Nanosatellite attitude air bearing system using variable structure control

This paper details a novel fault tolerant variable structure control law using sliding mode control which can be used to improve fault tolerance in nanosatellite attitude control systems. A locally asymptotically stable adaptive fuzzy first order sliding mode controller is used to solve the local attitude control tracking problem. Simulation results validate the tracking and fault tolerant performance of the proposed controller in the presence of noise and reaction wheel faults. The controller is also tested with embedded attitude control hardware on a spherical air bearing system and compared with a PID controller and 2nd and 3rd order sliding mode controllers. The proposed controller is more tolerant to faults and uses less energy for attitude control, and has a steady-state error of 0.8 degrees while PID accuracy in the same system is 5 degrees.