Onl p disturbancerejectionusingperiodicfeedbackcontrol (

In this paper, the performance of discrete time periodically time-varying controllers for rejection oflp specic and uniform disturbances is analyzed. For control of linear time-invariant plants, this paper distinguishes linear time-invariant controllers from linear non-time-invariant periodic controllers in the performance analysis. For a given linear non-time-invariant periodic controller, a linear time-invariant controller is constructed and necessary and sucient conditions are presented under which the linear time-invariant controller gives strictly better lp control than the non-time-invariant periodic controller. c 1999 Elsevier Science B.V. All rights reserved.