单片机控制的步进电机脉宽调制式细分驱动系统

在对步进电机细分驱动原理进行深入研究的基础上，提出了一种新的步进电机细分驱动电路─—单片机控制的脉宽调制式细分驱动电路，并对步进电机的恒力矩均匀细分控制进行了论述。     

基于FPGA的步进电机细分驱动器

在对步进电机细分驱动原理进行研究的基础上,提出了一种采用FPGA实现步进电机恒转矩细分驱动的方法.利用FPGA芯片中的嵌入式阵列块(EAB)构成LPM-ROM来存储步进电机各相细分电流的数据,并把斩波控制电路集成到FPGA内部,极大地提高了系统的集成度和稳定性.微控制器只需提供细分数等参数,就能精确控制步进电机的运行,特别适用于某些实时控制场合.     

用GAL芯片实现新型步进电机环形分配器的细分

通过对步进电机细分技术及环形分配控制方法的分析，应用ＧＡＬ集成电路设计了一种细分步进电机环形分配器，文章介绍了其原理和使用方法。     

步进电机高细分可调控制系统

利用MSP430混合处理器与步进电机专用驱动芯片DRV8812,结合"电流矢量恒幅均匀旋转"细分方法,设计一种混合式步进电机步进角64-1024细分数可调的控制系统。该系统可以通过接收上位机指令实时调节电机细分数、每秒脉冲数、转向,实现步进电机高速低细分、低速高细分运行,最小步进角可达0.1’。     

基于矢量控制的步进电机可变细分

提出应用ＭＣＳ－５１单片机对数控机床步进电机进行可变细分控制，可明显提高步进电机运行平稳性、降低振荡、提高加工精度．文中提出步进电机矢量控制原理和恒转矩细分的概念．     

二相混合式步进电机恒力矩细分驱动系统设计

本文分析了混合式步进电机的工作原理,并且针对二相混合式步进电机。提出了一种基于AT89C51单片机控制的恒转矩SPWM微步细分驱动系统。详细阐述了各部分工作原理和功能实现方法。结果表明方案可行,实现细分精度高、运行平稳可靠。     

基于DSP的步进电机控制系统与上位机的串行通信设计

首先简述了基于DSP的步进电机控制系统及步进电机的细分控制原理,给出了步进电机的驱动接口电路。重点论述了上位机与基于DSP的步进电机控制系统之间的串行通信设计,上位机使用VC 的MSComm控件实现串行通信,给出了DSP的串行通信的硬件接口电路,并给出了部分程序代码。实验证明,实现监控此方案可行有效。     

步进电机 PWM恒转矩细分驱动技术研究

从一个新颖的角度，分析了步进电机细分驱动原理，并重点讨论了步进电机的电流PWM驱动技术和恒转矩驱动技术及其应用实例。     

基于FPGA的步进电机控制设计

在研究步进电机驱动原理的基础上,介绍基于FPGA的步进电机控制器的设计,提出了一种采用FPGA芯片实现步进电机恒转矩驱动的方法,实现步进电机控制,并利用QuartusⅡ进行仿真并给出仿真结果。利用FPGA芯片中的嵌入式阵列块（EAB）构成LPM_ROM来存储步进电机各相细分电流的数据,并把斩波控制电路集成到FPGA内部,从而提高了系统的集成度和稳定性。采用VHDL语言控制可以根据步进电机的不同,改变模块程序的参数就可以实现不同型号步进电机的控制,有利于步进电机的广泛应用。     

基于FPGA的两相步进电机细分驱动器设计

采用步进电机驱动的机构中,为了提高定位精度,文章提出了一种高性能的步进电机细分控制系统设计,该系统由FPGA和专用集成电路IXMS150 PSI构成,在FPGA中嵌入Cos/Sin表,通过查表控制步进电机两项绕组电流,实现了高精度的步进电机细分控制系统,提高了步进电机的运行精度,消除了低速震荡现象,该系统可用于机器人,打印机和光学平台等精密位置控制系统。     

