河流水质模型的逼近方法及误差分析

提出一种平稳河流水质模型简化方法.通过分析存在弥散和忽略弥散作用两种情况下的Streeter-Phelps模型的解,给出了忽略弥散作用的条件和最大误差分析,进而给出多河段模型的一般表达式.数值计算和实际验证结果表明,该方法可给出工程满意的结果.     

传感器实时动态补偿方法与误差分析

为了改善传感器动态特性,用零极点相消的补偿原理拓宽传感器系统的工作频带.研究了极点建模误差对传感器补偿效果的影响.分析一阶系统、二阶系统的极点建模误差与工作频带拓宽之间的关系,给出相应的关系图.得出结论:一阶系统,补偿效果只与建模误差有关,补偿效果较明显;二阶系统,补偿效果由误差与阻尼比决定,阻尼比越大,要求其极点实部精度越高,而其虚部精度要求越小,且阻尼比小于0.1时,其实部误差可以忽略不计,仿真结果与理论一致.定量分析补偿后噪声的放大程度与工作频带拓宽之间的关系,为实时补偿提供依据.并在数字信号处理器(DSP)中实现实时补偿系统,实时观察输出结果,验证了该系统的稳定性和可行性.     

An error estimation method in finite element structural analysis

In the paper a new interpretation of the finite element approach is described and illustrated numerically. The conventional shape functions of the displacement—and stress—type finite element models are treated as constraints imposed on the continuous medium considered. This enables a consistent error estimation analysis based on a concept of so-called reaction forces and deformation incompatibilities.     

基于一种简化Allan方差法的IMU误差分析

为了分析惯性测量单元(IMU)的随机误差项系数,采用了Allan方差分析方法,同时,针对大数据量情况,为了减小计算量并保持Allan方差分析的准确性,结合双对数曲线特点,给出了一种简化的Allan方差算法,并使用该算法对一种微机械(MEMS)惯性测量单元的长时间静态数据进行了分析.结果表明:该方法可以有效地辨识出IMU各误差项系数.     

基于CRC机制的信号回流检测方法与误码分析

针对实验过程中出现的CRC误码,主要利用信号回流检测方法对原理图进行分析和改进,增加了上拉电容以缩短回流路径使其到地,减少了彼此间的干扰,从而解决CRC误码。实验结果表明,在单板的宽广处多放一些小电容到地,能给信号增加一个较好的回流路径,对于稳定电源去除噪声十分有益。     

An error analysis for the finite element method applied to convection diffusion problems

This paper analyzes the finite element method applied to a convection diffusion model problem. Linear elements are used for the trial space. The error is measured in a norm closely related to the L_p norm. When the test space is composed of linear elements with parabolic upwinding, the method is shown to be optimal when the input data is piecewise smooth—a condition which is usually observed in practice. Without these smoothness assumptions, the method is shown to be non-optimal, even if the class of test spaces is extended to include any elements which have a shape independent of the mesh size.     

小波分析法在光纤陀螺随机误差补偿中的应用

光纤陀螺随机漂移是惯性导航系统产生误差的重要因素。尽量降低陀螺仪的漂移率是进一步提高惯性导航系统精度的重要途径,也是保证光纤陀螺静态误差补偿精度的前提。从抑制光纤陀螺随机噪声的角度出发,利用小波分析法对光纤陀螺的静态输出进行滤波处理,通过对比滤波前后陀螺的输出曲线、标准差以及各项随机误差系数,能够看出:该方法有效地补偿了光纤陀螺的随机误差。     

Some properties of the output error method

The output error identification method is studied in various respects. The stationary points of the associated loss function are investigated. Sufficient conditions for a unique local minimum are given. The loss functions can be minimized using a quasilinearization algorithm. Such an algorithm will give good local convergence. It is, however, shown that global convergence does not always occur. The output error method is also compared with some other estimation methods from the accuracy point of view. It is proved that a prediction error method will give better accuracy. An instrumental variable technique may give better or worse accuracy depending on the actual noise correlation.     

Efficient error estimation and adaptive meshing method for boundary element analysis

This paper describes a new and efficient error estimator by using the Direct Regular Method and h or h-r adaptive meshing for BEM analysis. This posteriori error estimator correctly indicates the discretization errors on each element. Based on the error distribution, and the adaptive meshing is generated automatically. The accuracy and convergence of this method are demonstrated by the numerical results on the stress concentration problem and the crack problem.     

