22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-4.10.2

IDENTIFICATION OF THE AEROELASTIC MODEL OF A LARGE TRANSPORT AIRCRAFT FOR CONTROL LAW DESIGN AND VALIDATION

C. Le Garrec, M. Humbert, M. Lacabanne
Aérospatiale Matra Airbus, Toulouse, France

Keywords: aeroelastic model, large transport aircraft, control law, design and validation

Since the introduction of the digital technology into flight control systems the structural behaviour is an important issue of the control law design, firstly to guaranty that no instability of a flexible mode is created by the flight control law. However, if a model of the structural dynamics is in hand, in a form convenient for control design, the flexible mode behaviour can be changed from a constraint into a new objective of the control design, offering a wide range of new benefits for the aircraft : ride quality improvement, passenger comfort augmentation, dynamics load reduction ... Such models can be derived in the state space form from the flutter theoretical models, but if flight test results are available better models are obtained by a direct identification of this model from flight test data. This paper presents an identification procedure of an aeroelastic state space model from flight data, for control law design and validation purposes. The procedure is split into a first estimation of the model by the E.R.A ( Eigensystem Realization Algorithm) followed by a model refinement using the output-error minimization procedure.. Flight tests results on a large civil transport aircraft are presented.

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