ESO-based robust predictive control of lunar module with fuel sloshing dynamics

An extended-state-observer (ESO) based predictive control scheme is proposed for the autopilot of lunar landing. The slosh fuel masses exert forces and torques on the rigid body of lunar module (LM), such disturbances will dramatically undermine the stability of autopilot system. The fuel sloshing dynamics and uncertainties due to the time-varying parameters are considered as a generalized disturbance which is estimated by an ESO from the measured attitude signals and the control input signals. Then a continuous-time predictive controller driven by the estimated states and disturbances is designed to obtain the virtual control input, which is allocated to the real control actuators according to a deadband logic. The 6-DOF simulation results reveal the effectiveness of the proposed method when dealing with the fuel sloshing dynamics and parameter perturbations.