The robust sliding mode observer for nonlinear actuator loop of flying wing aircraft is proposed in this paper

which is used to estimate the actuator faults. Firstly

the nonlinear characteristic of electro-hydro actuator loop is analyzed

considering the fault types and reason

the nonlinear fault model of actuator loop is built. Then

the main design procedure of robust sliding mode observer is given

the optimization scheme is provided considering the nonlinearities in the actuator loop

and the observer gain design method is provided through convex optimization procedure under linear matrix inequalities; meanwhile

the case that the upper bound of fault unknown is considered

and the adaptive law is added in the sliding mode gain

thus

the sliding mode motion can reach and maintain on the sliding mode surface in limited time. Finally

the equal error injection concept is provided to estimate the unknown faults of actuator loop

and the numerical example is provided to demonstrate the effectiveness of the proposed method in this paper.