Composite Adaptive Attitude Control of Asteroid-Orbiting Spacecraft With Regressor Integral Excitation

This article (correspondence) develops a composite adaptive control system for the attitude trajectory tracking of a spacecraft in elliptic orbit around a uniformly rotating asteroid. It is assumed that the spacecraft's moment of inertia and the asteroid's gravitational parameters are unknown. The adaptation law designed here includes a positive semidefinite regressor-dependent matrix integral. For its synthesis, the tracking error as well as two model prediction errors are used. This enhances parameter excitation and causes faster decay of the parameter error. By the Lyapunov analysis, local convergence of the tracking error is established. In addition, it is shown that the trajectories of the system converge to two manifolds. Simulation results for a spacecraft on prograde elliptic orbit around asteroid 433 Eros are presented. These results show nadir-pointing attitude regulation. Interestingly, six out of nine unknown parameters are estimated accurately for certain proportional perturbations in the model parameters.