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采用一种基于钢球对碰撞的窄脉冲冲击激励装置,结合外差式激光干涉仪对加速度计进行了绝对法冲击校准,分析了该装置所产生波形的特点。利用加速度计的输入输出信号,采用相关二步法对表征加速度计动态特性的数学模型参数进行了辨识,与绝对法振动校准结果的比较说明了加速度计模型以及动态校准的可靠性。最后基于动态校准得到的加速度计模型,设计了数字补偿滤波器,通过对加速度计动态特性的补偿,提高了加速度计的带宽,减小了动态误差。 相似文献
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针对目前陀螺导航装备缺乏动态性能测试方法的状况,本文提出并实现了车载动态性能测试系统.并根据航向数据非连续变化的特点,提出了基于周期平移的小波阈值降噪算法.该算法通过对信号的分段周期平移、阈值降噪、逆平移的方法实现降噪,有效地克服了常规小波阈值降噪算法带来的Pseudo-Gibbs现象.仿真及实测数据表明采用该算法能够在有效剔除异常点、消除噪声的同时,消除降噪信号中的Pseudo-Gibbs现象.跑车实验表明车载动态性能测试系统为陀螺导航设备提供了有效的解决方案和统一的测试平台. 相似文献
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针对动态计量中加速度计动态特性计量的问题,本文主要论述了基于绝对法冲击校准的加速度计动态计量.依据加速度计物理结构,采用一个二阶微分方程来描述其输入输出特性,并将该方程转化为一种特定的形式,然后利用绝对法冲击校准加速度计的数据,采用一种新的方法在频域确定了方程的未知系数从而得到了加速度计动态特性参数.最后采用激光绝对法振动校准对加速度计进行了校准试验,并将得到的复灵敏度结果与模型的频率响应进行了比较,一致性的结果证明了该方法的有效性. 相似文献
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本文介绍了一种能沿任意波束指向全程动态聚焦的数字波束合成器的设计,此合成器用于相控阵B超成像系统。回声信号的延时量分解为“指向延时”和“聚焦延时”两部分,分别用产生相控发射激励的时序逻辑电路和一个“动态聚焦延时量表”实现。通过对A/D采样时钟的控制及对A/D采样时钟、地址计数时钟和存储器写时钟的时序配合,实现了同相位数据点采样及无冗余数据的缓冲存储器。所设计的数字相控波束合成器只用廉价的高速数字电路即可实现,成本极低。实验结果验证了该方案的可行性。 相似文献
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局部均值分解(Local mean decomposition,简称LMD)方法是一种新的自适应时频分析方法,并成功运用于滚动轴承故障诊断中,但对噪声比较敏感。为消除噪声对诊断结果的影响,提出了一种小波包降噪与LMD相结合的滚动轴承故障诊断方法。该方法首先利用小波包去除信号中的噪声,然后,进行LMD分解,并将分解后PF分量与分解前信号的相关系数作为判断标准,剔除多余低频PF分量,最后,选取有效PF集进行功率谱分析,提取故障特征。通过仿真数据和真实滚动轴承数据的故障诊断实验,其结果验证了本文方法的有效性。 相似文献
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在处理一列测量数据时,如果其中有粗差未予剔除或将一些误差较大而不属粗差的观测值剔除,都会歪曲了测量结果,所以首先需要判别测量列中是否包含有粗差的观测值。供判别粗差的一些熟知法则有:莱依达法则、肖维勒法则和文中给出的较好 t 判别法,本文再介绍一个简便的判别法——狄克逊法则,然后再谈如何用极差计算随机不确定度的方法。一、剔除坏值对某一个量同一条件下,独立测得 n 个值: 相似文献
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弹道明胶是一种超软材料,其波阻抗很低,采用经典的霍普金森杆测试技术无法获得其在高应变率下的力学特性。该文采用3种基于霍普金森杆的改进方法分别对其动态压缩力学特性进行测试,并对比3种方法的优缺点。实验结果表明:铝杆配合半导体应变片的测试方法对透射信号的提升有限,无法获得弹道明胶的动态力学数据;基于聚偏氟乙稀(polyvinylidene fluoride,PVDF)压电薄膜传感器的方法避免对透射信号的测量,可以获得满意的测试数据;撞击杆直接加载法在小应变阶段的测试结果可信,但在大应变阶段的测试结果无效。综合来看,使用PVDF压电薄膜传感器的测试方法可以较好地获取弹道明胶的动态力学特性。 相似文献
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A recurring theme in recent design theory has been a desire to relate design method to scientific method: to create the ‘science of design’ or a ‘design science’. There is an inherent paradox in such a desire since design and science are clearly very dissimilar kinds of activities. Further, the concept of ‘scientific method’ now seems to be in epistemological chaos. For these reasons, attempts to model design method on scientific method seem misplaced. It is proposed that it would be more fruitful to regard design as a technology, rather than as a science. The paper seeks to establish the basis for such a view, drawing especially on the idea that both design and technology involve the application of types of knowledge other than the purely ‘scientific’ kind. 相似文献
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The natural element method (NEM) is a meshless method. The trial and test functions of the NEM are constructed using natural neighbor interpolations which are based on the Voronoi tessellation of a set of nodes. The NEM interpolation is linear between adjacent nodes on the boundary of the convex hull, which makes imposition of essential boundary conditions easy to implement. We investigate the performance of the NEM combined with the Newmark method for problems of elastodynamics in this article. Applications are considered for a cantilever beam with different initial load conditions. The NEM numerical results are compared with the finite element method. NEM shows promise for these applications. 相似文献
