基于模糊树的Hammerstein-like模型对超磁致伸缩作动器的建模与控制

基于模糊树提出一种带有动态非线性环节的Hammerstein-like建模方法以描述超磁致伸缩作动器的率相关迟滞非线性特性。所提方法能在一定频率范围内建立一个统一模型,使之不仅能较好地描述单一频率输入信号下的迟滞环,也能较好地描述复合频率输入信号下的迟滞环。同时,基于所提Hammerstein-like模型,设计前馈逆补偿+PID反馈控制策略,实现参考输入信号的跟踪实验,实验结果表明,该控制策略能较好地跟踪频率范围为1的参考输入信号,跟踪精度令人满意,满足工程要求。     

A high dynamic range magnetooptic current transformer with advanced signal processing

In the power industry, current must be measured for metering and protection purposes. For such measurements, the use of magnetooptic current transformers offers many advantages. Conventional sensors, however, need two magnetooptic transformers to realize the required high dynamic range. Using a combination of analog and digital signal processing algorithms, the inherent low noise of the photonic input signals is maintained. The system design is based on a rigorous investigation and optimization of the error sources in the signal processing chain. The validity of this approach was confirmed by a demonstrator which achieved a dynamic range from 0.05 to 100 times the rated current and whose rms error was less than 0.5 %.     

A high dynamic magnetooptic current transformer with advanced signal processing

In the power industry, current has to be measured for metering and protection purposes. Conventional sensor setups need two transformers to realize the high dynamic range. By the described mixed analog/digital signal processing algorithm, the inherent low photonic noise of the input signals was maintained up to the full sensor output. The system design is based on a rigorous investigation and optimization of the error sources in the signal processing chain. The results are proved by a demonstrator, achieving a dynamic range from 0.05 to 100 times the rated current and a ratio root mean square error of less than 0.5%.     

光纤电焊电流测量技术研究

针对直流逆变电阻焊机焊接电流精确测量的需求,提出基于光纤电流传感技术的焊接电流测量方法。建立了光纤电流传感器闭环检测系统动态模型,通过优化系统的前向增益,提升了传感器响应速度和带宽。仿真和实验结果表明:传感器的上升时间约为4.1 μs,在DC~30kHz范围内幅频特性衰减小于0.3%。基于该动态模型计算传感器对焊接电流纹波分量的响应,仿真结果表明:系统的动态跟踪能力可满足对纹波电流的测量需求。利用等安匝法对光纤电流传感器进行校准,在直流5~50kA范围内,传感器的测量误差优于±0.05%。现场实验结果证明了光纤电流传感器用于直流逆变焊接电流测量及电焊电流测试仪现场校准的可行性。     

Frequency multiplier with a feedback

Conclusions A multiplier with a feedback has the unique combination of the following properties: a wide range of multiplied frequencies (10:1 and wider); a large and easily variable scaling factor; it is independent of the input signal voltage shape or amplitude; it can operate with a variable input frequency; it is insensitive to stray frequency modulation of the input signal at frequencies above the effective modulating range; a possibility of direct multiplication of the difference of two frequencies, or even a linear combination of several frequencies; and a possibility of correcting the nonlinearity of transducers, if this nonlinearity is not too large.Thus, it meets virtually all the requirements which can be specified for a frequency multiplier intended for working in a frequency-digital measuring system.     

改善步进电机电流响应速度的抗饱和PI控制

目的为了提高连续式包装机的生产效率,提出一种新型的抗积分饱和PI电流控制器设计方法。方法针对PI控制器积分饱和现象引起的步进电机绕组电流响应过慢问题,根据控制器输入输出状态,确定抗饱和增益值的大小,调整积分作用效果。在控制器输入变化较慢时,充分发挥积分器的作用,减小超调量;在输入变化较快时,使积分器更快地退出饱和,提高系统响应速度。结果实验结果表明,该方法较传统PI控制和反计算固定增益PI控制能更精确地控制绕组电流,有效提高了电流响应速度和减小了超调量。结论该方法使绕组电流更好地跟随参考值变化,改善了电机在不同运行状态下的动态性能。     

