等效采样与移动拟合结合的超声测厚方法

针对高频超声回波信号需要高频采样频率采集的问题,提出了一种应用常规采样频率采集高频超声回波信号的方法,弥补了满足采样定理需要高频数据采集的局限性。主要是通过设计等效采样方法,把多周期的采样信号重构排序至单周期内,提高等效采样频率。针对超声回波信号关联被测工件厚度的包络特点,应用模拟乘法器降低采样信号衰减的基础上,提出FFT的粗估与移动正弦拟合算法精确提取包络相位信息的超声测厚方法,解决了传统通过峰值点位置特征直接计算工件厚度精度低的缺陷问题。实验对20 mm以内的钢板厚度检测表明：该方法绝对误差小于0.01 mm,重复性测量标准误差小于0.003 mm。     

冲击信号测量系统中下限频率的正确选取

本文通过分析冲击信号测量系统下限频率对三种典型冲击信号测量的影响，得出一组冲击信号脉宽及峰值的测试误差与系统下限频率、信号脉宽之间的关系曲线。同时，本文还给出了一套在给定误差的条件下，正确选取冲击信号测量系统下限频率的方法。关键词：     

音频信号分析仪

系统采用Atmega128单片机作为主控制器,并运用快速傅里叶变换(FFT)对音频信号进行频谱分析。输入音频信号经过双门限电路处理后,一路送入A/D采样,另一路经真有效值电路转换后送入A/D采样,结果经单片机处理,最后送液晶显示。该系统测量信号频率范围覆盖20 Hz～10 kHz,电压峰值范围10 mV～10 V,FFT得到的频谱分辨率为20 Hz,最终可得到音频信号的频谱与正弦信号失真度。     

轨道移频信号频率参数检测方法的研究

为了进一步提高轨道移频信号频率参数的测量精度,运用欠采样(带通采样)定理和ZOOM-FFT算法对频谱进行细化,根据轨道移频信号的频谱对称特性,引入重心法校正技术,在采样点数为2048情况下,使测量精度比规格要求提高了约3.5倍。     

考虑电网频率变化率的改进相位差校正法研究

针对电网信号基波频率动态变化时相位差校正法测量结果存在较大误差,甚至可能测量失败的问题,提出了一种考虑频率变化率的改进相位差校正法。指出了非同步采样造成的频谱泄漏是相位差校正法测量误差的主要来源,尤其当基频动态变化导致基波频率偏移较大时,非同步采样使测量精度严重降低。推导了基于频率变化率修正的归一化频率校正量公式,在线测量时,频率变化率用前次与当次测得的基波频率进行差商运算求得,再据此对测量结果进行了修正。分别使用考虑频率变化率的方法和原方法对变频电网信号进行了数值仿真研究。研究结果表明,改进相位差校正法有更高的测量精度,对基波的测量精度提高一个数量级,采样窗长为IEC标准规定窗长的50%,能满足频率动态变化时谐波在线测量的精度与实时性要求。     

基于MSP430F149的自适应功率因数测量仪的研究

本文介绍了基于MSP430F149的功率因数测量硬件系统及其算法设计。本测量系统对待测信号进行采样后,作数字低通滤波和DFT运算以估算其频率,从而根据信号频率灵活调整采样周期,能够工作在很宽的频率范围内。在采用LCD显示的同时,通过RS232接口可以在PC机上实时显示测量结果和信号波形,人机界面友好。     

利用信号拼接提高调频连续波激光测距系统的分辨力

提出了一种对等频率间隔的采样信号进行拼接来提高调频连续波激光测距系统的测距分辨力的方法。研究了调频连续波激光测距的原理,设计搭建了基于一种双干涉系统的光纤调频连续波激光测距系统。利用辅助干涉系统产生的时钟信号对测量干涉系统的信号进行等光频间隔的采样,然后对采样信号进行拼接。使用LabVIEW设计了信号错误检测处理、采样和拼接的信号处理系统。利用该测距系统进行了实验验证,结果显示,将等光频间隔的采样信号进行拼接的方法可以突破激光器扫描范围的限制,减少光源非线性的影响,从而提高系统的测距分辨力。得到结果表明,在测量距离为8.7m时,该系统的测距分辨力可达70μm,30组测量结果的重复性标准差为35μm。     

