Flight-Test Evaluation of an Adaptive Controller for Flying Qualities Specification and Protection

Abstract

The human pilot is a crucial component of the pilot/vehicle system. This article focuses on the in-flight ability of an adaptive receding horizon optimal controller to specify favorable flying qualities. Moreover, in the case of a deteriorated vehicle, the controller serves to protect the desirable flying qualities by automatically compensating for the new aircraft characteristics. Although the receding horizon optimal controller is able to protect the handling qualities as long as adequate physical control authority exists, particularly severe failures can result in heavily limited authority where encounters with actuator rate limits may occur. The controller itself is robust to rate-limit encounters, however, the handling qualities suffer because the authority no longer exists to deliver the performance expected by the pilot. To protect handling qualities and mitigate the risk of pilot-induced oscillation past this exhaustion of control authority, the controller is integrated into the Smart Adaptive Flight Effective Cue system (detailed elsewhere). The piloted flight tests demonstrate the capability of the receding horizon optimal controller to 1) deliver specified flying qualities, 2) protect those flying qualities in failure cases where adequate authority exists, and 3) operate in tandem with the Smart Adaptive Flight Effective Cue system to protect the pilot/vehicle system in cases of severely limited authority.