Discrete-time model reference control schemes of milling forces using fractional order holds

Increasing competence makes to develop and implement more complex control schemes on manufacturing environments. In this paper, a discrete time model reference control for practical milling using different discretization of the continuous-time plant is presented. The different models of the scheme are obtained from a set of different discretizations of a continuous-time milling system transfer function under a fractional-order-hold of correcting gain beta isin [-1,1] beta (- FR OH). The objective is to design a supervisory scheme which is able to find the most appropriate value for the gain beta in an intelligent design framework. A tracking performance index evaluates each possible discretization and the scheme chooses the one with the smallest value of the index in order to generate the real control input to the plant. Two different methods of adjusting this value are presented and discussed. The first one selects it among a fixed set of possible values, while the second one the value of beta is updated by adding or subtracting a small quantity.