Measurement of active power by time domain digital signal processing

This paper compares DSP time domain algorithms of one-phase active power measurement by non-coherent sampling that are superior to some frequency domain algorithms in active power estimation of non-sinusoidal signals. The measurement bias, uncertainty and sampling time necessary for the required accuracy are compared for various data windows with the use of simulations and measurements. Both monofrequency and multifrequency signals are dealt with. Analytical formulas are presented for the active power bias for rectangular and general cosine windows and for standard uncertainty of active power measurement. A simple method is described for correction of the multiplexing delay in power measurement using multiplexing DAQ boards. The information from this paper can also be used for measuring energy consumption and three-phase power.     

海底热液口温度场高精度声学测量方法研究

介绍了海底热液口温度场原位声学测量的基本原理、总体最小二乘重建方法和抛物插值算法。在云南省龙陵县茄子山水库进行湖底试验研究,基于总体最小二乘重建方法准确地还原出湖底热泉的温度场原位分布;将抛物插值算法应用于声波飞渡时间延时估计,并对抛物插值前后重建出的温度场进行最大绝对误差、最大相对误差和均方根误差分析。实验表明:总体最小二乘重建方法和抛物插值算法可用于海底热液口温度场的原位测量,且重建精度比较高。     

Estimating ultrasonic time of flight using envelope and quasi maximum likelihood method for damage detection and assessment

Time of flight (TOF) is widely used to locate and size faults in ultrasonic non-destructive evaluation (NDE). In this paper, we propose a novel model-based method for ultrasonic echo parameter estimation. The ultrasonic signal is assumed to be composed of an unknown number of Gaussian echoes corrupted by white Gaussian noise. Firstly, the Hilbert transform is used to extract the envelope of the signal. It is shown that the parameter estimation of the signal is improved by using the envelope. To estimate the parameters of the envelope of the signal, quasi maximum likelihood method is used. The number of echoes is estimated using consistent Akaike information criterion. Two measures are used to evaluate the performance of the proposed method: (a) probability of detection of backscattered echoes and (b) the error of estimated time of flights. The proposed method is then compared to the cross-correlation method and the maximum likelihood method which uses the original signal. Simulated and experimental signals are used to evaluate the performance of each method. Both experimental and simulated results show that the proposed method can improve the parameter estimation which ultimately enhances the damage detection and assessment.     

基于三次hermite插值lmd方法的往复压缩机故障诊断技术

针对往复压缩机振动信号的强非平稳特性和多分量耦合特性,提出了一种基于三次hermite插值的lmd方法.该方法结合三次hermite插值法的优良保形特性,以其对信号极值点进行插值包络,提高局部均值函数和包络估计函数的拟合精度.以往复压缩机轴承故障振动信号为研究对象,通过与原有lmd方法的对比,验证了此方法的优越性,实现了轴承间隙故障的准确诊断.     

Non-parametric estimation of the amplitude ratio of sinusoidal signals with common frequency

The systematic bias error of the amplitude ratio estimation owed to leakage effect can be effectively reduced by employment of the non-parametric multi-point interpolation of the discrete Fourier transform in the quotient of amplitudes. Simple single-step algorithms for fast measurement and estimation of the amplitude ratio of sinusoidal signals with the same frequency from two channels are presented. The paper analyzes and compares the systematic bias errors and the noise error behaviors of the amplitude ratio estimation changing the order of Rife–Vincent windows class I, which are designed for maximization of the window spectrum side-lobe fall-off, and minimum side-lobe level (MSL) windows, which are designed for minimization of the energy in the window spectrum main lobe. Estimation errors are shown in relation to the number of signal cycles in the measurement interval.     

传感器调零误差对直线误差分离的影响规律及其确定方法分析

分析了多点法直线 EST中传感器初始调零误差对直线误差分离结果的影响 ,指出不同方法的影响规律不同 :时域三点法中调零误差使直线形状误差按抛物线规律呈非线性增大 ,对直线误差评定产生很大影响 ;时域二点法中调零误差使直线形状误差线性增大 ,但对评定无影响 ;频域三点法的直线误差则不受调零误差的影响。提出了通过构造软基准来确定调零误差的两种方法 :时域频域结合法和对称反转配置法 ,可以克服常规方法的局限性     

Gaussian-Taylor signal-to-noise ratio estimation for scanning electron microscope images

A new and robust parameter estimation technique, named Gaussian-Taylor interpolation, is proposed to predict the signal-to-noise ratio (SNR) of scanning electron microscope images. The results of SNR and variance estimation values are tested and compared with piecewise cubic Hermite interpolation, quadratic spline interpolation, autoregressive moving average and moving average. Overall, the proposed estimations for noise-free peak and SNR are most consistent and accurate to within a certain acceptable degree compared with the others.     

