Robust control techniques for geostationary satellites with rotating solar arrays

The reduction in propellant mass achievable by using electric thrusters for geostationary satellites is counterbalanced by the higher power demand. To maximize the power generated, it is possible to control the solar arrays orientation that guarantees the optimal Sun-tracking. However, the torque generated to maintain fixed the relative orientation between the solar arrays and the Sun represents an internal disturbance source that, combined with the environmental ones, may compromise the fulfillment of the fine-pointing specifications required by the payloads onboard the satellite. To optimize the power generation while guaranteeing the desired Earth-pointing orientation, a first-order sliding mode control and a tube-based robust model predictive control are combined with a linear-quadratic regulator for the arrays Sun-pointing. Both robust controllers proves to be able to reject disturbance torques, also due solar panels re-orientation.