An integral sliding mode augmentation scheme for fault tolerant control

In this paper an integral sliding mode control allocation scheme is used to enhance the functional capability and reliability of an existing commercial-aircraft controller by introducing fault tolerance. The design philosophy is to distribute the control signals to primary control surfaces in the nominal fault free scenario, whilst the secondary control surfaces are only activated when the effectiveness levels of the primary control surfaces are not sufficient to handle the situation in the presence of faults/failures. The key advantage of the proposed scheme over other sliding mode control allocation schemes is that the one proposed in this paper can be retro-fitted to an existing state feedback controller designed using only the primary actuators. Simulation results using the FTLAB747 software, show good results, and validate the effectiveness of the proposed scheme.