Positioning error guarantee method with two-stage compensation strategy for aircraft flexible assembly tooling

Abstract

Flexible assembly tooling is an important manufacturing equipment for aircraft products, the positioning error of its end locating effectors determines the final assembly precision directly. To realize its accurate positioning, a precise and effective error compensation method based on two-stage strategy, is proposed. Based on the structure and working conditions of locating unit, an assembly measuring field is set up, for acquiring the actual geometric error status and the various time-varying assembly parameters in practical assembly site. Considering the transfer and accumulation of actual geometric error and deformation error, the positioning error mechanism model at the pre-compensation stage is proposed. Then with the actual assembly conditions and the measured training/testing data set of the positioning error, the SLFN motion prediction model for the locating unit is proposed, aiming at clarifying the nonlinear and strong coupling relationship between the input motion value and the output positioning error. And the SLFN data model has a good fitting and prediction ability. Combining the advantages of error mechanism modeling and measurement data modeling, a semi-mechanism model is proposed at the accurate compensation stage. Where the positioning error is predicted with SLFN model for a given input motion value, acting as an error generator. Experiment results showed that the final measured average error is 0.036 mm, having an enhancement ratio of 25.77 % contrasting with the error mechanism model. This accurate modification and compensation solution makes the relationship between causal factors and output positioning error more comprehensive, and the overall effect is more consistent with the practical situation, i.e. a higher precision value and an accurate input/output relationship can be gained.