A Systematic Procedure for Designing Non-Diagonal Weights to Facilitate H-infinity Loop Shaping

Presented at CDC'97, December 1997.

A Systematic Procedure for Designing Non-Diagonal Weights to Facilitate H-infinity Loop Shaping

G. Papageorgiou and K. Glover

Abstract

The first step of the H-infinity loop shaping design procedure is to specify desired closed loop performance by shaping the singular values of the nominal plant with a pre- and/or a post-compensator. Designers usually choose diagonal weighting functions but it is not always possible to obtain the desired loop shape with diagonal weights. This paper develops a systematic procedure for designing non-diagonal pre- and post-compensators. Such non-diagonal weighting functions enable the designer to shape each singular value of the nominal plant separately. To illustrate the procedure an H-infinity loop shaping controller is designed for a plant whose singular values can not be shaped accurately using diagonal weights.