Positive/negative hardware overtravel faults, Feedback loss fault, Feedback noise fault – Rockwell Automation 1784-PM16SE SoftLogix Motion Card Setup and Configuration Manual User Manual
Page 319
Publication 1784-UM003A-EN-P – June 2003
Motion Object Attributes 311
Positive/Negative Hardware Overtravel Faults
If either the Positive Hard Overtravel Status or Negative Hard Overtravel
Status bit attributes are set it indicates that the axis has traveled beyond the
current position limits as established by hardware limit switches mounted on
the machine. To recover, the axis must be moved back with normal operation
limits of the machine and the limit switch reset. This fault condition is latched
and requires execution of an explicit MAFR (Motion Axis Fault Reset) or
MASR (Motion Axis Shutdown Reset) instruction to clear.
Feedback Loss Fault
If the Feedback Loss Fault bit is set for a specific feedback source, it indicates
that one of the following conditions occurred:
The differential electrical signals for one or more of the feedback channels
(e.g., A+ and A-, B+ and B-, or Z+ and Z-) are at the same level (both high or
both low). Under normal operation, the differential signals are always at opposite
levels. The most common cause of this situation is a broken wire between the
feedback transducer and the servo module or drive.
Loss of feedback “power” or feedback “common” electrical connection
between the servo module or drive and the feedback device.
This fault condition is latched and requires execution of an explicit MAFR
(Motion Axis Fault Reset) or MASR (Motion Axis Shutdown Reset)
instruction to clear.
Feedback Noise Fault
If the Feedback Noise Fault bit attribute is set for a specific feedback source, it
indicates that simultaneous transitions of the feedback A and B channels has
been detected by the servo module which is referred to generally as feedback
noise. Feedback noise (shown below) is most often caused by loss of
quadrature in the feedback device itself or radiated common-mode noise
signals being picked up by the feedback device wiring, both of which may be
able to be seen on an oscilloscope.
Figure 13.7 Feedback Noise