Справочник Пользователя для National Instruments FP-3000
Chapter 3
Example Applications
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National Instruments Corporation
3-13
PID Control
Instantiate a PID Block
Now that your input and output blocks are functioning, you can “close the
loop” by creating a control block and putting the loop under automatic
control. To instantiate a PID block, follow these steps:
loop” by creating a control block and putting the loop under automatic
control. To instantiate a PID block, follow these steps:
1.
Right-click on FP-3000 in the configurator.
2.
Select Instantiate New Block. This causes a dialog box to appear that
lists all of the blocks supported by the FP-3000 and allows them to be
instantiated.
lists all of the blocks supported by the FP-3000 and allows them to be
instantiated.
3.
Select Proportional Integral Derivative Block from the list, then
click on the OK button.
click on the OK button.
Assign a Tag to the New Block
By default, new blocks are created without a tag. To assign a tag, follow
these steps:
these steps:
1.
Right-click on Proportional Integral Derivative Block, then select
Set Tag.
Set Tag.
2.
Enter the tag you choose in the dialog box. The tag can be up to
32 characters in length and should not contain the dot (“.”) character.
32 characters in length and should not contain the dot (“.”) character.
3.
Click on OK.
Scale the PID
The PID has a
PV_SCALE
for scaling its input. The
PV_SCALE
should
match the output scale (
OUT_SCALE
) of the AI block. To set the PID, enter
the following:
PV_SCALE
EU at 100%
1775
EU at 0%
-273
Units Index °C
Decimal
2
The AO block takes a percentage range from the controller of 0 to 100
percent, so adjust the PID block to output that range. To set the
percent, so adjust the PID block to output that range. To set the
OUT_SCALE
parameter of the PID, enter the following:
OUT_SCALE
EU at 100%
100
EU at 0%
0
Units Index %
Decimal
2