基于改进变步长LMS算法的谐波电流检测法

针对传统基于瞬时无功功率理论谐波电流检测中的二阶低通滤波器无法同时满足检测精度和响应时间的问题,提出了基于改进的双曲正切函数变步长LMS算法(IVSSLMS)的低通滤波器提取p轴和q轴中直流分量的方法;将两个谐波电流的间隔时间通过适当的调节采样间隔次数来延长,目的是为了达到高次谐波的自相关性能迅速降为零。从理论上分析了算法性能的优越,给出了参数的取值,并在simulink中搭建了仿真模型,仿真实验结果表明,改进后的低通滤波器直流分量的跟踪速度提升了一倍,得到基波正弦波形的THD值下降了0.37%。并得出以下结论:在同样输电条件下,采用改进变步长LMS算法构成低通滤波器加快了直流量的跟踪,提取的基波分量更加接近于理想波形,提升了谐波检测的瞬时性和准确性。

基于x-LMS算法的直升机主动消振电力作动器系统研究

直升机前飞时,气动环境会导致不同方位角的桨叶出现气动载荷的瞬间不对称,通过基础结构传递会在机身形成大幅度的低频振动。为了消除多方向幅值变化的振动力,利用结构响应主动控制原理,设计了基于x-LMS算法的主动消振电力作动器系统,并进行了减振实验。首先,通过比较确定了单台作动器中两台电机同向旋转的方案。通过两台作动器的组合使用,推导出输出力的数学模型。其次,采用负载相位差交叉耦合的控制策略设计系统控制框图。针对存在耦合的相位外环,通过回差阵特征值法确定满足系统稳定裕度要求的参数范围,再根据灵敏度函数和输入跟踪性能在所得的参数稳定域内寻找最优解。然后,提出了基于x-LMS算法的直升机主动振动控制系统,并通过仿真验证了该系统的减振效果。最后,研制的实验样机进行了动稳态实验以及减振实验,验证了系统的实际减振效果。

基于Adam算法的LMS优化

虽然传统的LMS算法简单有效,但它的收敛速度较慢,容易受到初始权值选择和步长设置的影响。为了解决这个问题,我们引入了Adam算法的自适应学习率特性到LMS算法中。Adam算法通过一阶矩估计(mean)和二阶矩估计(variance)来估计梯度的均值和方差,并根据这些估计值来调整学习率。这样可以对梯度下降的方向和速度进行更精细地控制。通过Adam算法对LMS优化,LMS算法在更新权重时能够更加高效地利用梯度信息,从而提高训练速度和收敛性能。此外,优化后的算法还具有一些超参数,如beta1、beta2和eps等,需要根据具体的应用场景和数据特点进行调节,以获得最佳的优化效果。仿真结果表明优化方案比传统LMS算法在收敛过程中的震荡要更小。

基于CEEMDAN-VSSLMS的滚动轴承故障诊断

针对传统机械轴承故障诊断模型易受系统噪声干扰、特征识别效率低等问题,提出一种基于信号固有模式深度建模分析的轴承故障诊断方法。首先,将采集到的轴承振动信号进行噪声自适应完全经验模态分解(CEEMDAN),获得不同时间尺度的局部特征信号,使用相关系数判别并去除虚假模态分量,再利用可变步长最小均方算法(VSSLMS)对剩余IMF分量降噪并进行重构;然后,将降噪后的振动信号进行离散小波变换(DWT)得到时频谱图,并利用形态学开运算进行特征增强;最后利用改进GoogLeNet网络模型对特征图进行训练,通过Softmax分类器完成特征归类,从而实现轴承故障诊断。将提出的故障诊断方法应用于不同工况下的轴承故障数据集,试验结果表明,所提方法在噪声干扰下具有较高的诊断精度。

