Yokogawa YVP110 - Manual (Page 84)

<16. PID Function Block>
16-3
IM 21B04C01-01E
16.9 Feed-forward
Feed-forward is an action to add 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
16.4.
When the status of FF_VAL is Bad, the value of
LUV(Lust usable value) is used instead of FF_VAL.
If LUV contains no value, the feed-forward action is
not carried out.
F1604.ai
FF_SCALE
OUT_SCALE
FF_GAIN
Value in engineering unit
PID computation result OUT
0-100%
FF_VAL
X
Figure 16.4 Feed-forward
16.10 External-output Tracking
(LO)
External-output tracking is an action of outputting
the value of the remote output TRK_VAL set from
outside the PID block, as illustrated in the figure
below. External tracking is performed when the
block mode is LO.
F1605.ai
Scaling
(based on TRK_SCALE
and OUT_SCALE)
PID control
computation result
OUT
TRK_IN_D
TRK_VAL
LO mode
Figure 16.5 External-value Tracking
To change the block mode to LO:
(1) Set Track Enable in CONTROL_OPTS (see
Section 16.12) 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.
16.11 Measured-value Tracking
Measured-value tracking, also referred to as SP-PV
tracking, is the action of equalizing the setpoint SP
to the measured value PV when the block mode
(MODE_BLK.actual) is Man in order to prevent a
sudden change in control output from being caused
by a mode change to Auto.
While a cascade primary control block is performing
automatic control in Auto or Cas mode, when the
mode of its secondary control block is changed from
Cas to Auto, the cascade connection is opened and
the control action of the primary block stops. The
SP of the primary controller can also be equalized
to its cascade input signal CAS_IN in this case.
The settings for measured-value tracking are made
in the parameter CONTROL_OPTS, as shown in
Table 16.3.
16.12 CONTROL_OPTS
CONTROL_OPTS is a parameter that stipulates
control options as shown below.
Table 16.3 CONTROL_OPTS of PID Block
Bit
Options in
CONTROL_
OPTS
Description
0 Bypass
Enable
Switch for activating the control
action bypass
1 SP-PV Track
in Man
Equalizes SP to PV when MODE_
BLK.target is set to Man.
2 SP-PV Track
in Rout
Equalizes SP to PV when MODE_
BLK.target is set to ROut.
3 SP-PV Track
in LO or IMan
Equalizes SP to PV when MODE_
BLK.actual is set to LO or IMan.
4 SP Track
retained
Target
Equalizes SP to RCAS_IN or
CAS_IN when MODE_BLK.target
is either in IMan, LO, Man or ROut
and MODE_BLK.actual is set to
RCas or Cas.
5 Direct Acting Set the PID block to be a direct
acting controller.
7 Track Enable While this option is set, if the value
of TRK_IN_D becomes '1', the
mode transfers to LO.
8 Track in
Manual
Set this option when the mode
should be transfered to LO even
when MODE_BLK.target is set to
Man. This option is invalid when
Track Enable option is not set.
9 Use PV for
BKCAL_OUT
Sets the value of PV in BKCAL_
OUT and RCAS_OUT, instead of
the value of SP.
12 Obey SP limits
if Cas or RCas
Puts the setpoint high/low limits in
force in the Cas or RCas mode.
13 No OUT limits
in Manual
Disables the high/low limits for
OUT in the Man mode.