Optimal control of continuous tandem cold metal rolling

The continuous tandem cold rolling of metal strip is a highly nonlinear multi-variable complex process the control of which presents additional challenges over those encountered in the control of stand-alone tandem cold rolling. These challenges arise during the passage of the weld, which joins the head of the next strip to the tail of the present strip to maintain the continuity of rolling. This paper presents the results of an investigation of the application of a control technique based on the state-dependent Riccati equation (SDRE) method to continuous tandem cold rolling, particularly during passage of the weld. Two methods of control during this regime of operation are evaluated and a preferred method is selected. Using the preferred method it was determined by simulation that the SDRE-based technique has the capability for successfully controlling the mill during weld passage, so that this approach offers a strong potential for improvement in the control of the continuous tandem cold rolling processes.