Abstarct: In this thesis, firstly a set of nonlinear Kalman filters will be designed to detect and identify faults occurred in sensors. These filters have the capability to detect faults in sensors accurately and correctly in circumstances where statistical characteristics of noise are not definite. Moreover, by examining different sensor fault scenarios, the ability of proposed approaches to detect and identify the faults of an unmanned aerial vehicle is simulated. In order to do this, the structure of an active fault tolerant system will be utilized. In this structure, the information obtained from fault detection unit would be sent to the fault tolerant controller design unit. In this unit, baxsed on the non-singular terminal sliding mode control, the fault tolerant controller will be designed which would preserve stability and optimal performance of the system on condition that an error occurred in the sensor.