A coordination technique of precision holes in large truss structure

The engine frame of a launch vehicle is a large-diameter truss structure, which has the characteristics of weak stiffness and large welding deformation. As a transitional structure of connecting the engine and the rocket body to transmit thrust, its connecting hole on the upper and lower ends face has the coordination requirements of high precision and consistency. Aiming at this problem, a precision hole coordination scheme is proposed, which uses pre fitting and quadratic fitting method to coordinate the envelope problem of bottom hole, uses pin hole positioning to coordinate the secondary benchmark, and realizes the overall coordination of precision holes. At the same time, a prediction model of position degree based on BP neural network is proposed to predict the position degree of butt hole after machining.Through the actual processing verification, this method can realize the overall coordination of the 5-meter truss structure docking hole, and ensure the high precision requirements of the docking hole. Moreover, the algorithm can effectively predict and verify the test results of position degree, improve the inspection reliability, and provide a way of thinking for the overall coordination of aerospace large-scale product processing.