Evaluation of a NMPC Flowrate Controller for a Hot Rolling Finishing Mill for Steel Bars

Abstract

In this work, the material flowrate control of a hot rolling finishing mill for steel bars is evaluated in simulation. First, a reduced model for control purpose is developed and described. This model uses nonlinear equations from the rolling theory and leads to the nonlinear control structure. The simulations are tested on a hot rolling mill simulator that implements a more detailed process behavior and is outside of the scope of this work. For controlling this plant, a Nonlinear Model Predictive Control (NMPC) is tested in various conditions. It is compared as a benchmark with a classical Linear Quadratic Regulator with integral action (LQI). The controller is implemented with help of CasADi and the control problem is solved by a SQP solver. The NMPC uses an underlying EKF as disturbance observer to handle the reference tracking problem.