Adaptive control for fault tolerant autonomous carrier recovery

Abstract

This paper presents the use of adaptive control methodologies for the recovery to an aircraft carrier of an autonomous fixed wing aircraft. The control architecture used is model reference adaptive control that is implemented in the pitch, roll, yaw, and airspeed axes to provide 6 degree-of-freedom control of the aircraft. Control systems are developed for the NAVAIR ExJet aircraft model. The structure of the controller includes a first-order linear model follower and an adaptive critic controller. Adaptation is used to augment the command signal produced by the adaptive critic controller, the following methods are used: adaptive bias corrector, optimal control modification, and local linear model compensation. An inverse controller, based on a state space model, generates the control effector commands. The control system reference inputs are rotational rates and airspeed, an outer-loop controller is provided to direct the aircraft to the landing point. Control system design is through the use of metrics based on the nominal error, time delay margin, and landing accuracy. The control system is evaluated under nominal, effector failure, and control system modeling error conditions. The control system defined is capable of providing the desired control under nominal, failure, and modeling error conditions.