A Multi-observer Switching Strategy for Fault-Tolerant Control of a Quadrotor Helicopter

This paper deals with fault tolerant control of the attitude of a four-rotor helicopter (quadrotor). A set of non-linear estimators/observers is implemented to estimate the attitude of the quadrotor. Each estimator has been designed in order to be sensitive to faults in all sensors but one. The attitude estimate that exhibits the smaller error when compared to the attitude computed from the mechanical model is selected to feed the controller. Thus the strategy proposed selects, at each instant, the estimator/observer that minimizes a suitable switching criterion. Simulations of the controlled system, under various scenarios, illustrate that the proposed switching strategy is able to maintain performance levels and to preserve stability under the occurrence of sensor failures.