Aeroservoelastic Analysis of a SensorCraft Vehicle and Comparison with Wind Tunnel Data

Abstract

The flexible body dynamics of wing bending (both vertical and fore -aft modes) for high aspect ratio blended wing -body tailless aircraft challenges the traditional nonlinear flight con trol 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 research and development program titled, Aerodynamic Efficie ncy Improvement (AEI), Lockheed Martin Aeronautics (LM Aero) Company worked with the Air Force Research Laboratory (AFRL ) to address aeroservoelastic wing technology integration for the next step of SensorCraft development. The LM Aero key performance obje ctives were in gust load alleviation (GLA) for aircraft stability and reduced structural weight and also, body freedom flutter (BFF) suppression to alleviate current airspeed restrictions. Combining system identification technology and flight control law d evelopment, the LM Aero team derived control laws to achieve gust load alleviation and flutter suppression on a half span aeroservoelastic model mounted to an innovative wall apparatus allowing pitch and plunge degrees of freedom. Wind tunnel tests were co nducted 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 speeds greater than 20% above the un -augmented flutter speed. In addition analytical models wer e developed prior to the test as “virtual” wind tunnel model to develop and refine test procedures. These analytical models were then tuned to measured ground test data to support post -test analysis and comparison against test data. The paper discusses d evelopment of the analytical models, their tuning to ground test data and comparison against wind tunnel data.