Diameter control of copper rod in hot rolling processes

Abstract

This paper aims to address the issue of fluctuations of copper rod diameter during the process of hot rolling. In addition, it proposes a solution to control the diameter of the copper rod in order to improve the quality of the hot rolling mill products. The change of copper rod diameter during the process of hot rolling results from disturbance effects (such as temperature, torque loading, and plant ageing) which leads to the deterioration of product quality. To overcome changes in the copper rod diameter, a proportional-integral-derivative (PID) based on a particle swarm optimization, auto tuning diameter controller was designed to reduce the fluctuations in the rod diameter and different control techniques with variable structure PID controllers were proposed, evaluated, and compared by extensive simulation tests. The PID diameter controller was designed based on the experimental data that showed that the speed of the rolls leads to sensible differences in the copper rod diameter. It was also designed to guarantee that the synchronization between the stands of the rolling mill is maintained so that the metal flow rates from the first stand to the last one is kept constant. Moreover, it was designed in a way which assures that the tension of the cast bar will remain unchanged and does not conflict with the tension controller. The design of the diameter controller, modeling, validation, verification and simulation of the rolling mill process is presented, which involves the reduction of the copper rod diameter by passing the hot cast bar through a preset roll gap between two work rolls that are driven by a DC motor. A proposed combined-control of motor speed and rod diameter controller reduces fluctuations in the rod diameter.