Adaptive reconfigurable control based on a reduced order system identification for flutter and aeroservoelastic instability suppression

The paper presents the design of a reconfigurable adaptive control (RAC) system for limit cycle oscillation (LCO) suppression of aircraft/store configurations. With the F/A-18 as a baseline aircraft, rapid suppression of LCO (at 5.6 and 8.8 Hz) has been successfully demonstrated through five cases of numerical simulations studied. The developed RAC system is a modular control design in that the LCO controller can readily be combined with the rigid-body flight (RBF) control, thereby minimizing the impact on the existing flight control system for retrofit. The RAC system consists of a nearly developed on-line modal parameter estimation (MPE) for system identification and on-line modified model-following reconfigurable (MMFR) algorithm for rapid flutter/LCO control (requires only 0.2 and 0.8 sec). The ZAERO software system using an expedient nonlinear unsteady transonic method (ZTAIC) is employed to generate plant matrices. Reduced-order techniques using proper orthogonal decomposition (POD) and minimum state (MIST) methods reduce the system to seven states, rendering an on-line algorithm to be operated within fractions of one second.