Real-time nonlinear attitude control system for nanosatellite applications

This paper develops a fault-tolerant attitude controller for next-generation nanosatellites. The proposed fault-tolerant attitude control algorithms in this study are based on first-order and high-order sliding-mode control theories as well as fuzzy logic systems to achieve low cost and real-time autonomy. A locally asymptotically stable adaptive fuzzy first-order sliding-mode controller is chosen as the best solution to the local attitude control tracking problem. This novel fault-tolerant controller is validated by simulation results with reaction wheel Coulomb friction, saturation, noise, dead zones, bias faults, and external disturbances. Simulation and testing results presented in the paper demonstrate that the attitude control system can provide successful pointing and tracking in the presence of system uncertainties for a specified class of reaction wheel failures.