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Mathematical Problems in Engineering
Volume 2010, Article ID 231594, 17 pages
Research Article

Results of Short-Period Helicopter System Identification Using Output-Error and Hybrid Search-Gradient Optimization Algorithm

1Grupo Especial de Ensaios em Vôo (GEEV), Comando-Geral de Tecnologia Aeroespacial, 12.228-904 São José dos Campos, SP, Brazil
2Instituto Tecnológico de Aeronáutica, Comando-Geral de Tecnologia Aeroespacial, 12.228-900 São José dos Campos, SP, Brazil

Received 4 October 2009; Revised 27 March 2010; Accepted 20 May 2010

Academic Editor: Miguel Cerrolaza

Copyright © 2010 Ronaldo Vieira Cruz and Luiz Carlos Sandoval Góes. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This article focuses on the problem of parameter estimation of the uncoupled, linear, short-period aerodynamic derivatives of a “Twin Squirrel” helicopter in level flight and constant speed. A flight test campaign is described with respect to maneuver specification, flight test instrumentation, and experimental data collection used to estimate the aerodynamic derivatives. The identification problem is solved in the time domain using the output-error approach, with a combination of Genetic Algorithm (GA) and Levenberg-Marquardt optimization algorithms. The advantages of this hybrid GA and gradient-search methodology in helicopter system identification are discussed.