Abstract

Output-only modal testing is an attractive new technique with potential applications in civil, mechanical, and aerospace engineering. It may effectively be used for model validation, model updating, quality control, and health monitoring through the determination of modal characteristics of the structures. This approach to modal testing has great potential for ground and on-orbit modal testing of space hardware, especially for flexible structures such as membrane payloads where the operating excitations, such as firing of AC thrusters and ambient thermal shock, are difficult or impossible to measure. The latest versions of output only modal testing technique that considers a noise model to have better estimation of modal parameters from output response time series data is very new and can be very successfully employed to test satellite structures. The main objective of this research is to validate the output-only modal technique approach to extract modal parameters of the appendages with the help of finite element transient analysis and to further verify it through experiments. This research includes a study of the dynamics of satellite appendages and associated excitation method to investigate analytically and experimentally the output-only modal testing approach. Application of the proposed method is investigated and the efficiency over traditional FRF modal testing approach is shown. For identification of modal parameters, satellite solar panel, antennas or other satellite appendages are modeled as linear plate or beam models. It has been proven analytically that the multiple-point excitation is a better loading condition compared with driven base or single point excitation using output-only modal testing technique. It has also been established experimentally that the driven base excitation is better loading condition compared to single point excitation. The effect of using less number of nodal responses instead of using all the nodal response has been investigated. Finally, it has been confirmed both analytically and experimentally that the new versions of output only modal testing approach can be employed to identify the modal parameters of satellite appendages on orbit efficiently.