任意波发生器的总体评价

介绍了任意波发生器的定义及主要技术指标,包括静态、动态、瞬态、矢量、调制、标准波形和任意波形等参数指标,叙述并讨论了它们的校准方法。对任意波发生器校准的内容、实质、目的、难点、技术等问题进行了充分的讨论和叙述。     

波形记录仪触发延迟线性的实验研究

提出了使用正弦波激励评价触发延迟线性度和触发抖动的新方法,通过一个波形在有触发延迟和无触发延迟时,采集序列间的相位差对应的时间差来最终判定触发延迟结果。用该方法实现的触发延迟线性度测量方法,将触发延迟直接溯源到激励信号的频率量上,无需额外的精密延时器等装置,减少了测量环节,并且可以实现任意延迟的精确测量。以不同频率、不同触发延迟、不同采集速率下的实验结果的对比给出了触发延迟线性校准的结论性意见,同时验证了所述方法的有效性和切实可行性。     

三角波信号沿线性度的统计分析评价方法

介绍了三角波信号沿线性度参数的一种统计分析评价方法 ;在均匀分布的条件下 ,通过使用波形测量手段和直方图统计分析方法 ,对三角波信号的幅度分布直方图、沿线性度等指标进行了评价 ,详细讨论了方法的实现过程以及有关技术问题 ,并对相应参数指标进行了误差分析 ;实验验证结果表明了该方法的有效性和实用性 ,该方法可应用到三角波信号源的性能指标评价中。     

任意波发生器应用及校准述评

介绍了任意波发生器,以及任意波发生器的应用原因(产生复杂信号;产生没有其它合适信号源的信号;产生仿真信号);介绍了几种典型的应用情况(扰乱理想波形;模拟传感器;替代信号源;模拟电路与数字电路的混合测试;复杂调制;多功能信号源),讨论了如何产生任意波形(标准波形库;图像编辑;数据传输;数据表修改;FFT编辑器;公式编辑器);对任意波发生器校准现状、校准内容、以及校准对策进行了综述、总结、分析和讨论.在充分评述了任意波发生器校准所需要的各种技术基础上,展望了其校准技术的发展趋势.     

任意波发生器静态特性的评价

介绍了任意波发生器的主要静态特性指标、校准方法及实现过程。通过一组实验．获得了实际校准结果,并对校准中需要注意的问题进行了讨论。所述方法涉及的静态特性内容比较全面。具有足够的测量准确度、分辨力和稳定性。可用于任意波发生器的静态指标评价和计量。     

A Differential Capacitive Torque Sensor With Optimal Kinematic Linearity

This paper presents a new design for a torque sensor based on a differential capacitive technology. An arc-radial mechanism is adopted to achieve high rotary/radial motion linearity. Kinematic model of this assembly is derived via vector loop equations. A nonlinearity index is formulated and practical kinematic constraints are imposed. Results show that very high kinematic linearity could be achieved by this new device     

Improved Bias Supply for Tunnel-Diode Picosecond Pulse Generators

An improved bias supply for tunnel-diode (TD) picosecond-pulse generators is described. The supply is stable with temperature and, in a commercial 35-ps (nominal) risetime tunneldiode pulse generator/sampling oscilloscope system, has produced a 4:1 reduction in time-base jitter and 2:1 reduction in time-base drift. Also described is a tunnel-diode pulse generator, which, when used with the bias supply, produces a stable pulse having a flat-top sag of no more than 2 percent in 1 ?s.     

Traceable Waveform Calibration With a Covariance-Based Uncertainty Analysis

We describe a method for calibrating the voltage that a step-like pulse generator produces at a load at every time point in the measured waveform. The calibration includes an equivalent-circuit model of the generator that can be used to determine how the generator behaves when it is connected to arbitrary loads. The generator is calibrated with an equivalent-time sampling oscilloscope and is traceable to fundamental physics via the electro-optic sampling system at the National Institute of Standards and Technology. The calibration includes a covariance-based uncertainty analysis that provides the uncertainty at each time in the waveform vector and the correlations between the uncertainties at the different times. From the calibrated waveform vector and its covariance matrix, we calculate pulse parameters and their uncertainties. We compare our method with a more traditional parameter-based uncertainty analysis.     

Gaussian Pulsed Current Waveform Welding for Aluminum Alloys

A new welding method, which uses a Gaussian current waveform with a smooth curve and concentrated energy input, was applied for welding of aluminum alloys of various thickness. Current peak modulation and base modulation models are proposed in the article. Five welding experiments were carried out using ER4043 1.2 mm aluminum wire, the results showing that the welding process was found to be stable, and that current and voltage waveforms were regular with no broken arcs or short circuits. Moreover, the arc voice sound was soft with low splatter. Weld seam surfaces were bright with regular scaly stripes and proper weld height and penetration.     

Achieving Improved Position Detection Using a Modified Triangular Perturbation Signal

High-resolution position detection using a one-dimensional zero-dead-band photosensor receptor has been shown [1] to be possible by applying a high-frequency triangular perturbation to a normalized target image. It is shown here that for a nonzero dead-band ? between the receptor elements, position detection becomes increasingly uncertain as ? increases. By periodically changing the magnitude of the perturbation and the system gain, it is shown that accurate position detection is still possible for a receptor with nonzero dead-band.     

