Optimal assembly of a skin panel onto the fuselage framework based on force control technology

Abstract

It is important for fuselage assembly to align the skin panel onto the frame, i.e. to reduce the gaps and subsequently lessen the need for shimming, but conventional position control method cannot always meet the requirement. This study proposed a direct force control technology, which can be directly promoted to a full-rate production without making any dedicated assistance and complex finite element analysis. This strategy was based on a force sensor mounted on a flexible tooling locator to feed back the pressing force information to the controller system. To achieve a certain compressing status, the system was controlled to achieve a desired force rather than reach a specific position. After obtaining four ideal force values from an experimental study during a prototype trial-production, a force-size interval that provides a certain grey degree of confidence was proposed for the flexible tooling control system using a parameter estimation approach for small samples based on the grey distance measure. Compared with conventional position control method, force control technology can achieve better compressing status, since it enables a reduction of all gap values between the skin panel and the framework by 0.15 mm on average or even 0.2 mm at most in the same assembly process.