Pseudo Control Hedging and its Application for Safe Flight Envelope Protection T.J.J. Lombaerts * , Delft University of Technology, P.O. Box 5058, 2600 GB Delft, The Netherlands G.H.N. Looye † , German Aerospace Center DLR, M¨ unchner Straβe 20, 82234 Wessling, Germany Q.P. Chu ‡ , J.A. Mulder § , Delft University of Technology, P.O. Box 5058, 2600 GB Delft, The Netherlands This paper describes how the previously developed concept of Pseudo Control Hedg- ing (PCH) can be integrated in a Fault Tolerant Flight Controller (FTFC) as a safe flight envelope protection system of the first degree. This PCH algorithm adapts the reference model for the system output in case of unachievable commands due to control input satura- tion. As an example, this algorithm has been applied in the pitch rate and velocity control loops of a high fidelity Boeing 747 simulation model where its beneficial influence has been illustrated. The nonlinear adaptive control law used for this example is a triple layered nonlinear dynamic inversion algorithm, based upon the concept of time scale separation. Nomenclature A x ; A y ; A z specific forces along body X/Y/Z axis [m/s 2 ] C dimensionless coefficient F force [N] I inertia matrix [kgm 2 ] L; M ; N combined aerodynamic and thrust moment around the body X/Y/Z axis [Nm] S wing area [m 2 ] T c dimensionless thrust [-] V airspeed [m/s] X data matrix X; Y ; Z combined aerodynamic and thrust forces along the body X/Y/Z axis [N] b wingspan [m] c mean aerodynamic chord [m] g gravity constant [m/s 2 ] m mass [kg] p; q; r roll, pitch and yaw rate around the body X/Y/Z axis [rad/s] u input u b ; v b ; w b airspeed velocity components along body X/Y/Z axis [m/s] u e ; v e ; w e airspeed velocity components along earth fixed X/Y/Z axis [m/s] x; y; z position coordinates along X/Y/Z axis [m] (reference frame varies) x state vector Subscript * Researcher and lecturer, Control and Simulation Division, Faculty of Aerospace Engineering, e-mail: t.j.j.lombaerts@tudelft.nl, AIAA student member † Researcher, Institute of Robotics and Mechatronics, Department of System Dynamics and Control, AIAA member ‡ Associate professor, Control and Simulation Division, Faculty of Aerospace Engineering, AIAA member § Professor, Control and Simulation Division, Faculty of Aerospace Engineering, AIAA member 1 of 17 American Institute of Aeronautics and Astronautics AIAA Guidance, Navigation, and Control Conference 2 - 5 August 2010, Toronto, Ontario Canada AIAA 2010-8280 Copyright © 2010 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Downloaded by TECHNISCHE UNIVERSITEIT DELFT on January 2, 2014 | http://arc.aiaa.org | DOI: 10.2514/6.2010-8280