Development of a Flexible Embedded Aircraft/Control System Simulation Facility

The paper presents the development and testing of a exible embedded aircraft/control system simulation facility in the MATLAB/SIMULINK environment. It models structural exibilit y with the associated unsteady aerodynamics, analytical human pilot control in a longitudinal pitch-tracking task and atmospheric turbulence and windshear. The aircraft nonlinear equations of motion are developed using Lagrange’s equation and the Principle of Virtual Work. The analytical human pilot model, which incorporates the inherent limitations of human behavior in control tasks, is developed using Linear Quadratic Gaussian (LQG) control theory. The turbulence and windshear model based on Dryden turbulence power spectral density function is used for the purpose of investigating the dierences in exible and rigid-body aircraft responses to atmospheric disturbances. The elastic deformations are described through the use of normal modes and it is shown that, in general, lowering the in vacuo frequencies of vibration of the elastic modes results in the degradation of the aircraft handling qualities. Modal analysis, time history and statistical measures of response variables for eleven variations of the study vehicle, one rigid and ten distinct elastic congurations are carried out, in order to identify the eects of structural exibility on the modeling, handling qualities and control of aircraft. The correlation between the analytical pilot rating evaluated using the longitudinal tracking task and the response of the aircraft in open-loop due to atmospheric turbulence demonstrates that the general pilot rating could be used as a direct indication of the ride comfort and the probability of excitation of the fuselage bending modes for the elastic models.

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