Development of mechatronic means for raster and coded scales measurement

Abstract

Mechatronic constituent parts of the comparator for angular accuracy control are discussed in the presentation. Measurement of circular raster and coded scales has some specific features and some requirements are given to the equipment for angular position measurement. It is a photoelectric reading devices and instruments for centering and leveling the surface of the turn table with the circular scale fixed on it. Further the very measuring process is to be performed comparing the position of the scale's strokes against the ones generated from the reference measure - angle standard. For the use in this comparator a digital camera is applied. The amount of information given by modern cameras allows to perform an in - depth analysis of digital images of the objects observed, as well as images of circular scales used in angular encoders. The camera usage is for signal generation from the strokes of the raster or coded scale and here the signal is applied for initial circular scale adjustment on the table of the angle comparator. The capture event of the circular scale image and image processing procedure are performed by the host computer. The software performs setting of all required camera properties before starting the capture event. The settings include n number setting, object's setting, color compensation, exposure duration and digital image format. Further signal processing and its output into the PC is used for the scale's stroke's position determination against the signal from the reference angle standard. The result of measurement is determined as phase shift between the two signals transferred into the angular values. Some theoretical dependencies, graphs and diagrams and technical and metrological specifications together with some experimental results are presented as well.