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阐述了两相混合式步进电机的细分控制原理,提出了以MSP430单片机为微控制器,通过DAC7612产生相差为π2的细分电流控制信号,以集成步进电机驱动芯片为驱动器,实现了两相混合式步进电机的细分运行控制,电流细分精度达到1/2048。 相似文献
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采用透射电镜观察了快冷态Ti-5Al-4Sn-2Zr-1Mo-0.25Si.0.3~1.2Nd合金(Ti-55合金)稀土相的形貌,发观稀土相尺寸细小(4~34nm),呈球状,均匀弥散地分布在基体中,晶界上稀土相呈椭球状,沿晶界排列。采用图像分析仪对铸态Ti-55合金稀土相进行了分析,结果表明,4种成分合金的稀土相平均尺寸为3.25~3.50μm,平均圆度系数为0.56~0.63,呈椭球状,棒状及不规则状,分布于晶界与晶内,其均匀弥散度劣于快冷态Ti-55合金的稀土相。 相似文献
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基于压电比例阀驱动的氙气微推进系统是目前国际的发展趋势。压电比例阀作为该类型推进系统的核心组件,其性能将直接影响系统流量特性和推力。本文首先采用AMESim软件对某型氙气工作压力为0.3MPa的压电驱动氙气微推进系统进行建模,并对系统填充过程中的气瓶与减压阀工作特性进行分析。然后研究了不同减压阀反馈腔压力条件下的减压阀与压电比例阀的阀芯运动和氙气质量流量特性。最后,分析了压电比例阀驱动电压对开机过程中的压电比例阀阀针位移、氙气质量流量特性的影响规律。结果显示,压电比例阀阀针在通电后迅速开启,其最终的稳定升程为3.7μm。系统的氙气质量流量的稳定值为5.63mg/s。减压阀反馈腔内的氙气压力越大,压电比例阀开启后的氙气质量流量稳定值越大且响应时间越长。仿真结果表明,本次研究的氙气微推进系统可以通过改变驱动电压实现对氙气质量流量的线性调节,系统氙气质量流量可在较短时间内达到目标值。 相似文献
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为了提高运动机构的稳定度,步进电机驱动控制通常采用电流细分的方法,从而将一个步距角分解成若干小步。实现步进电机电流细分驱动通常的方法是将电流闭环引入到驱动控制电路中,由此增加电流采样、比较等软硬件功能模块的同时也增加了单机的复杂度,削弱了步进电机本质上开环驱动的优势。为了提高宇航型号步进电机驱动控制器单机的可靠度,提出了一种基于反熔丝FPGA的纯开环驱动方案,通过预置占空比的方式,在不引入电流闭环的前提下实现步进电机电流细分。通过样机调试,验证了设计的有效性,为后续工程研制提供参考。 相似文献
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Ti600合金的性能与显微组织的研究 总被引:11,自引:0,他引:11
Ti600 合金是一种新型近α高温钛合金,其名义成分为Ti-6Al-2.8Sn-4Zr-0.5Mo-0.4Si-0.1Y(w t% )。测试了该合金在热暴露前后拉伸性能和蠕变性能,并进行了透射电镜和光学显微镜观察。研究结果表明:合金的机械性能优异,与美国Ti1100 性能水平相当;在常规热处理条件下,合金组织是一种典型的针状组织,该组织具有良好的抗蠕变性能。Ti600 合金热暴露后,合金中存在的α2 相(Ti3Al)和S2 相(Ti5Si3)使合金的室温塑性降低。讨论稀土氧化物对合金显微组织及性能的影响,表明稀土的加入对改善合金蠕变性能有较大作用。 相似文献
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《航空标准化与质量》1979,(Z4)
本规范业经国防部批准,陆军、海军、空军所属各部必须遵照执行 1. 范围 1.1 范围 本规范规定了飞机及导弹燃油系统所用的电动机驱动的燃油切断阀。 1.2 分类 燃油切断阀应分为下列形式和规格,订货时应予规定(见6.2节): Ⅰ型——电动机驱动的阀 Ⅱ型——带有手动超控装置的电动机驱动的阀 Ⅲ型——带有热释压装置的电动机驱动的阀 相似文献
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提出了一种控制步进电机的设计方法,结合MCU、FPGA和增量型编码器构成了一个完整的运动控制平台。系统由总线接口单元、闭环控制单元、PWM脉宽调制单元和LMD18200驱动单元组成。实践表明,利用LMD18200驱动逻辑能够使步进电机高效稳定地运行,有效降低了电机运行中的噪声和起动、停止时的振动,使用效果好于大部分常规步进电机驱动方法。 相似文献
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能量包线随机平均法在双线性迟滞系统随机响应分析中的应用 总被引:3,自引:0,他引:3
本文将能量包线随机平均法应用于分析单自由度双线性迟滞系统对白噪声激励的随机响应,详细分析了位移、速度及总能量的平稳响应各统计量随系统粘性阻尼、次斜率及激励强度的变化。解析结果与数字模拟结果比较表明,该方法优于迄今为止用于双线性迟滞系统随机响应分析的其他近似方法。 相似文献
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Alan F. M. Moorwood 《Space Science Reviews》1996,77(3-4):303-366
Bursts of massive star formation can temporarily dominate the luminosity of galaxies spanning a wide range of morphological types. This review is concerned primarily with such events in the central 1 kpc region of spiral galaxies which result from bar driven inflows of gas triggered by interactions or mergers. Most of the stellar radiant luminosity of such bursts is absorbed by dust and re-emitted in the far-infrared and is accompanied by radio and X-ray emission from supernova remnants which can also act collectively to drive galaxy scale outflows. Both evolutionary stellar models and estimates of the gas depletion times are consistent with typical burst durations of 107–8 yr. Spatially-resolved studies of nearby starburst galaxies reveal that the activity is distributed over many individual star forming complexes within rings and other structures organized by interactions between bars and the disc over a range of scales. More distant and extreme examples associated with mergers of massive spirals have luminosities > 1013
