基于KPCA和SVM的火箭发动机试验台故障诊断方法

为了解决液体火箭发动机试验台的故障诊断问题,提出了一种基于核主元分析(KPCA)特征提取和支持向量多分类机(SVM)的故障诊断方法,该方法首先利用核主元分析对试验台标准故障样本进行特征提取,通过特征分析,建立适合于试验台故障状态识别的层次多分类支持向量机,并对其进行训练,然后将试验数据在主元上投影,输入到训练好的支持向量多分类器,对试验台故障状态进行识别.该方法充分利用了核主元分析强大的非线性特征提取能力和支持向量分类机良好的小样本泛化特性,解决了试验台故障诊断中的小样本、非线性模式识别问题.对试验台的试验结果表明,该方法是有效的、可行的.     

Center of rotation estimation for rocket nozzle by infrared reflective makers and image sequences

The determination of an accurate center of rotation of rocket motor nozzle or other object to be measured is of great interest across a wide range of applications,such as rocket,missile,robotics,industry,spaceflight,aviation and human motion analysis fields,particularly for clinical gait analysis.A new approach was proposed to estimate the moving objects’ instantaneous center of rotation and other motion parameters.The new method assumes that the two segment of object to be measured are rigid body which rotates around a center of rotation between each other relatively.The center of rotation varies with time in the global coordinate system but is fixed in the local coordinate system attached to each segment.The models of rocket motor nozzle and its movement were established.The arbitrary moving object’s corresponding to motion equations were deduced,and the least square closed-form solutions of the object’s motion parameters were figured out.It is assumed that the two high speed CCD cameras mounted on the 750 nm infrared(IR) filter are synchronized and calibrated in advance.The virtual simulation experiment using 3D coordinates of markers was conducted by synchronized stereo image sequences based on 6-DOF motion platform and the experimental results prove the feasibility of our algorithm.The test results show that the precision of x,y,z component on center of rotation is up to 0.14 mm,0.13 mm,0.15 mm.     

基于EMD和SVM的传感器故障诊断方法

为了解决自确认压力传感器的故障诊断问题,提出了一种基于经验模式分解(EMD)和支持向量机(SVM)的传感器故障诊断方法,该方法对传感器输出信号进行经验模态分解,将其分解为若干个固有模态函数(IMF),对每个IMF通过一定的削减算法增强故障特征,然后计算每个IMF和残余项的能量以及整个信号的削减比作为特征向量,以此作为输入来建立支持向量多分类机,判断传感器的故障类型.通过压力传感器的故障诊断结果表明,该方法能有效的应用于传感器的故障诊断中.     

坐标测量机的新发展——并联运动机构坐标测量机

从空间机构学的角度出发,可将坐标测量机分为串联机构坐标测量机和并联机坐标测量机两大类.由于并联机构坐标测量机测量精度高,测头位姿灵活,同时又具有“硬件”简单,“软件”复杂的特点,因而,正在成为坐标测量机领域研究的新热点.文章首先分析了普通笛卡尔串联机构坐标测量机的发展现状及存在问题,然后介绍了并联机构坐标测量机的结构及特点,并对国内外有关并联运动机构理论及其在坐标测量机领域的研究现状与发展趋势进行了综述,最后,对并联机构坐标测量机研究过程中应注意的主要问题进行了探讨.     

材质识别多功能触觉传感器

本文介绍一种材质识别多功能触觉传感器,它呈平面单一构造,但具有三种传感器功能。该传感器由制做在柔性绝缘薄 上的两只金属线圈构成,有４个输入输出端子,当它作早感线圈使用时,吾感性功能,可以识别金属和半导体材料;当它看作一个平面状电容时,呈容性功能,可以识别绝缘材料;当当它用于控温电路时,该传感器呈温觉功能。由试做的传感器能识别一些典型的材料如铁、铝、黄铜、橡胶、木材、有机玻璃和发泡塑料等。实验结果表     

一种矢量量化码书搜索的快速算法

本文提出了一种采用均方误差(MSE)测度的矢量量化码书搜索的快速算法.该算法在码书设计的每次迭代前预先计算各码字的和值(一个矢量各分量的和)并保存在码书中.在迭代过程中,利用输入矢量的和值、各码字的和值以及均方误差三者之间的各种特性排除大部分候选码字而免去许多均方误差计算.测试结果表明,相对于穷尽搜索方法,计算量得到明显的降低,计算时间减少约90%,同时只需要很少的预先计算量和额外存储量.     

