To assess if a given manufactured artifact conform to a template CAD model, the artifact is measured by a coordinate measuring system to obtain a point cloud. The point cloud is compared to the CAD model by fitting the point cloud to the CAD model. One of approaches is based on a method required to determine footpoint parameters. The footpoints are the projection of the points in the point cloud onto the CAD surface. In this paper we introduce a new efficient method for estimating footpoint parameters.
The form qualities of precision components are essential for their functionalities. The Peak-to-Valley parameters are widely adopted to assess the form accuracy of optical components. The commonly used least squares method is prone to over-estimation, thus the Chebyshev fitting should in turn be implemented. In this paper the original minimax optimization problem is converted into an unconstrained differentiable minimization problem by exponential penalty functions. The fitting accuracy and numerical stability are balanced by employing an active-set strategy and adjusting the configuration...
In the majority of cases coordinate measurements of free-form surfaces are carried out along a regular u„ev grid. The local geometric deviation, i.e. the distance of a particular measurement point from the CAD model of the nominal surface, is established for each point. The measurement aims at evaluating the form deviation and thus the greatest deviation of the actual surface from the CAD model. Obtaining data of a discrete character is inseparably connected with losing information on the surface properties. The present paper proposes an approach to estimating form deviation of free-form...
This paper describes an approach to generating reference data sets to evaluate the performance of algorithms used in coordinate metrology for form and geometric tolerance assessment. The approach starts with the reference results, e.g., the solution feature parameter values, and then determines the coordinate data. In this way, the expensive development of reference software is avoided. In this paper we consider the generation of reference data associated with determining the best-fit surface according to the least squares (Gaussian) and Chebyshev criteria.
The paper presents the implementation of analog data acquisition system, in particular controlling with a 6- channel ADC converter AD7656 via the FPGA Xilinx Spartan 3 series. The procedures for data sending from the ADC to the FPGA buffers, their conversion and subsequent transmission to TigerSHARC DSP are described. The digital representations of ADC analog input signals are sent to the FPGA through three lines of serial interface at the physical layer compatible with standard SPI. After processing in the FPGA they are sent to the DSP, with the participation of the lines in standard LVDS....
The rotating coil technique is extensively used in high-precision measurements for accelerator magnet testing. One of most relevant error sources is the drift arising from the integrator offset. In this paper, a correction algorithm for the offset drift in digital integrators is presented. Preliminary experimental results for the measurement correction of the main field of a superconducting dipole magnet of the Large Hadron Collider at CERN show the effectiveness for fast rotating coil measurements.
Optical chemical sensors usually utilize immobilized reagents in a solid matrix usually in the form of a monolith or a thin film. The reagents immobilized into the sensor are responsible for the extraction of the analyte into the sensing material and generating an optical signal proportional to the change in the concentration of the analyte. In the work presented here we propose to use transparent polymethacrylate matrix (PMM) for physical immobilization of analytical reagents. The using of PMM allowed us to combine the capability of the solid phase to immobilize reagents without losing the...
A bilateral comparison between the National Metrology Institute (NMI) from Brazil (INMETRO) and Russia (UNIIM) for determining the amount content of potassium dichromate to assess the comparability of their measurements were performed. Samples of high purity potassium dichromate were exchanged and analysed by the INMs. The technique used was constant-current coulometry. Good comparability for one of the samples was obtained. After bias corrections in their measurements, both INMs will be able to certify reference materials of potassium dichromate that can be used for guaranteeing the quality...
This paper describes a method for the determination of hydrogen chloride gas in ambient air. The method involves analyte gas sampling in aqueous solution by using diffusion scrubber coupled ion chromatography with suppressed conductivity detection for subsequent ion analysis. Method detection limit is less than 0.05ppbv. Semi-automated a half hourly measurement results for Seoul air are presented.