Multivariable control of interstand tension and exit height of the material for bar and wire rod rolling

To meet user requirements of higher dimensional accuracy of bar and wire rod products, the development of sophisticated dimension control technology for continuous rolling has been desired. As a result of basic research, a multivariable control system of interstand tension and exit height of the material at each stand using roll speed and gap as input vector has been developed based on the continuous rolling model and the optimal regulator theory. The validity of the multivariable control technique was verified by computer simulation and model mill experimentation. This paper describes (1) modeling, (2) control system design, (3) simulation and (4) experiment of the multivariable control of interstand tension and exit height of the material at each stand of bar and wire rod rolling using optimal regulator theory. On the basis of this new control system, a precision bar rolling system was practically implemented at the bar mill of Muroran Works, Nippon Steel Corporation in 1990