μ-analysis for Robust Control in Spacecraft with Large Appendages

摘要

Flexible spacecraft with large appendages such as the Tracking and Data Relay Satellite (TDRS) requires special attention in addressing stability robustness. The control system must be capable to handle the loop interaction effects and plant configuration variations. The classical single loop stability analysis may no longer guarantee robustness due to loop coupling especially when the control loops interact with low flexible modes. This paper describes a Multi-Input-Multi-Output (MIMO) stability check using the μ-analysis to guarantee robustness. The classical gain (GM) and phase margins (PM) have been extended for MIMO systems using the μ-analysis. Furthermore, instead of a certain fixed ratio between the guaranteed bounds on GM and PM for a specified μ-value, a recent result shows improvement can be made by correlating any combination of such margins to a specific μ-value. Consequently, a more specific stability analysis can be performed resulting in a less conservative control system design.