Spacecraft attitude control using model-based disturbance feedback control strategy

In this paper, the performance of the spacecraft attitude control system is enhanced using model-based disturbance feedback control (DFC) strategy in the presence of disturbance. This control strategy is applied to a single-axis spacecraft attitude control with thruster, reaction wheel, and magnetic torqrod actuators, separately. An anti-windup observer-based modified PI-D is utilized for each actuation system as a main controller. The controller gains are tuned using genetic algorithm when the time average of absolute value of pointing error is chosen as an objective function. The performance of DFC with the modified PI-D controller is investigated under disturbance and model uncertainties. The numerical simulation shows that the DFC strategy can reject disturbance effect and improve the pointing error for the three mentioned actuators; however, for a very large value of external disturbance, a critical value for uncertainty is observed for the thruster lag at which the pointing error is suddenly increased. For this critical value, the control system cannot tolerate any longer lag uncertainty in comparison with the two other actuation systems. Increasing the value of disturbance decreases the tolerable value of uncertainty in the thruster lag.