Fault Tolerant Control of Uncertain Fractional-Order Nonlinear Systems Based on Sliding Mode Disturbance Observer

Aiming at fault-tolerant capability of fractional-order nonlinear systems with unknown parameters, actuator faults and external bounded disturbances, an adaptive fault-tolerant controller incorporating sliding mode disturbance-observer is developed. Actuator faults are treated as internal disturbances and can be combined with external disturbances. A sliding model fractional-order disturbance observer (SMFODO) is put forward to approximate the composite disturbances, and the convergence of the estimation error of the disturbance observer is guaranteed. The developed fault-tolerant controller and the adaptive updating rule of unknown parameters guarantee the stability of the closed-loop system and the expected output tracking performance. Finally, numerical simulations are conducted to show the feasibility of the developed method.