Rockwell Automation GMLC Reference Manual - Manual (Page 283)

Publication GMLC-5.2 - November 1999
246 Motion Blocks
Analog Offset Control Loop Operation
When you use the analog offset function, the controller reads the value
from the Flex I/O analog input module, adjusts the polarity if requested,
and computes the difference between it and the specified analog setpoint.
This value is then divided by the Analog Input Scalar, multiplied by the K
constant specified for that particular axis (the Feedback page of the
Conversion Constant set in the Configure Axis Use dialog box), and
provides an analog error value in encoder counts. The servo loop in the
motion controller seeks to null (reduce to zero) this error between the
setpoint and the actual analog input. This is done using the encoder counts
in commanding motion that is required for maintaining the analog
setpoint. When you operate in Analog Offset mode, the motor transducer
information and its feedback loop implementation remain unchanged. The
figure below shows the servo loop after an Analog Offset block is
executed.
Two Analog Offset axes system variables are available in GML
Commander:
• the Analog_Offset_setpoint