基于拉丁超立方抽样及响应面的结构模糊分析

在对边值模糊分析方法和优化边值模糊分析方法研究的基础上,将拉丁超立方抽样和响应面方法引入结构模糊分析,提出一种基于拉丁超立方抽样及响应面的模糊分析方法。讨论这种方法的数学运算,并与Monte Carlo方法进行比较。最后基于这种方法,对一个用隐式方程描述的有限元悬臂梁模型进行模糊分析,得到变形模糊结果。     

Advanced median method for timing jitter compensation

Timing jitter is one of the main factors that influence on the accuracy of time domain precision measurement. Timing jitter compensation is one of the problems people concern. Because of the flaws of median method, PDF deconvolution method and synthetic method, we put forward a new method for timing jitter compensation, which is called advanced median method. The theory of the advanced median method based on probability and statistics is analyzed, and the process of the advanced median method is summarized in this paper. Simulation and experiment show that compared with other methods, the new method could compensate timing jitter effectively.     

基于照片的实体建模方法的现状及展望

基于照片的实体建模方法指通过摄像、图像处理获得物体三维模型的方法。该方法源于计算机视觉,是一种方便快捷的三维建模方法。对基于照片的实体建模基础理论与方法进行了论述,并对目前国内外的研究动态进行了分析,提出了进一步研究的方向。     

工业控制软件中数据存储方法分析

针对工业控制软件中数据存储的方法进行了分析,并以全自动校圆机的数据存储为例,论述了Txt方法、Excel方法和Access方法的各自实现方案,进而比较它们的优缺点。Txt方法适合简单的数据存储,Excel方法适合复杂的数据存储,而Access方法适合需求一致性和安全性的数据存储。具体使用哪一种方法,需要依据实际的数据存储需求而定。     

Rigid-plastic finite-element method for analysis of three-dimensional rolling that requires small memory capacity

At present, caliber rolling is analyzed using the three-dimensional rigid-plastic finite-element method. In this paper, a new method of analysis which requires less memory capacity than the conventional method is proposed. In the conventional method, the shape of the whole region is updated after the functional of the region is minimized, whereas in the proposed method, the shape of part of the region (large region) is updated after the functional of the large region is minimized. The load, torque, material shape, hydrostatic stress and equivalent strain rate obtained using the proposed method agree with those obtained using the conventional method within the allowable range of convergent error. Also, although the computation time for the proposed method is rather long compared with that for the conventional method, the memory capacity required for the proposed method is small compared with that for the conventional method. Finally, analysis of various types of caliber rolling in which the number of finite elements in the large region coincides with that in the whole region in analysis using the conventional method is carried out and reasonable stress and strain distributions are obtained.     

一种改进的增量谐波平衡法及其在非线性振动中的应用

对于一般的增量谐波平衡法而言,在求解分段线性系统周期响应时存在收敛速度慢的缺点。针对这一缺点,本文根据最小二乘法原理和增量过程提出了一种改进的增量谐波平衡算法,通过和原有算法进行对比发现二者之间存在着统一的算法形式,因此只要对原有算法作简单的改进即可方便地使用此方法。利用此方法成功计算了齿轮传动分段线性系统的周期解,通过对计算结果比较,发现迭代次数要比一般的增量谐波平衡法少30%左右。从而可以看出这种算法具有收敛速度快的优点。     

柔性机构的动力学综合法建模与分析

首先对现有的多柔体动力学建模方法进行了分析与比较，指出“把多体动力学与有限元相结合的综合动力学建模法”是适合于大型复杂柔性机构动力学分析的较好方法。其次，结合有限元方法详细讨论了“综合法”的程式化建模过程。最后，通过分析综合法建模的特点，讨论了多柔体系统“综合法”动力学分析的发展趋势。     

