Control of a spacecraft with time-varying propellant slosh parameters

This paper studies the thrust vector control problem for an upper-stage rocket with fuel slosh dynamics. The control inputs are the gimbal deflection angle of a main engine and a pitching moment about the center of mass of the spacecraft. It is assumed that the rocket acceleration due to the main engine thrust is large enough so that surface tension forces do not significantly affect the propellant motion during main engine burns. The prominent sloshing modes are represented by a multi-mass-spring model with time-varying parameters. A time-varying nonlinear feedback controller is designed to control the translational velocity vector and the attitude of the spacecraft, while suppressing the sloshing modes. A simulation example is included to illustrate the effectiveness of the controller.