Multivariable control of wire rod rolling using optimal regulator theory

To meet user requirements for higher dimensional accuracy of wire rod products, a multivariable control system for the exit height and width of the billet at the finishing stand using roll gap as input vector has been developed based on the continuous rolling model and the optimal regulator theory. The linear state equations of tandem rolling in the finishing block mill are derived from the static rolling model using influence coefficients and a roll gap driving dynamic model. Control system designs of finishing height and width in the finishing block mill are introduced. The control law is implemented by state vector feedback and disturbance vector feedforward. To evaluate the control performance, step responses due to entry diameter and temperature change are computed and measured on a four-stand tandem model mill. The computed and experimental results confirm the validity of the control systems considered. Using this system, a precision wire rod rolling system is scheduled to be put into operation in 1993 at the Muroran Works of the Nippon Steel Corporation