Abstract: The measurement of shaft hole diameter is a key technology in the engine box tests, and it is also a necessary mean to enhance the quality of engine production. In order to improve the shaft hole diameter online measurement level, while overcoming the limitations of existing methods, it propose a new type of optical multi-directional shaft hole diameter measurement method. Drawing on the layout of the pneumatic measuring instrument, the method uniformly distributes the laser displacement sensors in the probe cross-section, and in accordance with the structural characteristics of the engine box, matches the probe length and measuring cross-section layers. To evaluate the influence of assembly error and random errors to the measurement accuracy, genetic algorithms is used to analysis of the internal diameter measurement mathematical model to find the key factors affecting the final measurement error which is a basis for guiding measurement. It is compared that the measurement values and test values of the shaft hole diameters at different positions in the hole by combining with the calibration process, and it is proved that the measurement error of this method is better than 5 μm. The result verifies that this method can be used to achieve precision automated online measurement of the shaft hole diameter.

Key words: Calibration, Genetic algorithms, Online inner diameter measurement, Optical multi-direction