SVPWM控制技术分析与研究

变流器的控制有多种方式,其中基于SVPWM技术的矢量控制方法因其诸多优点已经得到广泛的应用。本文对SVPWM技术的原理、控制方式和缺点进行了阐述,并提出相应的解决方法。     

工业园区边界污染气体定量分析及来源研究

工业园区中边界污染气体的浓度不仅受工业园区无组织污染源的排放影响,也受园区道路机动车尾气的扩散影响。利用AG-FTIR-DA3000型开放光程傅里叶变换红外光谱(Open-FTIR)测量系统,对厂区边界污染气体进行实时在线测量,确定污染气体厂界实测浓度。同时,针对机动车尾气扩散影响厂区边界污染气体浓度的问题,通过AG-FTIR-DX4000型便携式傅里叶变换红外光谱(FTIR)测量系统,确定不同排放标准下机动车尾气污染源浓度。利用便携式FTIR测量结果、风速风向、大气稳定度、车流量等变量因素建立参考坐标,给出了高斯扩散的数理模型。并结合Open-FTIR,对Open-FTIR的测量路径进行积分计算并构建点线源扩散模型,从而建立各种排放标准的烟团线源扩散表。将Open-FTIR实测浓度与构建的点线源扩散模型模拟浓度相结合,分析工业园区边界污染气体的来源。结果表明：厂区边界污染气体主要包括一氧化碳、甲烷、乙烯、乙醛、丙烯、甲醇、丙醛、异丁烯、甲醛、二氧化硫,其中一氧化碳、甲烷、乙烯浓度受机动车尾气的扩散影响。早晚高峰期时,机动车尾气的扩散对边界污染气体浓度影响较大;非高峰期,在1:00时与...     

步进电机式转速小时表设计

本文介绍了步进电机式仪表特点,并着重介绍了一个以微控制器P89LPC9401为核心,步进电机做机心驱动转速表指针,LCD作为小时表显示器的步进电机式转速小时表实现方案.     

基于有限元法的电机软起动控制模块PCB电磁兼容设计与仿真

电机软起动控制模块PCB板载DSP芯片并运行于300 MHz以内的高频和2 ns以内的信号边沿速率。为解决由于高边沿速率带来的电磁兼容性问题,应用有限元法分别对自动布线和电磁兼容手工布线后的软启动控制模块PCB进行仿真,得到300 MHz、900 MHz和1.5 GHz下PCB的近场辐射值。仿真表明,PCB手工布线后其电场和磁场近场辐射在各频点下的最大值分别有42%~81%和41%~84%的改善。说明通过电磁兼容手工布线提高了PCB的电磁兼容性。     

机载平台惯导系统稳定回路故障分析

稳定回路是平台式惯导系统的重要组成部分,其作用是隔离载体的角运动,稳定回路的精度和可靠性直接影响惯导系统的精度和可靠性。根据故障统计和分析,稳定回路故障的主要部位分别为:外环轴承、直流力矩电机、导电环以及稳定回路控制线路。在对稳定回路动态刚度进行推导的基础上,分析了以上四个部位引起稳定回路故障的机理和故障原因,提出了相应的改进措施。这些措施已经逐步应用于惯导系统中。故障统计表明,采取措施后的惯导系统稳定回路故障有了明显降低,所采取的措施有效可行。     

Atmega16在开关磁阻电机调速系统中的应用

针对开关磁阻电机调速系统的设计要求，提出了以Atmegal6作为CPU，并利用该单片机硬件和软件上的优点来提高系统处理速度，简化外围电路和提高性价比的设计方法。     

Task complexity effect on vocal reaction time in aged speakers

The aged population is at risk for impaired speech communication due to the increased likelihood of deterioration of central nervous system (CNS) processes that underlie cognition, language, and/or speech motor control. Vocal reaction time (RT) may provide a means of quantifying the efficiency of CNS processes that underlie speech production. The present study used a simple RT paradigm to investigate effects of the complexity of the required task on vocal RT in normal young and aged speakers. Task complexity was represented by two levels: a single word and a short sentence. Only the aged subjects showed a significant task complexity effect on vocal RT. Furthermore, the between-group RT difference increased as a function of task complexity. Specific causes for the increase in vocal RT for the aged subjects are presently unknown, but likely reside in altered respiratory biomechanics and reduced efficiency of CNS motor processing.     

DSC study on the motor protein myosin in fibre system

We have examined by DSC the complexes of myosin with actin in fibre system in the absence of nucleotides and the intermediate state of ATP hydrolysis by mimicking stable complex with myosin and ADP and beryllium fluoride in muscle fibres. Comparing the DSC results with other structural analogues of phosphate P_i leads the conclusion that the AM.ADP.BeF_x complex favours the AM.ADP.P_i complex in fibre system. The deconvolution of DSC scans resulted in four transitions, the first three transition temperatures were almost independent of the intermediate state of the muscle, the last transition temperature was shifted to higher temperature, depending on the actual intermediate states of ATP hydrolysis. In AM.ADP.V_i state the transition temperature at the second and third transitions (actin binding domain and myosin rod) varied only slightly, whereas the last one (the fourth transition) shifted markedly to higher temperature depending on the ternary complex, e.g. in case of ADP plus BeF_x it was 77.7 °C, the highest value in weakly binding state of myosin to actin. The sum of calorimetric enthalpies of the first and last curves was practically constant, but their fractions depended on the state of the muscle. In strongly binding state of myosin to actin (rigor, ADP state) the fraction of the first transition was much larger, than the last one, whereas in weakly binding state of myosin to actin, the fraction of the first transition decreased at the expense of the last one. It supports also the view that these transitions are parts of the same portion of the myosin molecule.     

一种新型永磁同步电机用无位置传感器控制算法

目前在永磁电机控制领域中，使用无位置传感器的电机调速方式获得了广泛的应用与发展。通过过去几十年的不懈研究，出现了多种无位置感应器控制算法，通常这些算法可以被归为两类，即仅适合于电机高速区使用的算法以及仅适合于电机低速区使用的算法，但是到目前为止，没有任何一种算法能够在电机的整个调速范围内都有效。本文提出了一种新型的融合了高速算法和低速算法优点的混合算法，该算法在电机的整个调速范围内都能有效的估算转子位置。