the deep features of the variation pattern between logging and seismic data.A mapping relationship model between high-frequency logging data and low-frequency seismic data is established via nonlinear mapping.The seismic waveform is infinitely approximated using the logging curve in the low-frequency band to obtain a nonlinear mapping model of this scale,which then stepwise approach the logging curve in the high-frequency band.Finally,a seismic-inversion method of nonlinear mapping multilevel well–seismic matching based on the Bi-LSTM network is developed.The characteristic of this method is that by applying the multilevel well–seismic matching process,the seismic data are stepwise matched to the scale range that is consistent with the logging curve.Further,the matching operator at each level can be stably obtained to effectively overcome the problems that occur in the well–seismic matching process,such as the inconsistency in the scale of two types of data,accuracy in extracting the seismic wavelet of the well-side seismic traces,and multiplicity of solutions.Model test and practical application demonstrate that this method improves the vertical resolution of inversion results,and at the same time,the boundary and the lateral characteristics of the sand body are well maintained to improve the accuracy of thin-layer sand body prediction and achieve an improved practical application effect.

Evolution of Dark Spatial Soliton in Quasi-phase-matched Quadratic Media

We theoretically investigate the evolvement of dark spatial soliton withcascading quadratic nonlinearity in quasi-phase-matched second harmonic generation. It is shown thatthe dark solitary wave can propagate stably when background intensity is large enough, in whichdiffraction of beam can be balanced by the cascading quadratic nonlinearity. We also analyze theinfluence of phase-mismatch on the stabihty of dark soliton propagation.

Nonlinear optical holograms for spatial and spectral shaping of light waves

Shaping either the spatial or the spectral output of a nonlinear interaction is accomplished by introducing basic concepts of computer-generated holography into the nonlinear optics regime. The possibilities of arbitrarily spatially shaping the result of a nonlinear interaction are presented for different phase-matching schemes allowing for both one- and two-dimensional shaping. Shaping the spectrum of a beam in nonlinear interaction is also possible by utilizing similar holographic techniques. The novel and complete control of the output of a nonlinear interaction opens exciting options in the fields of particle manipulation, optical communications, spectroscopy and quantum information.

A numerical study on matching relationships of gravity waves in nonlinear interactions

Applying a fully nonlinear numerical scheme with second-order temporal and spatial precision,nonlinear interactions of gravity waves are simulated and the matching relationships of the wavelengths and frequencies of the interacting waves are discussed.In resonant interactions,the wavelengths of the excited wave are in good agreement with the values derived from sum or difference resonant conditions,and the frequencies of the three waves also satisfy the matching condition.Since the interacting waves obey the resonant conditions,resonant interactions have a reversible feature that for a resonant wave triad,any two waves are selected to be the initial perturbations,and the third wave can then be excited through sum or difference resonant interaction.The numerical results for nonresonant triads show that in nonresonant interactions,the wave vectors tend to approximately match in a single direction,generally in the horizontal direction.The frequency of the excited wave is close to the matching value,and the degree of mismatching of frequencies may depend on the combined effect of both the wavenumber and frequency mismatches that should benefit energy exchange to the greatest extent.The matching and mismatching relationships in nonresonant interactions differ from the results of weak interaction theory that the wave vectors are required to satisfy the resonant matching condition but the frequencies are permitted to mismatch and oscillate with amplitude of half the mismatching frequency.Nonresonant excitation has an irreversible characteristic,which is different from what is found for the resonant interaction.For specified initial primary and secondary waves,it is difficult to predict the values of the mismatching wavenumber and frequency for the excited wave owing to the complexity.