Fault tolerant flight control system design using a multiple model adaptive controller

Abstract

This article presents a fault tolerant flight control system using multiple model adaptive control (MMAC). To apply this method to the aircraft, model reference adaptive control is extended to a linear discrete-time multiple-input multiple-output system. Multiple models can be determined by various flight conditions with respect to possible aircraft fault situations. In this article, the damages of control effectors are considered as aircraft faults. The aerodynamic coefficients of fault model are derived by a damaged control surface area. In the MMAC, how to select a proper fault model and how to switch into the selected model are significant issues. The conventional mode switching method, however, has a tendency to make the system fluctuate because of frequent mode switching, and therefore may deteriorate the performance of the aircraft. In this study, the modified adaptive mode switching scheme and new decision logic are proposed to improve the adaptiveness in the transient state dynamics of system. Numerical simulations are performed for a linear discrete-time aircraft model to validate the effectiveness of the proposed method.