Observer-Based Fault-Tolerant Spacecraft Attitude Tracking Using Sequential Lyapunov Analyses

The spacecraft attitude tracking problem is addressed with actuator faults and uncertainties among inertias, external disturbances, and, in particular, state estimates. A continuous sliding-mode controller designed using angular velocity estimates from an arbitrary stable stand-alone observer. Rigorous analysis shows that the ensures robust stability of entire closed-loop system as long observer yields uniformly ultimately bounded estimation errors. In addition, a sequential Lyapunov utilized to obtain convergent sequence analytical successively tighter upper bounds on steady-state error. Therefore, our results can be used predict performance given selected gains or facilitate gain selection bounds. Numerical examples demonstrate utility proposed theory.