L
and molecular gas masses > 1010
M
implying star formation rates > 1000 M
yr–1 which can only be sustained for 107 yr. In the most luminous merging systems, however, the relative importance of starburst and AGN activity and their possible evolutionary connection is still a hotly debated issue. Also controversial are suggestions that starbursts in addition to a black hole are required to account for the properties of AGNs or that starbursts alone may be sufficient under certain conditions. In a wider context, starbursts must clearly have played an important role in galaxy formation and evolution at earlier times. Recent detections of high redshift galaxies show that star formation was underway at z 4 but do not support a continuing increase of the strong evolution in the co-moving star formation density seen out to z l. Primeval starburst pre-cursors of spheroidal systems also remain elusive. The most distant candidates are radio galaxies and quasars at z = 4–5 and a possible population of objects responsible for an isotropic sub-mm wave background tentatively claimed to have been detected by the COBE satellite. 相似文献
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数字天顶仪作为一种地面使用的星敏感器,主要用于高精度定位。为提高仪器的工作效率需要对星图识别的快速性进行研究。通过对恒星像点理论坐标与图像坐标的分析,构建坐标转换模型。依据星表中恒星的分布及星等筛选出视场范围内的亮星,并构建导航星表。结合导航星表完成3颗亮星的准确识别,在识别亮星的基础上解算坐标转换模型的参数。通过构建的坐标转换模型对视场范围内的恒星进行坐标转换,将转换后的星点坐标与提取的星点图像坐标进行匹配完成星图的识别,这样能够提高星图识别的快速性。实验数据表明:在保证识别星点数量的基础上,采用亮星辅助下基于坐标转换的星图识别方法使时间缩短为改进三角形星图识别算法的五分之一。 相似文献
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Ronald H. Kaitchuck 《Space Science Reviews》1989,49(3-4):51-61
Time-resolved spectroscopy during the eclipse of short-period Algol systems, has shown their accretion disks to be small, turbulent structures with non-Keplerian velocity fields and asymmetries between the leading and trailing sides of the disk. These transient disks are produced by the impact of the gas stream on the mass-gaining star, and occur in systems where the star is just large enough to ensure the stream collision is complete. These emission line disks and the excess continuum emission do not always occur together. The permanent accretion disks in at least a few of the long-period Algol systems have features in common with the transient disks including non-Keplerian velocity fields. 相似文献
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Franco Giovannelli 《Space Science Reviews》1994,69(1-2):1-138
In this work I will try to give the most general complete view, comparatively with the conciseness, on RU Lupi, which is an Extreme Classical T Tauri star.T Tauri stars (TTSs) form a class of low luminosity stars which are going to the Main Sequence. They are young contracting objects that are in a particular Pre-Main-Sequence (PMS) evolutionary phase. The study of the Pre-Main-Sequence Stars (PMSSs) can provide crucial information on stellar evolution and formation of planetary systems, and therefore also indirect information on the processes occurred in the primeval solar system.For this reason, firstly I will briefly comment a sort of classification