Comparison of On-line and Off-line Parameter Estimation Techniques Using the Nasa F/a-18 Harv Flight Data

In recent years several Parameter Identification (PID) techniques have been proposed for on-line real-time applications. Historically aircraft parameter estimation has been performed off line using recorded flight data from specifically designed maneuvers. Flight data from the NASA F/A-18 High Alpha Research Vehicle (HARV) aircraft is used for this study and is compared with baseline wind tunnel estimates. This paper shows a comparison of the results of a recently developed frequency-based PID technique with the results from the traditional Maximum Likelihood method. The comparison is performed for both longitudinal and lateral-directional dynamics for maneuvers at an angle of attack of α=20° and α=30°. Results of the two estimation processes are compared with available wind tunnel estimates. Symbols b wing span ft c mean aerodynamic chord ft Ci aerodynamic coefficient 1/rad or 1/deg g gravity acceleration ft/sec I moment of inertia slug/ft J cost functional ---k numerical coefficient ---m aircraft mass slug p roll rate deg/sec q pitch rate deg/sec q dynamic pressure ---R conversion from radian to degrees ---q dynamic pressure lbs/ft r yaw rate deg/sec S wing area ft t time sec T thrust lbs. V velocity ft/sec W diagonal weighting matrix ---Y vector of known responses ---X matrix of known inputs ---Graduate Research Assistant, AIAA Member Professor Research Assistant Professor, AIAA Member Copyright  2001 by the authors. Published by the American Institue of Aeronautics and Astronautics, Inc. with permission. Greek α angle of attack deg β sideslip angle deg β vector of parameters to be estimated ---∆ incremental change ---δ control surface deflection deg ∇ gradient ---ξ parameter vector to be estimated ---θ pitch angle deg φ roll angle deg σ estimate standard deviation ---Σ summation ---ψ yaw angle deg ω frequency rad/sec Subscripts a aileron ---D drag force ---dht differential horizontal tail ---e elevator ---L lift force ---l rolling moment ---lef leading edge flap ---m pitching moment ---n yawing moment ---o basic airframe ---r rudder ---sa symmetric aileron ---tef trailing edge flap ---wind wind axis ---pv pitch vane ---Y lateral force ---yv yaw vane ---Acronyms CG Center of Gravity ---DOF Degrees Of Freedom ---DFT Discrete Fourier Transform ---DFRC Dryden Flight Research Center ---DTFT Discrete Time Fourier Transform ---EE Estimation Error ---FTR Fourier Transform Regression ---HARV High Alpha Research Vehicle ---LS Least Squares ---ML Maximum Likelihood ---NR Newton-Raphson ---OBES On-Board Excitation System ---PID Parameter Identification ---SVD Singular Value Decomposition ----