Function Block - Fisher FIELDVUEDVC6200f Instruction Manual

Instruction Manual
D103412X012
PID Function Block
Overview
The PID function block (figure E‐4) 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 E‐4. Proportional+Integral+Derivative (PID) Function Block
BKCAL IN
CAS 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 VARIABLE FROM 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.
B2720
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.
Standard Out + GAIN
e(x)
Series Out + GAIN
e(x)
where
GAIN: proportional gain value
τ
: integral action time constant (RESET parameter) in seconds
r
s: Laplace operator
τ
: derivative action time constant (RATE parameter)
d
BKCAL OUT
OUT
PID
t
s
1
1 ) ) d
t s ) 1 T t
r
d
t s ) 1
1 ) 1 t
s ) d
T t s ) 1
r
d
) F
s ) 1
)F
DVC6200f Digital Valve Controller
PID Function Block
February 2017
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