水稻类病变突变体lms1的表型鉴定与抗病分子机制分析

类病变突变体是研究植物细胞死亡和抗病分子机制的重要遗传材料。通过辐射诱变粳稻品种武运粳7号,获得一个少见的抗病性下降的类病变突变体lms1(lesion mimic and disease susceptible mutant 1)。与野生型相比,该突变体叶片自发出现红褐色斑点,其株高、穗长、每穗粒数以及单株产量降低,但千粒重增加;对水稻白叶枯病的抗性显著下降,组织染色表明突变体的叶片中存在明显的细胞死亡以及活性氧的过量积累。遗传分析表明,lms1突变体的表型受单隐性核基因控制,利用图位克隆技术将lms1基因精细定位于水稻9号染色体Indel7和Indel8两个分子标记间,物理距离为62 kb。定位区间内候选基因的PCR扩增测序结果表明,其中一个编码泛素羧基末端水解酶的OsLMP1(Lesion Mimic Phenotype 1)基因第1个外显子中插入了一段长度为654 bp的序列,导致其蛋白翻译提前终止。利用蛋白组学技术分析了lms1突变体与野生型对照的蛋白积累水平,共鉴定到19个差异蛋白(7个上调、12个下调),主要参与氧化还原、叶绿素合成、光合作用等代谢途径。上述结果为进一步研究OsLMP1基因的功能及其调控细胞程序性死亡与抗病性的分子机制提供借鉴。

一种基于动态门限与LMS算法相结合的多径干扰抑制算法

在船舰行驶过程中,信号的传输在岛屿反射与海面散射影响下易产生多径效应,使船舰的无线地空数据接收系统受到影响。为提高接收机的接收性能,首先完成了多径信道的建模,搭建了三径信道模型,并在此模型下,将动态门限法与最小均方(LMS)算法进行改进结合,并用此算法完成了信号处理的研究与仿真。仿真结果表明,所提算法优化方案可以提高在此种情况下信号接收系统的准确性。

A novel dynamic step size LMS optimization scheme for interference reducing in FBMC-QAM

Filter bank multicarrier quadrature amplitude modulation(FBMC-QAM)will encounter inter-ference and noise during the process of channel transmission.In order to suppress the interference in the communication system,channel equalization is carried out at the receiver.Given that the con-ventional least mean square(LMS)equilibrium algorithm usually suffer from drawbacks such as the inability to converge quickly in large step sizes and poor stability in small step sizes when searching for optimal weights,in this paper,a design scheme for adaptive equalization with dynamic step size LMS optimization is proposed,which can further improve the convergence and error stability of the algorithm by calling the Sigmoid function and introducing three new parameters to control the range of step size values,adjust the steepness of step size,and reduce steady-state errors in small step sta-ges.Theoretical analysis and simulation results demonstrate that compared with the conventional LMS algorithm and the neural network-based residual deep neural network(Res-DNN)algorithm,the adopted dynamic step size LMS optimization scheme can not only obtain faster convergence speed,but also get smaller error values in the signal recovery process,thereby achieving better bit error rate(BER)performance.

一种可用于低信噪比环境的变步长LMS算法

论文研究了自适应最小均方误差(Least Mean Squares,LMS)滤波算法的步长选取问题。在分析现有算法的基础上,通过构造步长与误差信号之间的非线性函数,提出一种新的变步长LMS算法。新算法采用误差信号的自相关估计值控制步长,而不是直接利用瞬时误差控制步长,避免了噪声干扰,降低了稳态失调,可工作于低信噪比环境。同时新算法步长控制无记忆效应,提高了收敛速度。仿真表明,新算法的稳态失调和收敛速度均优于现有变步长LMS算法。

Underwater four-quadrant dual-beam circumferential scanning laser fuze using nonlinear adaptive backscatter filter based on pauseable SAF-LMS algorithm

The phenomenon of a target echo peak overlapping with the backscattered echo peak significantly undermines the detection range and precision of underwater laser fuzes.To overcome this issue,we propose a four-quadrant dual-beam circumferential scanning laser fuze to distinguish various interference signals and provide more real-time data for the backscatter filtering algorithm.This enhances the algorithm loading capability of the fuze.In order to address the problem of insufficient filtering capacity in existing linear backscatter filtering algorithms,we develop a nonlinear backscattering adaptive filter based on the spline adaptive filter least mean square(SAF-LMS)algorithm.We also designed an algorithm pause module to retain the original trend of the target echo peak,improving the time discrimination accuracy and anti-interference capability of the fuze.Finally,experiments are conducted with varying signal-to-noise ratios of the original underwater target echo signals.The experimental results show that the average signal-to-noise ratio before and after filtering can be improved by more than31 d B,with an increase of up to 76%in extreme detection distance.

