GLA and Flutter Suppression for a SensorCraft Class Concept Using System Identification

Abstract

The flexible body dynamics of wing bending (both vertical and fore -aft modes) for high aspect ratio blended wing -body tailless aircraft challenge s the traditional nonlinear flight cont rol system design process. The frequencies associated with these modes interact with the short period mode and necessitate an integrated flight control law development process. In a recent joint researc h and development program titled , Aerodynamic Efficien cy Improvement (AEI) , Lockheed Martin Aeronautics (LM Aero) Company worked with the Air Force Research Laboratory (AFRL) , NASA Langley Research, Northrop Grumman Corporation, Tao Systems Inc., and NextGen Aeronautics to address aeroservoelastic wing techno logy integration for the next step of SensorCraft development. The LM Aero key performance objectives were in gust load alleviation (GLA) for aircraft stability and reduced structural weight and also, body freedom flutter (BFF) suppression to alleviate cur rent airspeed restrictions. Combining system identification technology and flight control law development , the LM Aero team derive d control laws to achieve gust load alleviation and flutter suppression on a half span aeroservoelastic model mounted to an in novative wall apparatus allowing pitch and plunge degrees of freedom . Wind tunnel tests were conducted at the NASA Langley Transonic Dynamic Tunnel . Gust derived peak wing bending moments were reduced by more than 50% in many cases. BFF was suppressed at s peeds greater than 20% above the un -augmented flutter speed.