等精度频率信号采集测试系统

频率信号采集测试系统采用PCL-836多功能计数器/定时器卡基于等精度测频方法实现,讨论了基本的测量原理并对系统的硬件线路实现和软件设计作了详细的介绍和分析.     

基于卡尔曼滤波技术解算惯导的水平偏差

针对测量船惯导系统水平及航向精度检测需求,提出了采用卡尔曼滤波技术解算惯导水平偏差的新方法。对经纬仪校准惯导的基本原理及陀螺的随机飘移分析,利用经纬仪测星方法,在惯导飘移误差小于7′,标定误差可在2″以内,可有效地消除惯导的随机游动误差分量,将使测量船的整体测量精度得到显著的提高。     

利用相位估计算法实现ps量级的高精度时间间隔测量

高精度时间间隔测量广泛应用于时间同步、卫星导航、航天测控、激光测距以及核电子等场合.目前主流的时间间隔计数器能达到25 ps分辨率,约100 ps的准确度.本文把被测信号作为采样参考频标信号的触发信号,利用参考频标的相位记录被测信号的触发点,然后利用插值FFT对参考频标信号的采样数据进行相位估计,提出了一种理论上分辨率和精度均优于1 ps的时间间隔测量方法.实验测试结果表明原理样机达到了10 ps的测量精度.进一步改进样机的设计,有望达到1 ps的测量精度.     

新型智能测速仪研制

介绍一种基于８９Ｃ５１单片机系统的新型智能测速仪的测量原理、硬件组成和软件设计。该仪表采用了一种新的自动测速方法;在高速时,运用闸门时间自动调整的电子计数器测频法;在低速时,运用被测信号周期自动调整的电子计数器测周法,在宽量程度范围内实现了高精度、实时快速测量。     

基于相位重合的全同步测频方法研究

文章对基于相位重合的全同步测频方法进行了研究。相位重合理论是目前比较流行的用于频率测量的理论,在检测被测信号与标频信号的相位重合脉冲后触发闸门,使计数闸门、被测信号和标频信号三者达到全同步,彻底消除了±1个字误差。相位重合检测电路、闸门、计数器等模块均在可编程逻辑器件FPGA中完成,使用方便,易于修改,经仿真达到了预期效果。     

轻量化惯导系统振动响应分析与减振器优化

惯导系统轻量化设计产生的结构柔性对其振动响应会产生不可忽略的影响。针对某型轻量化惯导结构,采用基于频响函数的子结构综合方法,建立了惯导系统的动力学模型,并应用此模型分析了IMU柔性对惯导系统的影响,并提出了一种减振系统参数优化设计方法。通过减振器优化,惯导系统的角位移明显减小,有效抑制了振动耦合。最后通过振动实验验证了优化方法的准确性,同时发现惯导系统经减振器参数优化后提高了振动过程中惯导系统航向和姿态测量精度。     

基于单片机的频率测量的几种实用方法

利用MCS－51系列单片机的定量／计数器可以非常方便地进行信号的频率测量，文中给出了3种基于单片机的测频方法及程序，且系统硬件电路结构简单，软件设计容易。     

基于新校频算法的GPS可驯铷钟系统研究

在GPS可驯铷钟系统中,校频是驯频的前提.常用高精度校频算法的不足在于需要昂贵的高分辨时间间隔计数器.提出了一种新的校频算法.使用最小分辨率为0.1μs的低分辨时间间隔计数卡,测量铷钟和GPS定时接收机二者秒信号的时差,然后设计了卡尔曼滤波算法,并在单片机中实现,对时差数据进行平滑,克服由于GPS的秒信号、铷钟的秒信号的不稳定和测量噪声带来的影响,估计出高精度的时差数据,从而在较短时间内获得很高的校频精度.该方法将GPS作为频率基准,间接得到了铷钟相对于与GPS的频差,避免了使用昂贵的高分辨计数器.使用该校频算法,对PRS10铷钟进行驯频,研制了可驯铷钟系统.对系统的测量结果表明在不影响铷钟短期稳定度的情况下,频率准确度一般优于5×10-12.     

单轴旋转惯导系统建模与仿真

建立了单轴旋转式捷联惯导系统数学模型和仿真模型,采用的导航算法能有效避免转台测角误差对系统定位精度造成的影响;仿真结果表明旋转IMU能提高抑制惯导定位误差的累积,提高惯导定位精度、姿态精度和速度精度也同时得到提高。     

激光陀螺抖动偏频电路的设计与实现

目前消除激光陀螺闭锁误差常用的方法是采用机械抖动偏频及向抖动驱动信号中注入随机噪声。根据某型激光捷联惯导系统所选用的激光陀螺的特性,采用微控制器、锁相环及D／A转换器等器件设计了激光陀螺抖动及加噪电路。该电路具有抖动起振快、加噪简单有效、工作可靠性高等特点,并具有自检测功能。从设计的激光捷联惯导系统实际运行看,该电路能很好地满足系统功能及性能要求。     

调制域测频原理及工程实现

本文介绍了调制域这一新概念,着重分析了调制域测频方法,给出了所实现的调制域测频系统框图,展示了调制域测试的关键技术：内插技术和无间隔计数技术,介绍了游标内插法,独立提出了斜波内插法和孪生链。     

基于延迟内插的调制域分析

介绍了调制域分析技术的原理，重点介绍基于FPGA的零空闲（ZDT）计数和测量补偿技术。测量补偿采用延迟内插法，相对于传统的游标内插法和斜坡内插法，此方法电路简单，转换速率高，测时分辨率可以达到ps级。本方案可应用在高精度连续测频、高精度连续测量时间间隔，测ns秒级窄脉冲等各种场合。     