基于sigmoid-sinh分段函数的变步长FxLMS算法

为改善滤波-x最小均方(filtered-x least mean square,FxLMS)算法在噪声主动控制时无法兼顾收敛速度和稳态误差的问题,提出了基于sigmoid-sinh分段函数的FxLMS(SSFxLMS)算法,并引入蚁狮算法对SFxLMS(sigmoid filtered-x least mean square)、ShFxLMS(sinh filtered-x least mean square)、SSFxLMS算法的参数进行优化。分别采用高斯白噪声和实测簇绒地毯织机噪声为输入信号,采用FxLMS、SFxLMS、ShFxLMS、SSFxLMS算法进行噪声主动控制仿真,对比分析这4种算法的性能。结果表明:与其他3种算法相比,采用SSFxLMS算法对高斯白噪声和簇绒地毯织机噪声进行控制时,误差信号的平均绝对值更小,平均降噪量与收敛速度也有大幅度提升。由此可知,SSFxLMS算法有效改善了FxLMS算法无法兼顾收敛速度和稳态误差的问题,研究结果为噪声主动控制算法设计提供了一定的参考。

基于镜像修正FxLMS控制算法的船舶管路振动主动控制

针对船舶管路减振和抗冲击的需求,本文根据镜像修正自适应滤波算法,设计出了一种管路振动主动控制策略,能够有效地控制管路在低频下的振动,并且在次级通道发生突变时,控制系统可再次快速收敛,进行稳定控制。本文先对镜像修正自适应滤波算法进行理论研究,分析算法的迭代及控制过程;再通过仿真分别验证算法在不同参考信号输入下的收敛性及稳定性;最后搭建实验台架,通过试验验证算法的实际控制效果。试验结果表明:该控制策略在管路振动主动控制中能够降低15.37%的振动强度,比自适应滤波算法控制策略的控制效果好8.85%。所以镜像修正自适应滤波算法能够及时有效地进行管路振动控制。

基于自适应LMS算法的跨声速风洞模型系统辨识

针对风洞试验模型系统辨识不准确的问题,利用自适应LMS(least mean square)滤波器模型对跨声速风洞模型进行系统辨识。由于实测信号中存在多模态耦合,为了提高系统辨识精准度,首先对输入输出信号作了FRF(frequency response analysis)分析得到试验模型俯仰方向前两阶模态,其次利用快速Fourier变换进行模态解耦,接着利用自适应LMS滤波器模型、传递函数模型、多项式模型对俯仰方向单模态进行系统辨识,最后得到了基于自适应LMS滤波器模型的俯仰方向一阶、二阶模态滤波器系数。通过对比不同数学模型的输出与输入之间的相关系数和均方误差及辨识结果,表明自适应LMS滤波器模型具有更高的系统辨识精准度和更简洁的数学模型结构。为后续风洞试验模型振动主动控制计算法的设计提供有力支撑。

基于LMS算法的短波通信数据干扰控制技术

短波通信原理简单,已广泛应用于大型无线通信系统。但在实际应用中,很多因素会影响短波通信,造成数据干扰,因此应采取有效的控制措施。基于此,分析短波通信的基本内容与主要特点,并在剖析短波通信干扰的基础上,分别从短波通信信号特征提取、干扰数据识别、数据干扰控制及实验测试4个方面,探讨基于最小均方(Least Mean Square,LMS)的短波通信数据干扰控制技术。

