Tadao Kurata

Binarization of scanning Moiré fringe pattern

Abstract This paper describes a digital picture processing method to obtain a binary scanning moire pattern. In this method, a bias component due to the illumination light distribution is eliminated from the scanning moire fringe pattern to detect the zero-crossing points of the moire profile. The binary fringe pattern is then obtained from the zero-crossing points. Experiments indicate that the method is useful for facilitating three-dimensional automatic measurement using moire topography.

Moire deflectometry by the method of fringe scanning interferometry.

A novel high precise quantitative measuring method of the refractive index by appling the fringe scanning and the scanning moire methods to moire deflectometry is described. Since the proposed setup is founded on the shadowgraph apparatus, this system can be manipulated simpler than the interferometer. Then the automatic measurements can be performed by microcomputer. When this method is applied to the measurement of the fast air flow in the Laval nozzle, it is confirmed that close agreement between measured results and theoretical values is obtained. Furthermore the pressure mapping in the nozzle can be measured by assuming the relationship of the adiabatic change. These results show that this method is useful in the fields of flow visualization.

Analysis of moiré fringes produced by centrosymmetric gratings

Abstract A method of describing centrosymmetric gratings (radial, circular and spiral) is presented. The moire-fringe profile produced by centrosymmetric gratings is analysed using polar coordinates. The concept of the angle of intersection for two superimposed gratings is examined and it is shown how from this study moire patterns formed from centrosymmetric gratings can be analysed automatically by digital computer. Examples of theoretically predicted patterns, generated by the proposed procedure, are compared with actual moire-fringe patterns. This method provides for the first time a procedure that can be used in engineering for improving the contrast of moire patterns and for sharpening these patterns.

Optimal servomechanism of an electrohydraulic cylinder system with a bounded control.

In this paper, the problemsd ealing with the designa linear system under an input constraint is investigated. In this optimal system, constructed using the error system theory, the manipulated variable has a velocity deviation, a positional deviation and a steadystate input velocity. It becomes clear that this manipulated variable can be defined as an equation of one optimal feedback gain from the timedomain analysis in a step response. Therefore, the optimal feedback gain can be obtained after consideration of the controller saturation. It is also clear that the parameters of the quadratic performance index decrease from two variables to one variable theoretically by making use of performance criterion ITSE. Therefore, the equation of the optimal feedback gain can be derived from a more simplified equation. This theory is applied to an electrohydraulic servomechanism with a nonsymmetrical cylinder, and the validity of its theory is proven by the carrying out of experiments.