内燃机瞬时转速测试系统开发

瞬时转速测量的主要误差为晶振脉冲计数误差和转角计量误差。转角计量误差包括角标器分离误差，曲轴扭振产生的误差。论文对瞬时转速的滤波方法进行了分析，认为FIR低通滤波器对高频干扰有抑制作用，对低频干扰信号抑制作用较差，不适于瞬时转速信号滤波。切比雪夫与巴特沃思滤波器对低频干扰信号的抑制效果更好，推荐采用6阶巴特沃思低通滤波器对瞬时转速信号滤波。     

动态频率测量的滞后误差分析及改进方法

采用常规方法测量动态频率时会产生滞后误差,该误差与被测信号的频率变化率以及测量结果的更新间隔时间成正比。为了降低滞后误差,对3种常规的频率测量方法进行改进研究。改进测周法,提出了周期跟踪法,当测量信号周期的定时器计时值超过上一个信号周期时,将定时器计时值作为信号周期并实时更新测量结果,从而缩短测量结果的更新间隔时间以降低滞后误差;改进多周期同步法,提出了分步移动式多周期同步法,在信号边沿中断程序中记录信号周期,并根据最近的若干个信号周期记录来计算信号频率,将测量结果的更新周期由多个信号周期缩短为单个信号周期,滞后误差最多可降低约2/3;改进计数法,提出了分步移动式计数法,采用计数器对信号数进行连续计数,将用于统计信号数的计时时间的1/n设置为定时器中断周期,在定时器中断程序中读取并记录计数器数值,根据最新记录的n个计数器数值来计算信号频率,将测量结果的更新间隔时间缩短为计数法的1/n,滞后误差最多可降低约2/3。     

Multifrequency channel microwave reflectometer with frequency hopping operation for density fluctuation measurements in Large Helical Device

In order to measure the internal structure of density fluctuations using a microwave reflectometer, the broadband frequency tunable system, which has the ability of fast and stable hopping operation, has been improved in the Large Helical Device. Simultaneous multipoint measurement is the key issue of this development. For accurate phase measurement, the system utilizes a single sideband modulation technique. Currently, a dual channel heterodyne frequency hopping reflectometer system has been constructed and applied to the Alfve?n eigenmode measurements.     

Measurement of ultrasonic velocity with improved accuracy in pulse echo setup

In the present work a personal computer based circuit adopted in pulseecho setup has been developed for the measurement of time-of-flight between the two successive echoes using a differential time measurement with a 16 bit counter and an external clock frequency of 32 MHz. A control program is developed in C to display the time of flight and wave propagation velocity on a user screen. The technique, so developed, minimizes the errors in time delay measurements due to the variation in threshold trigger points of echoes and improves the ultrasonic velocity measurement.     

Application of dfb diode laser sensor to reacting flow (II) —liquid-gas 2-phase reacting flow—

Diode laser sensor is conducted to measure the gas temperature in the liquid-gas 2-phase counter flow flame. C₁₀H₂₂ and city gas were used as liquid fuel and gas fuel, respectively. Two vibrational overtones of H₂O were selected and measurements were carried out in the spray flame region stabilized the above gaseous premixed flame. The path-averaged temperature measurement using diode laser absorption method succeeded in the liquid fuel combustion environment regardless of droplets of wide range diameter. The path-averaged temperature measured in the post flame of liquid-gas 2-phase counter flow flame showed qualitative reliable results. The successful demonstration of time series temperature measurement in the liquid-gas 2-phase counter flow flame gave us motivation of trying to establish the effective control system in practical combustion system. These results demonstrated the ability of real-time feedback from combustor inside using the non-intrusive measurement as well as the possibility of application to practical combustion system. Failure case due to influence of spray flame was also discussed.     

一种宽范围测速系统的设计

针对光电编码器的宽范围测速系统存在低速振动测速不准和高速巨量中断导致实时性欠佳的问题,采用抗振动M/T测速方法结合可预置N分频器,低频时采用脉冲电平逻辑滤波,清除干扰,保证测速的准确性,高频时采用分频计数,降低处理器中断处理的次数,提高测速系统运行的效率,从硬件和软件两个方面较好地解决了这个问题,并据此研制以32位嵌入式处理器(LPC2114)为控制器的宽范围测速系统,同时给出系统的硬件和软件设计方案。研究结果表明该设计方法是有效的。     

Ultra-high-precision time control system over any long time delay for laser pump and synchrotron x-ray probe experiment

An ultra-high-precision clock system for long time delay has been developed for picosecond time-resolved x-ray diffraction measurements using synchrotron radiation (SR) pulses and synchronized femtosecond laser pulses. The time delay control between pump laser pulse and the probe SR pulse was achieved by combining an in-phase quadrature modulator and a synchronous counter. This method allowed us to change the delay time by a nearly infinite amount while maintaining the precision of +/-8.40 ps. Time-resolved diffraction measurements using the delay control system were demonstrated for precise measurement of an acoustic velocity in a single crystal of gallium arsenide.     

Lock-in amplifier error prediction and correction in frequency sweep measurements

This article proposes an analytical algorithm for predicting errors in lock-in amplifiers (LIAs) working with time-varying reference frequency. Furthermore, a simple method for correcting such errors is presented. The reference frequency can be swept in order to measure the frequency response of a system within a given spectrum. The continuous variation of the reference frequency produces a measurement error that depends on three factors: the sweep speed, the LIA low-pass filters, and the frequency response of the measured system. The proposed error prediction algorithm is based on the final value theorem of the Laplace transform. The correction method uses a double-sweep measurement. A mathematical analysis is presented and validated with computational simulations and experimental measurements.