Analysis of coupled torsional disturbance behavior of micro-stepped solar array drives

Accurate dynamic models are necessary to determine the effects of vibration on precision based space operations. This study provides mathematical models for kinematics and coupled micro vibrations analysis of a rigid aluminum plate driven with external excitation torque. The excitation is given to the system through a bi-phase micro-stepped solar array drive assembly (SADA). Generalized coordinates and principles of transformations are used to describe the kinematics i.e. the relative position and orientation of assembly. Additionally, the system dynamic characteristics are determined through the Lagrange energy method to research coupled frequency response by observing vibratory behavior of drive and internal system components. Simulations and experimentation, performed on piezoelectric test platform installed with gravity unload mechanism, are used to validate and demonstrate the applicability of mathematical approach. Analysis reveals that when an electric current signal from a drive with n* subdivisions (SDs) excite the system, corresponding electric current pulse excitation harmonics of motor appear along with natural modes of structure that can amplify system response at resonant frequencies. The results and proposed methodologies can be used to design precise spacecraft controllers.