Adaptive Fuzzy Fault Tolerant Control of Unmeasured States Nonlinear Systems Based on Fault Alarm

In this paper, an output-feedback fuzzy adaptive fault tolerant control design method is presented for a class of nonlinear systems having unmeasured states and actuator faults (bias and gain faults). Firstly, fuzzy logic systems (FLS) are adopted to identify the unknown nonlinearity, and the hyperbolic tangent function is employed as the robust term to overcome the actuator faults. Then, the threshold strategy about tracking error is constructed as system fault alarm. By use of the adaptive backstepping modular scheme, a robust fuzzy adaptive fault tolerant control strategy is presented. It is shown that all the variables in all subsystems are bounded, and also the tracking error converges to a small neighborhood of zero. Finally, the applicability of the proposed controller is well carried out by a simulation example.