Mice embryology: A microscopic overview

In this work, we studied the embryology of mice of 12, 14, and 18 days of gestation by gross observation, light microscopy, and scanning electron microscopy. Grossly, the embryos of 12 days were observed in C‐shaped region of the brain, eye pigmentation of the retina, first, second, and third pharyngeal arches gill pit nasal region on the fourth ventricle brain, cervical curvature, heart, liver, limb bud thoracic, spinal cord, tail, umbilical cord, and place of the mesonephric ridge. Microscopically, the liver, cardiovascular system and spinal cord were observed. In the embryo of 14 days, we observed structures that make up the liver and heart. At 18 days of gestation fetuses, it was noted the presence of eyes, mouth, and nose in the cephalic region, chest and pelvic region with the presence of well‐developed limbs, umbilical cord, and placenta. Scanning electron microscopy in 18 days of gestation fetuses evidenced head, eyes closed eyelids, nose, vibrissae, forelimb, heart, lung, kidney, liver, small bowel, diaphragm, and part of the spine. The results obtained in this work describe the internal and external morphology of mice, provided by an integration of techniques and review of the morphological knowledge of the embryonic development of this species, as this animal is of great importance to scientific studies. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Gait definition and successive gait-transition method based on energy consumption for a quadruped

In nature,to realize the smooth motion for different speeds,the continuous gait transition is usually required for the quadrupeds.Thus,the gait simulation of quadrupeds is a requisite step to obtain the stable and energy-efficient gait for the walking machines.In this paper,the definitions of the two gait parameters,phasic difference and duty factor are presented,which can determine the gait of the quadrupeds.Then,several typical gaits of the quadrupeds are analyzed such that the seven standard gaits and corresponding parameters are summarized.Additionally,the variance law of the two parameters,which determine the relationship of gait transition,is analyzed.Furthermore,the quadruped gait derivative spectrum (QGDS) is proposed and the gait definition of the quadrupeds is presented.To minimize the power consumption,the choice criterion of gait,the optimal gait in terms of the motion speed,duty factory,and power consumption for the walking machines,is developed.Last,the continuous variance of the gait is implemented by the simulation of the gait transition from walk to trot,which evaluate the choice criterion and transition of gait.     

过渡金属作用下的金刚石石墨化机理研究*

从电子和原子角度解释了过渡金属对金刚石石墨化催化作用的机理,即过渡金属具有空d轨道,并且在某一面上与金刚石(111)面原子符合对准原则。为了验证此结论,基于第一性原理建立铬、铁、钴、钛、铂、铝、铜原子与金刚石原子的作用模型,进行仿真计算,得到不同过渡金属对金刚石石墨化的影响规律。仿真结果表明：Cr、Fe、Co、Ti、Pt作用下的金刚石结构出现不同程度的石墨化现象,而Al、Cu作用下的金刚石无石墨化现象。不同金属作用下金刚石原子结构的平面度由小到大依次为铁、铬、钴、钛、铂、铝、铜;碳原子间方差由小到大依次为铁、铬、钴、铂、钛、铝、铜;系统能量变化由大到小的顺序依次为铁、铬、钴、铂、钛。通过比较,铁、铬、钴原子对金刚石石墨化具有明显的催化作用,铂、钛原子有一定的催化作用,而铝、铜原子则无催化作用。当金属具有空d轨道且与金刚石在一定面上符合对准原则,未配对电子越多,金属对金刚石石墨化的催化作用越强;反之,当金属价电子层无d轨道或d轨道电子是充满状态时,金属对金刚石石墨化无催化作用。该研究为利用金刚石石墨化机理刃磨金刚石刀具提供了理论基础。     

