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Self-tuning control in Cold Rolling Mills

Outokumpu stainless is using sefl-tuning AGC control in all the cold rolling mills since they have found out that it achieves a better production result than other control methods.

Adaptive toolbox

  • Self-tuning feedback control
  • Self-tuning mass flow control
  • Self-tuning feedforward control
  • Adaptive gap position/force control
  • Adaptive roll gap preset function
  • Adaptive mass flow preset function
  • Thick end disturbance reduction
  • Auto AGC control start-up sequence 


Adaptive control in MicroController XC (pdf 186kB)
Improved AGC Control using adaptive technique in Cold Rolling Mill (pdf 616kB)

Self-tuning control in Cold Rolling Mills

The major difficulty in strip thickness control is the high speed combined with changing strip qaulities and the high accuracy that is required. The control system will face a “new process” for each new strip entering the mill. This is exactly the kind of problems that are effectively solved by self-tuning regulators.

First Control’s self-tuning AGC Control uses only one regulator setup for all rolling. The regulator adapts by itself to different strip qualities and rolling speeds. There is no need to make special tuning for different strip qualities, the regulator normally works well already after one test coil.

This also means that the Mill reaches a good production level almost directly. The tuning work after that consists mainly of adjustments in signal filters, protective network, timing etc.

The self-tuning regulator is predictive and uses many regulator parameters internally, which means that it can take more intelligent control action than is possible with a conventional design, based on gain-scheduled PID regulators.

Our experience from various AGC installations shows clearly that the improvement in thickness deviation is about 50-75% with First Control’s self-tuning thickness control.

Examples of self-tuning AGC control

Below we show two recordings of self-tuning strip thickness control in the new Mitsubishi-Hitachi mill at Outokumpu Stainless in Sweden. The recordings are made using the Replay package in the FirstOpNet client.

Thin strip 0.200 mm

The exit thickness is kept within 0.6um throughout the strip. Some large disturbances are removed by mainly self-tuning feedforward control. Note the change in strip hardness in the middle, which is efficiently controlled by self-tuning mass flow control

Thick strip 1.000 mm

The entry thickness is heavily disturbed due to earlier manual running. Nearly all entry disturbances are removed in exit thickness by very precise self-tuning feedforward control.