THE RESEARCH OF GRADATION FUSION ALGORITHM BASED ON MULTISENSOR ASYNCHRONOUS SAMPLING SYSTEM

This letter explores the distributed multisensor dynamic system, which has uniform sampling velocity and asynchronous sampling data for different sensors, and puts forward a new gradation fusion algorithm of multisensor dynamic system. As the total forecasted increment value between the two adjacent moments is the forecasted estimate value of the corresponding state increment in the fusion center, the new algorithm models the state and the forecasted estimate value of every moment. Kalman filter and all measurements arriving sequentially in the fusion period are employed to update the evaluation of target state step by step, on the condition that the system has obtained the target state evaluation that is based on the overall information in the previous fusion period. Accordingly, in the present period, the fusion evaluation of the target state at each sampling point on the basis of the overall information can be obtained. This letter elaborates the form of this new algorithm. Computer simulation demonstrates that this new algorithm owns greater precision in estimating target state than the present asynchronous fusion algorithm calibrated in time does.

Electro-optic Sampling of Proton-bombarded GaP Crystal

An electro-optic sampling system utilizing proton-bombarded GaP crystal as probe material has been built. Microwave signals propagating on the indium -tin oxide coplanar waveguide were measured by the system. Measurements of bombarded sample gave the resistance value of four orders greater than that of un- bombarded. The electric field shield effect induced by doped GaP was effectively decreased to approximate semi-insulator material. The system has the voltage sensitivity of about 40 mV/21/Hz with the microwave frequency of 1.15 GHz.

Non-PLL high-precision synchronous sampling method among lots of acoustics acquisition channels for underwater multilinear array seismic exploration system

Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.

Simulation and Error Analysis of Electro-optic Sampling Measurement of Ultrashort Electron Beam Bunch Length

For the development of high energy physics,it is needed to improve the performance of the relativistic electron bunch.The measurement of the ultrashort relativistic electron pulse becomes one of the key technologies.The electro-optic sampling measurement of relativistic electron pulses is a promising method.This method is nondestructive, non-intrusive,and real-time monitoring.Distance and angles of the reference frames will cause system deviations.In this paper these system deviations are analyzed by simulation.It provides a reference for the experiment.

Stabilization of a high-order harmonic generation seeded extreme ultraviolet free electron laser by time-synchronization control with electro-optic sampling

A fully coherent free electron laser(FEL) seeded with a higher-order harmonic(HH) pulse from high-order harmonic generation(HHG) is successfully operated for a sufficiently prolonged time in pilot user experiments by using a timing drift feedback. For HHG-seeded FELs, the seeding laser pulses have to be synchronized with electron bunches. Despite seeded FELs being non-chaotic light sources in principle, external laser-seeded FELs are often unstable in practice because of a timing jitter and a drift between the seeding laser pulses and the accelerated electron bunches. Accordingly,we constructed a relative arrival-timing monitor based on non-invasive electro-optic sampling(EOS). The EOS monitor made uninterrupted shot-to-shot monitoring possible even during the seeded FEL operation. The EOS system was then used for arrival-timing feedback with an adjustability of 100 fs for continual operation of the HHG-seeded FEL. Using the EOS-based beam drift controlling system, the HHG-seeded FEL was operated over half a day with an effective hit rate of 20%–30%. The output pulse energy was 20 μJ at the 61.2 nm wavelength. Towards seeded FELs in the water window region, we investigated our upgrade plan to seed high-power FELs with HH photon energy of 30–100 e V and lase at shorter wavelengths of up to 2 nm through high-gain harmonic generation(HGHG) at the energy-upgraded SPring-8Compact SASE Source(SCSS) accelerator. We studied a benefit as well as the feasibility of the next HHG-seeded FEL machine with single-stage HGHG with tunability of a lasing wavelength.

Tunable compact asynchronous optical sampling system using Er-doped fiber laser

We report a compact,tunable,self-starting,all-fiber laser-based asynchronous optical sampling(ASOPS)system.Two Er-doped fiber oscillators were used as the pulsed-laser source,whose repetition rate could be set at 100 MHz with a tuning range of 1.25 MHz through a fiber delay line.By employing phase-locked and temperature control loops,the repetition rate offset of the two lasers was stabilized with 7.13×10^(−11)fractional instability at an average time of 1 s.Its capabilities in the terahertz regime were demonstrated by terahertz time-domain spectroscopy,achieving a spectral bandwidth of 3 THz with a dynamic range of 30 dB.The large range of repetition rate adjustment in our ASOPS system has the potential to be a powerful tool in the terahertz regime.

Electro-optical sampling non-synchronous delay scanning measurement of electron beam bunch length at BFEL

The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-synchronous delay scanning technique based on the electro-optical sampling measurements is presented. Based on Beijing Free Electron Laser （BFEL）, the electron beam bunch length was measured with the electro-optical sampling technique for the first time in China. The result shows that the electron beam bunch length at BFEL is about 5.6±1.2 ps.

