Flexible aircraft model identification for control law design

The large commercial aircraft, developed today by manufacturers, are characterized by a high flexibility which results in a stronger interaction between the flight control system and the structural modes. The active control of the first elastic modes is needed to meet the performance requirements. This paper proposes an identification methodology of a flexible aircraft from flight test data, which is appropriate for control law design with modern control techniques (LQG, H2/H∞). In a first step a procedure based on Eigensystem Realization Algorithm (ERA) is used to determine an initial aeroelastic model which is subsequently combined with a linearized rigid-body model and optimized by an output-error minimization method. Two application examples show the good performances of the approach.