时间序列线性／非线性在线检验

给出了ＡＲ模型参数二阶矩Ｙｕｌｅ－Ｗａｌｋｅｒ方程和四阶矩Ｙｕｌｅ－Ｗａｌｋｅｒ方程估计的等价最小二乘估计，以及二阶矩和四阶矩Ｙｕｌｅ－Ｗａｌｋｅｒ方程参数估计的递推算法，在此基础上提出一种时间序列的线性／非线性在线检验方法。     

A Symmetric Triangle-Square Waveform Generator Using a Single Constant Current Source

A symmetric and accurate triangular waveform generating circuit is described. A simple approach in maintaining the symmetry and linearity of triangular waveform is made by using a single constant current generator to alternately charge and discharge a capacitor in a linear manner. This features perfect symmetry of the waveform over a wide frequency range while maintaining amplitude constancy. The circuit also provides square waveforms of equal on and off periods with rise and fall times of the order of a few nanoseconds. Continuous variation of frequency of the waveform generated is possible by changing a single parameter and it is feasible to have linear, exponential, or logarithmic modulation of frequency. It can be used as a triangle-square waveform generator and as a triangle-to-sine converter with the addition of a few components.     

Performance of Magnetic Pulsed-Eddy-Current System Using High Dynamic and High Linearity Improved Giant MagnetoResistance Magnetometer

Eddy-current nondestructive testing is commonly carried out using single-frequency time-harmonic excitations. Pulsed excitation offers a simple and effective alternative to classical eddy-current techniques and is classically implemented with coil(s) (transmitter and/or receiver). We present a pulsed-eddy-current-system alternative using a high-performance giant magnetoresistance magnetometer is presented. An analytical solution of the magnetic flux density created by the transient eddy current is given. Comparison with experimental results shows that the approximations are accurate (1% or better). System performances are presented and discussed versus sensor characteristics and compared to classical ones (transmitter/receiver coil systems)     

Triangular Self-Convolution Window With Desirable Sidelobe Behaviors for Harmonic Analysis of Power System

Weak harmonic components can easily be obscured by nearby strong harmonics due to the spectral leakage in the power system. To obtain a window suitable for solving the problem, the Triangular self-convolution window (TSCW) is constructed, with the Triangular window being the parent window to take advantages of its narrow major lobe and simple computation. A TSCW-based phase difference correction algorithm for calculating the power system signal parameters, such as frequency, phase, and amplitude, is presented in this paper. The TSCW has a low peak sidelobe level, a high sidelobe rolloff rate, and a simple spectral representation. Leakage errors and harmonic interferences are thus considerably reduced by weighting samples with the TSCW. The TSCW-based phase difference correction algorithm is free of solving high-order equations, and the overall method can easily be implemented in embedded systems. The effectiveness of the method proposed was analyzed by means of computer simulations and practical experiments for multifrequency signals without noise and with quantization noise.      

基于最小二乘法改进的随机圆检测算法

提出了一种利用最小二乘法迭代修正随机圆检测的改进算法.解决了由于随机圆检测算法中阈值选取不当,造成同一个圆被分割为多个圆的问题.首先根据随机选取四个点求解出的圆参数,得到属于假设圆的点集;然后由当前点集,利用最小二乘法重新计算得到新的圆参数;接着根据新参数,检测集合中属于当前假设圆的新点,加入到当前点集中,重新计算圆参...     

矩形波冲击时双线性包装系统的产品损坏边界

推演单自由度产品包装系统的双线性动力学方程．应用数值方法，求得矩形波冲击时双线性包装系统的产品损坏边界曲线，讨论双线性参数对损坏边界的影响。     

Effect of Write Current Waveform on Magnetization and Head-Field Dynamics of Perpendicular Recording Heads

The response of perpendicular magnetic recording heads with a single turn and two turn coils is calculated using a full micromagnetic model, including return pole and soft underlayer. We study the effect of coil current waveforms with different rise times and overshoots. For fast coil current rise times, the head field shows very little response, until the coil current changes its polarity and it is limited by the intrinsic magnetization dynamics. Even the effect of overshoot is limited by the same mechanism. Shorter yoke length and coil turns close to the air-bearing surface improve the head-field dynamics.     

模拟管线系统中方波脉冲电流阴极保护规律的研究

为了弄清脉冲电流阴极保护的基本规律,为现场应用提供科学的理论依据和参考,采用方波脉冲电流对模拟管线体系脉冲电流阴极保护的电位分布规律以及脉冲电流参数和其他因素对电位分布的影响进行了研究.在3.5 m(长)×2.0 m(宽)×3.0 m(深)的水池中,建立了均匀介质模拟水平管道体系,研究了方波脉冲电流参数(频率、幅值、占空比)、阳极距离等因素对方波脉冲电流阴极保护效果的影响,并将直流与方波脉冲电流的阴极保护效果进行了对比.结果表明,随着方波脉冲电流频率、幅值或占空比的增加,阴极极化电位分布曲线逐渐负移,极化幅度逐渐增加,且阴极表面的电位分布远比直流作用时均匀,有效保护深度明显延长,所需平均保护电流更小.     

Fast Calculation of Field Currents and Reactances for Doubly Fed Generators With Rotor Duct Pieces

Doubly fed generators have been used as adjustable-speed pumped-storage generator motors and wind turbine generators. Accurate determination of field currents and reactances is important for the design of these machines. We propose a calculation method to obtain the field currents and reactances of machines with rotor duct pieces under any steady-state balanced load condition. The method links two-dimensional static finite-element analysis (FEA) with an approximate calculation to consider three-dimensional (3-D) skin effect in the duct pieces. Its advantage is that the computational time is much smaller than 3-D transient FEA when the slip frequency is not zero. The method will contribute to improvement of the design of doubly fed generators with rotor duct pieces. It was applied to a 395 MVA machine, and the calculated field currents agreed well with the measurements. Variation in the reactances due to saturation is also discussed