静电拉伸薄膜反射镜成形控制方法研究

摘要：目的：针对发射系统承载空间与承载重量的限制与大口径、高分辨率反射镜使用需求之间的矛盾,开展轻质柔性薄膜反射镜地基试验研究,实现静电拉伸式薄膜反射镜精确成形控制。方法: 首先,基于泊松方程的薄膜小变形近似求解,针对口径Φ300mm的三环分布式电极静电拉伸聚酰亚胺镀铝薄膜反射镜,通过确定每环电极对面形的影响函数来确定分布式电极对反射镜薄膜成形的控制距阵,进而利用最小二乘法求得分布式电极对面形精确控制所需的分布电压。并用ANSYS软件有限元分析进行结果对比,分析相关误差因素,总结控制方法。结果：在薄膜中心变形量大约超过2.5mm以后,基于泊松方程的理论求解和ANSY有限元分析结果相差很大,计算面形与理想面形偏差也很大。结论：只有综合运用数值计算、有限元分析方法,通过确定分布式电极对面形的控制矩阵,运用最小二乘法求解分布式电压,才能准确地实现薄膜面形的预知和控制。     

静电拉伸薄膜反射镜的多电极成形控制

针对现有薄膜反射镜成形控制方法存在求解复杂,工程实用性差等问题,提出了基于反演求解的半解析成形控制方法.首先,基于Karman方程和静电场理论推导了所要拉伸的抛物面面形与施加压强分布的关系及实验所需的离散电极环电压值;其次,利用有限元软件建模和分析,验证所推导的压强分布;最后,在口径为300 mm的三环电极的静电拉伸反射镜实验平台上进行了验证实验.实验显示,拉伸面形最大变形量与理论值基本吻合,面形误差与传统均匀压强下的相比有所减少,最好的实验结果得到的PV值和RMS值较均匀压强下的值分别减少了9.76％和15.38％.仿真及实验结果表明:所描述的方法可以控制面形并提高面形精度,与传统的成形控制方法相比较具有简单实用等优点.     

薄膜反射镜静电成形机理研究

摘要：薄膜反射镜是一种正在发展中的新概念技术,它将解决反射镜孔径与重量相互制约的问题。采用静电拉伸法控制薄膜反射镜面形,具有结构简单、反射镜面形易于控制等优点,其原理为利用静电场上库仑力作用使薄膜产生面形变化,生成所需的光学曲面。由于薄膜变形力学,以及静电场理论的复杂性,目前薄膜成形及其面形控制在理论分析上仍未有定量的结果。本文主要从理论上分析了静电场中空间电势分布特性,以单电极静电场中的薄膜反射镜面形为考察因素,通过数值计算的方法得到薄膜反射镜上的静电力分布,运用有限元分析获得该分布下的反射镜面形,并将其与理想面形进行了比较。提出采用多电极闭环控制可获得更高的控制精度,对静电拉伸薄膜的研究工作具有重要的指导意义。     

薄膜反射镜静电成形单电极控制

静电拉伸薄膜反射镜是近年来发展起来的一种新型技术,薄膜反射镜具有质量轻、柔韧性好、可折叠等优点,在航天领域具有广阔的应用前景。静电拉伸薄膜反射镜的原理为利用静电场上库仑力作用使薄膜产生面形变化,生成所需的反射曲面。由于薄膜变形力学,以及静电场理论的复杂性,目前薄膜成形及其面形控制的研究工作都还不完善。本文在薄膜反射镜成形控制机理研究的基础上,设计了单电极式薄膜反射镜的控制试验,详细计算了控制成形所需的主要参数,设计了薄膜反射镜的夹持结构和控制电路,并利用刀口仪测量了形成的反射面的焦距,试验结果表明在10000V的高压下可以行程焦距约为2.1m的反射镜面,面形的PV值达到11.14λ, RMS值为1.86λ,通过改善夹持结构和选取性能优良的薄膜材料控制面形精度可进一步提高。     

