Rockwell Automation GMLC Reference Manual - Manual (Page 106)

Publication GMLC-5.2 - November 1999
Defining Feedback 69
For example, if the Unwind is 4 position units and the Unwind Reference
Point is -1 position units, the axis rotates up to 3 position units and
unwinds back to -1 position units.
The Unwind Reference value is entered in position and can be a positive
or negative number up to 10 digits. The default value is zero (0).
Encoder Filter
The Encoder Filter filters encoder input signals from a Master Only axis
(including a virtual axis) to other axes that are geared or pcammed to the
master axis. The Encoder filter provides a means to minimize noise from
externally controlled axes. Click on the Encoder Filter checkbox to
activate the Encoder Filter. When activated, the two parameters, Filter
Bandwidth and Filter Lag Limit, become active and must be set.
Filter Bandwidth
The Filter Bandwidth parameter sets the value to remove high frequency
noise above a specified bandwidth. The value must be set between 1 and
1000 Hz. A general rule for determining the Filter Bandwidth is to keep a
ratio for Filter Bandwidth to Servo Update at 1:10.
For example: If the controller has a servo update set at 500Hz the Filter
Bandwidth should be set at 50Hz.
All frequencies higher than the input value are filtered-out when the
encoder filter is ON .
Important: The ratio of Filter Bandwidth to Servo Update Rate (set in the
General page of the Configure Control Options dialog box)
should not exceed 1:10.