Modeling of Fuel Sloshing in a Spacecraft and Control it by Active Control Method Using Nonlinear Control

Fuel sloshing is one of the most important factors in disturb attitude of the spacecraft from desire in orbital maneuver. So, controlling this phenomenon is a critical problem in attitude control. There are active and passive control methods to control fuel sloshing. Active method has better responses to control fuel sloshing and its effect on attitude of the spacecraft in the same time; so, mostly this method is used. For this aim, it is necessary to model slosh dynamic. In this paper, slosh dynamic is modeled by a multi-pendulum model, and, then, coupled equations of the spacecraft and fuel slosh dynamic are derived. In the presented model, pendulums can move freely in 3D atmosphere, and this matter makes presented model closer to real. Coupled equations of the spacecraft and fuel slosh dynamic are nonlinear. Therefore, nonlinear control methods should be used to attitude control in more realistic mode. In this paper, two candidate Lyapunov functions are proposed; then, using these functions, controllers are obtained. The effectiveness of these controllers on attitude of the spacecraft and pendulums is described by a simulation. Although, there are some little differences in time responses based on two controllers, results of simulation illustrate good responsibility of controllers to control aims.