Preliminary User Manual UMAX023241 - Version: 1.1 24-63
1.8.
PID Control Function Block
Figure 13: PID Block objects
The PID Control function block is an independent logic block, but it is normally intended to be
associated with proportional output control blocks described earlier. When the
Control Source
for
an output has been setup as a ‘PID Function Block’, the command from
the selected PID block drives
the physical output on the AX023241 Controller.
The 2453h
PID Target Command Source
and 2454h
PID Target Command Number
objects
determine control input and the 2455h
PID Feedback Input Source
and 2456h
PID Feedback Input
Number
setpoints determine the established the feedback signal to the PID function block. The
2457h
PID Control Response
will use the selected inputs as per the options listed in Table 14.
Table 14: PID Response Options
0 Single Output
1 Setpoint
Control
2 On When Over Target
3 On When Below Target
When a ‘
Single Outpu
t’ response is selected, the Target and Feedback inputs do not have to share
the same units. In both cases, the signals are converted to a percentage values based on the
minimum and maximum values associated with the source function block.
When a
Setpoint Control
response is selected, the 2453h
PID Target Command Source
automatically gets updated to
Control Constant Data
and cannot be changed. The value set in the
associated constant in the Constant Data List function block becomes the desired target value. In
this case, both the target and the feedback values are assumed to be in same units and range. The
minimum and maximum values for the feedback automatically become the constraints on the
constant target. In this mode, the output of the block would be a value from 0% to 100%.
