An extended Craig-Bampton method for the modal analysis of mechanisms

In this paper, an extended Craig-Bampton method is proposed. Despite the common procedure widely used in structural dynamics to create superelements to be combined by means of joints; here, the joints are included in the reduction procedure. This novelty makes it possible to obtain larger superelements that might be subparts of a mechanism or even the whole mechanism. Starting from the classic Craig-Bampton method, the fixed-interface normal modes and interface constraint modes are redefined including the joints contribution. A new transformation matrix necessary to obtain the reduced stiffness and inertia matrices is presented. Finally, the case study of a deployable mechanism is studied. The results of numerical calculations are compared for validation with ANSYSr results.