Method and arrangement in connection with winder drive

An arrangement in connection with a continuous material web, the material web running from an unwinder to a winder, at least one of the winders being a center winder, wherein the center winder is controlled by an electric drive provided with a torque control, the arrangement comprising:

• means for providing an initial value for density of a material on the center winder;
• means for calculating a moment of inertia of a roll of material on the center winder;
• a mechanical tightness sensor configured to determine tightness of the material web;
• a tightness controller configured to produce a correction term for torque calculation on the basis of a material web tightness reference, the determined material web tightness and the calculated moment of inertia of the roll of material on the center winder;
• means for calculating a torque reference on the basis of the correction term produced by the tightness controller and the calculated moment of inertia of the roll of material on the center winder;
• means for controlling the torque of the center winder on the basis of the torque reference;
• and
• means for correcting a density value of the material on the center winder on the basis of the correction term produced by the tightness controller.

A non-transitory computer-readable recording medium having a program recorded thereon that causes a processor of a computer processing device to carry out operations in connection with a continuous material web, the material web running from an unwinder to a winder, at least one of the winders being a center winder, and the center winder being controlled by an electric drive provided with a torque control, the program causing the processor to carry out operations comprising:

• providing an initial value for density of a material on the center winder;
• calculating a moment of inertia of a roll of material on the center winder;
• determining tightness of the material web;
• producing, by a tightness controller, a correction term for torque calculation on the basis of a material web tightness reference, the determined material web tightness and the calculated moment of inertia of the roll of material on the center winder;
• calculating a torque reference on the basis of the correction term produced by the tightness controller and the calculated moment of inertia of the roll of material on the center winder;
• controlling the torque of the center winder on the basis of the torque reference;
• and
• correcting a density value of the material on the center winder on the basis of the correction term produced by the tightness controller.