Flight control of an X-29 type aircraft via a combination of LQ optimization techniques

We consider the longitudinal flight control of a forward-swept-wing inherently unstable aircraft with significant wing aeroelasticity. We employ Implicit Model Following (IMF) to design for handling qualities and Frequency Weighting (FW) to damp the aeroelastic modes. The former technique introduces into the performance index the equations of a model embodying the desired closed-loop characteristics; the latter has frequency-dependent weighting parameters in the index, thereby introducing dynamics into the state feedback. For the design problem at hand, the two techniques turned out to be complementary; a combination which exploits the advantages of both was successful.