The strip shape control of a cold rolling line is a multivariable process with a number of manipulated and controlled variables.

Among other things the following criteria have to be considered for the selection of a controller:

• The actuators have different actuator speeds, their response is not linear and they are coupled to each other, i.e. there are manipulated variable restrictions and the limitation of individual set values among each other;
• Dead times for the shape measurement and the shape actuators;
• Consideration of the shape data of the prior rolling passes;
• Disturbances due to the rolling process, e.g. dynamic load, speed and temperature changes, different rolling stock.

As to these requirements, conventional controllers reach their limit. The requirements can be met by the use of modern control modes (Advanced Process Control, APC) on the basis of a Model-Predictive Controller (MPC). The controller can predict the control behaviour of the process for the future by means of an integrated model and improves thus clearly the control quality and so the strip shape compared to a PID controller which intervenes only in case of a control deviation.The rugged controller structure leads to a high integrity in operational use, i.e. to a stable control response also in case of a discrepancy between measured and set values. Transparent and intuitive rules and operator interfaces are available for the controller adjustment and optimization, detailed knowledge about the complex structure of the MPC controller is therefore not necessary. Even in the cases of exact parameterization the controller finds the optimum value without any problem.