Development of a simple three-dimensional machine-vision measurement system for in-process mechanical parts

A machine-vision method was used to build a three-dimensional measurement system using a measurement algorithm and a perspective transformation. The image data from a double complementary metal oxide semiconductor were transmitted to a notebook personal computer to calculate the parameters. A three-dimensional measurement system for obtaining its feature points in the world coordinate system was used to calculate the measurement data. The experimental results were verified with a more precise measurement equipment, automatic transformer observation system. The three-dimensional measurement system introduced here was applied to two case studies. The first case considered the measurement of hole diameters, such as those found in the cylinder head of an internal combustion engine. By summarizing various experimental results based on studies of three kinds of hole designs, the maximum error was 0.373mm and the minimum error was 0.053mm, which is within the general range of manufacturing tolerances (+/- 0.5mm) used in engineering schematics. The second case examined the measurement of certain key dimensions of an aggregate truck bed, and the results showed that the measured difference between the three-dimensional method and automatic transformer observation system is less than 1.2%. The proposed three-dimensional measurement system is inexpensive, offers an easy set up, and provides a certain amount of accuracy and stability.