Abstract: How to keep and fasten reliably the adjusted posture of large components such as airplane bodies is a key issue in the application of posture adjustment and fixture. Based on the principle of aerostatic bearing and universal ball joints, a new posture following fixture method for large components is presented in this article. This method can be described as follows: first, insert the mandrel rigidly jointed with the large component into a sphere body which can rotate freely between the up-semi-ball-seat and down-semi-ball-seat; then, the mandrel pushes the sphere body to make it rotate between the up-semi-ball-seat and down-semi-ball-seat and translate with them. After the mandrel reaches the target location the hydraulic devices lock the up-semi-ball-seat, down-semi-ball-seat, the mandrel and the sphere body in order to keep and fasten reliably the mandrel without any posture change of large components. By unlocking the mandrel, up-semi-ball-seat, down-semi-ball-seat and the sphere body the adjustable posture of the large component may be resumed. The experimental and analytical results show that the new posture following and keeping fixture can meet the requirements of aircraft assembly and finish machining.

Key words: aircraft, assembly, finishing, posture adjustment, fixture, universal ball joint