基于Nuttall窗频谱校正的介质损耗因数测量

采用旁瓣峰值电平小且旁瓣渐近衰减速率大的窗函数对信号加权可减轻非同步采样和数据截断对介质损耗因数tanδ测量的影响。本文分析了Nuttall窗的旁瓣特性,提出了基于Nuttall窗双谱线插值FFT的tanδ测量方法,运用多项式拟合求出了实用的插值修正公式,推导了信号初相角及tanδ的计算式,并介绍了基于该算法的测量系统的硬件实现方案。仿真和试验结果表明,Nuttall窗函数抑制频谱泄漏效果好,基于Nuttall窗的双谱线插值FFT方法克服了谐波干扰、基波频率波动及白噪声对tanδ测量的影响,且设计实现灵活,测量结果精确、稳定,可用于介质损耗因数tanδ的离线测量与在线监测。     

基于PLC高速计数器在测频测速中的应用

本文主要介绍了在国外某电站采用OMRON PLC内置高速计数器,实现对电站发电机设备进行频率、转速测量方面的应用,论述了该频率、转速测量的硬件组成和软件编程设计。通过程序封装,将PLC高速计数器采样到的脉冲数进行程序计算转换为实时的频率、转速信号,并对转速信号进行百分比的开关量信号输出,方便监控发电机设备的转速。     

频率大范围变换下的电能计量

针对在频率不断变换的情况下对信号功率进行测量的问题,提出了一种可同时测量信号瞬时频率、基波有功功率和视在功率的算法。输入信号为已经滤除了直流和高次谐波的基波分量,通过自适应有限长单位冲击响应(FIR)数字滤波器测量了基波有功功率,通过Prony算法测量了信号的瞬时频率和视在功率,利用改进的最小加权二乘法(WLS)算法提高了功率的精确度。研究结果表明,在频率大量变化的情况下,该算法对信号频率、有功功率以及视在功率的测量的精确度可满足工程应用的需要。     

铁基超微晶软磁合金在暂态冲击电流测量中的应用

介绍一种新型材料——铁基超微晶软磁合金在暂态冲击电流测量中应用。因其具有高饱和磁感应强度、低矫顽力,低高频损耗、高起始磁导率和高频特性好等优点.我们用它作铁芯。利用磁感应原理来测量上升时间为几微秒和几百微秒、幅值在1kA以下的暂态冲击电流。     

气液两相流中的空隙率计研究

本文介绍了研制的新型三相脉冲电导式空隙率计.与国外代表性的Merilo旋转电场式空隙率计比较,其传感器结构和激励电源等均有新的创新.研究结果表明:仪表在线性度、测量精度、频率响应以及结构简化等方面,均有提高和改进.     

New Side-Looking Rogowski Coil Sensor for Measuring Large-Magnitude Fast Impulse Currents

This paper presents a new design of a side-looking “flat spiral” self-integrating Rogowski coil that is wound by twin coaxial cable with individual sheath. The coil is tested with different impulse current waveforms up to 7 kA peak value to improve its performance. The coil design is optimized to achieve bandwidth and sensitivity up to 7.854 MHz and 3.623 V/kA, respectively. The coil is calibrated versus two commercial impulse-current measurement devices at different coil-to-wire separations, coil inclination angles, and impulse current waveforms. Distortion of the coil output voltage waveform is examined by using the lumped-element model to optimize the connections of the four cable winding sheaths and the coil termination resistance. Finally, the coil frequency response is investigated to optimize the coil design parameters and achieve the desired bandwidth (large low-frequency time constant), high rate of rise, no overshoot, very small droop, high rate of fall, and no backswing.     

脉冲激振枪

Impulse exciting gun is a new type of impulse exciter developed by authors. When it works, the shock head in the gun impacts the object to be measured at a certain speed, so that an impulse. Force is exerted on the object in fraction of a second. At the same time, the force transaucer with the shock head converts the impulse force into electrical signal for output. Thus the impulse excition for the objects to be measured as well as dynamic measurement have been completed just once. Impulss exciting gun involves three main parts called adjusting mechanism, localizing mechanism and returning mechanism. Adjusting mechanism can easily change rigidity of impulse head and the initial velocity of impact, in order to control contact continuance (force impulse breadth) and maximal presure Fm.. (force impulse peak value) between the 'shock head and the object. The function of localizing mechanism is to control exerted force point and its direction more accuratly. And setting up a returning mechanism is to avoid touching again between the shock head and the object after they collide with each other. Outward appearance of the gun is in figure 1. As for main technique indexes of impulse exciting gun see table 1 and figue 4-3.Impulse exciting gun is not only of simple structure, but also reliable and convenient to use. Furthermore, force impulse breadth and its peak value and exerted force point and its direction may be accuratly controlled when used. Those special advantages of the gun over impulse exciters now available make it come into vise in some scientific research departments and colleges.     