基于异步光学采样的电光频率梳时间抖动测量

电光频率梳是一种单频激光器经相位调制构造的光学频率梳,具有重复频率高、灵活可调等特点,通过精确的色散控制,电光频率梳在时域上可以输出超短脉冲激光序列,其时间抖动特性对于开展精密测量等应用十分重要.本文提出一种基于双光梳异步光学采样原理测量电光频率梳时间抖动的方案.建立了时间抖动测量的理论模型并进行数值模拟.搭建了一台重复频率为10 GHz、脉冲宽度为2.6 ps的电光频率梳,并开展了时间抖动的测量实验.测量的直方图分析表明,电光频率梳的周期抖动为3.86 fs.测量装置主体为光纤结构,且不需要高速光电探测器,有望对电光频率梳、微环频率梳等新型高重频光学频率梳时间抖动的测量与优化起到关键作用.

异步测量系统的分布式序贯椭球相交融合估计

针对具有测量缺失现象的多源异步测量系统的状态估计,提出一种基于条件Kalman滤波的分布式序贯椭球相交(DSEI)融合算法。对系统测量缺失现象通过一组服从伯努利分布的随机变量进行建模描述;同步化状态空间模块利用状态迭代方法将异步测量系统在测量更新时刻进行同步;局部滤波模块采用条件Kalman滤波算法实现,保证滤波结果的完整性;融合估计模块在不考虑多传感器间相关性信息的前提下,设计DSEI融合算法对各个传感器提供的滤波结果进行融合。仿真实例验证了所提算法具有精度提高35%、迭代时间小于3 ms的优越性能。

基于采样的并行程序性能测量分析工具研究

在实际运行中,并行计算程序的性能常常在理论峰值与预期存在较大差距。使用性能分析工具进行程序调优是解决这一问题的高效手段。然而,程序员和开发者在使用性能分析工具时往往面临选择困难、配置和使用复杂等挑战。研究基于采样的并行程序性能分析工具有助于解决上述问题。相比于插桩技术,基于异步采样的性能工具可以更好地控制测量开销和测量数据大小。着重研究了三种典型的基于采样的性能分析工具:VTune Profiler、HPCToolkit和Nsight Systems,分析了其原理和功能,并且结合VASP等实际应用程序对工具的软硬件分析能力和并行编程分析能力进行了详细的探究和对比。根据这些工具在不同的应用场景下表现出的不同适用性和分析效果,提出了综合运用多种工具进行性能分析的方案,为开发者和程序员提供有益的参考。

应用于谐波测量的二次加权傅里叶变换关键参数分析

基于准同步采样的二次加权傅里叶变换方法(下称二次加权傅里叶变换方法)解决了可编程约瑟夫森电压标准(PJVS)应用于谐波电压测量中的过渡过程和非同步采样问题,极大地提升了谐波电压测量的准确度。为使二次加权傅里叶变换方法在实际应用中更加系统和完善,针对二次加权傅里叶变换的几个关键参数进行了研究,包括频率同步误差、谐波复杂程度以及阶梯电压的台阶数和采样点数,并对测量结果的影响展开讨论和分析,提供了测量参数设定的参考指标,给出了测量误差评估方法及示例,为二次加权傅里叶变换方法在实际测量中的应用提供了理论依据。

异步马尔科夫跳变系统的分布式融合估计

对带有相关噪声的多传感器异步马尔科夫跳变系统,提出了线性最小方差意义下的按矩阵加权分布式融合估计算法。系统中不同传感器间测量噪声相关,并与系统噪声同时刻相关,同时不同传感器以不同的采样速率均匀采集观测数据。在状态更新点利用伪观测法,并引入Dirac函数,通过状态增广,将异步马尔科夫跳变系统转化为状态更新点的单速率系统。进而利用Kalman滤波理论,提出了线性最小方差意义下的最优局部状态滤波器、系统噪声估值器和两传感器间的估计误差互协方差矩阵,提出了多传感器按矩阵加权分布式最优融合估值器。通过跟踪系统数值仿真实例,进一步验证了所提算法的有效性。

大型抽水蓄能机组启动工况保护自适应算法研究

大型抽水蓄能电站机组启动频繁,工况转换多变,保护采用电气一次设备辅助开关接点以及控制系统输出的接点信号等方式识别工况,根据运行工况合理配置保护并自动投退。低频启动阶段电压、电流信号频率极低,幅值小并且波动变化大,采用常规傅里叶算法,误差不能满足保护运行要求。本文分析了采用快速频率跟踪调整采样间隔方法的弊端,提出了基于异步采样数据的保护自适应算法,通过采用二阶低通滤波及与频率无关的有效值算法,仿真验证了算法的正确性。采用本算法的保护装置已经在国内多个抽水蓄能工程应用,设备运行良好。

