Performances Comparison of Linear and Sliding Mode Attitude Controllers for Flexible Spacecraft with Reaction Wheels

Abstract

In this study, two control algorithms for the three axes stabilized geosynchronous communication satellite Intelsat V are given. The spacecraft is assumed to be controlled via reaction wheels. First, linear control method is used to design an attitude feedback control algorithm for a rigid satellite with attitude angles. Linearized form of the spacecraft dynamics are given in attitude angles representation. Second, sliding mode control method is used for the attitude controller with equivalent control term for flexible satellite. The performances and disadvantages are discussed on design example for both cases. Modeling and simulation are done by using MATLAB-Simulink programming. The results show that using attitude linear controller may cause the mission cost to be high and decrease the maneuver performances for a geosynchronous satellite mission. Also linear attitude controller does not include neglected nonlinear effects, flexibility effects, etc. That is why the linear attitude controller has a very long settling time. On the other hand, attitude sliding mode controller for geosynchronous satellite with flexible solar arrays uses energy optimally with a great performance and relative small settling time. Moreover, attitude sliding mode controller includes all effects of nonlinear dynamics which is robust to bounded external disturbances and unmodelled dynamics.