发动机高速动平衡的振动相位分析

针对发动机转子高速动平衡转速波动、无法保证振动信号同步整周期采样的特点,提出了一种基于转速脉冲的振动信号重构技术,大大提高了相量测量的准确度和稳定性。经试验验证,这项技术是有效、可行的。     

A wall-thickness compensation strategy for wax pattern of hollow turbine blade

As an important index affecting the aerodynamic performance and the structural strength of hollow turbine blades, the wall-thickness precision of the blade is mainly inherited from the positional relationship between the corresponding wax pattern and the internal ceramic core. However, due to locating errors, the actual position of ceramic core is always deviated from the ideal position, which makes it difficult to guarantee the wall-thickness precision of the wax pattern. To solve this problem, a wall-thickness compensation strategy is proposed in this paper. Firstly, based on the industrial computed tomography (ICT) technique and curve matching algorithms, a model reconstruction method is developed, with which the 3D model of a trial wax pattern can be easily constructed. After that, focusing on eliminating the wall-thickness errors of the trial wax pattern, an optimization method for the pose of the ceramic core in the wax pattern is proposed. Then, by mapping the optimal pose of the ceramic core to length adjustments of the locating rods, the wall-thickness errors of the wax pattern can be greatly reduced. A case study is also given to illustrate the effectiveness of the proposed compensation strategy.     

光学景象匹配基准图的滤波方法研究

对光学景象匹配制导的实时图与基准图的特点进行了对比，分析了前人提出的实时图常用的滤波方法，认为这些方法并不完全适用于基准图的波波处理。然后根据基准图的特点提出了和同态滤波及最小方差滤波的两步法对基闪图进行滤波，这一方法特别适用于因薄云覆盖而引入的低频噪声的处理，并同时兼顾了图像的增强与恢复。通过实验证明，该方法效果良好，对于光学景象匹配基准图的预处理具有一定的实用价值。     

A novel signal processing approach for LEO space debris based on a fence-type space surveillance radar system

The increase in space debris can seriously threaten regular activities in the Low Earth Orbit (LEO) environment. Therefore, it is necessary to develop robust, efficient and reliable techniques to understand the potential motions of the LEO debris. In this paper, we propose a novel signal processing approach to detect and estimate the motions of LEO space debris that is based on a fence-type space surveillance radar system. Because of the sparse distribution of the orbiting debris through the fence in our observations, we formulate the signal detection and the motion parameter estimation as a sparse signal reconstruction problem with respect to an over-complete dictionary. Moreover, we propose a new scheme to reduce the size of the original over-complete dictionary without the loss of the important information. This new scheme is based on a careful analysis of the relations between the acceleration and the directions of arrival for the corresponding LEO space debris. Our simulation results show that the proposed approach can achieve extremely good performance in terms of the accuracy for detection and estimation. Furthermore, our simulation results demonstrate the robustness of the approach in scenarios with a low Signal-to-Noise Ratio (SNR) and the super-resolution properties. We hope our signal processing approach can stimulate further work on monitoring LEO space debris.     

基于Poisson圆盘分布的河流仿真技术

针对目前河流仿真所存在的计算效率低,渲染效果不够真实的问题, 介绍了一种基于物理规律的河流实时仿真的方法.提出了一种Poisson圆盘分布的算法,可实现屏幕空间的优秀的分布样式,该算法产生的分布粒子用于表达河流的速度场,进而重构河流表面; 采用一种纹理精灵的技术,通过纹理的动态访问和纹理混合,有效地实现河流表面的渲染.仿真实验证明:该方法可以产生渲染效果非常逼真的河流视景,并能够满足实时仿真的要求.     

贴体曲线坐标系中恢复函数的一种构造方法及应用

本文在结构网格下，从三点迎风紧致逼近出发提出了一种适合于有限体积离散的恢复函数生成办法，在光滑区它具有三阶精度，并且在捕捉激波时有较高的激波分辨率。典型的几个内流算例表明：用该方法得到的恢复函数去计算数值能量时能得到与实验数据较接近的数值解。     

波音747口框装配夹具数字化改造

为节省样板制造、更改依据保存及样板实物长期保存和维护带来的高额费用,实现装配夹具的全面数字化管理,迫切需要完成样板装配夹具数字化.以波音747口框装配夹具为例,给出了已有工具球孔但无孔位数据的定位器数字化改造方法以及无工具球孔的定位器数字化改造方法;创新运用功能性测量和实测反推理论值的方法,给出了整套夹具各个定位器的理论工具球数值.装配夹具的数字化改造精简掉工装定检和维修过程中样板的借用和搬运,尤其适用于样板尺寸大、不易搬运和使用不便的样板装配夹具,缩短了工装定检和维修周期,节省了成本,提高了经济效率.     

基于矢量控制的五相永磁同步电机相电流重构方法研究

针对五相永磁同步电机控制需要电流传感器数量多、成本高的问题,提出了一种五相永磁同步电机相电流重构方法。它只使用两个电流传感器便可实现对五相电流的全采集,能有效减少硬件电路的成本和复杂性,重构精度和速度能够满足五相电机控制的需要。最后在MATLAB仿真中对所提方法进行验证,仿真结果证实了所提方法的正确性和有效性。     

基于磁链重构的永磁同步电机分布参数模型

针对基于电感的永磁同步电机(PMSM)线性集中参数模型无法描述电机磁路饱和、反电动势非正弦等非理想特性的问题,提出一种基于磁链重构的PMSM分布参数模型,并进行了仿真和试验验证。首先通过有限元分析(FEA)获取电机不同工作点下的磁链,其次利用傅里叶级数展开和多项式拟合方法对磁链进行重构,再根据重构的磁链建立起PMSM分布参数模型,并进行了仿真和试验验证。仿真和试验结果表明,模型能准确描述PMSM在不同工况下的非线性特性。     

基于ap-Welch的随机角振动信号的 频谱估计方法研究

在转台的随机角振动试验中,频谱估计的精度是一个非常重要的指标,直接影响到频谱复现的精度.在分析经典的频谱估计方法的基础上,提出了一种基于ap-Welch频谱估计(基于全相位预处理的Welch频谱估计)的方法,从理论上证明了其比Welch频谱估计法具有更强的旁瓣抑制作用.仿真实验结果表明,ap-Welch频谱估计法能够有效提高频谱估计的精度,而且随着全相位阶数的增加,频谱估计的收敛特性也随之改善.