Improved Correction System for Vibration Sensitive Inertial Angle of Attack Measurement Devices

Inertial angle of attack (AoA) devices currently in use at NASA Langley Research Center (LaRC) are subject to inaccuracies due to centrifugal accelerations caused by model dynamics, also known as “sting whip.” Recent literature suggests that these errors can be as high as 0.25 deg. With the current AoA accuracy target at LaRC being 0.01 deg., there is a dire need for improvement. With other errors in the inertial system (temperature, rectification, resolution, etc.) having been reduced to acceptable levels, a system is currently being developed at LaRC to measure and correct for the sting-whip-induced errors. By using miniaturized piezoelectric accelerometers and magnetohydrodynamic rate sensors, not only can the total centrifugal acceleration be measured, but yaw and pitch dynamics in the tunnel can also be characterized. These corrections can be used to determine a tunnel’s past performance and can also indicate where efforts need to be concentrated to reduce these dynamics. Included in this paper are data on individual sensors, laboratory testing techniques, package evaluation, and wind tunnel test results on a High Speed Research (HSR) model in the Langley 16-Foot Transonic Wind Tunnel. NOMENCLATURE ω = angular rate r = radius of rotation *Electronics Research Engineer, Member AIAA †Senior Research Engineer Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental Purposes. All other rights are reserved by the copyright owner. Vl = linear velocity V = Voltage g = gravity AoA = α = Angle of attack AoAcorr = Corrected AoA G y/p = Yaw or Pitch acceleration due to centrifugal force (g) Vy/p = Yaw or Pitch correction voltages from D/A card My/p = Yaw or Pitch temperature scale factor (%/deg. F) T = Package temperature (deg. F) Vq = Q Flex voltage output b = Q Flex bias (V) S = Q Flex sensitivity (V/g) φ = Q Flex offset (deg.) DAQ = Data Acquisition System