Spacecraft Attitude Fault Detection and Recovery Using Non-Linear Observer and Reconfigurable Controller

Abstract

This paper addresses fault tolerant attitude control through the development of a fault observer and re-configurable control law. Using attitude sensor measurements for angular position and velocity, an estimate of the true torque on all three axes is accomplished using a pair of super twisting sliding mode observers. Modifications on the `broken' super twisting observer is applied in order to accommodate additional sensor feedback inputs. Using this method, reconstruction of torque faults can be accomplished and fault information is then sent to a re-configurable controller which switches to an appropriate control law to recover and mitigate the effects of the actuator fault. Simulation results are presented to show fault reconstruction and recovery with attitude stabilization in the presence of orbital disturbances - some which are partially unknown to both controller and observer.