21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-1.5.2

FLEXIBLE STRUCTURE CONTROL BY MODAL MULTI-MODEL APPROACH: APPLIED TO FLEXIBLE AIRCRAFT

Chiappa C., Magni J. -F.*, Le Gorrec Y., Kubica F.**, Doll C.
SUPAERO, France; * ONERA, France; ** Aerospatiale, France

Keywords: flexible structure control, modal multi-model approach, flexible aircraft

This paper presents a generalization to multi-input of a technique used .for designing control laws of SISO flexible structures. The first objective is to shift certain modes to the desired direction, generally towards the left in the complex plan, by means of a dynamic controller and a loop gain variation. The technique is based on the first order development of the variation of the system's eigenvalues. It is used for the stabilization of high frequency modes of a flexible structure which would have been destabilized during a previous loop (stabilizing a rigid body structure). The method of synthesis can be seen as a generalization to the MIMO case of phase control. Its multi-model feature provides high robustness and the solutions remain very simple. It consists of minimizing a quadratic criterion under linear constraints. The phase control can be combined with the gain control by assigning no motion to some eigenvalues or by minimizing a relevant criterion. We apply this procedure to the flexible aircraft.

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