Robust Fault-Tolerant Flight Control using a New Failure Parameterization

Most available approaches for adaptive accommodation of failures in flight control actuators result in a large number of parameters that need to be adjusted on-line. In this paper we propose a new failure parameterization that models a large class of failures in terms of a single parameter. The class of failures includes lock-in-place (LIP), float, hard- over and loss of effectiveness (LOE). It is shown that th; new parameterization accurately models this class of failures, and that the resulting model can be used for observer design to estimate the uncertain parameters on-line. The use of the resulting estimates in the adaptive reconfigurable control law at every instant is shown to result in a stable closed-loop system. The estimation and control algorithms are integrated within the thetas-FLARE (thetas-parameterized Fast on-Line Actuator Reconfiguration Enhancement) architecture. Properties of thetas- FLARE and convergence properties of the failure parameter estimates are illustrated through simulations of F/A-18 aircraft dynamics under multiple flight-critical failures.