Observer-based Sliding Mode Attitude Controller Design for Spacecraft with Fuel Slosh

For a kind of spacecraft with fuel slosh, a controller is designed to make the spacecraft system asymptotically stable, to suppress the fuel slosh while controlling the spacecraft attitude. An existing system model is adopted to analyze and verify the system characteristics. By considering the underactuated characteristic of the system, the system is transformed into a certain normalized form. A sliding mode control approach is proposed to design the controller. In addition, an observer is designed in considering that the displacement of the fuel slosh is unable to be measured in reality. By measuring the state of the velocity and attitude of the spacecraft, the estimated value of the sloshing displacement is close to the true value within a certain error range, and the estimated value is used to replace the sloshing displacement in the control law. A Simulation example illustrate the effectiveness of the observer and controller.