Cutoff probe using Fourier analysis for electron density measurement

This paper proposes a new method for cutoff probe using a nanosecond impulse generator and an oscilloscope, instead of a network analyzer. The nanosecond impulse generator supplies a radiating signal of broadband frequency spectrum simultaneously without frequency sweeping, while frequency sweeping method is used by a network analyzer in a previous method. The transmission spectrum (S21) was obtained through a Fourier analysis of the transmitted impulse signal detected by the oscilloscope and was used to measure the electron density. The results showed that the transmission frequency spectrum and the electron density obtained with a new method are very close to those obtained with a previous method using a network analyzer. And also, only 15 ns long signal was necessary for spectrum reconstruction. These results were also compared to the Langmuir probe's measurements with satisfactory results. This method is expected to provide not only fast measurement of absolute electron density, but also function in other diagnostic situations where a network analyzer would be used (a hairpin probe and an impedance probe) by replacing the network analyzer with a nanosecond impulse generator and an oscilloscope.     

基于Nd: YAG固体激光器预制连杆初始裂解槽研究

裂解槽的设计与加工是连杆裂解加工技术的核心和技术关键,将直接影响着连杆的裂解质量。为提高连杆裂解槽加工质量,采用Nd：YAG固体激光器对两种类型的连杆进行了裂解槽激光加工试验,分析了不同切割参数对裂解槽质量的影响,并对激光切割参数进行了优化。结果表明：激光峰值功率、离焦量、切割速度、脉冲频率、辅助气体压力、激光入射角等对裂解槽的加工质量都有很大的影响,其中激光峰值功率直接影响着裂解槽的加工深度,在切割速度与脉冲频率比值约为1：3以及非正离焦量状态下所加工的裂解槽对连杆的裂解都非常有利。     

基于准同步DFT的非整数谐波分析算法

在准同步DFT谐波分析算法的基础上,提出了一种基于非整数波概念的谐波分析算法。该算法的核心思想是:信号频率漂移导致频谱峰值出现的位置与理想位置不一致是短范围泄漏产生的根本原因,而信号频率的漂移可以通过测量相邻点基波相角差来获得,那么应用该漂移值对基波和高次谐波的波次值进行非整数修正就可以准确测量各次谐波的幅值和相角。仿真实验和工程实例证明,该算法能够有效抑制频谱的长范围泄漏和短范围泄漏,提高基波与高次谐波的幅值与相位测量准确度。     

杂散电容对交流法微电容测量电路噪声特性影响的分析

对电容成像交流法微电容测量电路由杂散电容导致的测量噪声进行了研究.利用运算放大器的噪声模型,对运算放大器输入电压噪声、输人电流噪声以及周边电阻元件的热噪声通过杂散电容作用于交流法微电容测量电路输出的影响进行了理论分析,给出了测量电路输出中噪声峰峰值的理论计算公式并进行了实验验证.理论分析及实验结果表明:交流法微电容测量电路前级运算放大器输入电压噪声通过测量端与地之间的杂散电容形成的噪声是该微电容测量电路输出噪声的主要来源.最后给出了电容成像系统前级运算放大器选型的指导原则.     

Tape-wound Rogowski coil for measuring large-magnitude pulsed currents

This paper presents design, calibration and testing of a new tape-wound Rogowski coil for measuring large-magnitude pulsed currents. The performance of the coil is tested by different impulse current waveforms up to 9 kA peak value. The coil is calibrated versus two commercial impulse-current transformers with different impulse current waveforms. The coil design is optimized to work in the differentiating mode and achieve useful bandwidth and sensitivity up to 1 MHz and 102 mV/kA, respectively. Waveform distortion of the coil output voltage is examined by using the lumped-element model to optimize the parameters of the external passive integrator. It is desired to optimize the integrator parameters and achieve the desired bandwidth without having droop and backswing. To do so, the coil frequency response is investigated by making fast Fourier transform (FFT) of the impulse current waveforms and PSPICE simulation of the lumped parameter equivalent circuit of Rogowski coil and the external integrator. Finally, it is found that the PSPICE calculated sensitivity for the optimized integrator parameters deviates from the corresponding measured one by a percentage relative error of–0.05%.     

基于API579—1／ASMEFFS-1的爆炸容器FAD评定方法

提出了爆炸容器FAD全过程评定方法,建立了含穿透裂纹的圆柱形爆炸容器计算模型,分析了其在三角波载荷作用下的动力响应,利用虚裂纹闭合技术计算了应力强度因子的动力响应特性,结果表明：爆炸容器的FAD评定方法可以有效区分冲量相同而峰值不同的冲击载荷的影响,峰值越大,载荷作用时间越短,容器评定结果越危险;采用传统等效静载荷法进行工程设计,具有较大的安全裕度;同时发现,FAD评定能有效地识别尺寸效应的后果,因此该方法对动载荷下的容器评定尤为有效。