Computer-based feedforward and constant volume flow AGC systems used on strip cold rolling mill

The author reports on the use of automatic gauge control (AGC) systems based on the constant volume flow (CVF) equation for use in a strip cold rolling mill. In the particular system described, a feedforward control system measures entry strip deviations every 50 mm, and sends a correction signal to the hydraulic screwdown as the deviation enters the roll gap, keeping the outgoing gauge constant. The calculation of the exit gauge at the work rolls is based on the CVF equation. This control calculates, from entry strip speed, exit strip speed, and entry thickness, the thickness of the strip as it leaves the roll gap itself. The calculated thickness in the roll gap is used as a feedback in a closed-loop system controlling the roll gap, so that the desired strip thickness is obtained