Effect of drive mechanisms on dynamic characteristics of spacecraft tracking-drive flexible systems

Spacecraft tracking-drive flexible systems (STFS) consist of drive mechanisms and flexible structures, including solar array and a variety of large-scale antennas. The electromechanical interaction inside drive mechanisms makes it quite complicated to directly analyze the dynamic characteristics of an STFS. In this paper, an indirect dynamic characteristic analysis method for operating-state STFS is presented. The proposed method utilizes the structure dynamics approximation of drive mechanisms that converts the electromechanical model of an STFS into a structure dynamic model with elastic boundary conditions. The structure dynamics approximation and the dynamic characteristic analysis method are validated by experimental and analytical results, respectively. The analysis results indicate that the gear transmission ratio and viscous friction coefficient are the primary factors in approximating boundary stiffness and damping. Dynamic characteristics of an STFS with a large gear transmission ratio are close to that of a flexible structure with a cantilever boundary. Otherwise, torsion-mode natural frequencies of the STFS become smaller and corresponding modal damping ratios become larger, as a result of the local stiffness and damping features of drive mechanisms.