Sloshing-aware attitude control of impulsively actuated spacecraft

Upper stages of launchers sometimes drift, with the main engine switched-off, for a longer period of time until re-ignition and subsequent payload release. During this period a large amount of propellant is still in the tank and the motion of the fluid (sloshing) has an impact on the attitude of the stage. For the flight phase the classical spring/damper or pendulum models cannot be applied. A more elaborate sloshing-aware model is described in the paper involving a time-varying inertia tensor. Using principles of hybrid systems theory we model the minimum impulse bit (MIB) effect, that is, the minimum torque that can be exerted by the thrusters. We design a hybrid model predictive control scheme for the attitude control of a launcher during its long coasting period, aiming at minimising the actuation count of the thrusters

Propellant Sloshing Torque H ∞ -based Observer Design for Enhanced Attitude Control

International audienceIn this paper a control-oriented LPV model of the sloshing torque arising during attitude maneuvers, supported by Computational Fluid Dynamics results, is presented and used for attitude control design. The proposed strategy essentially relies on the design of a robust LPV-based disturbance torque observer with the help of the structured multi-model H ∞ synthesis framework. The estimated torque is then used to improve a satisfying attitude controller initially designed without sloshing. The stability of the parameter-varying closed-loop system is finally proved with parameter-dependent Lyapunov functions