RIGID AND LIQUID COUPLING DYNAMICS AND HYBRID CONTROL OF SPACECRAFT WITH MULTIPLE PROPELLANT TANKS

The compound control methods are widely used to control the orbit translation and attitude maneuver of liquidfilled spacecraft with high accuracy. The dynamic boundary conditions on curved liquid free surface under low-gravity environment are transformed to general simple differential equations by using Fourier-Bessel series expansion method and the state vectors of coupled liquid sloshing equations are composed by the modal coordinates of relative potential function and the modal coordinates of wave height. The coupled dynamic equations for the rigid platform motion and liquid fuel sloshing are obtained by means of Lagrange equations in terms of general quasi-coordinates. The expressions of the sloshing forces and moments are obtained by analyzing the liquid model. An adaptive fast terminal sliding mode controller and a composite controller that combines the adaptive fast terminal sliding mode strategy and the input shaping technology are respectively designed to control spacecraft orbit translation and attitude maneuver for two cases. In the first case, the spacecraft carries one partially liquid-filled propellant tank. In the second, the spacecraft carries four partially liquid-filled propellant tanks. The efficiency and the accuracy of the controllers are examined through numerical simulations. The results indicate that liquid-control-spacecraft coupled resonance can appear in the controlled spacecraft system if the sloshing effects have not been sufficiently taken accounted of during designing attitude and orbit controller for spacecraft with multiple propellant tanks, and this resonance will result in the instability of the spacecraft attitude. Nevertheless, such disadvantages have been efficiently inhibited by using presented composite adaptive terminal sliding mode controller.