Design and Verification of a Linear Parameter Varying Control Law for a Transport Aircraft

Kurzfassung

This paper presents the design, implementation and simulator verification of inner loop control laws based on linear parameter varying controller design techniques for a CS-25 certified fly-by-wire test aircraft. The synthesis method provides, in contrast to standard gain scheduling techniques, stability and robustness guarantees over the whole defined parameter envelope. Furthermore, it includes the design of the scheduling already in the synthesis process and avoids its a posteriori design. For the controller design, grid based linear parameter varying models of the longitudinal and lateral motion of the aircraft are generated. The longitudinal motion is augmented with two different reference tracking modes: load-factor and pitch rate command. The two control laws are compared in flight by the pilot to validate the handling qualities. The lateral motion control law features a rate command / attitude hold behavior, similar to schemes commonly used in fly-by-wire transport aircraft. Results from a simulation based verification campaign using DLR’s 6 degree of freedom Robotic Motion Simulator are presented as final results in this paper. The simulator verification was conducted as preparation for flight tests of the designed control laws on a Cessna Citation II (550) aircraft.