Frequency domain techniques applied to the identification of helicopter dynamics

An important part of aircraft control system design is an analysis of system sensitivity to parameter variations and structural changes. In the paper frequency domain techniques are applied to the identification of helicopter dynamics using a scale model helicopter as a test system. A closed-loop identification in the frequency domain allows system structure and handling qualities to be assessed for a range of flight conditions. Simulations of the helicopter using linear models of longitudinal and lateral motion are described. The performance of two input signals in identifying the transfer functions of the models is compared. These signals are a sinusoidal frequency sweep and a low peak-factor Schroeder-phased harmonic signal.