Three-axis attitude control of a small satellite by magnetic PD-like controller integrated with passive pitch bias momentum method

The attitude acquisition problem of a magnetic small satellite under effect of environmental disturbances is solved by two methods. The first method stabilizes the nonlinear attitude in three-axis by purely electromagnetic actuation. The second method exploits the inertial stiffness provided by a pitch momentum wheel to gain insensitivity to disturbances. The simulation results obtained for the same initial conditions show the superiority of the non-aided method in terms of transient duration and energy consumption, on the other hand the disturbance rejection capability of the passively momentum-biased method. The steady state error can be reduced if the pitch bias momentum is employed passively whereas it is determined by the total magnitude of the disturbance torques in the case of purely magnetic control. The momentum wheel has a regularizing effect on the dynamics; it leads the system from irregularity to nonlinear stability then the magnetorquers become able to carry the states to equilibrium, also zero.