Fuzzy control algorithm for the prediction of tension variations in hot rolling

It is well known that the production of hot coils in uniform thickness depends on Various process parameters such as the material, the number of rolling stages, the reduction ratio of the thickness, the rolling speed, the front and back tensions, the friction between the material and rolls, the rolling temperature, and the rolling force at each stage of rolling. In the present study, the effect of front and back tensions on reducing the thickness deviations of hot rolled steel strips were investigated by developing a fuzzy control algorithm. In order to derive the fuzzy control rules, rigid-viscoplastic finite element simulations were carried out using the material property determined from the production data. A simple empirical relationship obtained under the steady-state condition was used for determining the strip thickness. As a result, the thickness variation was determined depending on the change of the magnitude in the rolling force, which is influenced by the front and back tensions in the rolling of steel strips. The results obtained from the present study can be used to establish a database for looper control in hot rolling processes by determining the effect of the front and back tensions and selected process parameters on the maintenance of the uniformity of the strip thickness. Through this study, the capability and usefulness of fuzzy application in thickness control in hot rolling was clearly demonstrated. (C) 1999 Elsevier Science S.A. All rights reserved.