Research On Ultra-precision Measurement And Calibration Method Based On The Error Separation Technique

With the development of new materials and ultra-precision machining technology, the size ofthe tested object is turn larger and larger, machining accuracy and surface quality is turn higherand higher. common measuring instruments can not provide hard benchmarks accuracy exceedingthe ultra-precision machining accuracy. Measurement and detect are more difficult than machining.In this background, error separation technology, which is a kind of measurement technique of avirtual soft benchmark accuracy higher than the hard baseline accuracy by application of aparticular measurement system and the appropriate combination of software to separate the errorinherent in the hard benchmark, has produced.Ultra-precision shape (error) measurements of the application of error separation technologymake the measurement accuracy achieve the current limit of achievable accuracy. To the NationalInstitute of Standards and Measurement and Testing Technology Research Institute, this is theessential technology to provide the highest standards of measurement. Secondly, the numericalcompensation of machine tools and other processing machinery is another major purpose of theshape of the mechanical movement of the measurement. High reliability, quick and simplecalibration method is essential. Finally, the shape of the application of error separation techniquescan to invest lower hardware to achieve the required measurement accuracy, in line with goals toestablish saving society. Therefore, as the core and foundation of the methodology, theoreticalstudy of the error separation techniques in ultra-precision measurement method is the keytechnology of modern processing and measurement techniques indispensable. The methods ofmeasurement and calibration for the application of this technology also have broad marketprospects.Supported by the Nature Science Fund of China (NSFC)(Project Number:50905116), theCooperation Project of University-enterprise (Contract No. H3007144) under the ultra-precisionmachining and measurement applications environment, combined with the project for the needs ofthe elevator car guide rail detection, ultra-precision measurement error separation techniques arestudied systematically. Theoretical research on the ultra-precise two-dimensional platformpositioning error self-calibration methods are conducted and optimized. The measuring device ofthe elevator car guide rail straightness has been developed.The main content and contributions of this thesis are summarized as follows:Firstly, the background, purpose and importance are introduced based on collecting and mastering a large amount of documents and references on error separation technology. Theimportance of research on ultra-precision measurement based on error separation techniques ispointed out. The research status and existing problems of error separation techniques, such asmultistep method, self-calibration method and multiple probe method are analyzed. The mainresearch content is based on this analysis.Secondly, the systematic research on self-calibration method based on linear equations isdone. From the proposing of error self-calibration algorithm for2D workbench location, expandsto3D space precision self-calibration method is deduced, self-calibration method from2D to3D ispreliminarily systematized. Compared with the existing self-calibration method based on Fouriertransform, the self-calibration method based on linear equations has advantages of convenientdeduction of theoretical error propagation rate, good capability of noise elimination and realizationof self-calibration for combination with more than3orientations.The achievements gained in the research of self-calibration method are summarized as below:1)2D self-calibration algorithm based on linear equations is proposed; error propagation rate thattransmitted to reconfiguration result by measured noise is deduced. Theory indicates that theuncertainty value of reconfiguration result for this algorithm is smaller than the standard deviationof measured noise.2)The realization of error free reconfiguration without considering measurednoise by simulation experiments for combination with less than5orientations; while consideringmeasured noise is confirmed, the reconfiguration error is in the statistic confidence interval.3)3Dspace precision self-calibration algorithm based on linear equations is proposed, the errorpropagation rate is deduced and simulation experiment is proceed; the theoretical character andsimulation result same with2D case stated before is found.4) Preliminary self-calibrationexperiment for shot error with visual image instrument is proved to be rational and also theeffectiveness of the proposed self-calibration algorithm is confirmed.Thirdly, focused on the measuring problem for ultra-precise long feet products, deeplyresearched the two sets of2-point with changing distance measuring method. From the existingtwo sets of2-point method that based on Fourier transform, the thesis deduces the calculationcondition and expands the parameters choosing area successfully. In this way, application for thismethod became easier. Also, influence to system brought by zero point error is deducedquantificationally. Then optimization of two sets of2-point method is proposed to eliminate theinfluence of zero point error in the situation completely without considering influence ofmeasurement noise. While considering measurement noise, the optimal estimation solution isdeduced to minimize the influence brought by zero point error. And by Monte Carlo Method, theuncertainty of this method is calculated. At the same time, multiple probe method based on linearequations was applied to the two sets of2-point method, and the method based on linear equationswas formed. Two sets of2-point method based on Fourier transform and linear equations arecompared. Finally experiment research is completed. The achievements gained from research of two sets of2-point method are listed as:1) Fromthe existing two sets of2-point method with changing distance that based on Fourier transform,the thesis deduced the calculation condition. The new condition avoids the situation in which theseparation distance between probes, in order to expand the real choosing interval of probeseparation.2) Influence to system brought by zero point error is deduced quantificationally. Thenoptimization of two sets of2-point method is proposed to completely eliminate the influence ofzero point error in the situation without considering influence of measurement noise. Theoretically,the precision of this solution not only depends on the volume of the measurement noise but alsohas no relation with zero point error.3) By Monte Carlo method, the uncertainty of this method iscalculated. The result, that the uncertainty of mid range on the measurement shape had the sameorder of magnitude with measurement noise, is proved.4) Two sets of2-point method which isbased on linear equations is deduced, linear equation system modeling and calculated theuncertainty of this algorithm has been finished. Without considering influence of measurementnoise, influence brought by zero point error can be eliminated to avoid influence to reconstruction.While considering the influence brought by measurement noise, the theoretical precision of thebest least square solution depends not only on the noise volume but not the zero point error.5) Acomprehensive comparison is made for two sets of2-point algorithm based on Fourier transformand linear equations respectively.6) It’s shown that, the algorithm based on linear equations isbetter than the algorithm based on Fourier transform only except for lower computing speed andlager memory.Fourthly, aiming at the measuring problems of longer guide rail straightness, further researchon compounded multiple probe method which was based on combination of reversal and multipleprobe method is proposed. In this thesis, based on the measuring principle of reversal6-probemeasuring method proposed by GAO, a reversal4probe measuring method is proposed whichcould also realize straightness reconstruction but using less probes. By modeling a3m longverification system, the sensor data collecting program which could run without PC is designed.Also, the practical program used for dealing with continuous scanning data and unusual data iscompiled. It is proved by experiment that the repeatability of reconstruction result was below30μm when reversal4-probe method and reversal6-probe method are applied under differentsituation of scanning speed and sampling interval. While using laser tracker to measure the sameguide rail, the difference of result was below50μm compared with reversal4-probe measurementmethod, which is also a credible proof of effectiveness of reversal4-probe measurement method.At the end of the thesis, the research achievements and the work were summarized, and thefollowing research is proposed. In the diversified shape measuring field of precise measuring,error separation technology plays an important role as the core and fundamental technology. Errorseparation technology will have more and more practical usage as the ultra-precision measuringneed grows.