Offline and Online Active Fault Tolerant System For Multirotor Drones

This paper studies the two different approaches for designing an active fault tolerant controller for an octorotor in case of total loss in rotor(s) controllability. We first propose a nonlinear Thau observer for detecting faulty actuator(s). It then passes through an offline method based on control mixing redistribution and reconfiguration, and an online method based on control allocation and reallocation. A comparison is then performed between these two methods based on simulating the behavior of the nonlinear system in case of total motor(s) fault. The obtained results show better performance and smoother actuators behavior applying the online method, although offline method has less computational cost on the flight controller.