H({infinity} ) and H(2) design techniques for a classof prefilters

This paper presents H({infinity}) and H(2) techniques for the design of a certain class of prefilters. In order to avoid high order prefilters we use a particular structure in which both prefilter and feedback controller share the same dynamics. The suboptimal H({infinity}) design problem is shown to be equivalent to a linear matrix inequality (LMI) constraint, and the solution of the H(2) optimal design may be obtained by a simple formula. The H (2) technique developed is illustrated on a helicopter example and compared with classical techniques