PCC-IV Instruction Manual (Rev. 0.1)
Page 6-26
Section 6
– Blockware Functions
Technical Reference
A Feedforward Input is provided which is summed with the P+I+D values prior to the Output Min/Max limiting logic.
This prevents Integral Term Reset-Windup when feedforward control strategies are used.
For control logic that does not use Integral action, an Output Bias (Parameter 12) is provided to allow changing the
PID
Output mid-point (i.e. the Output when PV=SP), see notes 8 and 9.
Track Mode: Multiple Track Mode Inputs are provided to allow Blockware based bumpless transfer during: Manual
to Auto, and Process Startup to Auto mode changes (see note 4). Track Mode causes the PID Output to be equal
to the Track Signal Input by forcing the "I" (Integral) term of P + I + D. See
FPT/H
(F38) for a bumpless transfer
Blockware example.
An Override Mode Input is provided to allow automatic Blockware based bumpless transfer in "Constraint" based
control strategies (see note 5). Override Mode forces the
"I" term to be equal to the Track Signal Input. Override
Mode will not be enabled unless Repeats/min is greater
than 0. An example of a Constraint based control logic is:
One of several boilers on a header is burning a process
off-
gas …modulate the burner’s firing rate based on Plant
Master firing rate, unless the off-gas supply pressure
drops, then reduce firing rate to maintain a minimum off-
gas supply pressure.
Non-linear systems such as pH, and furnace draft can be
controlled more effectively by using the Gap PID or
Adaptive gain
PID
modes (Parameter 9). Gap PID provides
a simple dual gain strategy (i.e., lower gain near setpoint,
higher gain farther away from setpoint). Adaptive gain PID
allows the gain to be changed continuously as a function
of a secondary variable using an
F(x)
Block (see notes 3
and 12).
---------------------------------------------------------------------------------------------
NAME: PID SINGLE USE FUNCTION: N OUTPUT TYPE: A
---------------------------------------------------------------------------------------------
Input Type Description Notes
_____________________________________________________________________________________________
1 A PV INPUT
2 A SP INPUT
3 A TRACK SIGNAL INPUT 1
4 A FEED FORWARD INPUT 2
5 A ADAPTIVE GAIN INPUT 3
6 D TRACK MODE 1 INPUT (1=TRACK) 4
7 D TRACK MODE 2 INPUT (1=TRACK) 4
8 D TRACK MODE 3 INPUT (1=TRACK) 4
9 D OVERRIDE MODE INPUT (1=OVERRIDE) 4
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 GAIN 10.00 100.00 0.10 2
2 INTEGRAL, REPEATS/MIN O=OFF 1.00 60.00 0.00 2 8
3 DERIVATIVE, MINUTES 0=OFF 0.00 30.00 0.00 2
4 SETPOINT FILTER 0=OFF,
1.00=MAX 0.00 1.00 0.00 2 6
5 MAX OUTPUT % 100.00 150.00 0.00 2 7,8
6 MIN OUTPUT % 0.00 50.00 -50.00 2 7,8
7 CONTROL ACTION 0=REV 1=DIR 0 1 0 3 10
8 DERIVATIVE ACTION 0=PV 1=ERROR 0 1 0 3 11
9 PID TYPE 1=PID,2=GPID,3=APID 1 3 1 3 3,12
10 GAP BAND (+/-% OF PV) 0.25 50.00 0.05 2 12
11 GAP GAIN MULTIPLIER 0.00 1.00 0.00 2 12
12 OUTPUT BIAS 0.00 100.00 -100.00 2 8,9
-10
-8
-6
-4
-2
0
2
4
6
8
10
-5
-4
-3
-2
-1
0
1
2
3
4
5
"P"
term
of PI
D, or
(E*G)
% Error (SP-PV)
GAP PID, GAP=2%, Gap Gain=.33, Gain=3
