A systematic procedure for designing non-diagonal weights to facilitate /spl Hscr//sub /spl infin// loop shaping

The first step of the /spl Hscr//sub /spl infin// 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 nondiagonal pre- and post-compensators. Such nondiagonal weighting functions enable the designer to shape each singular value of the nominal plant separately. To illustrate the procedure an /spl Hscr//sub /spl infin// loop shaping controller is designed for a plant whose singular values can not be shaped accurately using diagonal weights.