Active micro-vibration control based on improved variable step size LMS algorithm

The contradiction of variable step size least mean square(LMS)algorithm between fast convergence speed and small steady-state error has always existed.So,a new algorithm based on the combination of logarithmic and symbolic function and step size factor is proposed.It establishes a new updating method of step factor that is related to step factor and error signal.This work makes an analysis from 3 aspects:theoretical analysis,theoretical verification and specific experiments.The experimental results show that the proposed algorithm is superior to other variable step size algorithms in convergence speed and steady-state error.

Study of Variable Step Size LMS Adaptive Algorithm Based on Variable Region

This paper puts forward a new variable step size LMS adaptive algorithm based on variable region. The step size p（k） in the algorithm varies with the variation of the region of deviation e （k） to ensure the optimization of the three performance objectives including initial convergent speed, trace ability of the time-varying system and steady disregulation. The paper demonstrates the convergence of the algorithm accompanied by random noise,

Finite-difference modeling with variable grid-size and adaptive time-step in porous media

Forward modeling of elastic wave propagation in porous media has great importance for understanding and interpreting the influences of rock properties on characteristics of seismic wavefield. However,the finite-difference forward-modeling method is usually implemented with global spatial grid-size and time-step; it consumes large amounts of computational cost when small-scaled oil/gas-bearing structures or large velocity-contrast exist underground. To overcome this handicap,combined with variable grid-size and time-step,this paper developed a staggered-grid finite-difference scheme for elastic wave modeling in porous media. Variable finite-difference coefficients and wavefield interpolation were used to realize the transition of wave propagation between regions of different grid-size. The accuracy and efficiency of the algorithm were shown by numerical examples. The proposed method is advanced with low computational cost in elastic wave simulation for heterogeneous oil/gas reservoirs.

Joint receiving mechanism based on blind equalization with variable step size for M-QAM modulation

The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a training sequence,a blind equalization channel is implemented in the receiver to increase the throughput of the system. To improve the performances of both the blind equalizer and the system,a joint receiving mechanismincluding variable step size（ VSS） modified constant modulus algorithms（ MC-MA） and modified decision directed modulus algorithms（ MD DMA） is proposed to ameliorate the convergence speed and mean square error（ MSE） performance and combat the phase error when using high order QAM modulation. The VSS scheme is based on the selection of step size according to the distance between the output of the equalizer and the desired output in the constellation plane. Analysis and simulations showthat the performance of the proposed VSS-MCMA-MD DMA mechanismis better than that of algorithms with a fixed step size. In addition,the MCMA-MDDMA with VSS can performthe phase recovery by itself.

基于POD-αATS的油浸变压器瞬态温升降阶自适应变步长计算方法

针对油浸式电力变压器瞬态温升计算效率过低的问题,该文提出本征正交分解-αATS(proper orthogonal decomposition-adaptive time stepping based onαfactor,POD-αATS)降阶自适应变步长瞬态计算方法。首先,推导变压器绕组瞬态温升计算的有限元离散方程;其次,采用POD降阶算法改善传统瞬态计算中存在的条件数过大及方程阶数过高的问题;同时对于瞬态计算中的时间步长选择问题,提出适用于非线性问题的αATS变步长策略;然后,为验证方法的有效性,基于110 kV油浸式电力变压器绕组的基本结构建立二维八分区数值计算模型,同时将计算结果与基于110 kV绕组的温升实验结果进行对比。数值计算及实验结果表明,所提算法与全阶定步长算法在流场和温度场中的精度几乎相同,且流场计算效率提升约45倍,温度场计算效率提升约38倍,计算速度得到显著提高。这一点在温升实验中同样得到验证,说明该文所提算法的准确性、高效性及一定的工程实用性。

柔性机械爪力控的变步长自适应滤波算法

机械爪工作中,由于电源和机械震动会导致电流有波动,将测得的电流数据通过滤波,减少电流的波动,从而让力控的准确度更高。传统的自适应算法无法满足在快速收敛的同时,实现较高鲁棒性和较小稳态误差的要求。针对上述问题,文中提出一种新的自适应滤波算法。首先,建立基于双曲正切函数的变步长模型,实现更新步长因子的动态变值,其次,将滤波器权向量差及可变因子引入更新权值迭代算法中,以达到快速收敛和减少稳态误差的目的。通过实验证明,文中算法实现了快速收敛,并具有较小的稳态误差,提高了系统的鲁棒性。