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针对传统的空间圆弧拟合方法鲁棒性低、拟合精度不高等问题,提出了一种鲁棒性较强的空间圆弧拟合优化方法。首先,以拉格朗日乘子法为基础,基于平面条件约束建立目标函数,从而得出空间圆弧拟合方程;其次,采用RANSAC(random sample consensus,随机抽样一致)算法剔除错误跟踪点,将RANSAC算法的高稳定性应用到空间圆弧拟合的点云优化中,进而提高拟合精度。最后,通过实验分析验证了所提空间圆弧拟合优化方法的可行性,并与传统拟合方法进行比较,分析所提方法的拟合精度。实验结果表明:普通圆弧点云拟合的相对精度在0.003左右,复杂圆弧点云拟合的相对精度在0.01左右;相较于传统拟合方法,所提方法有效解决了拟合精度低及鲁棒性差等问题。研究结果表明提出的空间圆弧拟合优化方法一方面可运用拉格朗日乘子法增强鲁棒性,另一方面可通过采用RANSAC方法剔除错误点以提高拟合精度,具有广泛的工程实际应用价值。 相似文献
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Usually, the governing equations of the numerical manifold method (NMM) are derived from the minimum potential energy principle. For many applied problems it is difficult to derive in general outset the functional forms of the governing equations. This obviously strongly restricts the implementation of the minimum potential energy principle or other variational principles in NMM. In fact, the governing equations of NMM can be derived from a more general method of weighted residuals. By choosing suitable weight functions, the derivation of the governing equations of the NMM from the weighted residual method leads to the same result as that derived from the minimum potential energy principle. This is demonstrated in the paper by deriving the governing equations of the NMM for linear elasticity problems, and also for Laplaces equation for which the governing equations of the NMM cannot be derived from the minimum potential energy principle. The performance of the method is illustrated by three numerical examples. 相似文献
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A simple yet effective modification to the standard finite element method is presented in this paper. The basic idea is an
extension of a partial differential equation beyond the physical domain of computation up to the boundaries of an embedding
domain, which can easier be meshed. If this extension is smooth, the extended solution can be well approximated by high order
polynomials. This way, the finite element mesh can be replaced by structured or unstructured cells embedding the domain where
classical h- or p-Ansatz functions are defined. An adequate scheme for numerical integration has to be used to differentiate between inside and outside
the physical domain, very similar to strategies used in the level set method. In contrast to earlier works, e.g., the extended or the generalized finite element method, no special interpolation
function is introduced for enrichment purposes. Nevertheless, when using p-extension, the method shows exponential rate of convergence for smooth problems and good accuracy even in the presence of
singularities. The formulation in this paper is applied to linear elasticity problems and examined for 2D cases, although
the concepts are generally valid.
The first author would like to appreciate the financial support of his stay in Germany, where this research has been carried
out, by the Alexander von Humboldt foundation. 相似文献
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The body force method is based on the principle of superposition. The solution in the body force method is obtained by the
superposition of fundamental solutions so as to satisfy a given boundary condition. By means of these fundamental solutions
all problems can be solved in principle. In this paper, first the fundamental principle of the body force method is illustrated
and then its application to crack problems, elastic–plastic problems and elastodynamic problems are shown.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献