An optimisation algorithm for designing fixed-structure controllers using the QFT method

We propose a simple optimisation algorithm for designing fixed-structure controllers for highly-uncertain plants. The method can be used to automate the loop-shaping step of the quantitative feedback theory (QFT) design procedure and guarantees robust stability and performance to the feedback loop for all parameters in the plant's uncertainty set. To avoid over-designing the system, the algorithm can be used to minimise either the asymptotic gain or the cross-over frequency of the open-loop system. Some preliminary results of this work have appeared in Zolotas et al. (1999).