Nonlinear Direct Adaptive Control and Disturbance Rejection for Spacecraft

Abstract

In this paper, a Nonlinear Direct Model Reference Adaptive Control (NDMRAC) i s derived. The NDMRAC controller is compared to the Full State Feedback (FSFB) controller. Both of the controllers are applied to a rigid body spacecraft. To compare the controllers, the inertia matrix is suddenly changed in the simulation. Euler equations are used to estimate the evolution of the rigid body angular velocity and quaternions are used to describe the attitude position of the rigid body. The system is augmented or modified to account for the disturbances affecting the system under observation, so the NDMRAC control also implements a Direct Adaptive Disturbance Rejection (DADR) control which partially or fully eliminates the disturbance coming into the simulated system. The error of the system and the power spectrum density of the disturbance ar e used to analyze the performance of t he NDMRAC and DADR controllers.