薄膜反射镜的单电极控制静电成形

考虑薄膜反射镜具有质量轻、柔韧性好、可折叠等优点,研究了由静电拉伸法制备薄膜反射镜的新技术.介绍了薄膜反射镜的静电成形机理,计算了单电极模式下薄膜所受力场,设计了单电极式薄膜反射镜的控制实验.给出了控制成型所需的主要参数,设计了薄膜反射镜的夹持结构和控制电路,并利用刀口仪测量了形成的反射面的焦距.实验结果显示,未通电时薄膜反射镜面形的PV值达到11.14λ, RMS值为1.86λ,在10 000 V的高压下可以形成焦距约为2.1 m的反射镜面.通过Zernike拟合验证了数据的可靠性,结果表明,通过改善夹持结构精度和选取性能优良的薄膜材料,反射镜面形精度可进一步提高.     

新型薄膜反射镜的有限元分析

薄膜反射镜是实现大口径、低面密度空间光学系统的最新方向之一,材料采用柔性薄膜,具有重量超轻、体积小的特点.由于薄膜反射镜的挠度特性,利用传统的方法来获得面形的变化很困难.介绍薄膜反射镜的成形原理,建立符合实际情况的有限元模型,通过施加一定的边界条件,对薄膜反射镜进行非线性分析,得到一系列的挠度值,并和理论值进行比较分析,最大误差为0.07%.所得到的结论对于进一步研究反射镜成形和面形控制,以及薄膜厚度的选择具有一定的指导意义.＃     

空间薄膜反射镜面形设计及优化

在分析聚酰亚胺薄膜反射镜面形成型理论的基础上,结合光学系统对反射镜面形的要求,用有限元法求解了薄膜反射镜在一定预应力存在的条件下,受均布载荷作用产生变形的数值解,通过数据拟和给出了反射镜面形,并计算了理论面形与计算面形的误差;以反射镜镜面不同区域施加的载荷为设计变量,薄膜的屈服强度为状态变量,理想面形与计算面形的误差为目标函数,用ANSYS软件对薄膜反射镜面形进行了优化;最后以Zernike多项式为接口对反射镜面形进行了波前拟合,给出了优化前后反射镜的像差,证明了通过对薄膜反射镜施加适当的力场可以得到面形精度很好的抛物线面形。结果表明:改变力场可以控制薄膜反射镜面形,并得到需要的面形,为实际设计、构建聚酰亚胺薄膜反射镜提供了理论基础、设计依据和方法。     

微变形反射镜主要性能测试研究

微变形反射镜(MEMS-DM)是用于自适应光学中波前校正的重要元件。测试实验中对37单元微变形反射镜的光学影响函数矩阵进行了推导和全面测量,从而验证了其叠加性。由光学影响函数推导出了微变形反射镜的控制电压矩阵,利用电压矩阵校正了变形镜的初始面形。最后,对微变形镜校正波前畸变能力进行了测量和评估,得出关于优化微变形镜设计相关方面的一些结论。     

膜基反射镜的非线性有限元挠度分析

介绍一种获得较精确的膜基反射镜挠度数值解的方法。通过非线性有限元分析,对三种有限元网格划分方法进行研究比较,建立符合实际情况的有限元模型,给出薄膜分析中施加预应力的方法,分析研究膜基反射镜的挠度特性。首先在简易边界条件下,验证有限元分析结果符合固定支撑圆板挠度弯曲问题的理论值;然后运用此方法分析复杂边界条件下膜基反射镜的表面位移情况,获得膜基反射镜面形特征数据。获得的挠度值相对误差小于0.04%,为深入研究膜基反射镜成型及面形控制做了准备。     

大口径反射光学系统的支撑结构设计

给出了卡氏系统(卡塞格林系统)的支撑结构设计.大口径反射镜的面形精度与支撑结构的合理与否紧密相关,文中给出了主反射镜的的支撑方案,经理论和有限元分析,此方案主反射镜的变形量最小.在装调过程中,次反射镜支撑结构能有效地调节主反射镜与次反射镜的位置关系.在工作过程中,卡式系统主反射镜与次反射镜的距离要求非常严格,采用了殷钢杆拉顶的方法保证其位置精度.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.