Stock-controlling method for a storage yarn feeder with rotary drum

A stock-controlling method for a storage yarn feeder, said yarn feeder being provided with a drum which is driven to rotate by a motor controlled by a control unit for drawing yarn from a reel and winding it upon itself in the shape of a plurality of loops forming a stock, in which said control unit:

• estimates the stock on the drum on the basis of an information indicative of the amount of yarn which is unwound from the drum upon request from a downstream machine, and of an information indicative of the amount of yarn which is wound on the drum, and
• retroactively controls said motor to substantially stabilize said stock on a reference value,
• wherein said control unit also performs a parallel correction routine in which:
• compares said stock with said reference value to estimate a stock status
• RES <REF_RES or RES >REF_RES,
• wherein RES is said estimated stock and REF RES is said reference value,
• compares said estimated stock status with a presence signal generated by sensor means adapted to generate an absolute binary information indicative of the presence/absence of yarn in a monitored area of the drum,
• and
• in case of an inconsistency between said estimated stock status and said presence signal, said control unit corrects said stock so that it converges toward said monitored area of the drum.