A new approach to multivariable quantitative feedback theory: theoretical and experimental results

During the past three decades, several techniques have been suggested for robust performance design of multivariable systems within the framework of quantitative feedback theory. They are all characterized, and limited, by the use of loop transmission inversion. This paper proposes a new design approach within this framework leading to a technique which does not involve loop transmission inversion. Loop inversion is shown to be a superfluous step in present quantitative feedback theory techniques. The control design of compact disc mechanism with robust performance specifications and its successful implementation illustrates a realistic application of the new technique.