Advanced control to reduce the likelihood of cobbles in the tandem rolling of hot metal strip

The performance of our SDRE-based controller in the face of various extended uncertainties and disturbances was shown in our previous work to be highly successful. In our previous investigation we have taken the material of the workpiece to be of one phase (austenite) and of medium and low carbon equivalents. However, it is recognized that a disturbance such as a greater decrease in temperature while processing a material of extra-low carbon equivalent could result in a change in the phase of the workpiece. Such a change in phase can result in a wreck (a cobble) in the mill, with resulting downtime and the possibility of equipment damage. In this paper we expand our previous work to examine the effects of changes in the temperature of a workpiece of extra-low carbon equivalent and show that any resulting changes in the phase of the workpiece are effectively handled by our controller to reduce the likelihood of cobbles in the mill.