Reconfigurable Nonlinear Autopilot

The paper proposes a reconfigurable flight-control system for the tracking of altitude, heading, sideslip, and velocity commands. The control law can serve for the command of unmanned air vehicles or as an autopilot for piloted aircraft. The inner core of the algorithm consists of a reconfigurable control system providing tracking of pitch-, roll-, and yaw-rate commands. It is based on a model reference control law and a stabilized recursive least-squares algorithm. The outer loop is based on a linear design, with compensation for the nonlinear couplings arising from flight dynamics. Some parameters of the outer loop are identified in real time in order to adapt to varying flight conditions. The algorithm is evaluated using a nonlinear F-16 simulation model. The results demonstrate the consistent performance of the algorithm through various flight conditions, as well as its turn coordination capabilities, its reconfiguration after a floating left elevator failure, its ability to move across the power curve, and its tolerance to measurement noise and turbulence.