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。

基于改进狼群算法的无人机协同任务规划

多无人机在现代化作战中的运用日渐增多,无人机任务规划在无人机智能作战中至关重要。针对子系统能力约束下的无人机任务分配问题,提出一种Levy Flight(LF)优化下基于拍卖机制的混沌反向学习狼群优化算法CRL-AMIWPA。首先,定义无人机能力矩阵和任务场景,对无人机异构性、任务执行能力、执行任务能力最低需求建立同一矩阵描述,根据距离油耗和最迟任务完成时间的加权和建立目标函数,建立子系统约束下的任务分配模型;然后,设计狼群个体编码,每个编码方案包含一种任务分配策略,针对未达到任务需求最低能力的解,采用基于合同网的拍卖策略予以修正。另外,在狼群初始化阶段,采用Tent混沌算子和反向学习策略,将狼群个体均匀地分布在解空间中,以提高初始种群的多样性,最后,利用LF策略优化寻优过程,提高跳出局部最优解的能力。仿真实验结果表明,所提算法能有效解决在子系统约束场景下无人机任务分配问题,相比其他群智能算法和狼群算法,具有更优的寻优性和收敛速度。

基于变步长自适应降噪核脉冲信号分析的算法优化研究

针对提高核脉冲信号信噪比这一需求,本文以小波算法为基础,创建了新的阈值函数处理方法,可以满足核脉冲信号降噪基本需求;并进一步提出了一种新的优化变步长自适应非平稳信号降噪算法EVSL,实现核脉冲信号分析。对模拟核信号与原始测量信号同步处理后,与现有算法进行指标对比,结果表明EVSL算法能兼顾收敛速度与稳态精度,有效提高信噪比、保留实际有用信息,是一种有效的提升核脉冲信号质量的方法。

双曲正切函数的新型变步长LMS算法

针对自适应最小均方误差(Least Mean Square,LMS)滤波算法迭代步长在算法收敛速度、稳态误差间的折中问题,设计了一种基于双曲正切函数的新型变步长算法,算法以双曲正切函数为基础,建立步长因子μ(n)与误差信号e(n)的非线性函数关系,并引入参数α、β和m,设计了一种新的步长调整公式,使得在算法迭代初始阶段采用较大步长因子,达到更快的收敛速度,在接近收敛时采用较小的步长因子,获得更小的稳态误差。通过仿真分析了不同参数对算法性能的影响,与已有典型变步长算法相比,论文算法具有更快的收敛速度、更小的稳态误差和更优的追踪能力。

基于sigmoid-sinh分段函数的改进FxGMCC算法

为了解决滤波-x广义最大熵准则(FxGMCC)算法在处理噪声主动控制时存在快速收敛和低稳态误差之间的矛盾,分别采用sigmoid函数和sinh函数,提出了基于sigmoid函数的变步长FxGMCC(SFxGMCC)算法和基于sinh函数的变步长FxGMCC(ShFxGMCC)算法。然后,通过分析SFxGMCC算法和ShFxGMCC算法变步长性能,提出了一种基于sigmoid-sinh分段函数的SSFxGMCC算法。为了验证SSFxGMCC算法性能,分别采用alpha稳定分布噪声和混合噪声作为输入信号,对SSFxGMCC算法与FxGMCC算法、SFxGMCC算法与ShFxGMCC算法进行性能仿真实验。结果表明,与FxGMCC算法相比,采用SSFxGMCC算法在应对alpha稳定分布噪声和混合噪声时,在收敛速度得到提升的前提下,平均降噪量分别提升了16.5%和17.4%。由此可知,SSFxGMCC算法有效解决了FxGMCC算法在应对噪声主动控制时快速收敛和低稳态误差无法同时满足的问题。

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。

一种改进的广义旁瓣对消阵列语音增强算法

传统广义旁瓣对消(generalized sidelobe cancellation,GSC)算法在复杂声学环境下性能较差,语音增强效果不理想,需要加强其去噪能力以提高输出语音质量。对此,提出一种改进型广义旁瓣对消算法。构建基于频域GSC和时域GSC两级滤波的系统结构,利用一个选择滤波器输出两级滤波中质量较好的语音;并将GSC上支路权值修改为可自适应调节的形式,提高算法的适应性;GSC权值迭代时采用一种变步长自适应算法,步长因子根据信号信干噪比实时调整,防止滤波器权值发散。实验结果表明,相比于传统GSC算法,新算法在SINR、PESQ、STOI和SDR等指标上都有提升。

一种改进变步长的自适应电磁干扰对消算法

针对已有最小均方(LMS)自适应干扰对消算法初期收敛速度慢且整体误差偏大的问题,提出一种改进变步长LMS算法。该算法在保证收敛速度和误差精度要求下,简化了步长因子μ(n),且采取分段迭代的方法,克服算法初期收敛慢的缺点。在误差|e(n)|较大时,文中提出通过调整系数ε调节步长μ(n)的变化速度,增强了迭代稳定性。仿真结果表明:与正态分布曲线步长等算法相比,使用文中算法后,宽带与窄带电磁干扰信号的收敛速度至少提高13%,干扰对消后期望信号的输出信噪比至少提高26%。该算法可用于复杂电磁环境下的电磁干扰消除。

