Simulation Methodologies for Satellite Solar Array Dynamics



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The purpose of the present thesis is to furnish diverse studies on the dynamic response of satellite solar arrays. The term flexible structure or, briefly, structure has different interpretations and definitions, depending on source and on application. The solar array studied in the present thesis has flexible sub-structures and undergoes large deformations. Structural dynamics is an important basis of many engineering studies associated with engineering structures, such as design, construction, and control. It generally consists of two functions, i.e. free vibration analysis (modal analysis) and response analysis (steady-state and transient analysis). The thesis starts with introducing the solar array considered for our study and then continues with several structural analyses, including nonlinear pre-stressed static analysis, pre-stressed modal analysis, nonlinear full transient analysis and Fast Fourier Transform study on the transient response. The purpose of static analysis is to obtain the configuration of the array under implementing static loads. Modal analysis provides the natural frequencies and mode shapes which are the intrinsic dynamic properties of the structure. Transient analysis is used for evaluating the mechanical behavior of the structure. It gives relations between the intrinsic properties of structure and the external excitations. Transient analysis under different types of inputs will be used to track physical quantities like displacement, rotation, stress, and strain during specific satellite maneuvers. Pointing error will be introduced as a measure of accuracy of Sun tracking maneuver. It will be computed as a postprocessing step on the transient displacement results. To improve the pointing error which will consequently result in higher energy generating performance, two other staggering type input profiles are proposed for each orbit, GEO and LEO. Pointing error and vibration response under the proposed inputs are obtained to determine the efficiency of the new inputs. After a comparison, it will be shown that the proposed inputs are more efficient in the Sun tracking solar array maneuver. At the end, a novel approach in performing mode-superposition transient analysis using modal effective mass tables is introduced. Since it is very common among engineers to assume the first 10 percent or 20 percent of the mode shapes when mode-superposition method is preferred to obtain the transient response, this novel approach shows that even smaller numbers of mode shapes can be assumed to perform this type of analysis and still obtain acceptable results, only if the assumed modes contain the majority of the modal effective mass in a specific direction, depending on the loading condition.