Measurement principle and precision analysis of chamber parameters on images

A new kind of measuring principle of reading data across the diameter of a target image is proposed for high-accuracy measurements of artillery-chamber parameters. A new kind of ruler target mechanism is designed to read the cross-diameter data. The ruler target mechanism is pushed into the chamber by a driver mechanism. It moves along the axis of the chamber, and the sequence images are collected. The radial displacement of the cross-measurement claw can be obtained by processing the change of inscribed lines on the ruler target, and the current diameter, volume and conical degree of the chamber can all be acquired by referring to the demarcating annulus size. Measurement precision is analysed based on error propagation theory, with the diameter and volume parameters as examples. According to this principle, the measurement prototype is designed, and experiments are conducted on it. We show that the measurement error of the diameter is no more than 10 µm, and the volume error of the artillery chamber is less than 2‰, which satisfies the practical engineering requirement.