Fisher FIELDVUE DVC6200f - Proportional;Integral;Derivative; Function Block

Instruction Manual
D103412X012
Detailed Setup—PID Function Block
July 2013
126
PID Function Block
Overview
The PID function block (figure 4‐9) combines all of the necessary logic to perform proportional/integral/derivative
(PID) control. The block supports mode control, signal scaling and limiting, feedforward control, override tracking,
alarm limit detection, and signal status propagation.
Figure 4‐9. Proportional+Integral+Derivative (PID) Function Block
B2720
BKCALOUT
OUT
CAS IN
PID
BKCAL IN
FF VAL
IN
TRK
IN D
TRK
VAL
BKCAL_IN = THE ANALOG INPUT VALUE AND STATUS FROM ANOTHER BLOCK'S BKCAL
_OUT OUTPUT THAT IS USED FOR BACKWARD OUTPUT TRACKING FOR BUMPLESS
TRANSFER AND TO PASS LIMIT STATUS.
CAS_IN
= THE REMOTE SETPOINT VALUE FROM ANOTHER FUNCTION BLOCK.
FF_
VAL = THE FEEDFORWARD CONTROL INPUT VALUE AND STATUS.
IN
= THE CONNECTION FOR THE PROCESS VARIABLEFROM ANOTHER FUNCTION BLOCK.
TRK_
IN_D = INITIATES THE EXTERNAL TRACKING FUNCTION.
TRK_
VAL = THE VALUE AFTER SCALING APPLIED TO OUT IN LOCAL OVERRIDE MODE.
BKCAL_
OUT = THE VALUE AND STATUS REQUIRED BY THE BKCAL_IN INPUT OF ANOTHER
FUNCTION BLOCK TO PREVENT RESET WINDUP AND TO PROVIDE BUMPLESS TRANSFER
TO CLOSED LOOP CONTROL.
OUT
= THE BLOCK OUTPUT AND STATUS.
The block supports two forms of the PID equation: Standard and Series. You can choose the appropriate equation
using the MATHFORM [70] parameter. The Standard ISA PID equation is the default selection.
S
tandard Out + GAIN ex
ǒ
1 )
1
t
r
s ) 1
)
t
d
s
T t
d
s ) 1
Ǔ
)
Series Out + GAIN ex
ǒ
1 )
1
t
r
s
Ǔ
)
ǒ
t
d
s ) 1
T t
d
s ) 1
Ǔ
)
F
where
GAIN: proportional gain value
τ
r
: integral action time constant (RESET parameter) in seconds
s: laplace operator
τ
d
: derivative action time constant (RATE parameter)