Method and apparatus for dynamically controlling a web printing press

A method for dynamically controlling a driver of a nip roller in a web printing press, the method comprising:

• controlling a speed of the driver in a tension-control mode during a start-up phase of operation of the printing press, the controlling of the speed of the driver in the tension-control mode being based on the upstream web tension so as to maintain the tension at a first desired tension value;
• then
• achieving a steady-state speed of the driver;
• then
• determining a driver velocity ratio during a transition phase of the printing press operation, the driver being at a steady state speed during the transition phase, the velocity ratio being proportional to a ratio of the speed of the driver needed to produce a given desired tension value to a value of a velocity command of the web printing press;
• then
• controlling the speed of the driver in a velocity-control mode during a printing phase of the printing press operation, the controlling of the speed of the driver in the velocity-control mode being based on the driver velocity ratio for maintaining the tension at a second desired tension value;
• then
• switching to the controlling the speed of the driver in the tension-control mode at at least one of a time when the tension moves outside of a desired web tension limit band, a time when the tension is likely to move outside of the desired web tension limit band, in response to an operator input, and periodically;
• then
• determining a revised driver velocity ratio during a time when the driver is at a steady-state speed in the tension-control mode;
• and then
• switching to the controlling the speed of the driver in the velocity-control mode using the revised driver velocity ratio.