An Actuator Fault Tolerant Control for VTOL vehicles using Fault Estimation Observers: Practical validation*

A design of a Fault Tolerant Control (FTC) based on the fault estimation for VTOLs (Vertical Take-Off and Landing) aerial vehicles is developed in this paper. An analysis of static controllability is applied in order to test the performance degradation of the vehicle under actuator faults. For comparison purposes, the algorithm is developed using two different observers: a linear Proportional-Integral Observer (PIO) and a nonlinear Adaptive Observer (AO), that are applied to the attitude and altitude dynamics of the VTOL aircraft to estimate and compensate actuator faults in the prototype. These faults can occur as partial faults affecting simultaneously two or four actuators. Furthermore, fault isolation is proposed by evaluating the fault estimation signal. The fault control scheme is analysed in flight tests to illustrate its effectiveness. Experimental results show the good performance of the algorithms even in the presence of non-constant actuator faults and following a desired trajectory.