Novel Method of Rocket Nozzle Motion Parameters Non-contact Consistency Measurement Based on Stereo Vision

Abstract This study proposed a consistency measuring method of rocket nozzle motion with improved stereo vision which aiming at rapid and accurate determination of attitude parameters of rocket nozzle in ground test. Firstly, based on the spatial collinearity error equation and the introduction of additional fixed pose constraint relationship between stereo vision measurement cameras, the camera attitude parameters were accurately obtained by using multi-view geometric constraints and bundle adjustment optimization. This step solved the consistency problem caused by separate camera calibration, which can effectively increase the number of excess observations for block adjustment, improve the optimization accuracy, reduce the dimension of the normalized matrix and reduce the time needed for iterative calculation. Then, the transformation relationship between the visual measurement system and the rocket nozzle motion coordinate system was derived by the matching target feature points. The spatial coordinate system is also unified at this step. Finally, the instantaneous axis of the rocket nozzle motion was constructed by cross section method, which was then used to establish the calculating models of nozzle pivot point and swinging angle to realize the measurement of the nozzle motion parameters. The experimental results show that this novel method can effectively improve the measurement accuracy and stability, possessing good application prospect in actual engineering.