On-machine Measurement and Uncertainty Analysis for Semicircular Narrow Neck Thickness based on Ultra-precision Machine Tool

As flexible joint is a typical low-rigidity micro part, which have four narrow neck structures evenly distributed around its central axis, it is necessary to strictly control the dimensional accuracy of the narrow necks to improve the consistency of stiffness. However, the radius of the arc of the narrow necks is less than 2mm, and the thickness of thinnest part of the necks formed by two adjacent arcs is only tens of microns, which also has sub-micron accuracy requirement. These cross-scale dimensional characteristics and accuracy requirements give rise to extremely difficulty on the measuring process. In this paper, an on-machine measurement method for the semicircular narrow necks was presented and a measuring device was developed based on the comparative principle by making full use of the high linearity characteristic in the small measuring range of the sensor probes. Meanwhile, the on-machine measurement process based on ultra-precision machine tools was also introduced in details. The experiments results show that the uncertainty of the measurement method proposed is less than 0.2µm, and the repeatability is less than 0.1μm, which meet the measuring requirement of flexible joint. Furthermore, the effect of probe position, measurement force, environmental factor and the accuracy of the sensor on total measuring accuracy was analyzed, which could provide further evidences to improve the measuring accuracy. of micro-scale hybrid surface texture.

Two-step blind phase-shifting interferometry based on the extreme value of interference and least-squares iterative algorithm

To improve the measuring accuracy in two-step phase-shifting interferometry (PSI), a new approach combining the extreme value of interference (EVI) and the least-squares iterative algorithm (LSIA) is proposed to extract the phase from two-frame blind phase-shifting interferograms. This method first evaluates the phase shift between two interferograms by the EVI algorithm, and then constructs the fitted interferogram by the addition of two interferograms after filtering the corresponding background intensities, so the phase with high precision can be retrieved by combining two real interferograms and this fitted interferogram using the LSIA method. The proposed algorithm expands the flexibility of the LSIA method and has the high-precision performance compared with the existing algorithms in two-step PSI. Simulation and experiment are performed to verify the feasibility of the proposed algorithm.

Study oil density in flow, system of automated measurement and inaccuracies

The paper reviews the issues of specification of fluid fuel amount with high measuring accuracy transported through oil pipelines. The operation algorithm of vibration-frequency densitometer for automatic measurement of fluid fuel density with high measuring accuracy in technological process in the exploitation conditions is based on the hybrid test method. For this purpose test equations on measuring links using simple additive and multiplicative tests, as well as their combinations have been developed, test equations composed, and as a result of their solution the main test equation obtained. The mathematic-statistic estimation of the results of densitometer measurements correcting test algorithms for the definition of measurement errors and composing inaccuracies, the method of automated calibration are presented as well.