Rockwell Automation 2090 Ultra3000 Servo Drives Integration Manual - Manual (Page 142)

Publication 2098-IN005C-EN-P — March 2008
142 Minimizing the Effects of Feedback Signal Loss
Setting Position Error
Limits in Ultraware and
RSLogix 5000 Software Parameters for setting the position and velocity error limits according
to the specific needs of the user application exist in both the
Ultraware and the RSLogix 5000 software. Adjust these limit settings to
be as close to the maximum position and velocity error excursion limit
values of the application as possible, but wide enough to avoid
nuisance fault tripping. This lets the drive detect abnormal operating
conditions and proceed to proper fault handling as quickly as
possible. The method and the degree of adjustment will vary
depending on the application and on whether Ultraware or
RSLogix 5000 software is used.
Minimizing the Position Error Limit Setting
By minimizing the position error limit setting, the amount of motion
that can take place before the condition of Excess Position Error (E19)
is met can be restricted to a safe value. This safe value is dictated by
the application and is defined by you. Adjustment of the position error
limit setting is performed by using RSLogix 5000 or Ultraware
software, depending on the application.
Setting Position Error Limit Parameters
Adjust the Position Error Tolerance parameter if using RSLogix 5000
software. This parameter is found in the Limits tab of the Axis
Properties dialog. The range for this parameter is 0…2147483647
position units, with a default value determined by the motor or
encoder device selected.
You can convert a value, expressed in position units, to a number of
axis revolutions by using the raw feedback count, interpolation factor,
drive count, and conversion properties of the motor or encoder device
and of RSLogix 5000 software Axis Properties settings. In the
RSLogix 5000 software, the TTL encoder device interpolation factor is
fixed at 4, so 2000 raw feedback counts per revolution results in 8000
interpolated feedback counts per revolution. For sin/cos encoder
devices, the interpolation factor is fixed at 2048. The SR encoder
devices produce 1024 raw feedback counts per revolution, while the
SK encoder devices produce 128 raw feedback counts per revolution.
The resulting range of interpolated feedback counts per revolution is
262144…2097152, depending on which sin/cos encoder device is
used. Interpolated feedback counts are converted to drive counts by
using the Drive Resolution ratio constant found in the Drive/Motor tab
of the Axis Properties dialog. Drive counts are converted to position
Software Application Parameter
RSLogix 5000
SERCOS
Position Error Tolerance,
Axis Properties, Limits tab
Non-SERCOS
Ultraware Non-SERCOS Following Error Limit, Faults branch