基于角加速度的复合计算阶次跟踪方法

针对旋转机械振动信号分析中的计算阶次跟踪方法的局限性,提出基于匀角加速度方程的计算阶次跟踪方法,并将该方法与线性插值、三次样条插值等方法复合在一起,根据旋转机械转角加速度的大小,选择相应的方法进行阶次重采样,实现基于角加速度的复合计算阶次跟踪。在转速变化缓慢时,采用线性插值方法;在转速变化比较大时,采用匀角加速度方程方法;在转速变化剧烈时,采用三次样条插值的方法。复合计算阶次跟踪方法兼顾计算的效率和精度,对某滤波减速器性能试验台中交流伺服电动机在升、降速阶段引起的振动实测试验结果表明了此方法的正确性机可行性。     

经验模式分解的改进及其对球轴承缺陷的诊断

在分析经验模式分解存在问题的基础上，改进了经验模式分解的算法，提出用窗口平均法取代原极值包络法来计算局部均值。给出了窗口平均法的具体算法，并通过模拟信号进行了验证。结果表明，改进的算法减少了三次样条插值使用的次数，从而减少了信号分解的时间，并且所有的数据都参与了局部均值的计算，提高了数据的利用率。同时，用改进的EMD方法取代传统包络分析中的带通滤波器，对实际的缺陷轴承进行了诊断。结果表明，经验模式分解方法比传统的包络分析更有效。     

确定飞轮转动惯量的数值解法

本文提出一个确定飞轮转动惯量的数值解法。该法的主要工作是求解两个非线性方程。当等效力矩M＝M（φ）时,该法是一个精确方法;当M＝（φ,ω）时,该法是一个近似方法。此外,提出了[1]和[3]中的两个不妥之处。     

Application of the EMD method in the vibration analysis of ball bearings

In this paper, the empirical mode decomposition (EMD) method is introduced and the calculation of the local mean with the envelope method of the extrema is substituted by an improved method, in which the local mean is computed by using the average method of the successive extrema. Based on the improved EMD method, the vibration signals of ball bearings are analyzed in detail. The results show that the proposed method is superior to the discrete wavelet decomposition for the vibration analysis of ball bearings.     

附加轴向力法计算向心推力滚动轴承轴向力

向心推力滚动轴承本身所受轴向力通常采用判断“压紧”端和“放松”端的方法来求解,现有的判别方法既不完备,又容易出错。为了完善现有的判别方法,通过轴系结构的分析,引入轴承安装方式这一新增判别条件。为了简化计算过程,通过力学推导,提出了一种不需要利用判别方法,直接得到向心推力滚动轴承本身所受轴向力的新方法,称为附加轴向力法,即向心推力滚动轴承本身所受轴向力等于其本身派生轴向力与其本身所受附加轴向力之和,并通过与原先方法的结果对比验证了新方法的正确性。     

An improved three-point method based on a difference algorithm

The reason for the rounding error in a measurement system under the condition of a limited sampling period is analysed, and a three-point method based on the difference algorithm (D3P method) is proposed. The effect of the rounding error is reduced by differential approximation of the roundness error and reconstruction of the transfer function. The generalized three-point method (G3P method), the three-point method based on the first-order difference algorithm (I-D3P method) and the three-point method based on the second-order difference algorithm (II-D3P method) are compared and analysed by simulation. The results show that the accuracy of the D3P method is greatly improved compared with that of the G3P method under the restricted sampling period and that the D3P method retains high precision in the case of failed error separation of the G3P method. An experimental system was constructed to realize error separation, and the experimental results show that the D3P method has higher accuracy than the G3P method over a small sampling period.     

