Minimum Variance Control in Leveling Slivers

Abstract

This paper presents procedures to design a minimum variance control for leveling slivers in a double-zone drafting process. We model a random sliver and consider the drafting model as a stochastic system with a zero-mean white noise process and a constant sequence representing the input-sliver mean thickness. Such a model enables the proposed control algorithm not only to smooth out the irregularity of the output sliver, but also to regulate the mean thickness at the desired value. We develop the minimum variance control applicable to our stochastic model based on an optimal predictor. Since some parameters and the noise process are not exactly known, identification is used to refine the model, and the control law is thus designed based on the identified model. The simulation results demonstrate that the algorithm can achieve goals by adjusting the speed of either the back or front roller.