Accurate ultrasound speed measurement using an MLS-modulated continuous wave

The continuous wave shows greater potential than the pulse signal to achieve high-accuracy ultrasound speed measurement thanks to its stronger noise resistance. However, the accuracy of ultrasound speed measurement would deteriorate if echoes exist in the received continuous wave. This paper presents an applicable method using the maximum length sequence-modulated continuous wave. The present method improves the accuracy of ultrasound speed measurement further by resisting echoes. The time delay between the received signal and the transmitted signal is estimated accurately by combining the cross-correlation, parabolic interpolation and phase shift technique. Moreover, both the inherent delays induced by physical system and the path length of ultrasound are expediently corrected through least square estimation. As a result, accurate time of flight and ultrasound speed measurement are achievable. For example, the standard deviation of ultrasound speed measurement in distilled water is less than 0.003 m/s, and the deviation between the ultrasound speed measurement and the reference is less than 0.04 m/s.     

一种三次插值样条曲线的插补方法研究

针对复杂轮廓零件数控加工的实际需求,基于数据采样插补原理,对一种三次插值样条曲线的插补算法进行了研究.样条曲线进行参数化运算插补,先使用一系列首尾相接的微小直线段来逼近给定的插值样条曲线轮廓,再利用轨迹空间与参变量空间的对应关系,控制参变量,求取插补点坐标,得到整个离散化插补轨迹.此算法加工速度稳定性高,有利于高速高精地生成插补轨迹.     

Test bed for power amplifier behavioral characterization and modeling

Traditional test bed of power amplifier (PA) behavioral characterization and modeling based on vector signal analyzer (VSA) and often equipped with specialized software is both expensive and inflexible to modify to suit different scenarios. In this paper, a new test bed based on an oscilloscope or other general purpose data acquisition systems, which works as analog to digital converter (ADC) with a proper (radio frequency) RF bandwidth and maximum sampling rate, is proposed. The common impairments, e.g. transmitter IQ imbalances, channel delay, frequency offset, and carrier phase offset, are all well compensated. The accurately recovered envelopes of the PA’s input and output signals are used for a PA behavioral characterization and modeling. Furthermore, Relative envelope error (REE) parameter is proposed to evaluate the accuracy of envelope recovery. The experiment shows a very accurate RF signal envelope recovery, and a good performance of PA behavioral modeling.     

光电轴角编码器光电信号正交性偏差的相量校正方法

高精度光电轴角编码器中的细分是误差的主要来源,而细分误差中莫尔条纹光电信号的正交性偏差影响最大。采用相量校正方法对正交性偏差进行校正,实现电路简单,校正效果十分明显。以正弦信号为基准信号,而将余弦信号分解为0°和90°两个正交分量,0°分量就是产生正交性误差的原因,通过补偿掉该分量,即可基本消除正交性误差。为进一步减小细分误差,通过精密调节,使余弦信号的幅值与正弦信号严格相等,将正弦及其反相信号与余弦信号分别相量相加可得到严格正交的两个新相量,从而消除正交性误差。实验结果表明,经精密相位校正后,正交性偏差从1″降低到0.1″左右。     

基于小波变换的基波提取和频率测量

为了提高小波变换提取信号基波和测量频率的精度 ,采用分频特性较好的小波对信号进行滤波 ,并研究最佳分解级数的问题。在频率测量中 ,针对低频噪声的影响 ,提出极大值误点的判别方法 ,采用最小二乘法估计基频 ;针对非整周期采样误差的影响 ,采用抛物线插值的方法加以解决     

The dual channel sinewave model: Co-prime sparse sampling,parameter estimation,and the Cramér–Rao Bound

The seven-parameter sine fit algorithm for a dual channel signal model with common frequency has been considered in a prior work as an accurate procedure for parameter estimation. In this paper, we investigate an approach in the dual channel sine fit where the signals from both channels are uniformly subsampled with coprime pair of sparse samplers and present analysis of the frequency estimation problem from undersampled measurements thereby relaxing the demand on devices and instruments by lowering the required sampling frequency as well as bandwidth. The Cramér–Rao Bound based on the coprime subsampled data set is derived and numerical illustrations are given showing the relation between the cost in performance based on the mean squared error and the employed coprime factors for a given measurement time.     

基于六项余弦窗函数插值FFT的谐波分析方法

在分析电网谐波时,很难实现同步采样和整周期截断,因此采用傅里叶方法必然存在频谱泄露和栅栏效应。加窗插值FFT算法是减小频谱泄露和栅栏效应的有效方法。为减小长范围泄露,将六项余弦窗函数应用于电力系统谐波分析,并且推导出了谐波参数的插值修正公式,其插值系数具有简单的显示表达式,计算量小。对该算法与Hanning窗和Blackman-Harris窗插值FFT算法进行了Matlab仿真对比研究,验证了该算法具有更高的分析精度。对微波炉电流实测数据的分析结果进一步验证了所提算法的有效性。     

Impact of uncertainties in accelerometer modeling on the maximum values of absolute dynamic error

