Rockwell Automation 1771-TCM,D17716.5.108 TEMPERATURE CONTROL MOD - Manual (Page 39)

Chapter
5
5-1
Setting Gains
This chapter shows you how to independently set the gains for each PID
loop of the 1771-TCM module. This includes:
sequence of block-transfers
auto-tuning the loops
fine tuning the loops
block
identification
inferred decimal point
the configuration block
At initial start-up, you must write (block-transfer) the gains block to the
1771-TCM module. If you select auto-tuning, for any loop that is
successfully tuned, the gains for that loop in any gains block you had sent
to the module before hand will be ignored. Once auto-tuning is complete,
you must read (block-transfer) the gains block from the module to store it
in PLC processor memory. The module’s memory is volatile. Whenever
power to the module is interrupted, you must again send the gains block
to it.
If auto-tuning is not successful for any loops (as indicated in the status
block) the gains you had sent for those loops before auto-tuning will be
used by the module.
You select auto-tuning from the dynamic block. For each loop, you must
turn on a specific bit to enable auto-tuning for that corresponding loop. To
trigger the start of auto-tuning, you must also turn on a bit that applies to
all loops.
Important: Do not start auto-tuning for a loop unless its PV input is at the
ambient temperature. If not, the auto-tuning may not provide suitable
gains for the application.
The auto-tuning algorithm will not work correctly if the system lag time is
less than 100 seconds. In that case, the auto-tuning will calculate large
gain values, which will probably cause the PV to overshoot the set point.
Chapter Objectives
Sequence of
BlockĆTransfers
AutoĆtuning the Loops