Abstract: This article presents a dynamic model for a large flexible spacecraft with its end mass undergoing a large angle, high speed maneuvering. With consideration of the secondorder term of the coupling deformation field, a firstorder approximate dynamic model (FADM) of the flexible spacecraft system is developed by using the assumed mode method and the Lagrangian principle. Furthermore, a lower order simplified firstorder approximate dynamic model (SFADM) is derived by deleting the items related to axial deformation. Numerical simulation and theoretical analysis show that: the secondorder term has a significant effect on the dynamic characteristics of the system which can account for the dynamic stiffening of the spacecraft, while the traditional zeroorder approximate dynamic model (ZADM) presents invalid simulation results; the end mass has a “stiffening” effect on the flexible system in FADM, but a “softening” effect in ZADM; the SFADM describes the dynamic behavior well and can be used in controller design.

Key words: flexible structrues, spacecraft, coupling deformation, dynamic stiffening, attached mass, dynamic model