基于EEMD-RobustICA和Prony算法的谐波和间谐波检测方法

针对经验模态分解存在的模态混叠现象和Prony算法对噪声敏感的问题,将总体经验模态分解与鲁棒性独立分析法和Prony算法进行有机的结合,应用到谐波和间谐波的检测中。首先将含有噪声的谐波信号进行总体经验模态分解,得到不同阶数的固有模态函数,然后将其作为鲁棒性独立分量分析法的输入,对得到的独立分量进行软阈值去噪后进行逆变换得到重构后的固有模态函数,叠加得到去噪后的信号,最后用Prony算法对谐波和间谐波信号进行参数辨识,得到谐波和间谐波的参数。仿真结果表明,该方法具有较好的抗噪性,克服了Prony算法对噪声敏感的缺点,有效地提高了谐波和间谐波检测的精度。     

瞬时频率的Prony方法提取及MATLAB实现

瞬时频率是信号重要的瞬时特征参数,由于其在通信中的信号调制样式识别、电台"指纹"识别等诸多方面有着广泛的应用,故成为信号处理领域的一个研究热点.旨在有效的提取信号的瞬时频率,介绍了瞬时频率的定义、常用的瞬时频率提取方法及扩展的Prony方法的基本原理与步骤,采用Prony方法提取信号的瞬时频率,给出了算法流程和MATLAB实现的核心程序代码,对线性扫频信号和4FSK信号进行了仿真试验,与相位建模法、WVD法相比,估计的瞬时频率在低信噪比时的均方差较小,结果表明该方法可行,在低信噪比条件下有一定的优势.     

双稳随机共振系统信号调制噪声效应用于弱信号检测

通过对双稳系统随机共振模型的数值分析，得出在双稳系统输出信号中，有一个正弦信号成分和一个表现为维纳过程的噪声成分分别与输入的正弦信号和白噪声相对应。通过选择合适的系统参数，可以减小系统输出中信号和噪声之间的耦合效应。该系统可以大大抑制噪声，并在双稳系统中产生信号调制噪声效应。然后对双稳系统的输出信号作功率谱分析。不但可以辨识出淹没在白噪声中的微弱正弦信号的频率，还可以较精确地估算出微弱正弦信号的幅值。数值仿真表明，双稳系统的信号调制噪声效应可用于多个微弱正弦信号的检测。     

组合逻辑中瞬时错误传播的频域分析方法

提出一种新颖的频率分析方法来计算瞬时错误在组合逻辑电路中的传播．通过对输入信号进行傅里叶变换,分析组合逻辑电路的频率特性,并通过频域计算方法得到组合逻辑电路的输出．为了解决组合逻辑电路有时会工作在信号非线性区的问题,提出一种数学模型来精确描述瞬时错误在组合逻辑电路中传播过程．实验结果表明,该方法能保证在93％的平均精确度（和HSPICE相比）前提下,大幅提高评估速度．     

旋转机械振动与瞬时转速信号同步处理系统

旋转机械测试中,振动信号通常是随机非稳态信号,必须进行振动和转速信号同步分析。而目前转速测试,硬件实现复杂,实时性差,且不易实现对多路信号同步高速处理。为此利用DSP和PXI总线设计了旋转机械振动与瞬时转速信号同步处理系统。MAX125完成数据的采样及A/D转换;TMS320VC33作为主控芯片,对转速原始信号处理得到瞬时转速,同时对振动信号重抽样,精减数据;处理后,由PXI接口传送给主机。用三缸柴油机发动机转速原始信号和一路简单的正弦信号为实例,说明了该系统的应用,并得到了比较理想的结果。     

旋转机械振动与瞬时转速信号同步处理系统

旋转机械测试中，振动信号通常是随机非稳态信号，必须进行振动和转速信号同步分析。而目前转速测试，硬件实现复杂，实时性差，且不易实现对多路信号同步高速处理。为此利用DSP和PXI总线设计了旋转机械振动与瞬时转速信号同步处理系统。MAX125完成数据的采样及A／D转换；TMS320VC33作为主控芯片，对转速原始信号处理得到瞬时转速，同时对振动信号重抽样，精减数据；处理后，由PXI接口传送给主机。用三缸柴油机发动机转速原始信号和一路简单的正弦信号为实例，说明了该系统的应用，并得到了比较理想的结果。     

基于HHT与PNN的输电线路故障分类

针对电力系统输电线路一系列的短路故障,把希尔伯特黄变换(HHT)完成对暂态信号特征量的提取与概率神经网络(PNN)作为诊断故障分类器相结合的方式,作为对输电线路故障分类的方法.利用HHT能够充分反映局部暂态信号的特点,对集合经验模态分解(EEMD)后的故障信号进行小波阈值降噪,运用HHT进行重构,得到三相电流以及零序电流4组特征能量函数值,并作为4组特征量输入到经遗传算法优化过平滑因子的PNN中进行训练,最终得到分类器.经Matlab仿真实验显示,该方法能够有效优化信号波形并提高故障分类精度.     

