Integration of Active Flow Control Effectors into Aircraft Control Laws

Abstract

Application of Active Flow Control (AFC) effectors in aircraft automatic control laws has been limited to open-loop augmentation of baseline conventional surface control. In certain conditions, AFC effectors can be integrated into the primary actuation system to enable flight control without moving surfaces. The design of a control architecture that utilizes a unique AFC system involves modeling of the vehicle dynamics and analysis of open-loop stability and control characteristics. Nonlinear dynamics models representing a specialized X-Plane were integrated in a 6 degree-of-freedom simulation environment, which revealed additional control challenges such as nonlinear and coupled AFC effectiveness trends. A vehicle control law architecture was designed to maintain performance with AFC relative to conventional surface actuation. Closed-loop simulation results show that a linear control allocation method is adequate for restrictively small AFC inputs. For larger AFC inputs representative of maneuvering, a nonlinear control allocation method is required to recover ideal reference command tracking. Nonlinear signal processing methods were applied to validate recovery of frequency response robustness characteristics. The details of the X-Plane control laws and simulation results are discussed in the paper.