动载荷对结构功能一体化天线力电性能的影响

结构功能一体化天线是将集成微带天线阵列的射频电路嵌入到武器平台结构中,它既可作为力学承载的蒙皮结构,又可作为收发电磁波的微波天线,在未来飞行器中具有巨大的应用前景。针对服役中的结构功能一体化天线力电性能演化问题,通过分析结构变形与天线电性能的影响关系,利用相位差建立动载荷作用下结构功能一体化天线的机电耦合模型,利用最小二乘支持向量回归对结构变形的数据拟合来获得结构变形下的电性能。通过研制的2.5 GHz结构功能一体化天线试验装置,验证了机电耦合模型的正确性。利用验证后的耦合模型,通过数值分析获得了动态载荷对结构功能一体化天线力电性能的影响规律,其结果表明,动态载荷下天线结构变形会影响天线的主波束方向、增益和副瓣。     

20m金属桁架天线罩环控设计

针对金属桁架天线罩夏季高温情况时罩内温度高的问题,综合技术需求及经济实用的原则,对某工程项目喀什地区12 m S/X/Ka接收天线采用的20 m金属桁架天线罩进行了强制通风方案设计,仿真分析了天线罩内的温度场。仿真结果表明,该设计满足系统对天线罩内温度的要求。     

高铁平台卫通天线罩结构设计与仿真优化

为了实现高铁平台卫通天线易共形要求,同时满足高运行速度载荷和安装工况需求,文中采用自顶向下设计思路完成超低轮廓天线罩结构设计。在保证天线罩实现大入射角和高透波性能的前提下,首先考虑具备良好气动性能的工业设计方案,并对天线罩的结构强度、刚性和气动外形进行详细设计;同时对承载部件底罩进行静力学、谐响应仿真分析和优化,保证底罩满足一体化天线传动系统安装精度要求;最后完成罩体在高动态下的流固耦合仿真分析与优化。结论表明天线罩可满足电性能、机械性能和载车平台要求。     

20m金属桁架天线罩结构设计

随着Ka波段天线的应用,金属桁架天线罩以其优越的力学和电磁性能而受到人们的青睐。针对某12 m S/X/Ka接收系统的金属桁架天线罩,开展结构设计,并用ANSYS软件分析计算了天线罩的变形和应力;结果表明,天线罩的强度、刚度满足使用要求。该设计已运用于相关工程项目建设中。     

面向智能蒙皮天线电补偿的位移场重构

智能蒙皮天线能够将集成微带天线和传感元件嵌入到各类武器平台结构中,不仅具有电磁收发和力学承载性能,同时还具有服役状态感知与性能自适应功能.为了解决蒙皮天线因结构变形导致的电性能恶化问题,文中提出了一种嵌入光纤光栅的智能蒙皮天线结构,并利用模态分析和状态空间理论,从少量光纤光栅测量的应变实时重构天线结构的变形位移场.通过研制的智能蒙皮天线结构变形实验系统,验证了变形位移场重构方法的有效性.该位移场重构方法为智能蒙皮天线电补偿系统的研制奠定了基础.     

基于区间分析的非对称外形天线罩厚度设计

厚度误差是影响天线罩电性能的重要因素。对于非对称外形天线罩,厚度误差引入的电性能恶化程度会随天线扫描角变化。针对该问题,文中提出了一种基于区间分析的天线罩厚度设计方法。首先根据误差区间分析天线罩的方向图区间,从中提取电性能指标区间,进而分析不同扫描角下电性能指标区间随厚度的变化特性。通过对电性能指标及其变化区间作单一目标函数转化,给出不同扫描角下天线罩电性能指标及其变化区间最优的厚度设计结果。某正切卵形天线罩的仿真结果验证了该方法的有效性。     

考虑桁架柔性的可展开天线动力学分析

周边桁架式可展开天线的展开过程涉及复杂的动力学问题,对天线展开过程的研究有助于展开天线的设计、研制和优化。综合考虑天线展开过程中桁架结构的柔性变形和索网结构的变拓扑特征,建立了周边桁架式可展开天线展开过程的动力学模型。首先采用绝对节点坐标法的梁单元对外桁架结构建模,然后引入过渡函数来描述索段由松弛到张紧状态的转变,最后建立了周边桁架可展开天线的系统动力学方程。对天线进行动力学仿真分析,结果表明该方法能有效地分析天线的展开过程,桁架结构在内部索网张力的作用下会产生柔性变形,对驱动力和展开速度产生显著的影响。     

机载振动对共形阵列天线电性能的影响

环境载荷严重影响共形阵列天线的电性能,对研究和发展高性能共形天线而言,环境载荷是一个不容忽视的问题。文中从变形面的拟合出发,提出了一种变形后天线电性能的计算方法,利用此方法计算随机振动下共形阵列天线的电性能,分析随机振动对共形阵列天线电性能的影响。文中所提方法与结论可为工程技术人员设计高性能共形天线提供参考。     

冲击波载荷对平面阵列天线电性能的影响

从机电学科交叉的角度,研究冲击波载荷作用下平面阵列天线结构塑性变形对天线电性能的影响.首先,根据爆炸冲击波的超压时程模型,采用弹塑性结构的瞬态有限元方法,获得冲击波载荷作用下平面阵列天线结构的塑性变形.然后,将结构塑性变形引入到平面阵列天线远场方向图表达式中,得到冲击波载荷作用下天线电性能的数学分析模型.最后,针对某X频段工作的平面阵列天线,分析了冲击波载荷对其增益损失、副瓣电平及波束指向的影响关系.数值分析结果可用来预测冲击波载荷作用后平面阵列天线可否正常工作.另外,文中的分析方法也可用于其他类型天线的冲击波载荷影响分析.     

大口径高精度星载天线的热变形优化设计与仿真计算

大口径高精度星载天线在轨运行时,受太阳辐照、进出地影或遮挡影响,会周期性经历各种极端温度环境,导致天线的型面恶化和指向偏差。基于此,进行了某大口径高精度星载天线的热变形优化设计与仿真计算,首先针对高精度天线的结构组成特点,开展热变形影响分析,找出部件变形对天线型面和指向的影响机理。随后,给出了天线型面误差和指向误差的计算方法,研究了天线在轨温度变化情况及温度与热变形的评价关系。通过天线热变形误差敏感性分析,找出了影响天线热变形的关键因素,并在此基础上开展了热变形优化设计。最终的电性能仿真结果显示,在三个特征频率下,天线实际相位中心与理论相位中心偏差很小,均在允许偏差范围内,验证了热变形优化的有效性。     

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...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

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.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

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.