Geostationary Station-Keeping of Electric-Propulsion Satellite Equipped with Robotic Arms

We propose two approaches based on feedforward control and model-predictive control, respectively, to solve the station-keeping problem of an electric-propulsion geostationary Earth orbit (GEO) satellite, whose thrusters are mounted on two robotic arms on its anti-nadir face. This novel configuration enables a wider range of thrust direction, making it possible to regard the thrust direction as control variables. To solve this control problem, we present the quick feedforward controller (QFFC) and the fuel-optimal model predictive controller (FOMPC). The QFFC is developed based on the analysis of GEO dynamics and the thruster configuration. The FOMPC applies an optimization algorithm to solve the nonlinear model predictive control (NLMPC) problem with the initial value given by the QFFC. Numerical simulations suggest that both controllers could achieve stable station-keeping over multiple objective elements with fewer thrusters and fewer maneuvers. The QFFC has higher control accuracy and lower computational requirements than the FOMPC, whereas the FOMPC could significantly save fuel consumption. The robustness assessment and other discussions of the controllers are also presented.