On structured fault tree construction by modularizing control loops

The objectives of this article are: (1) to develop the fault trees for control loops in a way that they all appear in a proper form and as modules in the fault tree for the whole system; and also (2) to modularize each control loop in a system properly to establish its unit model. These two methods are essentially equivalent. Either of them can be applied to facilitate constructing fault trees for the whole system. To accomplish such equivalent or parallel objectives, we will first take the feedback and feedforward control loops in the heat exchanger system as examples and then: (1) construct the fault trees of deviations in controlled variable for the two control loops in the way that all of their non-basic terminal events should be deviations in variables on those streams that connect to the loop from their outside in the system; and (2) establish the unit model for each of such two loops. One of the purposes of (2), which will not be addressed here, is to regard each control loop as a dummy unit and hence reduce the system to facilitate system input and fault tree construction eventually for complete automation purpose.     

磁通负反馈空心线圈传感器特性和噪声研究

时间域空地电磁系统可以实现大深度探测,能够探测金属沉积矿床和地热储层,其接收装置常采用空心线圈传感器,传感器的匹配方式是输出端并联阻尼电阻,该电阻可以有效地抑制线圈的时域振荡,但是增加了传感器的噪声.研制了一种基于磁通负反馈机制的低噪声、大面积空地接收线圈传感器,通过理论分析给出了该方法的实现原理,建立了传统匹配方式和基于磁通负反馈方式的线圈等效模型,并深入分析了2种模型下传感器的幅频特性、带宽及影响空心线圈传感器信噪比的各噪声源,给出了2种方式下使传感器处于临界阻尼状态时系统噪声的仿真结果,将两者在相同带宽下的噪声有效值指标进行对比,证明了基于磁通负反馈方式的接收线圈能够达到与传统方式接收线圈一致的性能.噪声方面,在相同的线圈结构、温度不变(27 ℃)、频率范围为3 dB带宽的情况下,相比传统方式信噪比提高了10.6 dB.最后,采用小线圈传感器等效模型在野外进行了噪声测量,验证了理论的正确性.     

针对载波环路的高效干扰研究

通过针对二相相移键控（BPSK,Binary Phase Shift Keying）最佳干扰样式的研究,从理论上分析了载波环路的特点。根据载波环路的收敛特性提出了窄带噪声调相干扰样式,该调制样式能够破坏载波环路锁相环的收敛特性,使解调的误码率增高。通过加载几种不同干扰信号的实验,证明了针对载波环路的干扰要比常规的干扰方式更高效。得出了使用窄带噪声调相信号作为干扰源是BPSK调制信号的最佳干扰样式,可以进一步地节省干扰功率,提高干扰效率。     

DDS技术在网同步中的应用

网同步是数字通信网的基本要求,其功能是将同步信息从基准时钟源向各个通信节点传递,让整个通信网的时钟工作于相同频率,以满足通信网络传递业务的需求。DDS是第三代频率合成技术,从相位出发,直接采用数字技术合成所需波形。这里首先介绍了网同步技术的原理,并分析了基于PLL技术的传统网同步技术的缺点,然后介绍了DDS技术的概况以及优点,最后提出了一种基于DDS技术的网同步设计方案。     

A novel two-degree-of-freedom controller design for a permanent magnet linear synchronous motor control system

This paper proposes a novel two-degree-of-freedom optimal controller design for a permanent magnet linear synchronous motor position-control system. The param-eters of the controller are obtained by using a frequency-domain optimization technique. A systematic design of the controller and the detailed implementation of the proposed system are discussed. The closed-loop control system possesses good transient responses and good load disturbance responses. In addition, the system has a good tracking ability. Several experimental results are provided to validate the theoretical analysis.     

Novel matched amplifiers with low noise positive feedback. Part II: Resistive–capacitive feedback

The avalanche modo characteristics of bipolar transistors are considered. A theoretical analysis based on an extension to the Ebers-Moll transistor model is shown to provide satisfactory agreement with various experimental results in the avalanche mode.     

AVS解码器环路滤波的优化及实现

AVS编解码器采用环路滤波去除块效应来提高图像质量,而环路滤波复杂度高、运算量大,且滤波过程数据访问频繁,严重影响了代码的执行效率.为提高解码速率,通过分析滤波算法特点,调整滤波结构,优化滤波算法,部分代码采用DSP汇编语言.结果表明与传统的C相比,缩短了代码运行时间,提高了执行速度,达到实时解码的要求.     

基于负反馈的变压器多直流参考电压传递技术研究

现代仪器仪表的研发设计中,需要解决以较为经济简约与便于集成的方式,获取多个直流参考电压来保障其实现高准确度的难题.文中提出了基于方波调制解调的直流恒定电压传递方法,进而提出了利用变压器的多直流参考电压传递方案,应用了负反馈系统周期复校准技术与电容振荡特性,并进一步控制减少传递误差来维持系统稳定,设计了利用变压器实现多直流参考电压传递的配套电路模块,并对输出的多个直流参考电压进行了校准测试与分析.评估了设计中所有传递的直流参考电压传递误差均优于5×10-6,进行了传递测量不确定度评定,评估了所有传递校准点的相对测量不确定度优于1×10-6,符合设计预期,验证了此方法的可行性,具有显著的应用推广价值.     

Non-ideal behavior of a driving resonator loop in a vibratory capacitive microgyroscope

Many researches have been carried out on the dynamic characteristics of vibratory microgyroscope, but only a few have been carried out on the non-ideal behaviors observed in the driving loop of the vibratory microgyroscope. In this paper, characterization and evaluation of the non-ideal behavior of the vibratory microgyroscope, “peak-and-valley” magnitude phenomenon and phase lag distortion, are discussed. To characterize the non-ideal behavior of a microgyroscope driving loop, a new electro-mechanical simulation model based on the HSPICE of microgyroscope driving loop is proposed. The parasitic capacitive components of the driving loop are found to be the major sources of non-ideal behavior in microgyroscope and it is verified with the simulation results. The validity of the proposed simulation model and the parasitic effects on microgyroscope driving loop is evaluated with the actual fabricated gyroscope.