Instruction Manual

Load Initial Configuration Values
Chapter 7
7-14
Type of PID Algorithm
(INC02, PKC02, HDC02, and PLC02)
When executing pressure or screw RPM 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(B03) = : Then it uses:
0 Dependent Gains (ISA)
1 Independent Gains (AB)
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 Kc (dimensionless) Proportional Gain Kp (dimensionless)
Reset Term 1/Ti (minutes per repeat) Integral Gain Ki (inverse seconds)
Rate Term Td (minutes) Derivative Term Kd (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 gain constants by substituting
controller gain (Kc), reset (1/Ti), and rate (Td) values in these formulas:
Kp = Kc unitless
Ki =
Kc
60 T i
inverse seconds
Kd = Kc(Td)60 seconds
We recorded bit B07 (B03) = 1 for A-B independent gains on all
corresponding worksheets.
Select the Type of
PID Algorithm