Nonconservative QFT bounds for tracking error specifications

Abstract

SUMMARY An alternative to the traditional QFT tracking problem, in which upper and lower tolerances are imposed on the magnitude of the tracking transfer function, is to define the robust specification as a boundary on the deviation of such function from a predefined model. However, previous research exploring this approach reveals a certain overdesign and dependence on the choice of the nominal plant. This paper establishes a necessary condition on the controller from tracking error specifications. With this condition, the controller bounds introduce no overdesign, and the resulting two‐degrees‐of‐freedom design is independent of the choice of the nominal plant, similar to the traditional approach. Copyright © 2011 John Wiley & Sons, Ltd.