罗氏线圈电子式电流互感器积分特性研究

为降低电子式电流互感器(ECT)的暂态误差、提高稳态电流的测量准确度,提出了一种应用于罗氏线圈ECT信号采集系统的压频变换器模数混合积分器(VFC-ADI)方法。对罗氏线圈输出信号进行压频数值转换,由脉冲计数器完成数值计数,微处理器对计数值处理后得出被测电流的积分波形。选取VFC芯片AD7742进行仿真分析,仿真结果显示VFC-ADI方法能准确地反映一次侧暂态电流波形。对罗氏线圈ECT暂态故障电流及稳态电流进行试验测试,结果表明VFC-ADI方法能准确反映暂态故障电流特征;对于稳态电流测试,比差的变化范围为-0.15%~0.15%,角差的变化范围为-1′~1.5′,其输出值完全满足0.2 s级基本准确度测试要求。VFC-ADI方法在模数转换过程中实现了积分功能,数据处理结果表明其更接近于理想积分器。     

采用 DWA技术的多位Σ-Δ调制器的设计

设计一个内部采用2位量化器的二阶单环Σ‐Δ调制器．为解决反馈回路中多位DAC元件失配导致的信号谐波失真问题,该调制器采用了数据加权平均（Data Weighted Averaging ,DWA ）技术来提高多位DAC的线性度．Σ‐Δ调制器信号带宽为50 kHz ,过采样率（OSR）为64,采用MXIC公司的0．35μm混合信号CMOS工艺实现,工作电压为12 V ．后仿真结果显示,在电容随机失配5％的情况下,该调制器可以达到55．8 dB的信噪比（SNR）和60.4 dB的无杂散动态范围（SFDR）．打开DWA电路比关闭DWA电路的情况下,SNR和SFDR分别提高8 dB和13 dB ．整个调制器功耗为48 mW ,面积仅为0.6mm2．     

一种基于全差分积分器的时钟稳定电路设计

设计了一种用于超高速A/D转换器的时钟稳定电路。利用全差分连续时间积分器将差分时钟信号的占空比量化为电压信号,再通过跨导放大器产生控制电流来调整输出时钟的共模电平,达到调整输出时钟占空比的目的。电路采用0.18 μm标准CMOS工艺进行设计,工作电压为1.8 V,在2 GHz的最高时钟频率下,将占空比为20%~80%的输入时钟信号调整为(50±1)%,输出时钟抖动小于132 fs,具有抑制时钟抖动的能力。     

EAST托卡马克新型积分器系统控制器的研制

为了满足EAST托卡马克的实验需求,提升积分器系统的可维护性和可测试性,研制了新型积分器系统控制器。该控制器采用ARM微控制器和轻量级IP协议栈,实现了积分器系统的网络化控制。所提供的参数设置指令可远程设置和读取积分器板卡上放大器的放大倍数,而控制指令则提供了初始化、标准信号积分、脉冲积分、积分保持、标定和探针测试功能。经实验和EAST现场测试,该积分器系统控制器可满足EAST装置的实验要求。     

Fixed-time output feedback trajectory tracking control of marine surface vessels subject to unknown external disturbances and uncertainties

This paper proposes a novel fixed-time output feedback control scheme for trajectory tracking of marine surface vessels (MSVs) subject to unknown external disturbances and uncertainties. A fixed-time extended state observer (FESO) is proposed to estimate unknown lumped disturbances and unmeasured velocities, and the observation errors will converge to zero in fixed time. Based on the estimated values, a novel fixed-time trajectory tracking controller is designed for an MSV to track a time-varying reference trajectory by the extension of an adding a power integrator (API), and the tracking errors can converge to zero in fixed time as well. Additionally, the convergence time of the controller and the FESO is independent of initial state values. Finally, simulation results and comparisons illustrate the superiority of the proposed control scheme.     

A Lyapunov approach to the stability of fractional differential equations

Lyapunov stability of fractional differential equations is addressed in this paper. The key concept is the frequency distributed fractional integrator model, which is the basis for a global state space model of FDEs. Two approaches are presented: the direct one is intuitive but it leads to a large dimension parametric problem while the indirect one, which is based on the continuous frequency distribution, leads to a parsimonious solution. Two examples, with linear and nonlinear FDEs, exhibit the main features of this new methodology.     

Structural generation of two integrator loop filters using CDTAs and grounded capacitors

A versatile family of two integrator loop filter structures using current differencing transconductance amplifiers (CDTAs) and grounded capacitors is generated. The basic filter building blocks consist of current proportional blocks, current lossless integrators and a current lossy integrator based on the use of CDTAs as the major active components. It is demonstrated that the derived filter structures can realize a general class of second‐order current transfer functions. Since the resulting structures contain only CDTAs and grounded capacitors, they are general and very appropriate for integration, cascading and electronic tuning. The influences of the CDTA non‐idealities are also discussed. The functionality of the resulting filters has been verified by simulation results. Copyright © 2009 John Wiley & Sons, Ltd.