Abstract:

We propose a model predictive control (MPC) policy for simultaneous station keeping, attitude control, and momentum management of a low-thrust nadir-pointing geostationary satellite equipped with reaction wheels and on-off electric thrusters mounted on boom assemblies. Attitude control is performed using an inner-loop SO(3)-based control law with the reaction wheels, while the outer-loop MPC policy maintains the satellite within a narrow station keeping window and performs momentum management using electric thrusters. For reducing propellant consumption, our MPC uses two different prediction horizons: a short horizon for the states associated with the orbit’s inclination and a longer horizon for all other states. Furthermore, to handle the on-off nature of the thruster while retaining low computational burden, we develop a strategy for quantizing the continuous thrust command, which also allows for trading off the number thrust pulses and fuel consumption. We validate the controller in a closed-loop simulation with the high-precision orbit propagation provided by the Systems Tool Kit (STK), and assess the robustness to model uncertainty and measurement noise.