of stars in PMS phases (Section 2); then I will emphasize the main characteristics of TTSs and the current theories (Section 3). The up-to-date observational properties of RU Lupi (Section 4) and a discussion on their explanation within the framework of theories (Section 5) will allow me to draw the conclusions (Section 6) and to argue the most convenient line of investigation (Section 7) both experimental and theoretical for a better understanding of the underlying physics of these systems. Finally (Section 8), I will comment in general on the methodology of investigation of highly variable cosmic sources.An original result has been obtained in this work: the flare-like events (FLEs) of RU Lupi, occurring in all wavelength regions, are periodic with aP
FLE=27.686±0.002 days. This periodicity could be the rotational period of the star. 相似文献
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Ronald H. Kaitchuck 《Space Science Reviews》1989,50(1-2):51-61
Time-resolved spectroscopy during the eclipse of short-period Algol systems, has shown their accretion disks to be small, turbulent structures with non-Keplerian velocity fields and asymmetries between the leading and trailing sides of the disk. These transient disks are produced by the impact of the gas stream on the mass-gaining star, and occur in systems where the star is just large enough to ensure the stream collision is complete. These emission line disks and the excess continuum emission do not always occur together. The permanent accretion disks in at least a few of the long-period Algol systems have features in common with the transient disks including non-Keplerian velocity fields. 相似文献
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We present relative carbon and oxygen abundances derived via an optically thin recombination line analysis for five WO stars, and compare the derived abundances to recent evolutionary models. New recombination coefficients for O4+, O5+ and O6+ ions have allowed total oxygen abundances to be derived. The final C/He values range between 0.4 and 0.8 by number, consistent with C/He ratios previously derived for WC stars. O/He values range between 0.1–0.4, with C/O ratios between 2.1–4.8.A comparison of the derived abundances with the evolutionary models of Maeder (1990) and Schaller et al. (1992) shows promising agreement. We find reasonably tight agreement between the abundances derived for the WO stars. The degree of enhancement for the oxygen abundances in regions of low metallicity predicted by Maeder (1990) is not corroborated by our results.Additionally we present a revised, quantified classification scheme for WO subtypes. We extend the class to lower excitation, WO5, and place MS 4 (=WR 30a) in this class. Equivalent widths of the strongest lines of MS 4 are also presented. Finally, we present new observations of DR 1, a WO3 star located in the dwarf irregular galaxy IC 1613. 相似文献
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为了满足星上高光谱相机、全谱段光谱成像仪、星敏感器等时间精度敏感仪器的高精度时间同步需求,高光谱观测卫星上设计了可适应多种精度需求的时间同步方案。对于系统时间,综合通过星地时差集中校时、均匀校时、GPS总线校时、GPS硬件秒脉冲校时等校时方法进行时间修正;对于终端用户,分别给出直接采用广播的进行本地时间修正的时间同步方法、采用广播及内部秒脉冲的时间同步方法、采用广播授时和不同秒脉冲校时方案的地面时间重建算法。利用在轨数据,对卫星星敏感器、全谱段光谱成像仪及可见短波红外高光谱相机的曝光时刻时间重建方法进行了应用说明,并对不同方法的时统误差进行了分析。 相似文献