光纤光栅传感技术在桥梁施工监控中的应用

为了满足桥梁顶推法施工监控的复杂要求,分析了光纤光栅传感器的结构和原理;研究了应变和温度交叉敏感以及波长解调等光纤Bragg光栅(FBG)传感技术应用中的关键问题.根据对桥墩受力变形的分析,结合实例设计了传感器参数.将虚拟仪器与FBG传感器相结合,可以利用虚拟仪器技术在信号采集、分析、存储和传输等方面的优势,实现光纤光栅解调与施工监控于一体,保证了施工安全和桥梁质量.     

动物运动力学测试系统

研究蜘蛛、昆虫等微小动物在地面、墙面、天花板等不同表面的光滑或粗糙状况下自如运动时的附着机理,可以为特种仿生机器人的研究提供理论依据。研制了动物运动力学测试系统,包括由16只三维微牛级力传感器组成的传感器测试阵列;48通道的信号放大、调理以及数据采集与处理;动态图像的放大、记录与分析等。该系统在仿生学的研究中有很大的应用价值,是了解和深入认识动物运动步态及其接触力学规律的重要手段。     

Low temperature synthesis,structural characterization,and zero-field resistivity of nanocrystalline La1−xSrxMnO3+δ (0.0 ≤ x ≤ 0.3) manganites

This paper reports the synthesis of nanocrystalline strontium doped manganites by a simple and instantaneous solution combustion method, which is a low temperature initiated route to prepare fine-grained oxide powders with good surface area. Rietveld refinement of X-ray data indicates that the as-formed manganites exhibit a cubic phase with space group Pm3m. However calcined (900 °C, 6 h) samples transform into rhombohedral phase with space group R-3c. The scanning electron micrographs of the powders reveal that the sizes of very fine primary particles which are in an agglomerated form, decrease as strontium content increases. The infrared spectra of lanthanum manganites show two active modes at 400 and 600 cm⁻¹. From zero-field resistivity measurements, it is found that all the samples exhibit metal–insulator transition (T_M–I) in the range of 219–252 K, which is low as compared to the samples prepared by ceramic route. The lower (T_M–I) values might be due to smaller particle sizes in the range of 25–45 nm.     

AgTaO3 and AgNbO3 thin films by pulsed laser deposition

Silver tantalate AgTaO₃ (ATO) and silver niobate AgNbO₃ (ANO) films have been grown on to the LaAlO₃ (001) and sapphire Al₂O₃ (0112, r-cut) single crystals by pulsed laser deposition technique from stoichiometric ATO and ANO targets. X-ray diffraction study revealed epitaxial quality of ATO and ANO films on the LaAlO₃ (001) whereas on the sapphire r-cut substrate they are preferential (110) and (001) oriented. To characterize microwave films properties in the range from 1 to 40 GHz, coplanar line interdigital capacitors were fabricated by photolithography and lift-off technique. ANO film capacitors show superior properties: frequency dispersion was as low as 13%, voltage tunability (40 V, 200 kV/cm) was about 4.6% at 20 GHz, loss tangent ∼0.106 at 20 GHz, K-factor = tunability / tanδ from 49% @ 10 GHz to 33% at 40 GHz.     

The electrode/sample contact effects on the dielectric properties of the CaCu3Ti4O12 ceramic

In this paper, the contact effects at the electrode/sample interfaces on the dielectric properties of the CaCu₃Ti₄O₁₂ (CCTO) ceramic were studied. The experimental results provide clear evidence that the colossal dielectric constant in CCTO is related to the ceramic itself; however, it may also partly originated from the electrode/sample contact effects which depends on the surface resistivity of the sample. When the surface resistivity of the ceramic is as high as 1.2 × 10⁸ Ω cm, no obvious mobile space charges can be observed, and the dielectric properties of the sample is inert to the different metal electrodes and various sample thicknesses, indicating the colossal dielectric constant (near 2000 at 10 kHz) at room temperature is due to the true properties of the ceramic itself. However, after the surface resistivity is lowered to 3.1 × 10⁷ Ω cm through post-annealing the sample in N₂ atmosphere at 750 °C, obvious mobile space charges can be observed, and the dielectric properties of the sample become sensitive to the different types of contacts. The dielectric constant of the sample with Pt electrode shows a significant enhancement (up to 5000 at 10 kHz), comparing with that of the sample with Ag electrode. Clearly, in this case, the extrinsic contact contributes partly to the colossal dielectric constant of CCTO ceramic.     

基于立体成像几何特性的动态有限搜索匹配法

提出了一种基于立体成像几何特性的动态有限搜索匹配法。该法根据被测物体与摄像机标定参照物在空间上的相互关系及被测物体形态，确定被测物体特征点视差匹配大致范围。利用立体成像几何特性，采用动态有限搜索法，以求出的视差为参考，根据左(右)图像中特征点与所得匹配对应点的水平视差值，确定在右(左)图像中的搜索方向和搜索范围，采用灰度区域相关计算，确定下一个匹配特征点，并依此类推。由于特征点灰度不稳定，且随视点的不同而有很大差异，为能得到正确匹配，需结合几何相似性约束。通过对一已知三维坐标标准件的计算机仿真实验，证实了该方法的有效性。     

不确定串联非线性系统H∞鲁棒自适应控制

针对一类含有未知参数和干扰的非最小相位串联非线性系统,结合H_∞控制和自适应控制方法并利用李雅普诺夫函数递推设计方法设计了状态反馈H_∞自适应控制器,避免了求解Hamilton-Jacobi-Isaacs不等式设计控制器的困难.该控制器不仅保证闭环系统ISS(input-to-state)稳定,而且使得系统对于所有允许的参数不确定从干扰输入到可控输出的L₂增益不大于给定的值.最后,给出了一个仿真例子,仿真结果充分表明了所设计的控制器的可行性和有     

Application of Feedback Linearization Method in Airplane Automatic Landing Control System

Summarizes the I/O feedback linearization about MIMO system, and applies it to nonlinear control equation of airplane. And also designs the tracing control laws for airplane longitudinal automatic landing control system.     

基于换挡力的换挡摇臂多目标结构设计优化

换挡摇臂是换挡执行机构的关键零件之一,其变形与疲劳寿命对于换挡执行机构的正常工作具有重要影响。文中以某型电控电动式换挡机构的换挡摇臂为研究对象,首先通过多体动力学仿真计算获取载荷谱,基于有限元仿真计算换挡摇臂的应力分布,从而计算出换挡摇臂的变形与疲劳寿命;然后基于变形和疲劳寿命分析结果,选取换挡摇臂关键几何参数为设计变量,以换挡摇臂质量和换挡摇臂变形为目标,以换挡摇臂疲劳寿命为约束条件,通过响应面法对换挡摇臂结构进行多目标设计优化。结果显示,在换挡摇臂质量减轻的同时,变形不增反减。这充分说明文中建立的模型和优化方法具有一定的工程应用价值,为换挡摇臂的设计提供了重要的理论支撑。     

ABS磁电式轮速传感器故障诊断

轮速传感器故障是车辆ABS的常见故障之一.针对广泛使用的磁电式轮速传感器,在分析其结构特点和使用条件的基础上,以其故障模式进行了归纳和分类.设计了摩托车ABS轮速传感器的故障诊断系统的软硬伯,并完成了相关的试验验证.试验结果表明该系统能够实现预设功能,完成对轮速传感器常见故障的诊断.