Research On The Theory And Application Of Identifying Surface Wave Characteristics On Mechanical Parts

The size of form and position error reflects the accuracy of form andposition of mechanical part. Form and position error is an important technicalindicator to ensure achieving interchangeable. Therefore, how to get accuratemeasurement result is always the focus of the study in this field. Themeasurement of form and position error mainly includes extraction, filtering,fitting, error evaluation and other links. As the first step of measurement,extraction has great influences on the accuracy of measurement result and theefficiency of the measurement. So far, they all have not established anextraction criterion of form and position error no matter in academia or inengineering field. It’s significant to do research in this field.Extraction is an operation that collects discrete points from the geometricelements (the continuous signal) of measured object and requires this discretesignal can accurately reflect the information of form and position error afterbeing sampled. Therefore, the reasonable extraction can get an accuratemeasurement result and have higher efficiency of the measurement. It is apremise that grasping the characteristics of the continuous signal for obtainingextraction criterion which satisfies the above requirements. The characteristicsof the continuous signal include the composition of the signal, the signalspectrum and error statistical characteristics, etc. This article studied theproblem about the determination of extraction criterion from the angle ofidentifying surface wave characteristics on the surface of mechanical parts.Geometric shapes from any mechanical parts can be broken down into linecombination of simple geometric element. For example, the plane can bedecomposed into the combination of straight lines which belong to geometricelement and are orthogonal to each other; the cylindrical surface can bedecomposed into the combination of straight line and circle line. The two linesalso belong to geometric element. Therefore, the identification of wave signalscharacteristics on mechanical parts surface can be divided into identifying thecharacteristics of line which belongs to geometric element. The dissertationregarded the geometric elements line of straightness error as the basic researchobject and its harmonic characteristic and error statistical characteristics are analyzed. The straight line of straightness is not a periodic signal, but it can bethe generalized periodic signal by using the periodic extension. Then thespectrum diagram was investigated by means of the Fourier series expansion.The figure showed that the highest harmonic components can not be found andNy-quist sampling theorem is not suitable for deciding extraction points;Using statistic histogram and hypothesis test to study the error statisticalcharacteristics. The result shows that every error single is composed ofdeterministic error and random error. Different proportions of the two partsleads to the different normality test of any error signal. Based on the aboveunderstanding, the research put forward the concept of best extraction pointwhich satisfies the requirement of measuring accuracy and measuringefficiency. This method of error separation technique was proposed. Thedeterministic error and the random error were obtained after error separation.Getting the best extraction pointn1of the former after harmonic analysis andgettingn2of the latter by using computer simulation. It is absolutely thatnis much bigger thann1, so a conclusion can be made that normal distributionmodel can be used to study the problem about extraction points of straightnesserror in the computer simulation and deterministic error can be ignored. Atlast, the paper promoted the application of the conclusion to get the optimumextraction points in all sizes and all accuracy for straightness measurement.This study has an important reference value for deciding extraction of formand position error. The conclusion is an important supplement to the problemabout extracting points in the new generation of GPS.