Patent ID: 6904331

Claim:
A method for controlling a paper machine, comprising the steps of: solving difference equations obtained by differentiating heat transfer equations that hold true among a steam drum, web and canvas; predicting a dryer steam pressure after grade change; and using said predicted dryer steam pressure as a dryer steam pressure setpoint after grade change; wherein the initial value of a web's moisture percentage at a dryer part inlet is calculated according to changes in a bone dry coated weight and machine speed when solving said difference equations; and wherein the initial value of said web's dryer part inlet moisture percentage after grade change is evaluated according to the following equation; initial ⁢ ⁢ value ⁢ ⁢ of ⁢ ⁢ web ’ ⁢ s ⁢ ⁢ moisture ⁢ ⁢ percentage = MPNowInit + A 1 · BD 2 - BD 1 BD 1 + A 2 · V 2 - V 1 V 1 where BD 1 =bone dry weight before grade change BD 2 =bone dry weight setpoint after grade change V 1 =machine speed before grade change V 2 =machine speed setpoint after grade change; and A 1 , A 2 , and MPNOWInit=parameters.