Attitude control system design for cubesats configured with exo-brake parachute

This paper develops a novel attitude control strategy for an Earth orbiting CubeSat spacecraft by utilizing the exo-brake parachute to modulate the atmospheric drag forces as a source of attitude control authority, enabling orbital exo-sail maneuvers. In particular, the spacecraft attitude controls can be realized through the two dimensional exo-sail maneuvers in pitch and yaw directions. The uncertain atmospheric drag induced disturbance torque is estimated through an adaptive parameter estimation process which makes use of the adaptive least-squares minimization techniques. The covariance updating law with a variable forgetting factor is adopted and it can be shown that the convergent rate for the estimation errors can be chosen at the same level as the forgetting factor, in order to meet the design needs. The proposed approach is best suited for Earth orbiting micro/nano-satellite applications, which are configured with exo-brake parachute. With integration of exo-sail actuation mechanism and disturbance estimation, we demonstrate through simulations that exo-sail induced control torque for CubeSat attitude maneuver is feasible.