稳态耦合场的协同仿真

对多场耦合问题提出了一种进行协同仿真的实用方法。针对多场耦合问题的求解现状,提出使用协同仿真的求解方式以降低问题难度,给出了协同仿真的框架。针对其中网格不匹配问题,在对现有软件进行深入研究的基础上,提出了使用内嵌的后处理机制来进行异构网格间的载荷插值。使用该方法对一个稳态热应力问题进行分析,与传统的一体化耦合求解方法进行比较,结果表明此方法精度高、计算开销小,具有较强的实际操作性。     

一种计算随机变量函数均值和标准差的方法

在工程实践中常常需要对随机变量函数的均值和标准差进行计算。对于这种问题,通常采用的是Monte Carlo方法、Taylor级数展开法、Taguchi法及其改进方法、Rosenbluthe法及其改进方法等。其中最有效的是Monte Carlo方法,但其计算效率低。为此,提出利用数论方法产生分布均匀的数论网格点,以此伪随机数代表由Monte Carlo方法产生的随机数计算随机变量函数的均值及标准差。计算实例表明,这种利用伪随机数的方法不但克服了Rosenbluthe改进方法在处理高阶函数时计算结果偏离实际值的缺点,而且与Monte Carlo方法相比,提高了计算效率。     

力矩法、转角法上紧螺栓力矩可靠性分析

螺栓预紧力是衡量联接可靠性的重要指标,目前普遍采用力矩法和转角法上紧螺栓。实验表明,力矩法轴向预紧力较分散,不好控制;而转角法轴向预紧力较集中且好控制,转角法可靠性要优于力矩法。     

图像阈值分割的Fisher准则函数法

针对图像分割中的阈值选取问题，通过引入模式识别理论中的Fisher评价函数作为图像分割的准则函数，提出了基于Fisher评价函数法的图像分割新技术。该方法利用图像直方图计算各灰度级下的Fisher评价函数值，其最大值即对应于最佳分割闲值。对该方法进行了详尽的图像分割实验，并与著名的Otsu法、最大熵法、最小误差准则法进行了详细比较，结果表明该方法具有分割性能稳定、计算速度快以及受目标大小影响小等优点，是一种实用有效的图像阈值分割新方法。     

CAPP与PDM集成研究

从集成内容和集成方式论述OAPP与PDM的集成，并对不同的集成方式进行了分析和比较，得出结论封装组件集成方式是一种最实用和高效的集成方式。最后给出了封装组件方式集成案例。     

声无限元进展

声无限元在近几年来的发展尤为迅猛。相对于声学领域常用的边界元等其他方法,声无限元应用于声学问题的计算效率是极为优越的,因而适于求解很宽的声学频率和复杂声源形成的声场。介绍了声无限元的引出、原理和早期的声无限元,并根据提出方法的新颖性和受关注的程度,对近年来的声无限元统一归纳为五类,然后扼要介绍了各种方法的原理、所产生的问题以及参考文献中解决的办法。最后,对声无限元进行了前景展望。     

Accuracy analysis of Stewart platform based on interval analysis method

A Stewart platform is introduced in the 500 m aperture spherical radio telescope(FAST) as an accuracy adjustable mechanism for feed receivers.Accuracy analysis is the basis of accuracy design.However,a rapid and effective accuracy analysis method for parallel manipulator is still needed.In order to enhance solution efficiency,an interval analysis method(IA method) is introduced to solve the terminal error bound of the Stewart platform with detailed solution path.Taking a terminal pose of the Stewart platform in FAST as an example,the terminal error is solved by the Monte Carlo method(MC method) by 4 980 s,the stochastic mathematical method(SM method) by 0.078 s,and the IA method by 2.203 s.Compared with MC method,the terminal error by SM method leads a 20% underestimate while the IA method can envelop the real error bound of the Stewart platform.This indicates that the IA method outperforms the other two methods by providing quick calculations and enveloping the real error bound of the Stewart platform.According to the given structural error of the dimension parameters of the Stewart platform,the IA method gives a maximum position error of 19.91 mm and maximum orientation error of 0.534°,which suggests that the IA method can be used for accuracy design of the Stewart platform in FAST.The IA method presented is a rapid and effective accuracy analysis method for Stewart platform.