基于奈奎斯特采样的FPGA异步串行通信接口设计

在异步串行通信中,由于串行接口硬件设备的工作频率限制,以及信号跳变引起的抖动、环境干扰等影响,采用传统方法实现异步串行通信的通信接口无法可靠地完成高速率通信。文章采用VHDL语言,设计一种基于奈奎斯特的异步串行通信接口,包括数据接收、数据发送和2倍波特率的采样时钟三个模块。ISE和ModelSim联合仿真与实际工程的验证表明,使用新方法设计的接口在5 Mbit/s的高速率下,系统可稳定、可靠地与外部设备进行数字通信。

非同步采样下电力系统相量测量修正算法

非同步采样条件下,利用傅里叶变换进行相量分析将出现由频谱泄漏造成的误差。针对工频交流正弦信号中基波电压偏移且采样频率恒定而引起的非同步采样误差,推导了非同步采样下傅里叶变换结果表达式,建立了离散傅里叶变换相角与幅值的误差模型,得到相角和幅值误差与频率偏移量和采样初始相位角的函数关系,提出了基于基波正序分量法的相角与幅值修正算法。所提算法不需要对信号施加特殊的窗函数。仿真和实测结果表明,在基波频率波动剧烈、高斯白噪声存在、非同步采样程度较大的情况下,利用较少的计算量便可准确地获得信号的相角和幅值,适用于电力系统相量的高精度快速测量。

非同步采样的同步化谐波分析算法

为了消除采样过程中同步误差产生的频谱泄漏,提出一种基于搜索的同步化算法.该算法采用逆向搜索在非同步采样数据中截取整周期的采样序列,通过离散傅里叶变换(DFT)得到频谱,搜索频谱幅值得到基波谱线位置,计算基波及各次谐波的幅值和相位.误差分析和仿真结果表明,采样点数越多,算法精度越高,较高的采样频率有利于提高算法的分析精度.同步化谐波分析算法分为单周期和多周期两种方法,单周期法适合于非稳态周期信号的谐波测量,多周期法提供了一种精确分析稳态周期信号谐波的有效方法.

基于相关原理的相位差测量改进算法及应用

为提高相关法在非整周期采样情况下的相位差测量精度,增强算法的动态响应能力,提出了一种基于相关原理的相位差测量改进算法。该算法利用原两路同频信号产生具有90°相移的两个参考信号,经零相位滤波后,将原两路信号分别与两路参考信号进行相关运算,再利用相关和正弦函数的一些性质得到相位差的计算公式。理论分析和实验结果表明,该算法具有不必预先知道信号频率的特点,测量精度不受采样是否整周期的影响,且能实现相位差的动态检测,与传统算法相比,该算法测量精度更高,更具鲁棒性和普适性。

基于DFT的电力系统相量及功率测量新算法

随着全球定位系统(GPS)的全面民用化以及通信技术的发展，电力系统实时相量测量技术日益受到关注。传统的基于离散傅里叶变换(DFT)的频率跟踪算法对相角误差的考虑不全面，从而其频率、相角、幅值等计算结果也不够准确。文中对 DFT 在非同步采样情况下的误差产生机理进行了全面分析，给出了非同步采样情况下 DFT 相角计算结果的精确误差表达式，基于该相角误差公式，提出了一种新的基于 DFT 的电力系统相量测量算法。与传统算法相比，该算法具有精确度高、可以自适应地抑制谐波干扰、计算量不大等优点，并用算例验证了这些优点。此外，还给出了实用的利用传统 DFT 方法计算功率的误差估计公式。

加Blackman-Harris窗插值算法仿真介损角测量

为了更好地将加布莱克曼-哈里斯(Blackman-Harris)窗插值谐波分析法用于介损角测量,仿真分析了该算法及其在信号频率、3次谐波、直流分量、采样频率、A/D量化位数、采样时间长度、介损角真实值、白噪声及脉冲噪声变化时计算所得介损角误差的变化。仿真结果表明,频率波动时算法误差很小且稳定;算法随3次谐波分量的增加误差有很微小的增加;算法随直流分量的增加变化不显著;算法随A/D量化位数的增加误差减少,≥10位的量化位数能满足精度要求;随采样频率的增加误差稍有下降,但趋势不明显;随采样长度增加误差减少,0.1s的采样时间长度足够;介损角误差与真实值的关系不大;随白噪声和脉冲噪声含量的减少误差减少,对白噪声和脉冲噪声信噪比约80 dB能满足要求。

一种减小频谱泄漏的同步化算法

针对非同步采样情况下快速傅立叶算法进行谐波分析时所出现的频谱泄漏问题,本文分析了产生频谱泄漏的原因,提出一种应用插值函数的同步化算法,其目的是修正初次采样序列得到近似理想的同步采样点,以减小DFT分析产生的频谱泄漏。仿真结果表明该算法使频谱泄漏大大小于未同步化方法,具有良好性能、计算量小、适合于实时测量应用的特点。