Tracking Control of Uncertain Non - Iinear MIMO System Using Modified Sliding Surfaces for Attitude Large Maneuver of Satellites on Orbit

Designing a robust tracking control for a non-linear MIMO system with uncertainty is one of the most complicated control problems. In this paper, sliding mode changed to non-linear controllable canonical form by input-output linearization. This, sliding surfaces can be defined in a way that we can de-couple equations and indicate the sliding conditions of multi-variable controller system. The uncertain parameters will be estimated properly and the input equation improved to apply the restricted input condition. The control law will be improved in a way that in addition to increasing the tracking accuracy inside the boundary layer, the speed of convergence will increase outside of the boundary layer. In order to satisfy the balance of the filter, the thickness of the adaptive boundary layer is used. Thus, a robust tracking control is designed which can trace the angle of attitude of satellite for maneuvers with a very large angle (180 deg.) on a piece-wise smooth path. Finally, the simulation results are compared with Elmali & Olgac’s methods and it is shown that despite decreasing control signals, the tracking accuracy increases by several ten times. Keywords: Attitude, Control, Sliding-mode control, Non-linear System, Input-Output Linearzation