Tension-controlling method for a yarn unwinding from a storage yarn feeder to a textile machine.

摘要

The yarn tension is modulated by a yarn-braking device (20) controlled by a control unit (CU) which receives signals of measured tension (T_meas) from a tension sensor (22) and compares them with a reference tension signal (T_ref) in a control loop (CL) having a proportional-integral controller (PI) generating a braking signal (BI) which minimizes the difference ( e ) between the measured tension and the reference tension. As long as the reference tension (T_ref) remains unchanged, a first set of coefficients (Kps and Kis) is used in the control loop (CL) causing the control loop (CL) to have a relatively slow behaviour in relation to the error-compensating action. When a change in the reference tension occurs, the system switches to a second set of coefficients (Kpf and Kif) causing the control loop (CL) to have a relatively fast behaviour. The second set of coefficients (Kpf and Kif) is maintained as long as the difference ( e ) between the second value of the reference tension (T'_ref) and the measured tension (T_meas) remains greater or equal to a predetermined minimum value ( e_min ), then the system switches again to the first set of coefficients (Kps and Kis).