Spacecraft Attitude and Angular Rate Tracking using Reaction Wheels and Magnetorquers

Abstract

Spacecraft remote sensing applications may require slew maneuvers that prioritize small ground track errors during imaging, low power consumption and quick settling time. This paper investigates attitude control with a time-varying reference for a spacecraft model actuated by reaction wheels and magnetorquers, showing (a) an analytical solution for obtaining the required reaction wheel momentum reference in a rotational maneuver; and (b) the conditions for asymptotic convergence of attitude and angular rate tracking using a quaternion-based nonlinear control law; and (c) simulation results for a 6U CubeSat in Low-Earth-Orbit performing fixed-vector pointing and slew maneuvers. In particular, if a remote sensing spacecraft shall execute a short slew maneuver and the collection of data is not required to follow a fixed ground track, then utilizing the reference quaternion propagated from initial condition may be preferred. Based on the simulated single-axis slew maneuvers, better attitude tracking performance may be achieved when the magnetorquers are actively managing the reaction wheel momentum, but decreasing their effects in the transient period may result in quicker settling time depending on chosen error tolerances.