一种提高转台伺服系统精度的方法

转台正弦摇摆时换向误差较大,影响系统的跟踪精度。对此,提出了一种变增益算法,将速度回路的前向通道放大倍数设计为一个以系统输入速度作为自变量的函数,使其随着系统速度的变化而自动调整。在低速运行时,放大倍数较大,提高系统刚度,可获得较高的低速跟踪精度;在高速运行时,控制放大倍数,以保证系统的动态性能。设计了两种变增益函数进行实验,实验结果表明,该方法可以把换向误差从48 减小到10,是一种较为实用和有效的设计方法。     

Model-Based Compensation of SAR Nonlinearity

In the successive approximation analog-to-digital conversion principle, sample-and-hold (S/H) nonideality, producing an input signal variation that is less than the least significant bit (LSB) during the conversion time, gives rise to intrinsic and significant dynamic nonlinearity. In this paper, a method for compensating such nonlinearity is proposed. Theoretical fundamentals of the method are reported by paying particular attention to the accuracy of the compensation. With this aim, the dynamic phase distortion that is related to the intrinsic dynamic nonlinearity is modeled first. Then, a compensation technique based on the definition of compensated output levels maximizing the signal-to-noise-and-distortion (SINAD) ratio, namely, a particular case of the Max–Lloyd conditions for minimizing distortion in nonuniform quantizers, is applied. Simulation and experimental results show the method effectiveness in compensating the intrinsic dynamic nonlinearity and in incrementing the SINAD ratio in actual working conditions.      

飞机滑行作用下水泥混凝土道面板动响应分析

摘 要：研究了飞机滑行作用下机场水泥混凝土道面板动响应问题。将道面结构视为粘弹性层状地基上单块四边自由的矩形板,采用半解析法,建立力学模型和计算方法。飞机滑行作用在道面板上的荷载是由自身重量和滑行产生的升力决定的;并计算了飞机滑行作用下道面板的响应。采用在道面内部钻孔安装位移传器的方法,对H-6飞机以不同滑行速度通过道面板时,道面板产生的动挠度进行了实测。计算结果与实测结果对比表明,两者误差在3%以内。说明本文所建立的计算方法是正确的。该方法可用来进行机场水泥混凝土道面板在飞机滑行作用下动响应的计算。     

A linear operational transconductance amplifier for instrumentationapplications

A linear operational transconductance amplifier (OTA) is described that consists of a linear transconductor and a translinear current gain cell followed by three current mirrors. The proposed circuit has superior linearity and temperature characteristic when compared with the commercially available OTA. A prototype circuit with a transconductance of 50 μS has been built with discrete bipolar transistors producing a linearity error of less than ±20% over an input voltage range from -0.8 to 0.8 V. The prototype OTA circuit also exhibits a transconductance that is linearly dependent on a bias current varying over four decades with a sensitivity of 1 S/A     

Error of capacitive displacement transducers

Conclusions An analytical relationship of a differential capacitive transducer's error to its dimensions has been obtained. An analysis of this relationship and experimental investigations have shown that it is possible to manufacture such transducers with a considerably large measurement range and a nonlinearity error of the order of 10^–5 of the displacement range.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 17–20, August, 1967.     

传感器动态非线性分析及在动态建模中的应用

利用非线性系统的Volterra级数展开方法,并针对实际传感器中二次非线性影响较大的情况,利用一维和二维频谱分析方法,着重研究了二次非线性对传感器动态测试及动态建模的影响,最后针对具体传感器给出了应用实例。     

Errors in dynamic calibration of thermoelectric transducers with differences between their thermal inertias

Conclusions The existing method of dynamic calibration of thermocouples can also be used for calibrating other thermal elements, for instance, thermistors, in which case a thermocouple or resistance thermometer should be used as a reference instrument. However, errors may be incurred in dynamic calibration if there is a difference between the thermal inertia of the reference and calibrated thermal elements. This circumstance limits the application of the dynamic method. This method is advantageous when it does not reduce the accuracy of calibration and provides a gain in calibration time as compared with the static method. The criterion of this gain is the ratio of the time spent on calibration by the static and dynamic methods.Analysis has shown that the dynamic method with air calibration and an error of 1° provides a gain in time from 1.5 to 40 for all the thermistors under consideration with the exception of types KMT-4 and MMT-4. For a given calibration error of 0.1° it is advantageous to calibrate by the dynamic method (either in air or in oil) only thermistors type KMT-14.It is possible by means of the nomogram provided in the article to determine the applicability of the dynamic method for calibrating thermal elements of a type or under static calibration conditions not covered by the article.     

