A robust adaptive actuator failure compensation scheme for spacecraft with unmodeled dynamics

A robust adaptive actuator failure compensation scheme is developed for attitude tracking control of a spacecraft in the presence of unknown inertia parameters, unmodeled dynamics and uncertain actuator failures. A new robust adaptation scheme involving modification terms in the update laws is designed for estimating the failure patterns and failure values, in addition to estimating the inertia parameters, for direct adaptive actuator failure compensation. It is shown that such a robust adaptive design is able to ensure the desired closed-loop stability and that tracking errors can be made sufficiently small by properly choosing the design parameters despite the unknown inertia matrix, unmodeled dynamics and actuator failure uncertainties. Illustrative simulation results of an application to a spacecraft model are presented to verify the desired robustness properties.