The paper considers the impact of uncertainties associated with estimated parameters of the accelerometer model on the maximum values of absolute dynamic error. Assessment of such impact constitutes a novelty in determination of the maximum values of absolute dynamic error.The parameter estimation method of the accelerometer mathematical model in the frequency domain and the procedure for calculation of the associated uncertainties under the current regulations, are discussed in detail in the second section of this paper.The procedures for determining the maximum values of absolute dynamic error generated at the output of an accelerometer, when the input signals are constrained in magnitude and both in magnitude and rate of change, are discussed in the third section. This dynamic error has been determined in relation to the standard represented by the 15-th order Butterworth filter. The possibilities of application of both the continuous and the discrete procedures of error calculation have also been presented. For the execution of numerical integration, the Romberg method has been applied.Based on theoretical consideration, the results of both the parameter estimation of the Endevco87 accelerometer and calculation of the corresponding uncertainties are presented in the fourth section.The fifth section is devoted to the presentation of the most important assumptions, which allow the determination of the maximum values of absolute dynamic error.An assessment of the impact of the uncertainties associated with the estimated parameters on the value of absolute error is discussed in the last section of this paper.The numerical calculations were executed in the MathCad14 program.     

一种并行系统时基误差自适应估计方法

在并行采集系统中,通道间时基延迟的不一致性严重降低了系统性能.针对时间延迟估计算法多基于时域实现,需进行复杂的插值运算以获取采样间隔非整数倍时基延迟的问题,本文基于时基误差的频域模型,将通道间的误差信号建模为自适应滤波器,提出了一种无需插值的估计算法.计算机仿真及实际应用验证结果表明,该方法能动态跟踪时基延迟变化,有效地估计通道时延,具有迭代次数少、运算量小、实时性高的特点.     

半功率点法估计阻尼比的误差分析

从快速傅里叶变换（FFT）离散谱线中难以恰好找到半功率点，通常是通过线性插值法近似确定半功率点来估计阻尼。文中采用理论分析与数值仿真相结合的方法研究基于线性插值的半功率点法的主要误差因素和各自特性，特别是其中窗阻尼变化规律。研究结果表明，①应尽量接近整周期采样。②无阻尼系统因进行FFT截断也会出现虚假的窗阻尼，且真实阻尼不等无表观阻尼减去窗阻尼。③阻尼的相对误差主要取决于采样周期数与阻尼比，其物理意义是截断窗口内的信号衰减程度。④要保证阻尼10％的精度，窗阻尼要小于表观阻尼的2／3。     

An improvement EMD method based on the optimized rational Hermite interpolation approach and its application to gear fault diagnosis

A demodulation technique based on improvement empirical mode decomposition (EMD) is investigated in this paper. Firstly, the problem of the envelope line in EMD is introduced and the drawbacks of two classic interpolation methods, cubic spline interpolation method and cubic Hermite interpolation method are discussed; then a new envelope interpolation method called optimized rational Hermite interpolation method (O-EMD) is proposed, which has a shape controlling parameter compared with the cubic Hermite interpolation algorithm. At the same time, in order to improve the envelope approximation accuracy of local mean, the parameter determining criterion is put forward and an optimization with Genetic Algorithm (GA) is applied to automatic select the suitable shape controlling parameter in each sifting process. The effectiveness of O-EMD method is validated by the numerical simulations and an application to gear fault diagnosis. Results demonstrate that O-EMD method can improve the reliability and accuracy significantly compared with traditional EMD method.     

Calculation method for conjugate depths in quadratic parabolic channels

Quadratic parabolic channels are widely used in irrigation and drainage engineering projects. Up until today there are no an effective method for computing the conjugate depths of quadratic parabolic channels. In this paper, calculation method for calculating the conjugate depths of quadratic parabolic channels was studied. Dimensionless depths were selected to simplify momentum equation for determining conjugate depths. Iterative equation for downstream depth was developed by suitable mathematical transformation on the momentum equation. If one knows dimensionless upstream depth, one can obtain dimensionless downstream depth by using iterative equation. Based on a large number of data of dimensionless conjugate depths, explicit equations with simple form for conjugate depths of quadratic parabolic channels were obtained by running a MATLAB program. Relative error analysis indicates that the proposed explicit equations which are employed to calculate conjugate depths (downstream depth and upstream depth) have high accuracy and wide application range. In the practical range of downstream depth to upstream depth ratio [1, 77.33], the maximum relative error is less than 0.30%.     

An average inverse power ratio method for the damping estimation from a frequency response function

The well-known bandwidth method, especially the half-power bandwidth method [1], [3], [4] (Bishop and Gladwell, 1963; Nashif et al., 1985; Yin, 2008) is probably the simplest method for the damping estimation from a frequency response function (FRF). This method is quite efficient for simple model test cases when modes are well separated. However, the determination of the two frequencies corresponding to a given power ratio value requires numerical interpolations of experimental discrete data of frequency response functions. In this paper, an average inverse power ratio method is proposed. The average value is computed at two frequencies symmetrically located from a peak amplitude frequency. Then the damping ratio can be estimated by using a formula similar to that of the bandwidth method. In this way, the damping estimation becomes straightforward from the FRF data. This new method could be useful for engineers in practice due to its extreme simplicity.