100pA～1μA量程的微弱电流源研制

为了实现对微弱测量仪器进行测试与校准,根据恒流源电路的思想,研制了一种由运算放大器构成的微弱电流源。在微弱电流产生中,利用恒压源和高精度标准电阻,通过V-I变换来实现微弱电流的输出;设计反馈调节网络,来解决普通电流源实现微弱电流输出易受负载影响的缺点,消除负载对输出电流的影响,同时,实现100pA～1μA量程的微弱电流输出。为提高电流源的性能,电路中采取了屏蔽和滤波处理,来解决噪声的影响。经过测试,结果表明该电路的电流范围在100pA～1 μA之间,电流源稳定可靠。在1nA时,误差不超过0.08nA。     

Using sine wave histograms to estimate analog-to-digital converterdynamic error functions

This paper describes a new method for developing analog-to-digital converter (ADC) error function models using modified sinewave histogram methods. The error models may be used to digitally compensate for nonlinearities introduced by the converter. The histogram modification involves sorting of converter output samples based upon an estimated associated input derivative signal. This error model is based upon a previously unpublished result which shows that sinewave histograms yield distinctly different expected errors for each state based upon input signal slope associated with each output sample. This result thus provides a dynamic dependence for expected errors measured by means of histogram methods. Sorted sinewave histograms are used to estimate slope dependent expected errors at each ADC output state (code). The method provides improved error representation by providing error basis functions for every output code. Simulated results prove that this method removes all slope dependent errors for complex ADC architectures while experimental results for an 8-bit 200 MSPS ADC yielded more than 10 dB improvement in spurious-free-dynamic-range (SFDR) over the full Nyquist band. The new method is thus shown to possess wideband dynamic error character     

Frequency Domain Analysis for Dynamic Nonlinearity Measurement in A/D Converters

This paper discusses the problem of measuring the dynamic systematic error or the dynamic input-output characteristic of an analog-to-digital converter (ADC) stimulated by a sinusoidal input. First of all, it is shown that the statistical methods, although widely used, yield misleading results in dynamic conditions, i.e., when the converter characteristic presents hysteresis. Second, this paper presents a modified version of a frequency-domain method (Chebyshev test), previously developed by the authors for testing static devices. Both simulation and experimental results show that the Chebyshev test for dynamic nonlinearities is a very fast way to measure the input-output characteristic of an ADC affected by hysteresis error     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Method of Calculating the Additional Error of Measurement Transducers for Stochastic Signals

We consider measurement transducers for which the input signal can be represented as a Gaussian steady-state random process. A method is proposed for calculating a multiplicative additional error caused by influencing quantities. The models of the signal at the input of the transducer and also of the signal forming the additional error consists of harmonic components and steady-state random processes.     

Method of Calculating the Additional Error of Measurement Transducers for Correlated Input Actions

Consideration is given to measurement transducers for which the input signal can be represented as a steady-state random process. A method is proposed for calculating the additional multiplicative error due to influencing quantities. Models of signals at the transducer input and also of the signal forming the additional error consist of steady-state random processes.     

Verification of the Westervelt equation for focused transducers

This study investigates the validity of the Westervelt equation for focused transducers. The angular spectrum method is employed to analyze the second-harmonic acoustic field under the weakly nonlinear approximation. Although it is well known that the Westervelt equation is accurate for the case of quasi-plane waves, the present work demonstrates accurate solution for the highly focused case of a spherically-curved ultrasound transducer having an aperture angle of 80°. It is further found that the solution error is inversely dependent on the nonlinearity coefficient.