Matematični model ocene negotovosti pri merjenju ravnosti : doktorska disertacija

slovenian

doktorska dela

2009

Univerza v Mariboru, Fakulteta za strojništvo

Flatness measurement is a mean for flatness evaluations of measurement plates and other surfaces, which represent a basis for measurements of position and form. Procedures, measurement equipment and methods are well known, and despite all the efforts to simplify the procedures, we face the very same problems as before. Large part of these problems are the impact factors, whichinfluence the measurement. In order to be able to determine the measurement uncertainty, we must be able to evaluate these factors and their effects on the measurement itself. All impact factors are well known, less known is their impact on the measurement, and a resulting decision, which factors are taken into consideration and how, and which can be ignored or evenprevented. Sooner or later we face the deficiencies of existing methods. Usually, flatness measurements are performed using a Union Jack method, which brings a lot of advantages, together with some disadvantages. The main disadvantage of this method is only average coverage of the surface we measure. A coarser grid does improve the duration of the measurement, but as the grid gets coarser, the coverage factor gets smaller. With that, it is possible to neglect some of possible surface defects, which affect both the result and uncertainty. It seems as a denser grid would be needed for finer defects on the surface, and a coarser grid would be sufficient for larger irregularities. If the coverage of the surface is based on the density of thegrid, and the grid density could be determined based on the shape of the surface, we must ask ourselves the following question - what is the relation between the shape of the surface and the measurement uncertainty? Would it be possible and would it make any sense to define suitable measurement grids according to the type of the surface? To answer all these challenges, a MonteCarlo method comes of use. A measurement model serves as a basis for the algorithm, which is used to determine the measurement uncertainty over a series of simulations. Results for different types of measurement grid, adapted to the shape of the surface, are astonishing.

08.08.2023