Measuring the errors of form of industrial surfaces: prediction and optimization

To acquire maximum information on the geometrical errors of industrially made surfaces at a minimum cost, a method for estimating conditional probabilities of a random signal (Bayesian prediction) is applied to three-dimensional metrology. First, a surface is interpolated between data acquired on a coordinate measuring machine (CMM). Then, for a given probability, limit surfaces are computed that bind a region of space containing the known data and the most probable interpolation of the missing data of the surface. These bounds can be treated as the surface; their points can be considered as if they were actual CMM data when fitting a tolerance zone or a datum feature to the data. For Bayesian prediction, the basic hypotheses on the signal are stationarity, ergodicity, and gaussian density. Deviations from these hypotheses and their consequences on the prediction are taken into account and corrections are proposed.     

平均声压级近似计算误差分析

本文用凸集理论分析了平均声压级近似计算的误差,导出了最大误差计算公式,指出了测量数据在何种状态下误差达到最大值。     

Theory and characteristics of novel variable reluctance 1X resolver

Although brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current. It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown. It has been confirmed not only by simulation but also experiment that the 2-phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy.     

间断Galerkin方法的最优误差限

本文考虑了数性双曲方程的离散Ｇａｌｅｒｋｉｎ方法。如果精确到光滑的并且同是几乎均匀的，证明了对于分层常数元的最优的和超收敛的误差限。     

锚索测力计有关应用问题的探讨

通过分析锚索测力计因受力状态不同而带来的系统误差,提出了测力计实测锚固力的修正方法及部分测力计传感器失效后延续锚固力测值的计算方法.     

Shorts in self-checking circuits

It has been noted by several authors that the classical stuck-at logical fault model might not be an appropriate representation of certain real failures occurring in integrated circuits. Shorts are an important class of such faults. This article gives a detailed analysis of the effects of shorts in self-checking circuits and proposes techniques for dealing with them. More precisely, we show that, unlike other faults such as stuck-at, stuck-on, and stuck-open—which produce only single errors in the place they occur—shorts can produce double errors on the two shorted lines. In particular, feedback shorts can produce double errors on the two shorted lines. The double error is unidirectional for some feedback shorts and non-unidirectional for some others. Furthermore, in some technologies (e.g., CMOS), non-feedback shorts can also produce double non-unidirectional errors. We also show that unlike stuck-at, stuck-on, and stuck-open faults, redundant shorts can destroy the SFS property. Then we propose several techniques for coping with these problems and we illustrate the results by circuit implementation examples.The present study is given for NMOS and CMOS circuits but we show that it is valid for any other technology.     

机械结构与系统精度通用计算法及其应用——机器人机构误差分析与计算

本文详细论述了机械结构与系统精度的通用计算法,并以 PUMA 型机器人机构和圆柱型空间缩放机构为例,进行了误差分析,建立了相应的误差数模,证明了用精度通用计算法分析机器人机构误差是简单而适用的。     

Bayesian inference in disputed authorship: A case study of cognitive errors and a new system for decision support

Bayesian inference provides a formal framework for assessing the odds of hypotheses in light of evidence. This makes Bayesian inference applicable to a wide range of diagnostic challenges in the field of chance discovery, including the problem of disputed authorship that arises in electronic commerce, counter-terrorism and other forensic applications. For example, when two documents are so similar that one is likely to be a hoax written from the other, the question is: Which document is most likely the source and which document is most likely the hoax? Here I review a Bayesian study of disputed authorship performed by a biblical scholar, and I show that the scholar makes critical errors with respect to several issues, namely: Causal Basis, Likelihood Judgment and Conditional Dependency. The scholar’s errors are important because they have a large effect on his conclusions and because similar errors often occur when people, both experts and novices, are faced with the challenges of Bayesian inference. As a practical solution, I introduce a graphical system designed to help prevent the observed errors. I discuss how this decision support system applies more generally to any problem of Bayesian inference, and how it differs from the graphical models of Bayesian Networks.     

Cubic Bézier approximation of a digitized curve

In this paper we present an efficient technique for piecewise cubic Bézier approximation of digitized curve. An adaptive breakpoint detection method divides a digital curve into a number of segments and each segment is approximated by a cubic Bézier curve so that the approximation error is minimized. Initial approximated Bézier control points for each of the segments are obtained by interpolation technique i.e. by the reverse recursion of De Castaljau's algorithm. Two methods, two-dimensional logarithmic search algorithm (TDLSA) and an evolutionary search algorithm (ESA), are introduced to find the best-fit Bézier control points from the approximate interpolated control points. ESA based refinement is proved to be better experimentally. Experimental results show that Bézier approximation of a digitized curve is much more accurate and uses less number of points compared to other approximation techniques.