A posteriori error analysis for a cut cell finite volume method

We study the solution of a diffusive process in a domain where the diffusion coefficient changes discontinuously across a curved interface. We consider discretizations that use regularly-shaped meshes, so that the interface “cuts” through the cells (elements or volumes) without respecting the regular geometry of the mesh. Consequently, the discontinuity in the diffusion coefficients has a strong impact on the accuracy and convergence of the numerical method. This motivates the derivation of computational error estimates that yield accurate estimates for specified quantities of interest. For this purpose, we adapt the well-known adjoint based a posteriori error analysis technique used for finite element methods. In order to employ this method, we describe a systematic approach to discretizing a cut-cell problem that handles complex geometry in the interface in a natural fashion yet reduces to the well-known Ghost Fluid Method in simple cases. We test the accuracy of the estimates in a series of examples.     

Analytical estimation of error in flank milling of ruled surfaces

This article introduces a method to estimate geometric error during flank milling of a ruled surface. The various positioning schemes developed by researchers are intended to reduce this geometric error in order to mill with larger sized milling cutters while respecting the tolerance interval. There are two trends in positioning: either positioning is simple and right from the start it is easy to determine design of the maximum allowed milling cutter radius, or positioning is complex and determination of the maximum milling cutter dimensions can only be conducted after digital calculations of the error. It will then be necessary to choose another milling cutter radius and recommence the positioning procedure and error calculation in order to validate the tool. In the present study, a method to estimate error in the scope of complex positioning is presented. The aim is to be capable of choosing a maximum cutting tool radius that respects the tolerance interval.     

超声波流量测量的误差分析与补偿方法研究

为了提高超声波流量测量的精度,分析了影响测量精度的因素,对温度、流速和管道内置反射片所造成的测量误差进行了分析,提出了具体的误差修正补偿方法。实验表明：对上述影响因素产生的误差进行补偿与修正后,能够有效减小测量误差,提高测量精度。     

Worst-case error analysis of the aggregation method,with application to the selection of reduced-order models

A new type of error analysis is obtained for a special case of the aggregation method. A worst-case error is constructed for aggregation models approximating a given linear time-invariant completely-controllable completely-observable system. This worst-case error is then used to select ‘good’ models of a given order. An automatic procedure is suggested for obtaining the worst-case error bound for all possible models of a given order. The methods are tested on four example problems.     

An error analysis of the aggregation method,with application to the selection of reduced-order models

An error analysis is made for the aggregation method of model reduction. A heuristic technique, based on the error analysis, is introduced whereby dominant eigenvalues to be retained in a reduced-order model are selected. The error analysis and the selection procedure are numerically tested on two example problems.     

自整角机工艺误差的修正方法

在系统阐述自整角机工作原理的基础上 ,详细论述了在航空炮塔随动系统中 ,如何利用现有的自整角机来减小随动系统的误差以及消除假协调 ,从而使随动系统满足技战术指标。     

An error analysis and mesh adaptation method for shape design of structural components

A finite element error analysis and mesh adaptation method that can be used for improving analysis accuracy in carrying out shape design of structural components is presented in this paper. The simple error estimator developed by Zienkiewicz is adopted in this study for finite element error analysis, using only post-processing finite element data. The mesh adaptation algorithm implemented in ANSYS is investigated and the difficulties found are discussed. An improved algorithm that utilizes ANSYS POST1 capabilities is proposed and found to be more efficient than the ANSYS algorithm. An example is given to show the efficiency. An interactive mesh adaptation method that utilizes PATRAN meshing and result-displaying capabilities is proposed. This proposed method displays error distribution and stress contour of analysis results using color plots, to help the designer in identifying the critical regions for mesh refinement. Also, it provides guidance for mesh refinement by computing and displaying the desired element size information, based on error estimate and a mesh refinement criterion defined by the designer. This method is more efficient and effective than the semi-automatic algorithm implemented in ANSYS, and is suitable for structural shape design. This method can be applied not only to set-up a finite element mesh of the structure at initial design but to ensure analysis accuracy in the design process. Examples are given to demonstrate feasibility of the proposed method.