基于AT89C51单片机的等精度数显频率计

介绍了一种基于AT89C51单片机进行等精度数字测频的软、硬件实现方案。该方法简单实用,具有较广的使用价值。     

一种应用于高速低抖动电荷泵锁相环的高鲁棒性鉴频鉴相器

为改善现有鉴频鉴相器（PFD）中存在的问题,从理论分析的角度对现有的PFD进行了研究,并对其进行了基于电路结构的分类与比较．提出并设计了一种应用于高速低抖动电荷泵锁相环的高鲁棒性新型鉴频鉴相器．该PFD由2个上升沿触发的动态D触发器、2个上升沿检测和延时模块及2个或门组成．由于融合了2种复位机制,能避免UP与DN信号同时为高电平,因此,电荷泵的电流失配将不会恶化PLL的性能．而且,该PFD的鉴相特性中几乎没有鉴相死区、设计及仿真是基于1．8V电源电压的TSMC0．18ixmCMOS工艺．由理论推导和电路仿真可知,该PFD具有高工作频率（-1GHz）、高可靠性、宽鉴相范围（[±2π]）、零死区（〈0.1ps）、低抖动、低功耗（≈100μw）、低复杂度等特性、     

等离子体制备氮化铁磁流体用高频高压脉冲电源的研制

根据等离子体活化装置对电源的要求,利用新型功率器件IGBT设计了一种高频高压大功率脉冲电源,并对IGBT的驱动调制电路、保护电路以及电路频率范围的拓宽和功率提高进行了讨论.结果表明,该电源在功率输出、频率范围、波形等方面均能达到设计要求.     

基于柔性传感器的青少年健康实时监控系统设计

采用碳黑/硅橡胶复合柔性传感器研制低成本、低能耗、微体积的可穿戴式设备,实现多种青少年基础生理指标的集成检测。通过对运动时生理体征参数变化量的动态感知、传输和管理分析,解析个体的体征状况的变化趋势,研究干预方案执行过程的动态跟踪与监测技术难题,构建闭环的健康服务系统,通过对健康服务短期、中期、长期效果的量化测评以保证青少年保持健康的生活方式。     

PLC和变频器在电梯电气系统改造的应用

通过应用可编程序控制器和变频器改造客货电梯涡流制动器调速的交流调速系统和继电器-接触器控制电气系统的实例,给出改造中电器的硬件选择和主要控制环节的程序设计思路.改造后的电梯运行稳定,检修方便,节能效果明显.     

Theory and application of system integration for real-time monitoring of core rock-fill dam filling construction quality

The theory and method of system integration for the real-time monitoring of core rock-fill dam filling con- struction quality are studied in this paper. First, the importance analysis of system integration factors is carried out with the analytic hierarchy process. Then, according to the analysis result of integration factors, the conceptual model of system integration is built based on function integration, index integration, technology integration and information integration, the index structure of core rock-fill dam filling construction quality control is constructed and the method of function integration and technology integration is studied. The mathematical model of process monitoring is built according to monitoring objective, process and indexes. Research results have been applied in Nuozhadu core rock-fill dam construction management, realizing system integration through building appropriate monitoring work flow and comprehensive information platform of digital dam.     

基于FMS网吧实时远程监控系统的设计

结合Flash流媒体,ActionScript,Asp和数据库等技术,采用Flash Media Server构建了一个网吧实时远程监控系统,并给出了该系统的具体实现方法,以及核心技术的使用,为网吧监管部门的视频巡查和实时监控提供了技术支撑。     

基于LabVIEW的变压器局部放电监测系统设计

通过设计一款变压器局部放电的超高频监测系统,将微弱的超高频信号放大到足够的幅度,采用多级滤波去除带外干扰,以便于对传输线路所采集到的超高频信号进行处理与分析,并利用Lab-VIEW软件仿真与虚拟分析,对电力系统变压器的故障进行早期诊断,对变压器早期产生病变以及发展趋势发出预警,以确保电力系统变压器安全、可靠地运行。     

WAMS-based monitoring and control of Hopf bifurcations in multi-machine power systems

A method is proposed to monitor and control Hopf bifurcations in multi-machine power systems using the information from wide area measurement systems （WAMSs）. The power method （PM） is adopted to compute the pair of conjugate eigenvalues with the algebraically largest real part and the corresponding eigenvectors of the Jacobian matrix of a power system. The distance between the current equilibrium point and the Hopf bifurcation set can be monitored dynamically by computing the pair of conjugate eigenvalues. When the current equilibrium point is close to the Hopf bifurcation set, the approximate normal vector to the Hopf bifurcation set is computed and used as a direction to regulate control parameters to avoid a Hopf bifurcation in the power system described by differential algebraic equations （DAEs）. The validity of the proposed method is demonstrated by regulating the reactive power loads in a 14-bus power system.     

