Gust Load Alleviation for Highly Flexible Aircraft
High Altitude, Long Endurance (HALE) aircraft have become popular for dull, dirty, and dangerous missions. Long on-station times require high L/D ratios, high aspect ratios, high fuel fractions, and low structural weight – which all lead to increased flexibility. This increase in flexibility leads to an increase in loads due to gust encounter and also the possibility of entering in a divergent flight condition due to the gust. This work focuses on characterizing the response of a HALE aircraft to a gust disturbance and then designing a control system to track a desired trajectory, while rejecting a gust disturbance.
Develop gust response Linear Quadratic Gaussian (LQG) controller which minimized aircraft root curvature and therefore effectively controlled aircraft deformed shape.
Modify Dynamic Inversion (DI)control scheme first proposed by Shearer for trajectory control of Very Flexible Aircraft for use on flying wing aircraft model in presence of gust.
Develop Reference Governor (RG) control scheme using closed loop linearized aircraft model with DI controller in the loop to constrain wing curvature during aircraft maneuvering and in the presence of a gust disturbance.
Complete studies to characterize the sensitivity of the open and closed loop response to gust disturbances while varying aircraft stiffness properties..
Gust profile from UM/NAST
AeroVironment/NASA Helios experiencing high
dihedral due to gust