12 - 90
MELSEC-Q
12 CONTROL SUB FUNCTIONS
12.8.2 Follow up function
(1) Follow up function
The follow up function monitors the number of motor rotations (actual present
value) with the servo OFF and reflects the value in the present feed value.
Therefore, even if the servomotor rotates while the servo OFF, the servomotor
will not just rotate for the quantify of droop pulses the next time the servo turns
ON but positioning can be performed from the stop position.
(2) Execution follow up
Follow up function is executed continually during the servo OFF status.
OFF
Follow up function executed
ON
0
All axis servo ON (Y1)
Each axis servo OFF
command
Servo ON or OFF status
OFF
ON
Servo error detected
Fig. 12.51 Operation timings of follow up function
POINT
The follow-up function performs the process if the QD75 and the servo is turned
ON (servo LED indicates "b", "c", or "d".) regardless of the presence of the
absolute position system.
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