Subcommissural organ, cerebrospinal fluid circulation, and hydrocephalus

Under normal physiological conditions the cerebrospinal fluid (CSF) is secreted continuously, although this secretion undergoes circadian variations. Mechanisms operating at the vascular side of the choroidal cells involve a sympathetic and a cholinergic innervation, with the former inhibiting and the latter stimulating CSF secretion. There are also regulatory mechanisms operating at the ventricular side of the choroidal cells, where receptors for monoamines such as dopamine, serotonin, and melatonin, and for neuropeptides such as vasopressin, atrial natriuretic hormone, and angiotensin II, have been identified. These compounds, that are normally present in the CSF, participate in the regulation of CSF secretion. Although the mechanisms responsible for the CSF circulation are not fully understood, several factors are known to play a role. There is evidence that the subcommissural organ (SCO)--Reissner's fiber (RF) complex is one of the factors involved in the CSF circulation. In mammals, the predominant route of escape of CSF into blood is through the arachnoid villi. In lower vertebrates, the dilatation of the distal end of the central canal, known as terminal ventricle or ampulla caudalis, represents the main site of CSF escape into blood. Both the function and the ultrastructural arrangement of the ampulla caudalis suggest that it may be the ancestor structure of the mammalian arachnoid villi. RF-glycoproteins reaching the ampulla caudalis might play a role in the formation and maintenance of the route communicating the CSF and blood compartments. The SCO-RF complex may participate, under physiological conditions, in the circulation and reabsorption of CSF. Under pathological conditions, the SCO appears to be involved in the pathogeneses of congenital hydrocephalus. Changes in the SCO have been described in all species developing congenital hydrocephalus. In these reports, the important question whether the changes occurring in the SCO precede hydrocephalus, or are a consequence of the hydrocephalic state, has not been clarified. Recently, evidence has been obtained indicating that a primary defect of the SCO-RF complex may lead to hydrocephalus. Thus, a primary and selective immunoneutralization of the SCO-RF complex during the fetal and early postnatal life leads to absence of RF, aqueductal stenosis, increased CSF concentration of monoamines, and a moderate but sustained hydrocephalus.     

平接型双材料的载荷位移特征与界面失效机理研究

针对双材料界面强度不足与界面应力分布不均的问题,对双材料界面强度、界面应力分布不均、载荷位移曲线(LD)波动等方面进行了试验研究与理论分析,利用铝/聚乙烯(PE)、铝/聚丙烯(PP)、铝/聚甲醛(POM)双材料的实验结果,对材料的TS813粘结试样界面强度与Ergo5800粘结试样进行了比较分析,对弹性模量与PE、PP、POM材料的界面强度进行了对比,分析了载荷位移曲线与界面断口。研究结果表明:铝/非金属双材料界面抗拉强度随着弹性模量增大而减小,TS813试样界面强度为Ergo5800试样的4.44、2.17、2.89倍,铝/橡胶前者为后者76.47%;界面强度分布不均导致界面剥落情况不同与LD曲线中波动现象,同种材料试样与同种粘结剂试样,试样界面强度越低载荷波动越明显。     

Dynamic characteristics of a planetary gear system based on contact status of the tooth surface

Studies on the planetary gear have attracted considerable attention because of its advantages, such as compactness, large torque-to-weight ratio, vibrations, and high efficiency, which have resulted in its wide applications in industry, wind turbine, national defense, and aerospace fields. We have established a novel dynamic model of the planetary gear transmission by using Newton’s theory, in which some key factors such as time-variant meshing stiffness, phase relationships, and tooth contact characteristics are considered. The influences of gear axial tipping, operating conditions, and the meshing phase on the contact characteristics and the dynamic characteristics were researched systematically. It was found that the contact area of the tooth surface was moved due to the axial gear tipping, which obviously affected the meshing stiffness. With the increase in the inclination angle of the sun gear, the meshing stiffness decreases, which produces an evident influence on the high natural frequency in the planetary transmission system. In terms of the dynamic characteristics of the system, the component of rotating frequency appeared in the dynamic meshing force of the sun gear and the planetary gear. Moreover, the floating track of the center wheel varied significantly and exhibited an oval distribution as the inclination angle of the sun gear changed. When the inclination angle of the sun gear increased, the rotating frequency component increased significantly, but the other meshing frequency components remained unchanged; meanwhile, the deformation of the floating track also increased. If the inclination angle of the sun gear changes, the vibration state of the system and the collision impact could become more serious, and the lifetime of the planetary transmission system will reduce. Furthermore, when the load was increased, we found that the gear-tooth contact zone transformed from line contact to surface contact, the meshing stiffness increased, the effect of high natural frequency on the planetary transmission system became more evident, but its low-order natural frequency remained stable. With regard to the dynamic characteristics of the system, the components of the major frequency at the external gearing remained unchanged, but the rotation frequency of the sun gear and the meshing frequency amplitude increased linearly with the increase in load. In conclusion, the variation in the meshing stiffness of the planetary gear system had minor impact on the low-order natural frequency, but had a significant impact on the high natural frequency of the planetary transmission system due to the phase variation of the gear.     

