Rockwell Automation 9329 Drive Application Software Tension Control Gen. Units - Manual (Page 13)

FM – Tension Control
Drive Application Software – page 13 of 52
4.2 Supported Modes of Tension Regulation
4.2.1 Typical Tension Regulation Modes
The following modes of tension regulation are the most commonly employed. These
are not the only modes of tension regulation available, but are straight forward to
implement and commonly used in many industries.
4.2.1.1 Draw
Draw is the simplest form of tension control. The Draw control in the Process Line
Application Modules is supported through the RunJogSpdRf routine of the
LogixAndReference program. This type of tension regulation is typically used
without the tension regulator, but is sometimes used for speed offset in machines
that stretch the web. Variable diameter applications cannot be controlled with
only draw for tension regulation.
4.2.1.2 Dancer Position Control with Speed Trim
In this mode of tension control the tension (force) applied to the web is dependant
on the mechanical load applied to the dancer. The tension applied to the web is
independent of the regulating sections speed or torque as long as the mechanical
dancer has not reach it’s minimum or maximum travel limits. Typically, the
controlling section does not know the tension desired on the web. The controlling
section varies it’s speed to maintain the dancers position at typically 50% total
travel. The position feedback of the dancer is required by the controlling section.
4.2.1.3 Tension Feedback with Speed Trim
In this mode of tension regulation, the actual web tension is measured by a force
measurement device (load cell / transducer). The controlling section requires a
set point of web tension and the feedback of actual web tension. Based on the
values of these inputs the section will adjust (trim) it’s speed to maintain the
feedback tension equal to the set point tension.
4.2.1.4 Tension Feedback with Torque Trim (for Center Winder/Unwind)
This mode of tension regulation is recommended for Center Winder and Unwind
applications only. The actual web tension is measured by a force measurement
device (load cell / transducer). The controlling section requires a set point of web
tension and the feedback of actual web tension. The tension set point is used to
generate a base torque requirement. Based on the values of these inputs the
section will adjust (trim) it’s torque to maintain the feedback tension equal to the
set point tension.
4.2.1.5 Open Loop Torque Control (for Center Winder/Unwind)
This mode of tension regulation is recommended for Center Winder and Unwind
applications only. The actual web tension is not measured in this mode. As there
is not feedback device to “regulate” the tension, this mode of operation is called
“Open Loop”. The set point tension is used to calculate the required torque for
tension. If the losses for the machine change, the resultant tension on the web
will change as a result. The user can make adjustments to correct for losses.
4.2.1.6 Torque Follower
Torque follower is a special form of the “Open Loop Torque Control”. In this mode
the drive acts as in open loop torque control, but the torque set point is enter as
torque and typically communication from a master section. The torque set point in
the open loop torque control mode is entered as a tension set point.
4.2.2 Special Requirements Tension Regulation Modes
The following modes of tension regulation are specialized to particular industries or
require additional machine and mechanical data beyond what is typically available.
These additional requirements and sometimes the need of higher mathematics for
configuration, makes these modes of tension regulation more demanding on the