高温环境下测试信号传输的稳定性分析

针对测试过程中传输线受高温影响导致信号传输产生一定的不确定性的问题,提出了热电耦合的方法来研究导体的温度演变过程,计算温度变化影响下的电信号稳定性传输,并建立误差公式估算输入与输出电信号之间的关系。采用有限元方法建立了分析模型,讨论了外部环境与传输线的对流换热和通过电流时产生的焦耳热对导体产生的共同作用,以及影响电信号的稳定性传输的主要因素。此分析方法为提高高温环境下的结构测试的准确性提供了依据,对实际工程具有一定的指导意义。     

强干扰环境下网络情报数据滤波通信系统设计

传统通信系统在强干扰环境下进行通信时,系统会出现性能下降甚至无法通信的问题。设计并实现了一种新的网络情报数据滤波通信系统,设计强干扰环境下网络情报数据滤波通信系统的整体结构;按照网络情报数据滤波通信系统的标准以及分析强干扰的特性,对瞬态电压抑制模块、瞬态保护模块、语音信号输入模块进行设计,采用电磁滤波去噪的方法对故障修复模块进行优化,实现网络情报数据滤波通信系统的设计。实验表明,改进的网络情报数据滤波通信系统较传统的通信系统具有较强的抗干扰能力,通信效果好等明显优势。     

电力系统暂态稳定性的数值仿真研究

由于系统暂态失稳引发的大停电等事故频繁,所以加强对电力系统暂态稳定分析的研究具有重要意义。数值计算是系统仿真的重要手段,计算结果可以为系统的规划、设计、运行、分析、控制等提供依据。首先介绍了电力系统暂态稳定分析的主要方法,并利用时域法讨论了单机无穷大系统的暂态稳定性。其次,采用龙格库塔方法求解离散发电机转子的运动方程,得到了系统δ-t曲线。最后,运用上述方法计算实际问题,结果表明暂态稳定分析与初始运行方式、故障点位置、故障切除时间、故障后状态有关。因此,在实际生产中应注意结合上述特点减少事故发生。     

Temporary short circuit detection in induction motor winding using combination of wavelet transform and neural network

Monitoring system for induction motor is widely developed to detect the incipient fault. Such system is desirable to detect the fault at the running condition to avoid the motor stop running suddenly. In this paper, a new method for detection system is proposed that emphasizes the fault occurrences as temporary short circuit in induction motor winding. The investigation of fault detection is focused on the transient phenomena during starting and ending points of temporary short circuit. The proposed system utilizes the wavelet transform for processing the motor current signal. Energy level of high frequency signal from wavelet transform is used as the input variable of neural network which works as detection system. Three types of neural networks are developed and evaluated including feed forward neural network (FFNN), Elman neural network (ELMNN) and radial basis functions neural network (RBFNN). The results show that ELMNN is the most simply and accurate system that can recognize all of unseen data test. Laboratory based experimental setup is performed to provide real-time measurement data for this research.     

On the self-similarity of 1/f sequences synthesized by recursive filtering

This paper describes an approximate method for synthesizing sequences of statistically self-similar processes and analyses its performance to generate sample sequences with this statistical property. The method is based upon approximating the infinite dimensional difference equation which describes the FARIMA(0, α, 0) model by a finite dimensional difference equation. The parameters estimation for parameterizing the binomial coefficients is performed by using deterministic signal modeling techniques. The three techniques considered are: Prony, Steiglitz MacBride, and Shaw methods. In addition to allow considerable savings in memory requirements and great reduction in computation time, the performance analysis results show that the generated sequences are statistically self-similar in the sense that the estimated Hurst parameter is very close to that imposed in the sequence generator.     

