Corrective adjustment for reconfigurable assembly fixtures based on geometric constraints

Reconfigurable assembly fixtures are prone to experience instability caused by a decline in positioning ac⁃ curacy after prolonged use,which subsequently affects the quality of product assembly. Therefore,it is necessary to conduct effective monitoring on the positioning accuracy of such fixtures. The traditional periodic manual inspection method suffers from several limitations,including the inability to acquire real-time data on fixture usage status,difficulty in accurately evaluating fixture positioning accuracy,and the lack of systematic and effective methods for corrective ad⁃ justment. Geometric constraints,which define the specific geometric relationships among the key points of the fixture, serve as the intrinsic basis for accurate product positioning,and are the core foundation for ensuring positioning accu⁃ racy. To solve the above problems,this study proposes and develops a reconfigurable assembly fixture corrective ad⁃ justment method based on geometric constraints. The method comprises three components:positioning accuracy evaluation of the fixture based on geometric constraints,calculation of point adjustment quantities,and feasibility as⁃ sessment of locator adjustability using the Jacobian-Torsor model. First,the geometric constraint sets required to en⁃ sure compliant positioning accuracy of the fixture are analyzed,based on which the positioning accuracy of the fixture is evaluated. Then,for fixtures with out-of-tolerance positioning accuracy,the point adjustment quantities are calcu⁃ lated,and the target positions for point adjustment are determined. Finally,a Jacobian-Torsor model is constructed to characterize the assembly deviations of the locator and assess the adjustability of the locator,thereby assisting work⁃ ers in completing the corrective adjustment of the fixture. A reconfigurable assembly fixture for aircraft panels is used as a case study for verification. The results demonstrate that the proposed method can accurately evaluate the posi⁃ tioning accuracy of the fixture,effectively repair fixtures with excessive positioning deviation,and improve the fixture repair efficiency,thereby verifying the feasibility and effectiveness of the method.