Nonlinear Accommodation of a DC-8 Aircraft Affected by a Complete Loss of a Control Surface

Abstract

The occurrence of failures in the control surfaces of an aircraft may become a serious threat to the safety of both aircraft and passengers. That is, using fault-tolerant control (FTC) is vital for such critical systems. The nonlinear progressive accommodation (NPA) is a FTC strategy that consists in solving the State-dependant Riccati Equation (SDRE) in an iterative way. The aim of this work is to study the efficiency of the NPA, in the case of a non-classical stabilization problem and a different modelling of a nonlinear (NL) system, affected by a total actuator failure. That is, a modified NPA strategy is proposed by combining the SDRE control and a feed-forward compensator, derived from the Forward-Propagation-Riccati-Equation (FPRE). The system considered in this paper is a full NL model of a DC-8 aircraft with coupled dynamics. The modelling of the aircraft as well as the simulation of the healthy, affected and accommodated system are presented. The proposed NPA method allows the aircraft to achieve a trajectory-following mission despite the complete failure of its actuator. Most importantly, by preserving the system's stability, the developed approach can be considered as a good alternative to the use of redundant actuators in aircraft.