Control strategies for rolling mills

The author describes the main features of a distributed control system for industrial continuous processes and, in particular, for applications involving hot rolling mills for wire rods, round bars, and profiles. In rolling mills, a very good tension and loop control increases the plant efficiency, avoids cobbling, and allows a better material quality. Not only a good measurement of process quantities but also appropriate signal processing and good synchronized control algorithms are necessary. Results showing the control performance of the system and tension control in less than a 300 ms stand-distance are reported. R&D results using cycloconverter fed induction motors with field-oriented control are discussed. The first such system was installed for the revamping of a 15 stands mill and has been successfully operating since Sept. 1990; an increase of productivity of over 18% has been achieved