基于LMS自适应滤波的雷达随队干扰抵消

随队干扰是雷达对抗中常用的干扰方式,通常通过遮盖目标回波信号而使雷达失去探测能力,因此需要加以抑制。随队干扰经常是非平稳的随机信号,在此情况下,文中利用最小均方(LMS)自适应滤波器得到干扰的估计并将其从雷达接收信号中消除,从而给出了一种基于LMS自适应滤波的雷达随队干扰抵消方法。首先,建立了雷达接收信号模型,包括主阵列天线接收信号和辅助阵元接收信号;然后,给出了基于LMS自适应滤波的干扰抵消原理,它实际上将辅助阵元接收信号输入自适应滤波器得到随队干扰估计,从主阵列天线接收信号中减去此干扰估计从而实现干扰抵消,通过分析抵消器的性能发现,除了辐射干扰的目标难以探测外,编队中其他目标的信干噪比都得到了提高;最后,给出了随队干扰抵消的仿真实例,验证了上述干扰抵消方法的良好效果。

Algorithms and statistical analysis for linear structured weighted total least squares problem

Weighted total least squares(WTLS)have been regarded as the standard tool for the errors-in-variables(EIV)model in which all the elements in the observation vector and the coefficient matrix are contaminated with random errors.However,in many geodetic applications,some elements are error-free and some random observations appear repeatedly in different positions in the augmented coefficient matrix.It is called the linear structured EIV(LSEIV)model.Two kinds of methods are proposed for the LSEIV model from functional and stochastic modifications.On the one hand,the functional part of the LSEIV model is modified into the errors-in-observations(EIO)model.On the other hand,the stochastic model is modified by applying the Moore-Penrose inverse of the cofactor matrix.The algorithms are derived through the Lagrange multipliers method and linear approximation.The estimation principles and iterative formula of the parameters are proven to be consistent.The first-order approximate variance-covariance matrix(VCM)of the parameters is also derived.A numerical example is given to compare the performances of our proposed three algorithms with the STLS approach.Afterwards,the least squares(LS),total least squares(TLS)and linear structured weighted total least squares(LSWTLS)solutions are compared and the accuracy evaluation formula is proven to be feasible and effective.Finally,the LSWTLS is applied to the field of deformation analysis,which yields a better result than the traditional LS and TLS estimations.

Numerical simulation of inlet placement on sewage characteristics in the rounded square aquaculture tank with single inlet

To improve the self-cleaning ability of aquaculture tank and the efficiency of circulating water,physical and numerical experiments were conducted on the influence of inlet structure on sewage discharge in a rounded square aquaculture tank with a single inlet.Based on the physical model of the tank,analysis of how inlet structure adjustment affects sewage discharge efficiency and flow field characteristics was conducted to provide suitable flow field conditions for sinkable solid particle discharge.In addition,an internal flow field simulation was conducted using the RNG k-εturbulence model in hydraulic drive mode.Then a solid-fluid multiphase model was created to investigate how the inlet structure affects sewage collection in the rounded square aquaculture tank with single inlet and outlet.The finding revealed that the impact of inlet structure is considerably affecting sewage collection.The conditions of C/B=0.07-0.11(the ratio of horizontal distance between the center of the inlet pipe and the tank wall(C)to length of the tank(B))andα=25°(αis the angle between the direction of the jet and the tangential direction of the arc angle)resulted in optimal sewage collection,which is similar to the flow field experiment in the rounded square aquaculture tank with single inlet and outlet.An excellent correlation was revealed between sewage collection and fluid circulation stability in the aquaculture tank.The present study provided a reference for design and optimization of circulating aquaculture tanks in aquaculture industry.

