Dynamic Modeling and Attitude Control System of Underactuated Fuel Slosh with Flexible Appendages

This paper investigates the dynamics and attitude control of the pitching motion of an axisymmetric liquid-filled satellite with flexible appendages under the conditions of zero gravity and constant thrust (fixed axial acceleration). Using Lagrange method, the dynamics model of the flexible liquid-filled satellite is established. The flexible appendages are considered as Euler–Bernoulli beams, and the sloshing liquid is modeled as a spring-mass model. Considering the motion of the satellite in the orbit plane and pitching attitude motion, a sliding mode controller is designed by decoupling the satellite dynamics equation into a typical underactuated system. The influence of the vibration of flexible appendages and the slosh of liquid fuel on the attitude control of the spacecraft is considered. The results show that the designed controller can effectively suppress the liquid sloshing and the vibration of the flexible appendages in such a manner as to achieve the desired result and control target. (paper)