Using hydraulic roll force systems, steel makers have the ability to control precisely their steel sheet's gauge (thickness) while it is traveling at more than 50 miles per hour through the cold mill. Using feedback or feed-forward systems, a computer's gap sensor adjusts the distance between the reduction rolls of the mill 50-60 times per second. These adjustments prevent the processing of any off-gauge steel sheet. The principal components of a computerised AGC are :
1. Mathematical models that adequately describe the process.
2. Instrumentation to measure the required variables of the system.
3. Control equipment, including a digital computer, to perform the required functions for control of the system.