Modal Assignment Effects on Decentralized Control of a Large Space Structure

摘要

The more modes a designer can keep in the model of the sytem/space structure, the less inaccurate it will be. But the computational burden to an online computer, functioning as the controller, grows also. The thrust of this thesis is to implement time response output for the nontrivial model and investigate the effect on time response of certain modal assignments by fixed groups to any of the three controllers with another fixed group assigned as residuals. The inclusion of residuals provides in a limited sense a truth model for the analysis of stability and performance. There may be significant differences in time response caused by the fact that a controller is known to provide more relative controllability and less observability, or vice versa for its assigned modes. The investigation will involve initially the fixing of certain baseline parameters to allow a parallel comparison of reasonable results. Then line-of-sight pointing and defocus performance will be generated for comparison among various cases. The simulation model is a version of the so-called 'Draper-2' space structure model. The next section describes the selected model configuration and discuss its finite element representation. Then the modal control and matrix transformation methods will be explained. The implementation of the simulation program will be discussed. The last sections will detail the investigation, results, conclusions and recommendations. Keywords: Large flexible space structures, CSOL models, and Modal control.