FVP 110 Fieldbus Valve Positioner Manual
162
GE Energy
Feed-forward
Feed-forward adds a compensation input signal FF_VAL to the output of the PID control
computation and is typically used for feed-forward control. In practice, the value of the
change in FF_VAL is scaled to the range of the OUT, multiplied by the value of FF_GAIN,
and then added to the PID control computation result, as illustrated by Figure 73.
When the status of FF_VAL is Bad, the value of LUV (Last usable value) is used instead
of FF_VAL. If LUV contains no value, the feed-forward action is not carried out.
Figure 73 Feed-forward
External-output Tracking (LO)
External-output tracking outputs the value of the remote output TRK_VAL set from
outside the PID block (Figure 74). External tracking is performed when the block mode is
LO.
Figure 74 External-value Tracking
To change the block mode to LO:
1. Set Track Enable in CONTROL_OPTS (see “CONTROL_OPTS” on page 163) to
true.
2. Set TRK_IN_D to true.
However, to change the block mode from Man to LO, Track in Manual must also be set as
true in CONTROL_OPTS.
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