Rockwell Automation 1771-QDC, D17716.5.93(Passport) PLASTIC MOLDING MODULE - Manual (Page 107)

Load Initial Configuration Values
Chapter 7
7-21
Type of PID Pressure Algorithm
(FCC02, SCC02, TCC02, LPC02, INC02, PKC02, HDC02, PLC02, FOC02, SOC02,
TOC02, OSC02, EAC02, ERC02)
When executing pressure versus position or time profiles, the QDC module
can use one of two types of PID algorithms: dependent gains (ISA) or
independent gains (Allen-Bradley).
If B07 = : Then it uses:
0 Dependent Gains (ISA)
1 Independent Gains (AĆB)
Dependent gains (ISA):
Output = Kc[(E) + 1/Ti
o
∫ t (E)dt + Td*d(E)/dt]
Independent gains (AB):
Output = Kp(E) + Ki
o
∫ t (E)dt + Kd*d(E)/dt
Comparison of Gain Constants
Compare dependent and independent gains constants as follows:
Dependent Gains Constants: Independent Gains Constants:
Controller Gain K
c
(dimensionless) Proportional Gain K
p
(dimensionless)
Reset Term 1/T
i
(minutes per repeat) Integral Gain K
i
(inverse seconds)
Rate Term T
d
(minutes) Derivative Term K
d
(seconds)
Other variables used in any algorithm choice include:
Output = Percentage of full scale
E = Error (scaled) SP-PV (Setpoint-Process Variable)
PV = Process Variable (scaled)
Convert from dependent to independent gains constants by substituting
controller gain (K
c
), reset (1/T
i
), and rate (T
d
) values in these formulas:
K
p
= K
c
unitless
K
i
= K c
60 T
i
inverse seconds
K
d
= K
c
(T
d
)60 seconds
We recorded bit B07 = 1 for A-B independent gains on all corresponding
worksheets.
Select the Type of
PID Algorithm