Discrete-time Model Reference Control of Milling Forces under Fractional Order Holds. Part I: Known Plant

This paper introduces a novel model-reference discrete-time control scheme applied to milling processes. The novelty of the scheme relies on the use of a fractional order hold (FROH) instead of a traditional ZOH used in the manufacturing literature to obtain a discrete-time model of the continuous system. The additional degree of freedom introduced by the FROH through its correcting gain allows the designer to improve the transient response of the closed-loop system by an adequate choice of its value. Simulation examples showing the influence of the correcting gain in the closed-loop response are presented and compared. The control scheme is applied in this paper to known piecewise-constant plants being subsequently extended to unknown ones through adaptive control.