Rockwell Automation 1784-PM16SE SoftLogix Motion Card Setup and Configuration Manual User Manual
Page 357
Publication 1784-UM003A-EN-P – June 2003
Motion Object Attributes 349
Since Drive Status Attributes values are resident in the drive, these values need
to be transferred to the ControlLogix processor module on a regular basis. To
avoid unnecessary communication traffic transferring data that is not of
interest, it is necessary to explicitly activate transfer of the specific Drive Status
Attribute data from the drive using the Axis Info Select attributes. Thus, a
Servo Status Attribute value is ONLY valid if the attribute has been selected
by one of the Axis Info Select attributes. Otherwise the Drive Status Attribute
value is forced to zero.
In order for the above position unit-based attributes to return a meaningful
value, the ‘Conversion Constant’ Axis Configuration Attribute must be
established. Furthermore, attributes having velocity or acceleration units (e.g.
Position Units / Sec) must also have a valid coarse update period which is
established through association with a fully configured Motion Group Object.
Each of the Drive Status Attributes appears in the following Servo block
diagram.
Figure 13.16 Motor Position Servo Loop Diagram