Robust band tension control

A non-transitory automated processor-readable medium comprising machine code recorded on the medium, and wherein the code is configured such that when the code is executed by the automated processor, the code controls a control unit of a multi-stand rolling train rolling a metal strip firstly in a front roll stand of the multi-stand rolling train and then in a rear roll stand of the multi-stand rolling train;

• wherein a strip tension prevailing in the metal strip between the front roll stand and the rear roll stand, is detected by means of a looper applied to the metal strip between the front roll stand and the rear roll stand;
• wherein the processing of the code by the control unit causes:
• the control unit to receive the detected strip tension;
• a first tension controller of the control unit, to which the strip tension is supplied, to determine an adjustment additional setpoint value;
• a second tension controller of the control unit, to which the strip tension is supplied, to determine a velocity additional setpoint value;
• wherein the second tension controller determines a value less than zero as the velocity additional setpoint value when the strip tension lies below a lower strip tension limit, determines a value greater than zero as the velocity additional setpoint value when the strip tension lies above an upper strip tension limit, and returns the velocity additional setpoint value to a value zero the strip tension lies between the lower and the upper strip tension limits;
• adjusting of the rear roll stand according to the adjustment additional setpoint value, and adjusting of at least one of the front roll stand according to the velocity additional setpoint value with positive sign and the rear roll stand according to the velocity additional setpoint value with negative sign;
• and
• the first tension controller to determine the adjustment additional setpoint value using a determination rule on the basis of a deviation of the strip tension from a setpoint tension, which lies between the lower and the upper strip tension limits,
• wherein the determination rule sets a value not equal to zero as the adjustment additional setpoint value when the strip tension is between the lower and the upper strip tension limits.