一种新型的数据采集系统性能量化方法的研究

考虑到数据采集系统的精度对应于系统对信号的不失真传输及系统本身的时间稳定性问题,提出了一种新型的数据采集系统性能量化方法。该方法将数据采集系统看作为一个开环的线性时不变系统,把采集系统本身看作滤波器,其输入为需要采集的信号,输出为采集到的信号,然后利用LMS算法的基本原理反推通道模型参数,最后利用求得的模型参数计算数据采集系统对正弦信号的传输特性,实现了对数据采集系统的性能考核。对系统模型和量化方法的数学仿真结果表明,所采取的量化方法和系统模型精确地反映了数据采集系统的正弦信号的响应,可以作为实际数据采集系统的精度考核手段。     

Output transient trajectory shaping control for a class of nonlinear systems

This paper presents a transient trajectory shaping (TTS) control method for the SISO strict feedback nonlinear systems. The TTS control refers to explicitly constraining the system output tracking error transient trajectories within predesigned time‐varying boundaries while they are converging to equilibrium. By this method, the boundaries of system output transient trajectories can be designed a priori according to the system transient control performance requirements in both symmetric and asymmetric ways. With a class of time‐varying boundary functions, control laws can be devised by utilizing the enhanced differential unbounded function techniques. Such control laws can ascertain that the system output tracking errors travel within their respectively predesigned time‐varying boundaries while converging to origin. To handle the control input exaggeration issue in TTS, input constraint control techniques are proposed to effectively reduce the required control input magnitude for second‐order systems. A numerical example is utilized to show the effectiveness of the proposed TTS control methods. Copyright © 2013 John Wiley & Sons, Ltd.     

多变量自校正递推去卷滤波器

本文用时域上的新息分析方法，对于线性多变量系统的输入信号，提出了一种新的自校正递推去卷滤波器，它具有ＡＲＭＡ新息滤波器形式，可处理多变量非平稳ＡＲＭＡ输入信号、不稳定和／或非最小相位系统。仿真例子说明了其有效性。     

System identification in a networked environment using second order statistical properties

System identification for networked control is considered. Due to the time-delays in the network, it can be difficult to work with a discrete-time model and a continuous-time model is therefore chosen. A covariance function based method that relies on the second order statistical properties of the output signal, where it is assumed that the input signal samples are from a discrete-time white noise sequence, is proposed for estimating the parameters. The method is easy to use since the actual time instants when new input signal levels are applied at the actuator do not have to be known. An analysis of the networked system and the effects of the time-delays is made, and the results of the analysis motivate and support the chosen approach. Numerical studies indicate that the method is robust to randomly distributed time-delays, packet drop-outs, and additive measurement noise.     

战斗部殉爆试验多参数存储测试系统

为解决传统的战斗部殉爆试验可以给出殉爆距离，但不能获取试验过程中殉爆参量详细数值曲线的问题，设计了一种适用于殉爆试验的多通道并行采集存储测试系统。系统以FPGA为核心处理器，Nandflash为存储器，采用USB通信方式，实现殉爆过程中冲击波压力和振动加速度信号的采集、存储和传输。采用冲击波压力信号作为内触发信号，将Flash存储区域划分为负延迟存储区与连续采样存储区，保证有效信号被完整获取。性能测试结果表明，该系统能够完成4通道、500 kHz采样频率的参数采集和存储，整个装置体积为502 cm³，整体功耗只有1.85 W，可以对殉爆环境下冲击波压力和振动加速度信号进行有效采集。     

基于频域瞬时特征的跳频电台个体识别方法

通信电台发射的信号通常表现出一定的细微特征差异,针对这种细微特征差异,提出了基于最大Lyapunov指数和盒维数的跳频电台个体识别方法。基于改进的Prony算法,提取样本信号跳变时刻的瞬时频率,分离并定量计算其最大Lyapunov指数和盒维数等瞬时特征,采用基于构造型神经网络的分类方法实现不同跳频电台的个体识别。实际数据的实验结果验证了算法的有效性。     

Dynamics and stability of a delay-locked loop

We discuss the transient behavior of a delay-locked loop which is designed to generate a delay-error signal that is proportional to the difference in the autocorrelation function of the input signal at two points separated by a fixed time2tau_{1}. When the input signal is a sine wave, we present an exact solution which shows that the system is stable and achieves a delay lock with an ambiguity of an integral number of periods. The second input considered is that of a stationary, ergodic, and band-limited Gaussian signal. In this case we present an approximate analysis which predicts that for times long compared to the inverse bandwidth of the random signal that the delay error is log-normally distributed. For this case we develop the almost sure sample stability criterion [1]. When this criterion is met, the system sample solutions are stable with probability one independant of the system amplification. We also develop stability criteria which limit the system amplification for stability of the first and second moments of the time delay.     

多端口过压安全保护电路设计与研究

本文以三极管、二极管及电阻电容等元件,设计了一种计算机测试系统多端口信号安全保护电路。安全保护电路对系统单端输入和双端输入差分信号均可以实现过压保护功能。电路构思新颖,设计简捷,可移植性强,可应用于计算机系统多种信号安全保护电路中。