Nonlinear Aircraft Model Identification and Validation for a Fault-Tolerant Flight Control System

Abstract

This paper presents the results of a parameter identification study for determining a mathematical model of the WVU YF-22 unmanned research aircraft under both nominal and actuator failure conditions to simulate malfunctions on primary control surfaces. Specifically, both linear and nonlinear mathematical models were derived from measured flight data acquired from pilot and automated computer-injected maneuvers under nominal and failure conditions. From analysis, the stability and control derivatives were extracted to determine the aerodynamic forces and moments. The aerodynamic derivatives were then introduced into a simulation model implemented within a Simulink-based environment, and studies were conducted to validate the accuracy of the identified models. Additionally, "Empirical" and DATCOM analyses were conducted for the WVU YF-22 to further validate the nonlinear model obtained through the parameter identification study. Nomenclature a = linear acceleration (m/s 2 ) A = decoupled (failure) state matrix b = wing span (m) B = decoupled (failure) input matrix C = aerodynamic coefficient c = mean aerodynamic chord (m) e = error H = altitude (m) i = surface deflection (deg) I = moment of inertia (kg m 2 ) J = product of inertia (kg m 2 ) m = aircraft mass (kg) TP 1 2 p = roll rate (deg/s) q = pitch rate (deg/s) q = dynamic pressure (psi) r = yaw rate (deg/s) S = wing surface area (m 2 ) T = thrust (N) V = velocity (m/s) Greek Letters α = angle of attack (deg) β = angle of sideslip (deg) δ = control surface deflection (deg) θ = pitch angle (deg)  = roll angle (deg) ψ = yaw angle (deg) ρ = air density (kg/m 3 ) Subscripts A = aileron D = drag H = stabilator l = rolling moment L = lift, left m = pitching moment n = yawing moment R = rudder, right xx = about the x-axis (body) xz = about the x and z axes (body) Y = side force yy = about the y-axis (body) zz = about the z-axis (body) Downloaded by PURDUE UNIVERSITY on July 30, 2015 | http://arc.aiaa.org |

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