Design and flight test of a linear parameter varying flight controller

Abstract

Future aircraft generations require improved performance and efficiency to enable a reduced environmental footprint. To acquire this goal, for example new material and wing concepts are perused at the moment by the aircraft industry. These developments, which include aspects such as over-actuation and lowly damped flexible modes, give rise to more complex, multi-objective control problems. One candidate method, which delivers a solution to these problems for the whole flight envelope, is linear parameter varying (LPV) control. It naturally incorporates the controller scheduling in the synthesis process, guarantees stability and robustness over the entire parameter envelope, and enables intuitive multi-objective, multiple-input multiple-output (MIMO) controller designs. This paper proves the concept of LPV control in practice: The paper presents and discusses the LPV controller design process, simulation results, motion simulator test and finally, the in-flight validation of the control system on a Cessna Citation II aircraft. The developed inner loop controller structures are inspired by classical flight controllers used on state-of-the-art fly-by-wire airliners. The longitudinal aircraft motion is augmented with load-factor command and the lateral motion controller features a roll rate command with attitude hold behavior. The control laws are validated in flight by automated and actual pilot inputs with respect to functionality, flying and handling qualities. Test results are encouraging with the provided key findings and lessons learned aiming to provide a simplification for future LPV flight controller development and testing campaigns.

Flight Testing Total Energy Control Autopilot Functionalities for High Altitude Aircraft

“…This aircraft has been extensively utilized in several previous flight testing campaigns and has proven its reliability during the development cycle of various flight control system developments. Past flight tests have included, for example, Linear Parameter Varying (LPV) and Incremental non-linear dynamic inversion (INDI) inner loop control laws [6][7][8][9][10], resulting in a robust and well-known code generation and integration tool-chain. This implies that the Cessna Citation aircraft serves successfully as a hardware platform and can be utilized for validating the flight control code integration and functionality.…”

“…This baseline controller is a rate-command, attitude-hold controller based on gain-scheduled proportional and integral feedback, see [3] for details. For the flight experiments on the Cessna Citation, however, an INDI inner loop controller [8,12] and an LPV controller [7] are available. Both have the same input-output interface as the HALE baseline controller, i.e., receiving pitch angle commands from the autopilot and generating the elevator deflection angle 𝛿 𝑒 .…”

On the Handling Qualities of Two Flying Wing Aircraft Configurations

“…There are more refined versions of the CAP HQs criterions [77], often used in modern literature on aircraft HQs [78][79][80][81][82][83][84][85]. The usual approaches CAP need not to be refined further here, because it is related [73,76] to the manouever margin, considered in more detailed in Section 3.3.…”

Improved Gain Scheduling Control and Its Application to Aero-Engine LPV Synthesis

“…An aero-engine is a highly nonlinear, complex system operating under a variety of external conditions and flight conditions [1]. To design a control system that can guarantee safety and performance under various operating conditions is important [2]. Aero-engine control systems are firstly designed with linear controllers based on linearized engine models at some trimmed operating points.…”

“…x k = A k (α)x k + B k (α)e u = C k (α)x k + D k (α)e (2) is stable if there exists a matrix P > 0 that satisfies…”