集合相似度自连接算法研究

在当前信息技术条件下,如何提升数据处理效率成为未来工作中不容忽视的问题,本文在集合相似度融合算法的基础上,介绍集合相似度连接策略,对如何实现集合相似度自连接算法提出合理意见,并通过实验评估方法,综合判断本文方法的技术优势。根据研究结果可知,本文提出的新方法可以显著提升集合相似度计算效率,值得推广。

基于改进BP神经网络的网络流量预测

传统网络流量预测方法常面临精度不足、时间复杂度高的问题,且在处理复杂的网络流量时,难以达到理想的预测效果。为克服这些挑战,采用深度学习中的反向传播(Back Propagation,BP)神经网络算法,并结合改进的梯度下降法,通过引入动量项与变步长法相结合的方式,有效降低误差值,实现了对网络流量的准确预测。该方法旨在更好地满足用户需求,优化网络性能,并提升网络服务质量。实验结果表明,改进后的BP神经网络算法在网络流量预测中展现出良好的可行性与稳健性,同时达到了较高的预测精度。

基于变步长蚁群算法的电气巡检机器人路径规划方法

随着电力设备不断更新,电气巡检变得越来越重要,为提高巡检效率,减少人力成本,电气巡检机器人逐渐成为一种可行的解决方案。基于此,,文章提出一种基于变步长蚁群算法的电气巡检机器人路径规划方法,该方法将蚁群算法与变步长策略结合,通过建立电力设备和巡检点之间的图模型,将问题转化为TSP问题。然后,利用蚁群算法进行路径搜索,并引入变步长策略动态调整蚂蚁的步长,以加快搜索速度并避免陷入局部最优解。为验证该方法的有效性,在实际电力设备中进行仿真实验。结果表明,基于变步长蚁群算法的路径规划方法能有效地优化路径,减少巡检时间和成本。与传统的路径规划方法相比,该方法在搜索效率和路径质量方面都具有明显的优势。

基于变步长凸组合LMS自适应滤波高原动态血氧检测系统设计

针对基于光电检测方法的血氧仪只能在静止状态下测试血氧饱和度(血氧)的问题,提出一种基于变步长凸组合LMS自适应滤波动态血氧检测方法。方法对原始光电描记脉搏波信号经预处理后,通过固步长与变步长LMS自适应算法组合,以三轴加速度计采集信号作为运动噪声参考信号,获得理想脉搏波信号再准确计算血氧值。在此基础上,开发了一套基于物联网的穿戴式高原血氧检测系统,经过模拟正常行走及在不同海拔条件下测试,最大误差不超过4%,验证了算法的有效性和准确性。结果显示,基于物联网的血氧监测系统对于高原旅游中高原反应的实时监测与提醒具有实际意义。

Improved finite difference method for pressure distribution of aerostatic bearing

An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.

An efficient algorithm to compute transient pressure responses of slanted wells with arbitrary inclination in reservoirs

Compared with vertical and horizontal wells, the solution and computation of transient pressure responses of slanted wells are more complex. Vertical and horizontal wells are both simplified cases of slanted wells at particular inclination, so the model for slanted wells is more general and more complex than other models for vertical and horizontal wells. Many authors have studied unsteady-state flow of fluids in slanted wells and various solutions have been proposed. However, until now, few of the published results pertain to the computational efficiency. Whether in the time domain or in the Laplace domain, the computation of integration of complex functions is necessary in obtaining pressure responses of slanted wells, while the computation of the integration is complex and time-consuming. To obtain a perfect type curve the computation time is unacceptable even with an aid of high-speed computers. The purpose of this paper is to present an efficient algorithm to compute transient pressure distributions caused by slanted wells in reservoirs. Based on rigorous derivation, the transient pressure solution for slanted wells of any inclination angle is presented. Assuming an infinite-conductivity wellbore, the location of the equivalent-pressure point is determined. More importantly, according to the characteristics of the integrand in a transient pressure solution for slanted wells, the whole integral interval is partitioned into several small integral intervals, and then the method of variable substitution and the variable step-size piecewise numerical integration are employed. The amount of computation is significantly reduced and the computational efficiency is greatly improved. The algorithm proposed in this paper thoroughly solved the difficulty in the efficient and high-speed computation of transient pressure distribution of slanted wells with any inclination angle.