面向工程教育认证的旋转机械状态监控与故障诊断实验系统研发

为培养本科生创新思维和工程实践能力,达到工程教育认证中"具备解决复杂工程问题"的毕业要求,推动实验教学改革和实验设备多样化,设计了基于组态软件和LabVIEW的旋转机械状态监控与故障诊断实验系统。该系统能够满足过程控制相关专业的实验教学任务与创新拓展训练,取得了较好的应用效果。     

机房实验教学管理系统学生状态监控的设计与实现

针对传统的机房教学管理软件在计算机实验教学管理过程中遇到的问题,以在教学及考试过程中对学生上机状态、上机行为进行监控为目的,研究和探索监控方法和实现技术。     

应用于无线传感网频率合成器的0.5V低电压鉴频鉴相器设计

基于0.13μm CMOS技术设计了一个应用于无线传感网频率合成器、电源电压为0.5 V的鉴频鉴相器.它的功能是比较输入信号的频率和相位差,并输出一个与该差值成比例的电压.因电源电压是0.5 V,所以该电路采用低阈值晶体管.为了增大相位误差的检测范围和提高最大工作频率,该电路采用了脉冲锁存的结构.当输入信号频率为2 M...     

基于网络的教学质量实时监控服务系统的理论与实践

高校教学质量监控工作取得明显成效,当前仍需进一步解决以下问题：非网络状态,即教学质量监控的技术平台问题;非实时状态,即教学质量监控的常态运行问题;非服务状态,即教学质量监控的中心功能问题。广西教育学院努力构建基于网络的教学质量实时监控服务系统：以网络为教学质量监控的技术平台,以实时为教学质量监控的运行特征,以服务为教学质量监控的中心功能,以混合理论为教学质量监控系统构建的理论基础。     

基于Profibus_DP总线的发动机动力性能分布式测控系统

提出了一种发动机动力性能分布式测控系统,介绍了Profibus_DP总线的通信协议及系统的网络结构,主要参数的测量原理,并详细讨论了由工控机、图形操作终端、变频器及可编程控制器组成的测控系统的结构及工作原理,系统的软硬件设计方法.实际应用表明,系统组态灵活、编程方便、可靠性高.     

智能农机动力系统作业工况匹配与换挡优化

利用车辆经济性与动力性软件CRUISE,根据FJ1004 智能无人驾驶拖拉机的动力传动系统搭建了整车模型,通过柴油机的特性曲线分析匹配动力特性,依据工况特征加载拖挂特性,模拟机具消耗。通过工况仿真分析了拖拉机整车的动力性与经济性,与实验数据对比分析,最高车速误差为-0.76%;犁耕油耗和旋耕油耗误差分别为-1.2%和-1.3%。最后通过分析柴油AMT 拖拉机工作特性,结合MIGA 算法对换挡策略进行优化,确定最优功率和燃油经济性的换挡规律,在田间转移工况下油耗优化9.21%;在保证需求动力性的轻负载作业工况下油耗优化1.28%。为后续自适应工况换挡策略提供参考与优化方向。     

变压器多路温度监控系统设计

介绍了一种基于平衡电桥和电子开关矩阵实现的多路温度硬件测量系统以及软件实现监控的系统设计方案,详细介绍了应用电子开关矩阵MT8816组成的多点温度测量技术、平衡电桥实现的温度测量方式以及单片机程序和上位机软件程序的设计,并对该设计方案中的误差消除办法进行了分析。对于检测点较多的系统,采用本方案可以以最低的成本实现高精度的检测。     

用于高压电子式电流互感器的能力和数据复合光纤传输系统

This paper describes a prototype power delivery system developed for high voltage electronic current transformer (ECT) that uses laser light to transfer power to and communicates with the primary converter. The design is based on optical-to-electrical power converters, solid-state diode lasers and optical fibers. Command signals are transmitted via the same up-fiber used to send power from secondary power supply to primary converter. The upward data transmission is completed during the brief interruption of power delivery without affecting steady power-supply. A simple comparator added to the primary converter can take the command data. Experimental results show that the fibers can provide reliable up-link for data transmission at 200 kb/s from the secondary to the primary converter. Based on the delivery system, the secondary converter can control three auxiliary channels to provide additional information. These monitoring channels are used in a time-multiplexing mode to provide information about the operation temperature, voltage and current at the remote unit for monitoring the ECT. This preventive maintenance or built-in test can increase reliability by giving early warning for necessary maintenance request.     

Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions

This paper proposes an analysis and a direct power control （DPC） design of a wind turbine driven doubly-fed induction generator （DFIG） under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions.     

Cutting force and its frequency spectrum characteristics in high speed milling of titanium alloy with a polycrystalline diamond tool

In this paper, a series of experiments were performed by high speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) by use of polycrystalline diamond (PCD) tools. The characteristics of high speed machining (HSM) dynamic milling forces were investigated. The effects of the parameters of the process, i.e., cutting speed, feed per tooth, and depth of axial cut, on cutting forces were studied. The cutting force signals under different cutting speed conditions and different cutting tool wear stages were analyzed by frequency spectrum analysis. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The results indicate that a characteristic frequency in cutting force power spectrum does in fact exist. The amplitudes increase with the increase of cutting speed and tool wear level, which could be applied to the monitoring of the cutting process.     

An appraisal of techniques and equipment for cutting force measurement

INTRODUCTION Metal machining processes are characterised mainly by quick changes in quantified elements. In- dividual changes do not occur in isolation and they influence each other. The analysis of these changes require study of the complicated complete systems in their real situations. The study of cutting processes such as turning and facing, from dynamic aspects, is very important. The trend towards the measurement of cutting forces in machining leads to many theo- retical and practic…