6-12
<Toc>
<6. Parameters>
IM 05E01D02-41E
1st Edition : May 31,2000-00
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Selecting PID Constants According to the Deviation
PID constants can be selected according to the deviation in two ways. One method is to
select a group of PID constants only by a deviation from a program setpoint. The other
method is to use a reference point, as discussed earlier, as well as a deviation from a
program setpoint, to switch between groups of PID constants. Deviation-based switching
has priority over switching based on a reference point.
[Method 1]
As shown in the figure below, the controller selects the 4th group of PID constants if the PV
input value goes beyond the given deviation from the program setpoint.
[1]
The controller uses the 1st group of PID constants.
[2]
The controller uses the 4th group of PID constants (i.e., the 4.P, 4.I and 4.D operating
parameters for the 4th group).
Reference
deviation (RDV)
Maximum value of PV
input range (RH)
Minimum value of PV
input range (RL)
Program setpoint
Segment 1
Segment 2
PV input value
Reference
deviation (RDV)
[1]
[1]
[2]
[1]
[2]
[2]
[Method 2]
As shown in the figure below, the controller selects an appropriate group of PID constants
for each zone and, if the PV input value goes beyond the given deviation from the program
setpoint, selects the 4th group of PID constants.
[1]
The controller uses the 1st group of PID constants if the PV input value is both within
the zone set off by the minimum value of the PV input range and reference point 1 and
within the given reference deviation bandwidth.
[2]
The controller uses the 2nd group of PID constants if the PV input value is both within
the zone set off by reference point 1 and the maximum value of the PV input range
and within the given reference deviation bandwidth.
[3]
The controller uses the 4th group of PID constants if the PV input value goes beyond
the given reference deviation bandwidth.
Reference
deviation (RDV)
Maximum value of PV
input range (RH)
Reference point 1
Minimum value of PV
input range (RL)
Program setpoint
Segment 1
Segment 2
PV input value
Reference
deviation (RDV)
[1]
[3]
[2]
[3]
[3]
[2]
[1]
Summary of Contents for UP350
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