Flight Testing a Linear Parameter Varying Control Law on a Passenger Aircraft

Abstract

To improve performance and efficiency of future aircraft generations, multi-objective control design problems considering effects such as over-actuation and lowly damped flexible modes arise from new materials in the wing design. A candidate method, which delivers a solution to this problem for the whole flight envelope is linear parameter varying (LPV) control synthesis. It already incorporates the controller scheduling in the synthesis process, guaranteeing stability and robustness over the entire scheduling envelope, and enables intuitive multi-objective, multiple-input multiple-output (MIMO) controller designs. To prove the concept of LPV controllers in a realistic environment, the flight test campaign results of LPV inner loop control laws on a Cessna Citation II (550) aircraft are presented in this paper. The implemented inner loop controllers are inspired by classical flight controllers used on state-of-the-art fly-by-wire airliners. The longitudinal motion is augmented with load-factor command and the lateral motion controller, which is inherently of MIMO type, features a roll rate command with attitude hold behavior. The control laws are validated in flight by the pilot with respect to functionality, flying and handling qualities. Furthermore, auto generated input signals are used to excite the aircraft without pilot in the loop to allow for a comparability with simulation results.