非线性多功能传感器信号重构的抗差估计方法研究

在非线性多功能传感器的信号重构过程中,训练样本集不可避免地夹杂粗差数据。为了得到既有较强抗差性又有较高效率的估值,采用抗差最小二乘法在粗差干扰条件下进行参数估计。抗差最小二乘估计通过等价权把抗差估计原理与加权最小二乘形式结合在一起,因此在抵抗粗差的同时保持了最小二乘法的优点。非线性信号重构的粗差抑制结果表明,抗差最小二乘法计算速度快,且具有良好的抗粗差能力和收敛可靠性。     

Degradation of ground-based RADAR performance due to vegetation cover

Several studies indicate that vegetation attenuates and scatters radio waves. Although researchers considered vegetation as a soft obstacle in terms of total attenuation, actual measurements show that trees or shrubs could induce important attenuations. This opens a possible use when looking for radar invisibility shields to protect selected targets. Is it possible to use vegetation as an invisibility cover? If so, under which conditions this procedure would work? These are the questions this paper tries to answer, analysing the degradation in the probability of detection that a vegetation cover induces in the radar system. We present the results from large measurement campaigns on attenuation due to vegetation, performed at radar UHF and microwave frequencies; then we use them to evaluate the reduction in the radar performance when trying to detect a target protected by a vegetation cover. We demonstrate that vegetation covers lead to reductions in probability of detection to values below 0.1 considering single pulse radars, which means that the target would be undetectable. We conclude that the proposal would be reliable, even taking into account other additional effects, as pulse integration, the natural time variability of the induced attenuation, and the noise increase due to the vegetation scattering.     

温度均匀性对V形槽面黑体辐射特性的影响

为了解决同心圆V形槽结构面源黑体的温度不均匀性产生原因及其对辐射特性的影响等问题,提出了基于蒙特卡洛全光路跟踪的辐射特性评估方法.首先通过与精密方法的相互比对验证了该方法的正确性及准确程度,而后分析了温度不均匀性的产生原因及变化规律,最后对温度均匀性与辐射特性之间的影响关系进行了研究.结果表明,槽夹角越小、槽深度越深、工作温度与环境温度差异越大,温度均匀性越差;槽夹角和槽深度还会直接或间接的对有效发射率产生影响.作为结论,建议采用45°或60°槽夹角,槽深度不宜超过2 mm,建议附加热管技术以及保护套筒结构.     

Three-dimensional motion parameters estimation from stereo image sequences based on infrared reflective markers

In this paper,an innovative 3D motion parameters estimation method from stereo image sequences based on infrared(IR) reflective markers is presented.It was assumed that two high speed CCD cameras had been calibrated previously.The method consists of the following steps:1) the coordinate of several markers and depth map for each stereo pair was determined from the sequences of stereo images by relations of markers’ coordinate the correspondence between markers was established,2) the 3D motion parameters of the target was computed based upon the matched markers’ coordinate,and 3) translated 3D motion parameters estimation into the problem of least square according to the movement model of the object to be measured.Without using line,curve or corner correspondence,this method can calculate the depth of these markers feature easily and quickly in contrast to traditional approaches.The two CCD cameras work on 200 f/s,and each processing cost time is about 3 ms.It was found that,by using several markers and a large number of stereo images,this method can improve the computational speed,robustness and numerical accuracy of the motion parameters in comparison with traditional methods.The virtual simulation experiment was conducted using synthesized stereo image sequences based on 6-DOF motion platform and the experimental results proved the validity of our approach and showed that the translation and rotation precision is up to 0.1 mm and 0.1°.