Multitap RF Canceller with Single LMS Loop for Adaptive Co-Site Broadband Interference Cancellation

With the development of wireless communication technology,an urgent problem to be solved is co-site broadband interference on independent communication platforms such as satellites,space stations,aircrafts and ships.Also,the problem of strong selfinterference rejection should be solved in the co-time co-frequency full duplex mode which realizes spectrum multiplication in 5G communication technology.In the research of such interference rejection,interference cancellation technology has been applied.In order to reject multipath interference,multitap double LMS(Least Mean Square)loop interference cancellation system is often used for cancelling RF(Radio Frequency)domain interference cancelling.However,more taps will lead to a more complex structure of the cancellation system.A novel tap single LMS loop adaptive interference cancellation system was proposed to improve the system compactness and reduce the cost.In addition,a mathematical model was built for the proposed cancellation system,the correlation function of CP2FSK(Continuous Phase Binary Frequency Shift Keying)signal was derived,and the quantitative relationship was established between the correlation function and the interference signal bandwidth and tap delay differential.The steadystate weights and the expression of the average interference cancellation ratio(ICR)were deduced in the scenes of LOS(Line of Sight)interference with antenna swaying on an independent communication platform and indoor multipath interference.The quantitative relationship was deeply analyzed between the interference cancellation performance and the parameters such as antenna swing,LMS loop gain,and interference signal bandwidth,which was verified by simulation experiment.And the performance of the proposed interference cancellation system was compared with that of the traditional double LMS loop cancellation system.The results showed that the compact single LMS loop cancellation system can achieve an average interference rejection capability comparable to the double LMS loop cancellation system.

THE WEIGHTED KATO SQUARE ROOT PROBLEMOF ELLIPTIC OPERATORS HAVING A BMOANTI-SYMMETRICPART

Let n≥2 and let L be a second-order elliptic operator of divergence form with coefficients consisting of both an elliptic symmetric part and a BMO anti-symmetric part in ℝ^(n).In this article,we consider the weighted Kato square root problem for L.More precisely,we prove that the square root L^(1/2)satisfies the weighted L^(p)estimates||L^(1/2)(f)||L_(ω)^p(R^(n))≤C||■f||L_(ω)^p(R^(n);R^(n))for any p∈(1,∞)andω∈Ap(ℝ^(n))(the class of Muckenhoupt weights),and that||■f||L_(ω)^p(R^(n);R^(n))≤C||L^(1/2)(f)||L_(ω)^p(R^(n))for any p∈(1,2+ε)andω∈Ap(ℝ^(n))∩RH_(2+ε/p),(R^(n))(the class of reverse Hölder weights),whereε∈(0,∞)is a constant depending only on n and the operator L,and where(2+ε/p)'denotes the Hölder conjugate exponent of 2+ε/p.Moreover,for any given q∈(2,∞),we give a sufficient condition to obtain that||■f||L_(ω)^p(R^(n);R^(n))≤C||L^(1/2)(f)||L_(ω)^p(R^(n))for any p∈(1,q)andω∈A_(p)(R^(n))∩pRH_(q/p),(R^(n)).As an application,we prove that when the coefficient matrix A that appears in L satisfies the small BMO condition,the Riesz transform∇L^(−1/2)is bounded on L_(ω)^(p)(ℝ^(n))for any given p∈(1,∞)andω∈Ap(ℝ^(n)).Furthermore,applications to the weighted L^(2)-regularity problem with the Dirichlet or the Neumann boundary condition are also given.

利用LMS设备对制动Moan噪音的排查

文章介绍了常见的制动噪音的类型,以及LMS系统在制动噪音排查上的应用。并通过介绍某一新能源车型开发过程中Moan噪音的解决,详细介绍LMS设备在制动噪音上的排查过程和导致噪音的原因,改善了车辆的制动NVH性能,提高了产品竞争力。

基于改进变步长LMS算法的储能飞轮主动磁轴承-转子系统振动控制

针对储能飞轮主动磁轴承-转子系统的振动控制,在变步长最小均方差(LMS)算法的基础上采用一种改进的步长因子并对其可变参数和算法效果进行对比分析,改进算法在提高迭代收敛速度的同时还能保持一定的稳态误差。对基于有限铁木辛柯梁单元法建立的轴承-转子系统动力学模型的仿真结果表明,在转子的振动位移反馈信号进入控制器前,利用基于改进步长因子LMS算法的自适应滤波器可以有效识别并滤除与转子同频的信号分量,从而实现储能飞轮主动磁轴承-转子系统的不平衡振动控制。