Control for parent roll unwinding apparatus and methods

1. A method of controlling a converting line, the method comprising:

providing a controller of a control system of the converting line;

providing at least one independently driven roll downstream of an unwinder around which the web passes downstream after being unwound from the unwinder;

providing a tension sensor downstream of the at least one driven roll, the tension sensor being adapted and configured to sense a tension in the web as the web is passed downstream of the at least one driven roll, the tension sensor being configured to generate a signal indicative of sensed web tension to the controller; and

enabling the controller to generate a signal to change the speed of the unwinder based upon the tension signals generated by the tension sensor.

2. The method of claim 1 wherein the step of the providing the at least one driven roll incudes providing the at least one driven roll with high traction.

3. The method of claim 2 wherein the step of the providing the at least one driven roll with high traction includes providing the at least one driven roll with a tungsten carbide coating.

4. The method of claim 2 wherein the step of the providing the at least one driven roll with high traction includes providing the at least one driven roll with a plasma coating.

5. The method of claim 1 further comprising:

enabling the controller to control the speed of the at least one driven roll that is disposed between the unwinder and the tension sensor independently of the tension signals generated by the tension sensor.

6. The method of claim 5 wherein the step of enabling the control includes enabling the control to control the speed of the at least one driven roll that is disposed between the unwinder and the tension sensor based upon a reference speed associated with processing rolls in the converting line downstream of the tension sensor.

7. The method of claim 5 further comprising:

providing a spreader roll downstream of the at least one driven roll, a second driven roll downstream of the spreader roll, wherein the tension sensor is disposed downstream of the second driven roll; and

enabling the controller to control the speed of the second driven roll independently of the tension signals generated by the tension sensor.

8. A control system for a converting line, wherein the converting line has an unwinder for unwinding web material from a roll of web material and at least one independently driven roll for directing the web material unwound from the unwinder to the converting line, the control system comprising:

a controller; and

a tension sensor adapted and configured to be arranged downstream of the at least one driven roll, the tension sensor being adapted and configured to sense a tension in the web as the web is passed downstream of the at least one driven roll, the tension sensor being configured to generate a signal indicative of sensed web tension and transmit the signal of sensed web tension to the controller;

wherein the controller is configured to a generate and transmit to the unwinder a signal to change the speed of the unwinder based upon the tension sensed by the tension sensor.

9. The control system of claim 8 wherein the controller is configured to control the speed of the at least one driven roll that is disposed between the unwinder and the tension sensor based upon a reference speed associated with processing rolls in the converting line downstream of the tension sensor.

10. The control system of claim 8 wherein the controller is configured to control the speed of a second driven roll independently of the tension signals generated by the tension sensor wherein the second driven roll is disposed in the converting line downstream of a spreader roll, the spreader roll is disposed in the converting line downstream of the at least one driven roll, and the tension sensor is disposed in the converting line downstream of the second driven roll.

11. The control system of claim 8 wherein the controller is configured to control the at least one driven roll that is disposed between the unwinder and the tension sensor in a manner to balance outgoing web velocity and upstream span strain.

12. The control system of claim 8 wherein the controller is configured to control the at least one driven roll that is disposed between the unwinder and the tension sensor with a first control loop that subtracts baseline components to provide a target output of torque that relates directly to a force imparted on the web.

13. The control system of claim 12 , wherein the baseline components comprise at least one of losses and acceleration torque.

14. The control system of claim 12 wherein the controller is configured to control the at least one driven roll that is disposed between the unwinder and the tension sensor with a second control loop, the second control loop is a velocity control loop, the second control loop generates a baseline command for a target torque output, the second control loop is trimmed by the first control loop to generate a desired web force with damping based on at least one of a modulus of the web and tensile properties of the web.

15. The control system of claim 12 wherein the controller is configured to control the at least one driven roll that is disposed between the unwinder and the tension sensor with a second control loop, the second control loop is a velocity and position control loop, the second control loop generates a baseline command for a target torque output, the second control loop is trimmed by the first control loop to generate a desired web force with damping based on at least one of a modulus of the web and tensile properties of the web.