Fault-tolerant sliding mode satellite attitude stabilization using magneto-Coulombic torquers

Abstract

This paper presents a sliding mode attitude control scheme for satellites actuated by magneto-Coulombic torquers. A terminal sliding mode control with modified super twisting algorithm is designed considering the averaged dynamics of the magneto-Coulombic system to ensure fast convergence with negligible chattering in the presence of process noise and gravity gradient disturbances. It is shown that the proposed actual time varying super twisting control gets reduced to the averaged control. The same control scheme is thereafter extended to the situation under the failure of one of the three Coulomb shell pairs and it is shown that even if the actuator fails along one of the axes, the system can still be stabilized and forced to reach the origin in finite time. Global stability of the averaged attitude control system with finite time convergence is mathematically proved under the proposed control law. Simulations are carried out to validate the theoretical results under process noise and destabilizing gravity gradient. The proposed modified super twisting controller is shown to outperform a finite time sliding mode controller.