多壁碳纳米管增强无石棉垫片性能研究

为了优化配方并提高无石棉垫片的性能,以加入多壁碳纳米管(MWCNTs)的无石棉垫片为研究对象,对MWCNTs和无石棉垫片的主要组成材料进行均匀配方设计,对制备的无石棉垫片材料进行拉伸强度、压缩率与回弹率、密度和老化系数的性能测试;采用多元线性回归分析建立垫片各项性能与材料配方之间的回归模型,并进行验证。结果表明:综合性能最优时的配方(按质量分数)如下:多壁碳纳米管2. 48%、QY棉18. 58%、矿物棉23. 22%、高岭土23. 22%、云母6. 19%、滑石粉13. 93%、纸浆12. 38%;得到的回归方程式可以用来预估垫片材料的各项性能;不同组分材料对垫片材料性能的影响不一样,其中MWCNTs的含量对垫片的各项性能影响最大,且MWCNTs的加入能改善复合垫片材料的老化性能;随着MWCNTs含量的增加,无石棉垫片的拉伸强度、回弹率、密度和老化系数都增大,但压缩率逐渐减少。因此,在保证垫片材料的压缩率满足要求的前提下,适当增加MWCNTs的含量能显著提高无石棉垫片的性能。     

1214Bi易切削钢冶炼连铸工艺优化

通过对1214Bi易切削钢采用:1.C、Mn、S等成分控制优化;2.稳定出钢终点C、降低出钢温度、出钢前渣面喷碳还原等冶炼工艺优化;3.优化冷却工艺、提高结晶器振动频率、降低拉速等连铸工艺优化。降低了成本,改善了铸坯质量,提高了铸坯可轧制性。     

微小型空间相机碳纤维整体式主框架轻量化设计

针对某微小型离轴空间相机结构紧凑、质量轻的设计要求,设计了一个高度轻量化的整体式碳纤维主框架。首先,根据空间相机具体功能的设计指标和光学系统,确定主框架的材料和结构形式,设计出碳纤维整体式主框架的基本构型。接着对铺层厚度参数化优化,并考虑碳纤维复合材料的制造约束,确定了主框架碳纤维铺层的厚度、比例。将参数化优化的结果进行离散化,进行碳纤维铺层顺序的优化,确定了最佳的堆叠次序,完成了碳纤维的铺层优化设计,实现了主框架的轻量化设计,解决了复杂碳纤维零件优化的问题。然后对设计完的碳纤维主框架结构代入整机有限元模型中,进行有限元仿真分析,验证主框架的性能指标。最后,将整机装配完成进行动力学试验,并与有限元分析结果进行对比验证。经过优化,碳纤维主框架的质量为4.5 kg,相机一阶频率为81 Hz,动力学试验得到的相机整机的一阶频率为78 Hz,仿真误差为3.7%,符合仿真结果,进一步说明了设计的合理性以及正确性。本文提出的空间相机碳纤维整体式主框架设计方法对微小型离轴三反式空间相机结构设计以及碳纤维零件的轻量化优化设计具有一定的借鉴意义。     

Standard deviations of composition measurements in atom probe analyses-Part II: 3D atom probe

In a companion paper [F. Danoix, G. Grancher, A. Bostel, D. Blavette, Surf. Interface Anal. this issue (previous paper).], the derivation of variances of the estimates of measured composition, and the underlying hypotheses, have been revisited in the the case of conventional one dimensional (1D) atom probes. In this second paper, we will concentrate on the analytical derivation of the variance when the estimate of composition is obtained from a 3D atom probe. As will be discussed, when the position information is available, compositions can be derived either from constant number of atoms, or from constant volume, blocks. The analytical treatment in the first case is identical to the one developed for conventional 1D instruments, and will not be discussed further in this paper. Conversely, in the second case, the analytical treatment is different, as well as the formula of the variance. In particular, it will be shown that the detection efficiency plays an important role in the determination of the variance.