光纤陀螺捷联系统振动误差补偿研究

针对舰船振动环境对光纤陀螺捷联系统性能的影响,提出基于神经网络的非线性数学补偿方案。对加速度计信息作傅里叶分析,进行振动特征提取;利用提取的振动特征值作为输入向量进行BP神经网络训练,建立光纤陀螺误差输出模型;对陀螺进行在线补偿,减小振动引起的漂移误差,提高了捷联系统初始对准精度。     

光纤陀螺信号的数字处理方法

光纤陀螺（FOG）有着广泛地应用,如何有效地提高精度具有重要意义。根据FOG信号漂移的数学模型,分别采用了经典傅立叶分析的FIR低通滤波器和小波变换的阈值去噪对某型FOG的输出信号进行了消噪处理。实验证明了小波阈值在消除陀螺漂移和基座动态干扰应用中的优越性。     

光反馈激光器非线性仿真研究

一些传统计算方法对非线性系统的分析存在着一些困难。针对光反馈半导体激光器收发系统微分方程组的特点,对非线性性质做出了数学上的分析,考虑到在光反馈半导体激光器收发系统中,其微分方程含有延迟因子,无法直接利用多节点上的值的加权和来近似计算斜率。基于龙格-库塔法提出了一种有效的数值仿真算法,并在matlab平台上对给定参数条件下的发射端与接收端的归一化光场以及同步误差进行了仿真,证明了接收端光场信号可以很快与发射端光场信号一致,仿真结果表明仿真算法能有效对系统进行仿真分析。     

基于动态梯度的激光光斑中心定位算法

为提高激光光斑中心检测的长期稳定性、抗干扰性能和定位精度,在对相关圆心定位算法进行研究的基础上,通过理论分析与实验测试,提出一种基于动态梯度的激光光斑中心定位算法.该算法根据激光光斑特点,利用图像梯度对光斑进行标识与定位.实验结果表明,该算法定位精度高,有效提高了激光光斑中心检测的抗干扰性能和长期稳定性,适合对测量精度要求高的长期在线测量.这种新方法已被成功用于自动激光挠度测量系统中.     

基于激光扫描的室内环境三维模型重建

精确的环境三维模型在公共服务、救援、军事侦察等领域有着重要作用,激光扫描传感器在环境三维模型重建中应用广泛。本文提出一种由pioneer3-AT移动机器人（数据采集平台）和SICKL MS200激光扫描仪（测量环境距离信息）组成的三维环境模型重建系统。利用Player／stage开放软件实现对移动机器人和激光扫描仪控制来进行激光扫描数据采集并采用JPEG-LS压缩算法对扫描数据进行压缩以提高数据传输率。在远程主机通过OpenGL技术对扫描数据进行处理以显示室内环境三维模型。实验结果表明,可得到较精确的3维环境模型。     

提高小口径深孔阀门密封面抗高温水蒸气腐蚀性能的研究

设计了一套高温水蒸气腐蚀的试验装置,利用这套装置对比了用于小口矩深孔阀门密封面上的三种焊层的抗高温水蒸气腐蚀性能,这三种焊层分别为：激光熔覆ＷＦ１４１合金层,手工电弧堆焊“丝１１１”和“堆５４７Ｍｏ”合金层。采用金相显微镜、Ｘ射线射仪、扫描电镜和能谱分析仪对腐蚀试样进行了分析,讨论了合金成分、焊层工艺等对密封面高温水蒸气腐蚀行为的影响,结果表明,激光熔覆ＷＦ１４１合金层具有优异的抗高温水蒸气腐蚀性     

