一种大型桁架式结构精密孔协调技术

某型运载火箭发动机机架为大直径桁架式结构,具有刚度弱、焊接变形大的特点。作为连接发动机和箭体传递推力的过渡结构,其上下端面对接孔具有高精度、一致性的协调要求。针对此,提出了一种精密孔协调方案,其利用预拟合和二次拟合法协调底孔包络,采用销孔定位协调二次基准,实现精密孔的整体协调;同时,提出了基于BP神经网络的同轴度预测模型以预测加工后对接孔位置度。经过实际加工验证,该方法能够实现5 m级桁架式结构对接孔的整体协调,保证了对接孔的高精度要求,且该算法能够有效预测并辅助验证位置度检验结果,提高了检验可靠性,为航天大型产品加工整体协调提供了一种思路。

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.