Controllability Analysis for Multirotor Helicopter Rotor Degradation and Failure

This paper considers the controllability analysis problem for a class of multirotor systems subject to rotor failure/wear. It is shown that classical controllability theories of linear systems is not sufficient to test the controllability of the considered multirotors. Owing to this, a new necessary and sufficient condition for the controllability of multirotors is derived, where an easy-to-use measurement index is introduced to assess the available control authority. Furthermore, a controllability test procedure is approached, which is applicable to a class of multirotors subject to rotor failures/wear. The proposed controllability test method is applied to a class of hexacopters with different rotor configurations and different rotors efficiency parameters to show its effectiveness. The analysis results show that hexacopters with different rotor configurations have different fault-tolerant capabilities. It is therefore necessary to test the controllability of the multirotors before any fault-tolerant control strategies are employed.