基于改进的 Sage-Husa 滤波 MEMS陀螺阵列降噪技术研究

为充分挖掘 MEMS 陀螺的性能,提高 MEMS 陀螺在实际应用中的精度,通过搭建四陀螺阵列结合改进的 Sage-Husa 滤 波算法对陀螺阵列的输出信号进行降噪,在不改变陀螺加工工艺和显著提高生产成本的条件下有效提高了 MEMS 陀螺仪的实 际性能。 通过分析 MEMS 陀螺仪的系统误差和随机误差,搭建误差模型,利用传统卡尔曼滤波、移动平均滤波、小波阈值去噪 和改进的 Sage-Husa 滤波算法对单个陀螺和陀螺仪阵列进行降噪处理,实验对比发现改进的 Sage-Husa 滤波算法和陀螺仪阵列 结合后能有效降低陀螺的输出噪声。 利用 Allan 方差分析陀螺仪阵列经过改进的 Sage-Husa 算法滤波后的随机误差,四陀螺阵 列角度随机游走从 0. 40°/ h降低到 0. 03°/ h ,零偏不稳定性从 71. 11°/ h 降低到 5. 83°/ h,有效提高了 MEMS 陀螺在实际应用 中的性能。     

Progress in additive manufacturing on new materials: A review

Recent efforts and advances in additive manufacturing (AM) on different types of new materials are presented and reviewed. Special attention is paid to the material design of cladding layers, the choice of feedstock materials, the metallurgical behavior and synthesis principle during the AM process, and the resulted microstructures and properties, as well as the relationship between these factors. Thereafter, the trend of development in the future is forecasted, including: Effects of the particles size and size distribution of powders; Approaches for producing fine microstructures; Opportunities for creating new materials by AM; Wide applications in reconditioning of damaged components; Challenges for deep understanding and applications of the AMed new materials. The idea of “Develop Materials” or “Create Materials” by AM is highlighted, but a series of scientific, technological and engineering problems remain to be solved in future.     

Effects of microstructure on fatigue crack propagation behavior in a bi-modal TC11 titanium alloy fabricated via laser additive manufacturing

In this study, the crack propagation behaviors in the equiaxed and equiaxed-columnar grain regions of a heat-treated laser additive manufacturing (LAM) TC11 alloy with a special bi-modal microstructure are investigated. The results indicate that the alloy presents a special bi-modal microstructure that comprises a fork-like primary α (α_p) phase surrounded by a secondary α colony (α_s) in the β phase matrix after the heat treatment is completed. The samples demonstrate a fast crack growth rate with larger da/dN values through the equiaxed grain sample versus across the equiaxed-columnar grain sample at low ΔK values (<13.8). The differences that are observed between the crack propagation behaviors (in the crack initiation stage) of the samples can be mostly attributed to the different size and morphology of the α_p lamellae and α_s colony within the grains in the equiaxed and columnar grain regions rather than the grain boundaries. The cracks prefer to grow along the α/β boundary with a smooth propagation route and a fast propagation rate in the equiaxed grain region, where the α_p and α clusters have a large size. However, in the columnar grain region, small and randomly distributed α_p lamellae generate a zigzag-shaped propagation path with a reduction in the da/dN value. Additionally, the change in the size of the α_p lamellae in the equiaxed grains (heat affected bands, HAB) is also observed to influence the propagation behavior of the crack during the crack initiation stage.     

High strength and ductility of 34CrNiMo6 steel produced by laser solid forming

Because of the excellent mechanical properties of 34CrNiMo6 steel, it is widely used in high-value components. Many conventional approaches to strengthening-steels typically involve the loss of useful ductility. In this study, 34CrNiMo6 Steel having high strength and ductility is produced by laser solid forming (LSF) with a quenching-tempering (QT) treatment. Tempering of bainite is mainly by solid phase transformation in the previous LSF layers during the LSF process. The stable microstructure of LSF consists of ferrite and fine carbides. The microstructure transfers to tempered sorbite after heat-treatment. The tensile properties of the LSF steel meet those of the wrought standard. The UTS and elongation of LSF sample at 858 MPa, 19.2%, respectively, are greater than those of the wrought. The QT treatment enhanced the ultimate tensile strength and yield strength of the LSF sample. The ultimate tensile strength, yield strength, reduction in area, and elongation of the LSF+QT sample at 980 MPa, 916 MPa, 58.9%, and 13.9%, respectively, are greater than those of the wrought standard. The yield strength of the LSF+QT sample is approximately 1.27 times that of the wrought. The LSF samples failed in a ductile fracture mode, while the LSF+QT samples showed mixed-mode failure. The defects have only a small effect on the tensile properties owing to the excellent ductility of the LSF sample.